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Technologies, Inc. www.agilent.com
24001
E.
Mission
Liberty
take,
WA
99019
..':Pi;..
,.**:*%,
:
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Innovating
June
Dear Customer,
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8901B
MODULATION ANALYZER
Operation and Calibration Manual
2314A
SERIAL
This
manual provides complete information for
struments with serial-number prefixes:
and
Above
Information for
instruments with serial-number prefixes not listed
in
For additional important information about serial
numbers, refer
THIS
and
all
MAJOR
MAJOR
the above range.
to
MANUAL”
“INSTRUMENTS
in
NUMBERS
changes that apply
rev.
28MA
Y93
changes is also provided for
COVERED
Section
Sixth
1.
Edition
to
in-
your
BY
instrum
ent.
This
material
Government pursuant
der the clause at DFARS 52.227-7013
Copyright@HEWLETT-PACKARD
EAST
24001
MISSION AVENUE, LIBERTY LAKE, WASHINGTON, U.S.A.
Operation
Other Documents Available:
Service Manual (Volume 2,3,4) HP Part 08901-90114
Basic Operation
Microfiche operation and Calibration Manual HP Part 08901-901 15
Microfiche Service Manual HP Part 08901-90116
and
Calibration Manual HP Part 08901-90113
and
Application Guide 08901-901
may
be reproduced by
to
17
the Copyright License
or
for the
(AF’R
COMPANY
U.S.
un-
1988).
1989
99019-9599
Printed in U.S.A. : May 1995
HEWLETT
Fa
PACKARD
1
Regulatory Information
(Updated March
1999)
1
Regulatory Information (Updated March
Safety Considerations
GENERAL
This product and related documentation must be reviewed for familiarization with safety
markings and instructions before operation.
1999)
This product
"Safety Requirements for Electronic Measuring Apparatus," and
safe condition. This instruction documentation contains information and warnings which
must be followed by the user to ensure safe operation and
condition.
SAFETY EARTH GROUND
A uninterruptible safety earth ground must be provided from the main power source to the
product input wiring terminals, power cord, or supplied power cord set.
SAFETY
A
Indicates instrument damage can occur
A
Indicates hazardous voltages.
Indicates earth (ground) terminal
WARNING
has
been designed and tested in accordance with
SYMBOLS
~~~~~
A
WARNING
practice, or the like, which,
could result in personal
note denotes a hazard. It calls attention to a procedure,
IEC
Publication
has
been supplied in
to
maintain the product in a safe
if
indicated operating limits are exceeded.
if
not correctly performed or adhered to,
injury.
Do
not proceed beyond a
WARNING
1010,
sign until the indicated conditions are fully understood and met.
a
CAUTION
A CAUTION note denotes a hazard.
procedure, practice, or the like, which, if not correctly performed or adhered
to
to, could result in damage
not proceed beyond an CAUTION note until the indicated conditions are fully
understood and met.
or
It
calls attention
destruction of part or
to
an operation
all
of the product.
Do
2
Chapter
1
Regulatory Information
(Updated
March
1999)
Safety Considerations
WARNING
This product
protective earthing ground incorporated in the power cord). The
mains plug shall only be inserted
protective earth contact. Any interruption of the protective
conductor inside or outside of the product
product dangerous. Intentional interruption
Whenever
instrument must be made inoperative and be secured against any
unintended operation.
If
this
instrument is to be energized via an auto transformer (for
voltage reduction), make sure the common terminal
the earth terminal of the power source.
If
this product
the equipment could be impaired. This product must be used in a
normal condition (in which all means
No
operator serviceable
qualified personnel.
covers.
for
this Instrument
is
a Safety Class I instrument (provided with a
it
is
likely that the protection has been impaired, the
is
not used
in
a socket outlet provided with a
is
likely to make the
is
prohibited.
is
connected to
as
specified, the protection provided by
for
protection are intact) only.
parts
To
prevent electrical shock, do not remove
in this product. Refer servicing to
Servicing instructions are
for
use by qualified personnel only.
To
avoid electrical shock, do not perform any servicing unless you are
qualified to do
so.
The opening of covers or removal of parts is likely to expose
dangerous voltages. Disconnect the product from
while
The power cord
live for
it
is
being opened.
is
connected
5
seconds after disconnecting the plug
to
internal capacitors that
all
from
voltage sources
my
remain
its
power supply.
For Continued protection against fire hazard, replace the line fuse(s)
only
with
example, normal blow or time delay).
250
V
fuse(s) or the same current rating and type (for
Do
not use repaired fuses or
short circuited fuseholders.
Always use the three-prong ac power cord supplied with this
product. Failure
to
ensure adequate earth grounding by not using
this cord may cause product damage.
This product
Pollution Degree
INDOOR
is
USE
designed
2
per
ONLY.
for
IEC
use in Installation Category
1010
and
IEC
664
respectively.
11
and
FOR
This product has autoranging line voltage input, be sure the supply
voltage
is
within the specified range.
Chapter
1
3
Regulatory Information (Updated March
To
prevent electrical shock, disconnect instrument from mains (line)
before cleaning. Use a dry cloth or one slightly dampened with water
to clean the external case parts.
Ventilation Requirements: When installing the product in a cabinet,
the convection into and out
The ambient temperature (outside the cabinet) must be less than the
maximum operating temperature of the product by
watts dissipated in the cabinet.
cabinet is greater than
used.
Product Markings
1999)
Do
not attempt to clean internally.
of
the product must not be restricted.
If
the total power dissipated in the
800
watts, then forced convection
4"
C
for every
must
100
be
CE - the CE mark
is
a registered trademark
of
the European Community. A CE mark
accompanied by a year indicated the year the design was proven.
CSA
-
the
CSA
mark
is
a registered trademark
of
the Canadian Standards Association.
4
Chapter
1
CERTIFICATION
Hewlett-Packard Company certifies that this product met its published specifications at the time
from the factory. Hewlett-Packard further certifies
that
its calibration measurements are traceable to
of
shipment
the
United
States National Bureau of Standards, to the extent allowed by the Bureau’s calibration facility, and to the
calibration facilities of other International Standards Organization members.
WARRANTY
This Hewlett-Packard instrument product
of one year from date of shipment. During the warranty period, Hewlett-Packard Company will at its option,
either repair or replace products which prove
For warranty service or repair, this product must
prepay shipping charges
shall pay
HP warrants that its software and firmware designated by HP for use with an instrument will execute
programming instructions when properly installed on
of
all
shipping charges, duties, and taxes for products returned
the instrument, or software, or firmware will be uninterrupted or error free.
to
HP and HP shall pay shipping charges
is
warranted against defects in material and workmanship for a period
to
be defective.
be
returned
that
to
a service facility designated by HP. Buyer
to
return the product
to
HP from another country.
instrument. HP does not warrant that the operation
to
Buyer. However, Buyer
shall
its
LIMITATION OF WARRANTY
The foregoing warranty shall not apply
Buyer-supplied software
specifications for the product, or improper site preparation or maintenance.
or
interfacing, unauthorized modification or misuse, operation outside of the environmental
to
defects resulting from improper or inadequate maintenance
by
Buyer,
NO OTHER WARRANTY
WARRANTIES
OF
IS
EXPRESSED OR IMPLED. HP SPECIFICALLY DISCLAIMS THE IMPLED
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
EXCLUSIVE REMEDIES
THE REMEDIES PROVIDED HEREIN ARE BUYER’S SOLE AND EXCLUSIVE REMEDIES. HP
NOT BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
DAMAGES, WHETHER BASED ON CONTRACT, TORT, OR ANY OTHER LEGAL THEORY.
SHALL
ASSISTANCE
Product maintenance agreements and other customer assistance agreements are available for Hewlett-Packard
products.
