Wiltron 5400A Book

Infroducfion

The Wiltron 5400A Series Scalar Measurement

characterizing microwave amplifiers. This

Systems

application note

offer many features for

describes how these

features can be applied to more thoroughly test amplifiers in less time.

BeIow is a list of amplifier characteristics that a= commonly measured with

a scalar analyzer:

Minimum gain over the specified frequency range
Gain variation over the specified frequency range
Gain at specified output power
Gain variation with bias change
Input match over the specified frequency range
Output power over the specified frequency range
at 1 dB gain compression

a

Basic Measurement Setup

Figure 1 shows a basic measurement setup, capable of measuring the above
characteristics.

Press the [SYSTEM front panel key, then the i soft key. Press
the

[DISPLAY ON/OFF\

key on channel 2 to turn it off. Select the frequency

range to be tested and the desired power from the built-in source.
The measurement of

~TFiANSMlSSlON (A)1

displays the difference between the input

power to the amplifier to the output power. This requires a calibration sequence

to characterize the input power to the amplifier. Pressing the -1 front
panel key begins this sequence with instructions from the display menu area.
Display 1 shows one of the instruction menus.

1: TRANSMSSN (Al
2: OFF

10.0 dB/DIV

OFFSET 0.0 dB

Dispk?y 7

, p::

STOP: 5.0000 GHr

LEYEL: 0.0 dBm

2

START: 0.5000 GHz

401 pts

500 MHz/OIV

%’

It’s important to include in the calibration as many of the connection components
to the amplifier under test as possible (such as cables to and from the test ampli­fier and any high power attenuators) in order for the calibration to compensate
for their loss and frequency response. Once calibration is complete, connect the
test amplifier and adjust the display scaling to view the desired characteristics.

e j

Cursor Functions

5

Save/Recall

To alIow quick movement through different test sequences, this setup
and calibration may be sto&d and recalled using the -1 menus.
See Display 2.

: TRANSMSSN CA.1

: OFF

I I

START: 0.5000 GHz

401 pts LEVEL: 0.0 dBm

5.0 dB/DIV OFFSET l 30.0 d6

‘: SAVE/RECALL

: USE:THEN
! PRESS SELECT

500 HHzIDlV

STOP: 5.0000 Giiz 1:+~6.16 dB

MENU

SAVE TRACE

MEMORlES

Display 2

The cursor menus allow quick measurement of the gain characteristics.
For example, the minimum gain over the frequency range is found by
pressing

~iitk’E CURSOR TO- MINIMUMS See

1 _ _ _ ._. _ .~ _ _.I

1:

TRANSMSSN (AI

2: OFF

5.0 dB,DI"

OFFSET +X0.0 dB

Display 3.

/

CHANNEL I

HOVE CLIRSOR

Display 3

3

L

START: 0.1000 GHr

401 pts

500 MHZ/DlV

STOP: 4.OOQn GHz

LEVEL: 0.0 dBm

USE :THEN

PRESS SELECT

Similarly, the maximum can be found by

1

MOVE CURSOR TO - MAXIMUM 1.

The
variation may be found by moving the main cursor to /m and the
relative cursor to )NIINIMuM). See Display 4.

1:

TRANSHSSN (A)

2: OFF

I 'A J

5.0 dB/DIV OFFSET a30.0 dB
r-z-j

CURSOR

2.0777 GHz

RELATIVE<A)

.I: -3.25 dBr

0.9240 GHz

EXCHANGE

REF-CURSOR

Display 4

gain

0

Gain With Bias Change

START: 0.7000 GHz STOP: 4.0000 Gliz

401 pts LEVEL: 0.0 d&r

500 MHzlOIV

The gain variation with bias voltage change can easily be seen by selecting
the

[MAX-MIN TRACE.

function under the m front pane1 key and by

changing the bias voltage. See DispIay 5.

:

TRANSMSSN (A1 5.0 dB/DIV

: OFF

"PA

f

:

i :

! !

: : ~ .

t

START: 0.7000 GHr STOP: 4.0000 GHz ,:+30.30 dB

401 pt5 LLVEL: 0.0 dBm

500 MWOIV

OFFSET +30.0 dE!

/-zq

CURSOR

1:+30.30 68

1.2859

1

RELATIVE(A)

1: -1.33 dBr

0.0905 GHz

MENU

1 CURSOR

Display 5

GHr

Another way to quickly measure the variation is to store the gain display

,

under the

CHANNEL 1 MENU

key and to view imEMORY].
The cursor minimum function quickly finds the maximum variation over
the frequency range. See Display 6.

: TRN(-ME") (A)
: OFF

i

START: 0.7000 GHz STOP: 4.0000 GHz

401 pt5 LEVEL: 0.0 dBm

5.0 dB/DIV

500 HHr/DlV

4

OFFSET

O.O dB

1 1: -1.85 dB

1

/ PRESS SELECT

j CURSOR MENU

CURSOR

3.7855 GHr

FOR

Display 6

Figure 2 shows the addition of a Wiltron 560 Series SWR Autotester to the basic
setup. This setup adds measurement of return loss or SWR at the input of the
amplifier. It is important to note that any cables needed be inserted between the
RF output and the 560 SWR Autotester - not between the Autotester and the
test amplifier. This greatly improves return loss measurement accuracy as cable
mismatches do not mask the test amplifier performance.

Figure 2
Setup for

using a

SWR

amplifier measurements

Wiltron 560 Series

A&tester

Press the
the m key for channel 2 and $KE?%%%]. Press the

1

DISPLAY ON/OFF1

key on channel 2 to turn it on. Select 1-1 under

i

CALIBRATIONS

front panel
key and follow the instructions to calibrate for both return loss and insertion
loss. The maximum return loss over the specified frequency range can easily
be measured bv messinn

SET CHANT

and

ki6vi CURSOR TO MAXIMUMS

under

the -1 from panel UkeT See Display 7.

1: TRANSMSSN (Al
2: RETN LOSS

I

START: 0.7000 GHz

401 pts LEYEL: 0.0 dBm

10.0 dB/DIQ

(81 10.0 dB/DIQ OFFSET 0.0 dB

500 MHZ/OIV

OFFSET +30.0 dB

STOP: 4.0000 GHz

[I

CURSOR

1: +33.96 dB

2: .9.66 d8

1.6405 GHz

PRESS SELECT

FOR

CURSOR MENU

I

Display

7

The 5400A Series can display match in SWR as well as return loss (dB). Select
the m soft key under the channel 2 IMENU/ key. Adjust the offset and scaling
to best display the SWR measurement. See Display 8.

1: TRANSMSSN
2: SWR (B)

(A) 10.0 dB/GIQ OFFSET +30.0 68

0.50 /OIV OFFSET 2.00 SUR

5

START: 0.1000 GHr

401 pts

SO0 MHZ/DlY

STOP: 4.0300 wz

LEVEL: 0.0 darn

37ESS SELECT

FOR

CaRSOR HEN"

Ratio Measurement

One problem with the previous two setups is that the calibration is maintained

only when the power from the source stays constant. This precludes varying the
power to the test amplifier to measure gain at a specific output power or gain

compression. This problem is readily solved by adding a power divider to the

setup and measuring the ratio of the power from and to the test amplifier.

See Figure 3.

Figure 3
Setup for amplifier
measuremenfs with
the addition of
a power divider

The ratio remains unchanged when the input power is varied. Incidentally,
measurement stability is also improved as it is now mainly