For
any assistance, contact your nearest Hewlett-Packard Sales and Service Office. Addresses are provided at
the back of this manual.
iii
Saftey
Considerations Model
SAFETY CONSIDERATIONS
GENERAL
This product and related documentation must be reviewed for familiarization with safety markings and
instructions before operation.
This product
with a protective earth terminal).
BEFORE APPLYING POWER
Verify that the product
line voltage and the correct fuse is installed.
SAFETY EARTH GROUND
An uninterruptible safety earth ground must be provided from the main power source to the product input
wiring terminals, power cord,
set.
SAFETY SYMBOLS
A
is necessary for the user to refer to the instruction
manual (refer to Table of Contents).
f
procedure, practice,
performed
jury.
Do
the indicated conditions are fully understood and met.
is
a
Safety Class I instrument (provided
is
set to match the available
or
supplied power cord
Instruction manual symbol: the product will
be marked with this symbol when it
Indicates hazardous voltages.
Indicates earth (ground) terminal.
The WARNING sign denotes
hazard. It calls attention to a
or
the like, which, if not correctly
or
adhered to, could result in personal in-
not proceed beyond a WARNING sign until
Any interruption of the protective (grounding)
conductor (inside
ment)
terminal will cause a potential shock hazard
that could result in personal injury. (Grounding one conductor of a two conductor outlet
is not sufficient protection).
Whenever it
been impaired, the instrument
inoperative and be secured against any unintended operation.
If this instrument is to be energized via an
autotransformer (for voltage reduction) make
sure the common terminal is connected to the
earth terminal of the power source.
Servicing instructions are for use by servicetrained personnel only.
electric shock, do not perform any servicing
unless qualified to do
Adjustments described in the manual are per-
formed with power supplied to the instrument
while protective covers are removed. Energy
a
available at many points may,
sult
Capacitors inside the instrument may still be
charged even if the instrument has been disconnected from its source of supply.
or
disconnecting the protective earth
is
likely that the protection has
in
personal injury.
or
outside the instru-
musl
To
avoid dangerous
so.
if
contacted, re-
8901B
be made
The CAUTION sign denotes a haz-
ard. It calls attention to an
operating procedure, practice,
correctly performed
age to or destruction of part
not proceed beyond a CAUTION sign until the indi-
cated conditions are fully understood and met.
iv
or
adhered to, could result in dam-
or
the like, which, if not
or
all
of
the product.
Do
For
continued protection against fire hazard,
replace the line fuse(s) only with
of the same current rating and type (for exam-
ple, normal
repaired fuses
fuseholders.
blow,
time delay, etc.).
or
short circuited
250V
Do
fuse(s)
not use
Model
8901B
Saftey Considerations
ATTENTION
Static Sensitive
Devices
This instrument was constructed
charge) protected environment.
conductor devices used in this instrument are susceptible to damage
by static discharge.
Depending on the magnitude of the charge, device substrates can
be punctured
charge. The results can cause degradation of device performance,
early failure,
These charges are generated in numerous ways such
tact, separation of materials, and normal motions of persons
working with static sensitive devices.
When handling
devices, adequate precautions must be taken to prevent device darnage
or
Only those who are thoroughly familiar with industry accepted
techniques for handling static sensitive devices should attempt to
service circuitry with these devices.
In all instances, measures must be taken to prevent static charge
build-up on work surfaces and persons handling the devices.
For
further information on ESD precautions, refer to “SPECIAL
HANDLING CONSIDERATIONS
DEVICES”
or
destroyed
or
immediate destruction.
or
destruction.
in
Section VIII Service Section.
by
servicing equipment containing static sensitive
in
This
contact
an ESD (electro-static dis-
is
because most of the semi-
or
mere proximity of a static
as
simple con-
FOR
STATIC SENSITIVE
V
Model
8901B
Contents
CONTENTS
Section
Introduction
Operation and Calibration Manual
Service Manual
Specifications
Safety Considerations
Recommended Test Equipment
Instniments Covered
Options
SerialNumbe
Documentation Updating
A
Description
Signing Up for the Documentation Update Service
Hewlett-Packard Interface Bus (HP-IB)
Compatibility.
Selecting the HP-IB Address
Additional Equipment Information
Options
Accessories Supplied
Electrical Equipment Available
Mechanical Equipment Available
Description
RF
RF Fkequency Measurements
Modulation Measurements
Filters, De-emphasis Networks and Modulation Calibrators
Additional Features
Specialhctions
Extending Measurement Range
Programmability
Principles
RF Circuitry
LOCircuitry
IFCircuitry
Audio Circuitry
Modulation Basics
Amplitude Modulation
Exponential Modulation
Other Considerations
to
This Manual
............................................
.......................................
..................................................
.....................................................
................................................
...........................................
by
This Manual
.......................................
......................................................
rs
..................................................
.............................................
of
the Manual Update Packet
.................................................
.........................................
.........................................
......................................................
...............................................
........................................
.......................................
of
the Modulation Analyzer
Power Measurements
...........................................
.........................................
..........................................
..............................................
................................................
........................................
................................................
of
Operation Using A Simplified Block
...................................................
..................................................
..................................................
................................................
.................................................
............................................
............................................
.............................................
1
.
General Information
................................
.....................................
......................................
Diagram
.............................
.........................
...........................
1-1
1.1
1-1
1.2
1.2
1.2
1.2
1-2
1-2
. 1-2
. 1-2
. 1-3
. 1-3
. 1-3
. 1-3
1-3
1-3
1-4
. 1-4
. 1-5
1-6
. 1-6
. 1-7
. 1-7
1-7
. 1-7
1-8
. 1-8
. 1-8
1-8
1-9
1-11
1-11
1-11
1-12
1-12
1-15
1-17
vii
Contents Model 8901B
Section
Introduction
Initial Inspection
Preparation for Use
Power Requirements
Power Cables
Line Voltage and Fuse Selection
HP-IB Address Selection
Interconnections
Mating Connectors
Operating Environment
Bench Mounting
RackMounting
Removal and Installation
Storage and Shipment
Environment
Packaging
to
This Section
............................................
...................................................
.................................................
...............................................
...................................................
........................................
............................................
.................................................
...............................................
.............................................
.................................................
..................................................
of
Operating Information Pull-Out Cards
................................................
...................................................
.....................................................
Section
Introduction
Local
Remote Operation Section
Basic finctional Checks Section
Detailed Operating Instructions Section
Other Sources of Operating Information
Operating Characteristics
Operator’s Information
Fbes
Time Base 10 MHz Input and Time Base 10 MHz Output
Description
Turn-On Procedure
Instrument Features
Front-Panel Features
Rear-Panel Features
Remote Operation
Introduction to the Section
How to Use this Section to Make a Measurement
Programming the Modulation Analyzer
Overview
Valid
Invalid Characters
Programming Syntax
Code String Syntax (Sequence Dependency)
Programming Examples
Reference Tables
Data Output
Data Output Format
HP-IB Information
HP-IB Capabilities
HP-IB Address
to
This Section
Operation Section
............................................
.............................................
...........................................
.........................................
....................................
....................................
of
the Measuring Receiver
...............................
........................................................
....................................................
..................................................
.................................................
...............................................
...............................................
VIA
the Hewlett-Packard Interface Bus (HP-IB)
..........................................
.....................................
....................................................
Programming Codes
...........................................
...............................................
.............................................
............................................
................................................
....................................................
..............................................
................................................
..............................................
.................................................
2
3
................................
.
Installation
.....................
.
Operation
...............................
;
...............
.........................
.....................
.............................
2.1
2.1
2.1
2.1
2.2
2.4
2.4
2.8
2.8
2.8
2.8
2-8
2.8
2.9
2.9
2-9
3.1
3.1
3.1
3.1
3.2
3.2
3.2
3.2
3-2
3-3
3-3
3-3
3-4
3-6
3-9
3-13
3-13
3-13
3-13
3-13
3-13
3-14
3-15
3-16
3-17
3-17
3-18
3-18
3-19
3-19
3-20
viii
Model
8901B
Contents
Section
Modulation Analyzer Remote Capabilities (IEEE-488)
Triggering Measurements
Trigger Modes
Triggers
Clear
Remote/Local
Mode Descriptions
Mode Transitions
Local Lockout
Clear Lockout/Set Local
Service Request Message (SRQ)
SRQ MASK (Special Fbnction
StatusB
Abort
Pass Controlflake Control
Status Bit
Additional Information
Annunciators
Reading the HP-IB Address Switch and
TALK and LISTEN
Code Execution in the Modulation Analyzer
Basic bctional Checks of the Modulation Analyzer
Description
Equipment
Procedure
Basic bctional Checks
Description
Initial Setup
Equipment
Procedures
Detailed Operating Instructions
Introduction
Section Organization
How
FW
Frequency Measurements (RF, LO.
Modulation Measurements Contents
Audio Measurements Contents
Additional Capabilities Contents
(T2.
......................................................
yte
......................................................
to
Find Information About a Specific Measurement
Power and Level Contents
(TO
and
T3.
GET. and the CLEAR Key)
.................................................
...............................................
...............................................
.................................................
...................................................
...................................................
..................................................
...................................................
...................................................
....................................................
...................................................
..................................................
...................................................
...................................................
to
This Section
...........................................
..........................................
T1)
........................................... 3-26
.......................................
22)
......................................
..........................................
..............................................
Status
of
Descriptions
the Hewlett-Packard Interface Bus (HP-IB)
..........................................
.........................................
.............................................
........................................
IF)
.......................................
......................................
3
.
Operation (cont’d)
...............................
SRQ
Status
..................................
................................
Contents
....................................
.............................
............................
..............................
...................
.........................
.............................
3-20
3-21
3-22
3-23
3-24
3-25
3-25
3-25
3-25
3-26
3-29
3-31
3-32
3-32
3-32
3-32
3-32
3-33
3-34
3-34
3-47
3-47
3-47
3-47
3-56
3-56
3-57
3-57
3-57
3-67
3-67
3-67
3-67
3-69
3-109
3-133
3-197
3-205
Introduction
Equipment Required
Performance Test Record
Calibration Cycle
Abbreviated Performance
.....................................................
.................................................
...................................................
Section
4
.
Performance Tests
..............................................
Testing
..........................................
4.1
4.1
4.1
4.1
4.1
ix
Contents
Model
8901B
Performance Test
Performance Test
Performance Test
Performance Test
Performance
Performance Test
Performance Test
Performance Test
Performance Test
Performance Test
Performance
Performance Test Record
1
.
AM
2
.
FM
3
.
cPM
4 . Audio Filters
Test
5 . Audio Measurements
6 . Power Reference (Using Reference Comparison
7
.
Power Reference (Using DC Substitution)
8
.
Power Meter
9
.
SWR
10 . High-Selectivity (Options
Test
11
.
High-Selectivity Gain (Option Series
Section
..............................................
..............................................
.............................................
............................................
.............................................
4
........................................
........................................
Section
Introduction
Safety Considerations
Wipment Required
F'actory-Selected Components
Post-Repair Tests, Adjustments, and Checks
Related Adjustments
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
Adjustment
.....................................................
................................................
.................................................
............................................
.................................................
1
.
Power Supply
2 . Internal Reference
3
.
RF Level Detector Offset
4 . Sampler Efficiency and Offset
5
.
LO
Doubler Output Power and Balance
6
.
Voltmeter Offset
7
.
15
kHz
and
8
.
ALC
Reference
9
.
FM Calibrator
10 . FM Sensitivity
11
.
FM Flatness
12 . FM Distortion and Incidental
13 . cPM Sensitivity
14
.
AM
Calibrator
15
.
AM
16 . FM Distortion and Incidental AM . 455
17 . Tkack-The Mode Offset
18 . Power Reference (Using Reference Comparison
19 . Power Reference (Using DC Substitution
20 . Power Meter
21
22 . Battery Backup
Sensitivity
.
Audio True RMS Detector and Notch
............................................
.........................................
and
>20
Sensitivity
kHz
Low-Pass Filter Gain
..........................................
..........................................
.........................................
...........................................
.........................................
..........................................
.........................................
...........................................
.........................................
.
Performance Tests (cont'd)
...................................
.....................
.......................
032
and
033)
........................
030)
.......................
5
.
Adjustments
....................................
.....................................
...................................
............................
................................
..........................
AM
.
1.5
MHz
IF'
......................
kHz
IF
.......................
....................................
.......................
...........................
Filter
......................
Gain
4.2
4.8
4-14
4-18
4-20
4-25
4-26
4-29
4-31
4-33
4-38
4-40
5.1
5.1
5.1
5.2
5.2
5.2
5.5
5.6
5.7
5.8
5-10
5-12
5-14
5-15
5-16
5-17
5-18
5-19
5-21
5-23
5-24
5-25
5-27
5-28
5-30
5-33
5-35
5-37
X
General
Information
Model
8901B
MODEL
LINE POWER CABLE
8901B
1-0
Figure
1-1.
HP
8901B
Modulation Analyzer and Supplied Accessories
Model 8901B General Information
GENERAL INFORMATION
1-1.
INTRODUCTION TO THIS MANUAL
The HP 8901B
and the three volume
install, operate,
The information
5
are contained in this
Application Guide)
Service Manual
Service Manual Request Card
The Modulation Analyzer
Modulation Analyzers supplied with Options 001,002,003,004, and series 030.
Operation and Calibration Manual
Section
instrument description, options, accessories, specifications and other basic information. This section
also
1,
contains instrument theory of operation on a simplified block diagram level.
Operating and Service Manual
Service Manual.
test,
adjust, and service the Hewlett-Packard Model 8901B Modulation Analyzer.
to
operate and service this instrument
Operation and Calibration Manual
which is provided with each instrument. Sections 6 through 8 are contained in the
that
is
not included with the instrument but which can be obtained by mailing in the
is
General Information
Section
These four volumes contain
included in this manual.
shown in Figure
describes the instruments documented by this manual and covers
1-1
1
is comprised of an
is
made available
with all supplied accessories. These manuals document
Operation and Calibration Manual
all
the information required
as
follows: Sections 1 through
(that includes the
Basic Operation and
to
Section
address selection for remote operation), and storage and shipment.
Section
operating instructions for both local and remote operation.
Section
instrument against the critical specifications in Table
Section
2,
Installation
3,
Operation
4,
Performance Tests
5,
Adjustments
provides information about panel features and includes operating checks, and
provides information about initial inspection, preparation for use (including
provides the information required
1-1.
provides the information required
to
properly adjust the instrument.
to
check performance of the
Service Manual
Section
Section
tion information.
Section
Additional copies of the
separately through your nearest Hewlett-Packard office. The part numbers are listed on the title page
of this manual.
6,
Replaceable Parts
7,
Instrument Changes
8,
Service
provides the information required
provides ordering information for
provides backdating information, and retrofitting and modifica-
to
repair the instrument.
Operation and Calibration Manual
all
or the
replaceable parts and assemblies.
Service Manual
can be ordered
1-1
General Information Model 8901B
1-2.
SPECIFICATIONS
Instrwnent specifications are listed in Table
against which the
acteristics,
information for the user.
1-3.
SAFETY CONSIDERATIONS
This product is a Safety Class I instrument (that is, provided with a protective earth terminal).
The Modulation Analyzer
safety markings
the beginning of
Safety information pertinent
adjustment
1-4.
RECOMMENDED TEST EQUIPMENT
Table
and servicing the Modulation Analyzer.
instruments with equivalent minimum specifications may be substituted. Table 1-2 also includes
some alternate equipment listings. Table 1-3 lists
those contained in the Service Accessory Kit, HP 08901-60287.
1-5.
INSTRUMENTS COVERED
are not warranted specifications but are typical characteristics included as additional
and
this
or
service) is found throughout these manuals.
1-2
lists the test equipment
1-1.
instrum
ent may be tested. Information listed in this table as
and
all related documentation
instructions before operation. Refer
manual for a
summary
to
the task at hand
and
accessories recommended for use in testing, adjusting,
If
BY
THIS MANUAL
of the safety information.
any of the recommended equipment is unavailable,
These are the performance standards,
Supplemental
must
be reviewed for familiarization with
to
the
Safety
(installation,
a
number of accessories required in addition
Considerations
operation, performance testing,
page found at
or
limits,
Char-
to
Opt
ions
Electrical options 001,002,003,004, series 030, and various mechanical options
these manuals. The differences are noted under paragraph 1-8,
Parts,
Serial Numbers
Attached
The fist four digits
that is unique
having the same serial number prefix(es) as listed under SERIAL NUMBERS on the respective
manual title pages.
For information concerning a serial number prefix not listed on the title page
Changes supplement, contact
1-6.
MANUAL UPDATING
This manual may be revised as needed
changes. The latest revision
shown below.
are
documented in
Options,
and in the schematic diagrams in Section 8.
to
the instrument is a serial number plate. The serial number is in the form 1234A00123.
and
the letter are the serial prefix. The last five digits form the sequential
to
each instrument. The contents
your
nearest Hewlett-Packard office.
to
make corrections and
of
the manual
of
these manuals apply directly
to
document hardware and firmware
can
be purchased from the Hewlett-Packard locations
in Table 6-3,
to
or
in the Manual
Replaceable
suffix
instruments
1-2
rev.28MA
Y93
Model 8901B General Information
Inside the U.S.A.
Call
HP Parts Direct Ordering
available.
at 800-227-8164. They can
also
help determine
if
a new revision is
Outside the U.S.A.
Contact the local Hewlett-Packard Sales and Service office for ordering information.
1-7.
HEWLETT-PACKARD INTERFACE BUS (HP-IB)
Corn pati bil ity
The Modulation Analyzer’s capabilities are defmed by the following interface functions: SH1, AH1,
T5, TEO,
via open-collector
Standard 488- 1978,
the identical ANSI Standard
For
Remote Operation, Hewlett-Packard Interface
Selecting the
The HP-IB address switches
five-bit binary number. This number represents the talk and listen address characters which the
controller
talk only
HP-IB Address Selection
1-8.
ADDITIONAL EQUIPMENT INFORMATION
0
pt i ons
Options are variations on the standard instrument which can be ordered during the purchase. The
following list defines all currently available options. Refer
section for retrofit part numbers
L3, LEO,
SR1, RL1, PPO, DC1,
TTL
circuitry.
An
IEEE Standard and Digital Interface for Programmable Instrumentation
MC
1.1.
more detailed informationrelating
HP-IB
must
or
to
Address
are
located within the Modulation Analyzer. The switches represent a
generate.
listen only. A table in Section 2 shows all HP-IB talk and listen addresses. Refer
In
addition,
in Section 2 of this
that
DT1,
CO.
The Modulation
explanation of the compatibility code may be found in
to
programmable control
Bus
in Section 3 of this
two
more switches allow the Modulation Analyzer
Operation and Calibration
to
can be ordered after the purchase.
Analyzer
of
the Modulation Analyzer, refer
Operating Information
interfaces with the bus
manual.
manual.
to
be set
Electrical Equipment Available
IEEE
or
to
to
to
in this
rev.
Option
PUT, SENSOR input, MODULATION OUTPUT/AUDIO INPUT, and
CALIBRATION OUTPUTS.
Option
place of the standard reference oscillator.
rear panel.
28MA
Y93
001.
This option provides rear-panel (instead of front-panel) connections for RF
002.
This option provides a high-stability
In
addition, a
(1
x
10-g/day) internal reference oscillator in
10
AMYFM
MHz time base output
and
RF
POWER
is
provided on the
IN-
1-3
General Information Model
8901B
Option
for an external local oscillator signal. Both connections are located on the rear panel.
provided automatically with option
Option
at frequencies greater than
Option
sideband carrier noise
output for the internal local oscillator and an input for an external local oscillator signal
with these options.) This option
Options
Option
the
003.
This option provides both an output for the internal local oscillator signal and an input
004.
This option allows operation at line frequencies ranging from
030.
The High Selectivity Measurement option provides the capability
Option
Option
Option
Option
032.
This option provides a
033.
This option provides a
035.
This option provides a
037.
This option provides a carrier noise filter.
907-909.
910.
This option provides an extra copy of both the
Service Manual.
030
series instruments.)
66
Hz
is
restricted
(AM
or phase) quickly and accurately up
is
ordered with one of the following filter options:
These options are described in
to
12.5
kHz adjacent channel filter.
25
kHz adjacent channel filter.
30
kHz (Cellular Radio) alternate channel filter.
48
to
less than
126.5
Vac line input.
to
1.3
GHz with an external
Mechanical Equipment Available.
Operation and Calibration Manual
(This
400
Hz. Operation
to
measure single-
output
LO.
is
provided
is
(An
and
Accessories Supplied
The Accessories Supplied are pieces of equipment which are shipped automatically with every
Modulation Analyzer.
Line Power Cable.
on the destination of the original shipment. Refer
Information
Fuses.
2110-0043)
of original destination. Refer
Information
manual.
Fbes with a
are supplied. One fuse
manual.
The line power cable may be supplied in several plug configurations, depending
to
2.5A
rating for
is
factory installed according
to
Line Voltage
115
Vac
Power Cables
(HP
2110-0083)
and
he Selection
in Section 2 of this
and a 1.5A
to
the voltage available in the country
in Section 2 of this
rating for
230
Electrical Equipment Available
This equipment
HP-IB Controller.
compatible computing controller or computer for automatic systems applications.
Sensor Module.
using a single input connector. Switching back and forth between the Modulation Analyzer’s SENSOR
input and RF INPUT connectors happens automatically with these modules (which contain an internal
switch). The HP
range
50
MHz to
is taken with each sensor module
isolates the power sensor from the source-under-test, reducing mismatch. Microwave hardware and a
selected RF input cable further improve SWR and insertion loss.
is
available
The Modulation Analyzer has an HP-IB interface and can be used with any HP-IB
The HP
11722A
26.5
to
be ordered for the Modulation Analyzer
11722A
covers the Erequency range
GHz and
and
11792A
is
intended for use with the HP
to
minimize input
after
Sensor Modules enable you
100
kHz
to
2.6
GHz; the HP
11793A
SWR
and resulting errors. A low SWR attenuator
Down
the time of sale.
to
characterize a signal
11792A
Converter. Special care
Operating
Vac (HP
Operating
covers the
1-4
Model 8901B General Information
Down Converter.
The HP 11793A Down Converter, when used with a suitable local oscillator, extends
the useful range of the Modulation Analyzer into the microwave region. Provisions have been made in
to
the Modulation Analyzer
account for the frequency of the local oscillator and provide direct display
of the frequency of the microwave input signal.
Test Source.
high rates as well
adjusting the Modulation Analyzer; however,
The HP 11715A AMFM Test Source produces extremely linear AM and
as
a low-noise
CW
signal. This source
it
is
is
required for performance testing and
an excellent stand-alone instrument for generating
FM
at
very low-distortion FM in the broadcast band.
Service Accessory Kit.
accessories (such
Front-to-Rear-Panel Connectors Retrofit Kit (Option
as
components and full instructions for converting front-panel connections
A
Service Accessory Kit (HP 08901-60287)
is
available which contains
extender boards and cables) useful in servicing the Modulation Analyzer.
001).
This kit contains all the necessary
to
rear-panel connections.
Order HP part number 08901-60282.
Rear-to-Front-Panel Connectors Retrofit Kit (Standard).
This kit contains
all
the necessary
components and full instructions for converting Option 001 instruments with rear-panel connections
to
instruments with front-panel connections. Order
High-Stability, Internal-Reference Retrofit Kit (Option
HP
part number 08901-60283.
002).
This kit contains all the necessary
components and full instructions for installation of the high-stability, internal-reference oscillator.
Order HP part number 08901-60281.
Rear-Panel Local Oscillator Connections Retrofit Kit (Option
003).
This kit contains all the
necessary components and full instructions for installation of rear-panel local oscillator connections.
Order HP part number 08901-60280. (These connections are already included in all Option 030
Series instruments.)
Conversion to
frequencies greater than 66 Hz may be converted
However, operation at line frequencies greater than 66 Hz will be restricted
or equal
installation, performance will be identical
400
Hz Line Operation.
to
126.5 Vac. To convert to
Modulation Analyzers not equipped
to
operate at line frequencies from 48
400
Hz operation, order HP part number 08901-60095. After
to
the HP 8901B Option 004.
to
operate at line power
to
line voltages less than
Mechanical Equipment Available
The following
they were not ordered with the original shipment and are now desired, they can be ordered from the
nearest Hewlett-Packard office using the appropriate part number.
Front-Handle Kit (Option
part number 5061-9690 for the basic kit and 2190-0048 for lockwashers
Rack-Flange Kit (Option
rack using the flange kit. Order HP part number 5061-9678.
Rack-Flange and Front-Handle Combination Kit (Option
a rack-flange kit packaged together;
Order HP part number 5061-9684 for the basic kit and 2190-9609 for lockwashers
kits
might have been ordered and received with the Modulation Analyzer
907).
Ease of handling is increased with the front-panel handles. Order HP
(8
required).
908).
The Modulation Analyzer can be solidly mounted
909).
it
is composed of a unique part which combines both functions.
This
is
not a front-handle kit and
as
to
the instrument
(8
required).
to
440
options.
Hz.
If
1-5
General Information Model
8901B
Chassis Slide-Mount Kit.
mounted. Access to internal circuits and components
the instrument from the rack. Order HP part number
order adapters for non-HP rack enclosures, use HP
Chassis-Tilt, Slide-Mount Kit.
also allows the tilting of the instrument up
(17
in.) tilting slides. To order adapters for non-HP rack enclosures, use HP part number
1-9.
DESCRIPTION OF
The HP Model
characterizing signals in the
of
four separate instruments in its ability
the characteristics of the demodulated audio signal
flexibility allows you
a signal.
The Modulation Analyzer can measure an RF signal's frequency, frequency
(broadband, and off-channel), amplitude modulation (AM), frequency modulation (FM), phase
modulation (@M), and AM and FM noise components.
measure the audio signal's frequency and distortion.
The Modulation Analyzer
single key. The Modulation Analyzer's large digital display shows measurement results with excellent
resolution and
measurement results can be transferred
Hewlett-Packard's implementation of
THE
8901B
is
easy
This kit
This kit
is
extremely useful when the Modulation Analyzer
or
is
the same
or
down
the rear panel
1494-0017
part
number
as
the Chassis Slide Mount Kit above except
90".
Order
for
1494-0023.)
HP
is
possible without removing
432
mm
part number
(17
in.) fixed slides. (To
1494-0025
MODULATION ANALYZER
Modulation Analyzer
150
kHz
to
to
make those measurements most commonly needed
is
fully automatic and all major measurements can be made by pushing a
to
read. All Modulation Analyzer operations can be controlled and
via
IEEE
is
a complete measurement system
1300
MHz frequency range. It combines the capabilities
to
measure
the Hewlett-Packard Interface
Standard
RF
power, carrier frequency, modulation and
(as
well
as
those of external audio signals). This
It
recovers the modulating signal and can
488
and ANSI Standard
to
totally characterize
drift,
Bus
(HP-IB). (HP-IB
MC1.l.)
is
for
432
1494-0023.
for
accurately
power level
rack
it
mm
all
is
RF Power Measurements
The Modulation Analyzer delivers the accuracy and resolution of a high-performance power meter.
The HP
at frequencies from
limits using other power sensors. The HP
extended measurement capability.)
Input Power Protection.
damage from the accidental application of excessive power.
equipment used
Protection
opens and protects sensitive components, and the Modulation Analyzer displays an error message. The
circuit automatically resets whenever
RF Power Calibration.
available in every instrument. Also, the front-panel ZERO function enables you
module without removing it from the source-under-test. After the ZERO key
offsets are stored automatically.
RF
into the Modulation Analyzer's non-volatile memory. The instrument automatically compensates for
the power sensor's efficiency and mismatch loss at each frequency.
8901B,
Power Calibration Factors.
with the HP
100
kHz
to
measure transmitters.) The Modulation Analyzer is
is
provided by limiting diodes and an RF relay. When excessive power
11722A
to
2.6
Sensor Module, measures power from
GHz. (Refer
to
890lB
The Modulation Analyzer
a
key
is
depressed.
RF Power Calibration
RF Power Calibration Factors can be entered from the power sensor
is
Table
1-1,
Specifications,
also accepts all HP
is
equipped with input power protection
(This
8480
is
a common cause
tested
accomplished with the
+30
dBm
to
for specified frequencies
series power sensors
of
for inputs up
is
applied, the relay
50
MHz, 1 mW standard
to
zero the sensor
is
pressed, the new zero
-20
dBm
for
to
prevent
damage in
to
2W.
1-6
Model 8901B General Information
High Selectivity Measurements.
HP
8901B Modulation Analyzer. Used with a low-noise external
accurate single-sideband (SSB) carrier noise measurements
Options 030-037 add selective power measurement capability
LO,
the
HP
8901B performs fast,
to
1.4 GHz.
RF Frequency Measurements
In automatic operation, the Modulation Analyzer
1300 MHz frequency counter. The frequency counter automatically adjusts itself
is
changes. There
Analyzer is usually used
signals with significant levels of AM.
no need
to
manually set or adjust the input attenuator. Because the Modulation
to
measure modulated signals,
has
the performance
its
frequency counter
of a high-quality, 150 kHz
as
the input level
also
accurately measures
Modulation Measurements
The Modulation Analyzer has extremely low internal noise. Incidental AM, FM, and QM can be
measured on a wide range of simple and complex modulated signals. To complement
measurement capability, the HP 8901B characterizes audio signal level, frequency, and distortion.
(These features are also available for external audio signals.)
its
Filters, De-emphasis Networks and Modulation Calibrators
Post-Detection Audio Filters.
filters
detection audio
in
combination. Their cutoff frequencies have been chosen
or
as
such
overshoot for square-wave modulation
measured.
transmitter or signal generator testing. The
for filtering the recovered modulation. These filters can be selected individually
The Modulation Analyzer has
>20
kHz filter
so
that this type of modulating waveform can
two
high-pass and three low-pass post-
to
match those needed for applications
is
a Bessel filter.
It
also
be accurately
to
the
to
modulation
minimizes
De-Emphasis Networks.
in
used
50, 75, and 750
You can select whether the de-emphasis network affects the deviation measured. The ability
either the actual or “de-emphasized deviation” increases the usefulness of the Modulation Analyzer in
many applications.
Modulation Calibrators.
measurements
calibration standard. In all instruments, a precise AM and FM modulation standard
When the output of the calibrator
of modulation
automatically compensate
measured modulation
addition
to
ps.
of
AM
is
measured to create a calibration factor. The calibration factor can be used
The Modulation Analyzer contains four de-emphasis networks
the audio filters. These are the ones commonly used
When selected, the de-emphasis networks always affect the demodulated output.
One of the most difficult problems involved in making very accurate
depth or FM deviation
is
connected
all
subsequent measurements. The calibration factor is the ratio of the
to
the internally-computed modulation of the calibrator, expressed in
is
generating a precisely modulated signal
to
the Modulation Analyzer’s input, the amount
in
FM communications-25,
is
included.
Additional Features
Tuning Features.
signal and measures it.
In manual operation, you can determine the frequency
Entering the approximate frequency on the keyboard causes all but very close interfering signals
eliminated. This allows the Modulation Analyzer
A track mode feature enables you to track a signal,
manual tune operation.
In automatic operation, the Modulation Analyzer automatically tunes
to
which the Modulation Analyzer tunes.
to
selectively measure signals other ‘than the largest.
as
it
changes frequency, from either automatic or
to
that
can be
to
to
use as
7%.
the input
select
a
to
to
be
1-7
General Information Model 8901B
Store and Recall functions.
in non-volatile memory and recall them
Display Flexibility.
power can be displayed in watts, am, V, dBV, mV, dBmV, pV, and
LOG/LIN
the keyboard. These features eliminate the need for recalculating measurement results.
keys
The Modulation Analyzer offers numerous data-display formats. For example, RF
to
display results in
These functions enable you
as
needed.
dB
or
7%
relative
to
either a measured value or a value entered from
to
store eight complete instrument settings
dBpV.
Use
the RATIO and
Special Functions
The Modulation Analyzer can do more than
accessed using the numeric keys and a Special Function key. The Special hctions provide access
to
other measurements and functions, manual control of instrument functions, instrument operation
verification, and service
All
instrument functions not set using these Special Functions remain in the automatic mode. This
to
allows you
key alone, the display shows ten digits that indicate which functions are in automatic and the
those manually set.
There are also numerous Special Functions that can be used
various sections are operating properly. These, along with service special functions, make diagnosing
and repairing the Modulation Analyzer faster and easier.
Those Special Functions that are most commonly used in operating the Modulation Analyzer are
described on the
select any combination of manual or automatic operations. By depressing the special
Special hnction Information
aids.
is
apparent from the front panel. Many functions
in
verifying that the instrument and
pull-out card under the front panel.
state
are
of
its
Extending Measurement Range
Operation
path. This system then functions as a single instrument making microwave modulation, frequency,
power, and level measurements. You control operation from the Modulation Analyzer's front panel.
When the external
controller
Offset mode for your microwave power sensor.
to
42
GHz
is
LO
to
make the change. A separate, non-volatile calibration factor table
Programmability
The Modulation Analyzer
IB).
This, coupled with the diversity
with which these measurements can be made, and the flexibility of the Special bctions, make the
instrument ideal for systems applications. In many instances
in a system, speed measurements, reduce complexity and improve accuracy.
When the Modulation Analyzer is in remote, the front-panel annunciators make
determine the state the instrument is in; whether
1-10.
PRINCIPLES
The Modulation Analyzer
signal
the Modulation Analyzer contains an
and bandpass filter, a demodulator (detector or discriminator), and audio filters (tone controls). The
Modulation Analyzer, however, contains additional features which make
to
automatic tuning,
selectable measurement mode: signal frequency, power level, or modulation (AM, FM, or Phase
Modulation (@MI),
selectable audio detector (peak, average, or
audio counter,
OF
OPERATION USING
a
fixed, intermediate frequency
accomplished when an external
frequency must be changed, the Modulation Analyzer requests an external
is
completely programmable
of
measurements the Modulation Analyzer can make, the speed
A
SIMPLIFIED
is
a calibrated, superheterodyne receiver, which converts the incoming
(IF),
RF
amplifier, a local oscillator
LO
and mixer are included
via
the Hewlett-Packard Interface Bus (HP-
it
can reduce the number of instruments
it
is
in the talk, listen, or service request
which
rms
responding),
BLOCK
is
then demodulated.
DIAGRAM
(LO),
a
it
much more versatile:
in
the measurement
is
available in Frequency
it
very easy
state.
As
in a radio receiver,
mixer, an
IF'
amplifier
to
1-8
Model 8901B General Information
0
audio distortion analyzer,
0
measurement calibrators (AM, FM, or power level), and
0
HP-IB programmability.
The entire operation of the instrument
sets up the instrument at turnon, interprets keyboard entries, executes changes in internal hardware,
and displays measurement results and error messages. The computing capability of the Controller
also used
the AM or FM generated by the AM and FM Calibrators, and converts measurement results into ratios
(in
RF
Circuitry
The RF input signal normally enters an external Sensor Module such
Figure
input connector of the Modulation Analyzer. For the RF Power measurement, the input
directly into the Power Sensor, which converts the RF power absorbed by the RF Power Sensor into
a low-frequency, chopped, ac voltage whose amplitude
Power Meter amplifies the chopped signal and converts
voltmeter. (The voltmeter includes the Audio Peak Detector, Audio Average Detector, Voltage-to-Time
Converter, and Counter.) The calibration of the Power Meter can be verified by connecting the Sensor
Module
Power Reference Oscillator
%
to
simplify circuit operation. For example,
or
dB).
The Controller
1-2.)
For all measurements except RF Power, the Sensor Module routes the signal
to
the CALIBRATION
also
is
an accurate 1 mW reference.)
The Power Sensor
sudden, large overloads. Refer to Table
Characteristics, RF Power Ranges of HP
HP
11
722A
Sensor Module,
is
governed by a microprocessor-based Controller. The Controller
it
forms the last stage of the Counter, calculates
contains routines useful for servicing the instrument.
as
an HP 11722A. (See
signal
is
proportional
it
to
a
dc voltage which
RF
POWER OUTPUT connector on the front panel. (The 50 MHz
is
unprotected against and
1-1
under RF Power, Supplemental
8901B
for
information on maximum operating lemls.
Modulation Analyzer with
to
the average RF power. The
is
easily damaged
is
then measured by the
by
to
the
passes
is
FW
When the RF Peak Detector senses that the input signal level exceeds lW,
Relay. This
by the voltmeter,
The Input Mixer converts the input signal
than 10 MHz, the
frequency; an IF of 455 kHz can be manually selected for this frequency range. The 455 kHz
selected automatically for input signals between 2.5 MHz and 10 MHz. Below 2.5 MHz, the input
passes directly through the Input Mixer without down-conversion.
The instrument can be manually tuned
filtering may be necessary since low-frequency signals pass directly into the
Filter can be inserted (via a Special Function)
To measure the input frequency, the Counter measures the frequency of the LO and the frequency
of the
difference between the
which equals the input frequency.
is
done without intervention of the Controller. The output from the
is
used
to
set the Input Attenuator
to
the intermediate frequency
IF
is
1.5
MHz with the Local Oscillator
For
the input signal to pass through the Input Mixer without down-
conversion, the
LO
frequency of
respond to input frequencies
between
IF
from the output of the IF Amplifier and Filter. The Controller computes and displays the
150
LO
must still be present to turn the mixer
101.5
MHz
is
arbitrarily used. Thus the instrument will
of
kHz
and
2.5
MHz.
to
a desired signal even in the presence of larger signals, although
two
frequencies. For input frequencies below 2.5 MHz, only the
to
optimize the level applied
(LO)
tuned
NOTE
100
or
103
MHz
as
well
in
the RF path for this purpose.
it
opens the Overpower
RF
Peak Detector, read
to
the Input Mixer.
(IF).
For frequencies greater
1.5
MHz above the input
diodes
as
on. An
frequencies
IF.
The
RF
IF
IF
is
High-Pass
is counted,
1-9
w
w
0
I
I
SWITCH
MODULATION
lNPU1
POWER
SENSOR
ANALYZER
OVERPOWER RF
POWER
PO!!!
POWER REFERENCE
OSCILLATOR
INPUT
tNPUl
HP
'I
I
2,
-1
kHI
e.~
OR
2.5
Ynz
LP
FILTER OEYOOULAlOR
CI-
CI
-
-
CI-
L1
IF
AM
AM
OR
I
IF
PEAK
OElECTOR
II
I
AUDIO
FILTERS
AND
6A1N CONTROL
I
CHANNEL
FILTERS OElECTOR
iopiiow
'DP!!?!!
SERIES
IF
030
O!.!".
ONLY)
RYS
\
OlSlORTlON
I I
COUNlER
AUOlO
OElEClOR
AUDIO
DETECTOR
AUOIO
AV6
PEAK
AUDIO
RYS
WIDE
,
455
Model
8901B
LO
Circuitry
The
LO
LO
drives the high-level port of the Input Mixer and
has
four main modes of operation:
a
tuning
keyboard (manual tune mode),
a
automatically searching for an input signal, then tuning the LO
down-convert the signal (automatic tune mode),
a
automatically searching for an input signal, then configuring the
automatically tracks the signal (automatic tune track mode), and
a
tuning
keyboard, then configuring the LO in a feedback loop
(manual tune track mode).
to
the frequency required to down-convert a signal whose frequency
to
the frequency required
to
down-convert a signal whose frequency
is
one of several inputs
that
automatically tracks the input signal
General Information
to
the Counter. The
is
entered from the
to
the frequency required
LO
in
a feedback loop that
is
entered from the
to
The manual tune track mode
of other signals. The non-track modes are used when the
IF
Circuitry
The gain of the
1.5
the
nominal center frequency
455
In instruments with Option Series
also include
Filters set the
by entering a series of Special Functions which establish
Filter, then allow the relative
offset.
MHz
kHz Bandpass Filter (with a bandwidth of
IF
Amplifier
IF
is
selected, the
a
precision, variable-gain amplifier) and detected by the
IF
bandwidth and gain for the Selective Power measurement. The measurement
is
is
fixed. The
of
1.5
IF
useful when
IF
Filters determine the frequency response of the
IF
filter consists of a 150
MHz). When the
030,
the
IF
level
to
be displayed
Audio Circuitry
The modulation on the
is
recovered
The demodulated signal
filters
processed signal
and the voltmeter.
by
integrating the demodulated FM in the Audio
are
selected from the front panel, and for FM, the filtering may also include de-emphasis. The
is
passed
IF
is demodulated by either the AM or the FM Demodulator. Phase modulation
is
amplified and filtered in the Audio
to
the front-panel MODULATION OUTPUT/AUDIO INPUT connector
it
is
desired to follow an unstable signal in the presence
LO
noise (residual FM) must be minimized.
kHz
to
2.5
MHz bandpass filter (with a
455
kHz
IF
is
200
signal
selected, the
kHz).
is
further processed by the Channel Filters (which
IF
RMS Detector. The Channel
an
IF
reference in the center of the Channel
as
the
IF
frequency
Filters
Filters
is
detuned
and Gain Control circuitry.
and Gain Control circuitry. The
IF
filter
by
a
pre-determined
is
IF.
When
the Wide
is
made
The audio signal from the Audio Filters and Gain Control
Peak Detector, the Audio Average Detector or the Audio RMS detector. The Audio Average and RMS
Detectors are used primarily for measuring noise. The output from the detectors is routed into the
Voltage-to-Time Converter.
The Voltage-to-Time Converter within the voltmeter converts the dc input into a time interyal. During
is
the interval, the 10 MHz Time Base Reference
represents the dc voltage. Other inputs
an audio level detector and the AM calibrator.
The Distortion Analyzer measures the distortion of either the internal demodulated signal or an audio
to
signal applied externally
of
the input signal must be either 1 kHz or
measuring the amplitude of the signal before and after a notch filter that
two
ac signals are converted
Distortion
(The Audio RMS Detector can also be used
or the ac level of an external audio signal applied to the MODULATION OUTPUT/AUDIO INPUT
connector.)
is
computed
the MODULATION OUTPUT/AUDIO INPUT connector. The frequency
to
dc by a the Audio RMS Detector and then measured by the voltmeter.
as
the ratio of the voltage out of the notch filter
to
the voltmeter, which are not shown, include outputs from
counted by the Counter, and the resultant count
400
Hz. The distortion on the signal
to
measure the demodulated AM, FM,
is
converted
to
a dc voltage by the Audio
is
determined by
is
set
to
1
kHz
or
400
to
the voltage into the filter.
or
OM internally
Hz.
The
1-11
General Information Model 8901B
The frequency of the audio signal at the MODULATION OUTPUT/AUDIO INPUT connector,
or
whether internal
the input signal
function is
during the count is read by the Controller which computes and displays the signal frequency.
The AM and FM Calibrators provide a nominal 10.1 MHz signal with a precisely known amount of
or
AM
or
via the Sensor Module), the modulation is measured and the calibration factor of the AM
Demodulator
demodulation of the calibrator signal.
also
FM. When this
external,
is
used
used by the Voltage-to-Time Converter.) The number of time base pulses received
is
computed and displayed. Related front-panel functions are automatically set for proper
is
measured by a reciprocal-type Audio Counter. In the Audio Counter,
to
gate the 10 MHz Time Base Reference into the main Counter. (This gating
signal
is
applied
to
the instrument’s RF INPUT connector (either directly
or
FM
P
(a)
BASEBAND SIGNAL
1.5
1
.o
0.5
0
Figure
1-1
1.
MODULATION
The Modulation Analyzer can demodulate and measure three types of modulation: amplitude
modulation (AM), frequency modulation (FM), and phase modulation (@M). In general, modulation is
that
characteristic of a signal which conveys the information. A signal without modulation
continuous-wave (CW)
frequency. These
conveyed
or
both of these parameters
The RF signal which
baseband signal and can be of any arbitrary form (for example, voice, tone, noise). Demodulation
the process of recovering the baseband signal from the modulated carrier. The Modulation Analyzer
can measure the modulation on carriers in the range of
is specified
present
by
at
the MODULATION OUTPUT connector.
Amplitude Modulation
1-3.
BASICS
two
them
for
modulation
(b)
AMPLITUDE MODULATED CARRIER
I
A Baseband Signal and the Corresponding Amplitude Modulated Carrier
is
said to be
signal.
parameters, however, are static (time invariant). Consequently, the information
is
scant-you know only that a signal
is
CW signals contain
is
altered as a function of time, the signal
modulated is called the carrier. The modulating signal
rates
generally between
two
information-carrying parameters: amplitude and
is
present at a certain frequency. When one
is
said
to
150
kHz to 1300 MHz. Measurement accuracy
20
Hz
and
100
kHz.
The demodulated signal
be modulated.
is
referred to
as
a
the
is
is
1-12
As
the name implies, a carrier is amplitude modulated when its amplitude
time. Figure 1-3 shows a carrier with amplitude modulation and, for reference, also shows the baseband
As
signal.
This trace
minimum called the trough. A quantity which describes the amount of AM
you can see, the tips of the carrier trace out a waveform that resembles the baseband signal.
is
called the envelope. The envelope rises to a maximum called the peak and drops
is
varied
or
the AM depth
as
a function of
is
to
the
a
Model
8901B
General Information
modulation index. If the peak amplitude is called P and the trough amplitude is called
index
rn
(usually expressed in
In the example
of
Figure 1-4 shows
Figure
AM
signals with modulation indexes varying from 0 to
1-3,
%)
is
P
=
m=
defined
m=-
1.5
and T =
1.5
-
1.5
+
as
P-T
+
0.5
x
0.5
(a)
x
100%.
0.5;
100%
0%
AM
therefore,
=
50%.
(CW)
100%.
T,
the modulation
(b)
(c)
(d)
30%
70%
100%
AM
AM
AM
Figure
1-4.
AM
for
Various
Depths
1-13
General Information Model 8901B
When the baseband
average carrier level,
and the expression for modulation index becomes
This
is
the expression which the Modulation Analyzer evaluates when making an AM measurement,
Referring back
The Modulation Analyzer makes an AM measurement
known, fixed level by means of
and the amplitude of the recovered baseband
the detector
is
signal
A,
and the envelope peak,
A+r-A+r
m=
A+r+A-r
to
Figure 1-3, it
r,
which
is
is
symmetrical, the modulation index can
T,
relative
x
=
-
2A
100%
signal
27
A
=
x
=
is
100%
1
50%
x
100%
is
apparent that
m
=
-
0.5
1
an
automatic level control (ALC) circuit. The signal
(in
effect) multiplied by the constant
also
be expressed
to
the carrier. Then
r
=
-
x
100%.
A
and
T
=
0.5
so,
by
forcing the average carrier level,
measured with a peak detector. The output of
1OO/A
P
=
as
before
and displayed
in
terms of the
A+r,
and
T
=
A,
is
then demodulated,
as
the
9%
AM.
A-
to
r,
a
I
r
(a)
BASEBAND SIGNAL
(b)
I
Figure
The range
100%.
An example of such is suppressed-carrier AM. The Modulation Analyzer
such signals. Nevertheless, there are cases, when the Modulation Analyzer will display a modulation
index that exceeds
peak
of
modulation indexes
There are, however, types of modulation that produce modulation indexes greater than 100%.
100%.
is
greater than the average carrier level. This is illustrated in Figure 1-6.
This can occur,
AMPLITUDE MODULATED CARRIER
1-5.
AM with an Asymmetrical Baseband Signal
for
AM measurements by the Modulation Analyzer
for
example, on an asymmetrical waveform where a narrow
is
essentially 0 to
is
not intended for measuring
1-14
Model 8901B General Information
Figure
I
1-6.
AM with Modulation Exceeding
100%
as
Measured
I
by
the PEAK+ Detector
Exponential Modulation
Exponential (or angular) modulation
is
or phase of the carrier
is
impossible
analyzing the received signal unless specific information about the baseband
It
is
certainly true
a frequency modulator.
when the varactor bias
is
generated by a phase modulator. A varactor diode across an
varactor
driven from a well-buffered carrier source. This modulator simultaneously produces
The signal from both modulators will show readings on the Modulation Analyzer when in both the
FM
and
deviation, which
measuring
the average carrier phase. Phase and frequency have the relationship
frequency or frequency
QM
by integrating the demodulated FM.
This relationship
signal shown
an
FM,
assumed
The frequency goes up on the positive peak of the baseband signal and down on the negative peak. The
phase modulated signal, however,
a discontinuity where the baseband signal switches amplitude. The waveform of the figure was contrived
so
that
will occur when the baseband signal switches amplitude, but the phase shift
does not need
is
the constant zero except for a positive spike (impulse) where the baseband signal switches positive
and
a
negative spike where the square wave switches negative.
Now look
the baseband signal slopes upward and a continually decreasing frequency
The phase modulator produces a signal that resembles the signal from the frequency modulator for the
square wave baseband signal. This
is
slope
upward. When the slope is negative, the phase shift
frequency shift. For the triangle wave baseband signal, the shift in frequency when the slope changes
is proportional
to
tell
bias
is
varied.
QM measurement modes. When
is
QM,
the peak phase deviation
is
is
a
square wave. The three waveforms under
QM, and
that the phase modulator doesn't produce AM-only
a
180"
at
positive, the phase shift
AM
phase shift occurred exactly at a zero crossing of the carrier. In general, a discontinuity
to
occur at a zero crossing of the carrier. Mathematically, the derivative of a square wave
the triangle wave. The frequency modulator produces a continually increasing frequency
to
the change in slope.
varied. Frequency and phase modulation are very closely related. In fact,
whether the signal was produced by a frequency modulator or phase modulator by
to
say that a signal
A
varactor diode across the tank circuit of an
is
varied. It
(It
is
assumed
the maximum frequency excursion from the average carrier frequency. When
is
the derivative of the phase. In fact, the Modulation Analyzer demodulates
most easily visualized by some examples. Look at Figure 1-7. The
modulator respectively. (The
is
the generic name given
is
frequency modulated when the modulation
is
also true
that
that
the carrier
a
signal
is
on the slope of the filter and
to
modulation in which the frequency
signal
is
given.
is
generated by
LC
oscillator
is
phase modulated when the modulation
RF
filter
will
will
produce
produce QM when the
that
the
AM.)
in
FM, the quantity being measured
is
measured, which
is
the maximum phase excursion from
that
phase
is
the peak frequency
is
the integral of the
first
it
are the result of applying this signal
AM
waveform
is
peculiar. The frequency
is
because the derivative of a constant slope
is
continually increasing, thus producing a uniform frequency shift
is
is
continually decreasing and produces a downward
is
included only for reference.)
QM.
The
FM
waveform
generally constant throughout except for
is
not necessarily 180" and
as
the signal slopes downward.
is
a
is
as
constant. When the
it
FM
filter
is
baseband
to
It
is
expected.
as
1-15
General Information Model
uu
BASEBAND SIGNAL
BASEBAND SIGNAL
8901B
SIGNAL FROM FREQUENCY M
SIGNAL FROM PHASE MODULATOR
SIGNAL FROM AMPLITUDE MODULATOR
(a)
SQUARE WAVE BASEBAND SIGNAL
Now
note
the sine wave
the same except for the
frequency is highest when the baseband signal
phase modulated signal, the frequency
a positive direction. This occurs
is
when the slope
most negative.
0 D U LATO
of
Figure 1-7(c). The signals from the frequency and phase modulators
90'
phase shift between the
R
is
highest when the slope of the baseband signal
at
the positive-going zero crossing. Similarly, the frequency
SIGNAL F
SIGNAL FROM AMPLITUDE MODULATOR
(b)
Figure
is
most positive and lowest when most negative.
two.
1-7.
For
RO
M F REQU ENCY MO DU LATO
SIGNAL FROM PHASE MOOULATOR
TRIANGLE WAVE BASEBAND SIGNAL
Signals from
the frequency modulated signal, the
Requency,
Phase,
is
steepest
R
For
is
lowest
and
look
the
in
1-16
If
in the last example, the rate, but not the amplitude,
and lowest frequencies
often. However, for the signal from the phase modulator, not only do the frequency peaks occur more
often, but the excursions are large because the slopes
crossings. See Figure 1-7(d).
The
maximum
400
rad
or
baseband waveform will result in different readings in
frequency deviation which can be measured
400
kHz divided by the modulation rate, whichever is smaller.
of
the signal from the frequency modulator stay the same-they just occur more
of
the baseband signal
of
the baseband signal are steeper
is
400
kHz. The maximum phase deviation is
PEAK+
than
PEAK-.
As
is
increased, the highest
with
AM,
at
the zero
an asymmetrical
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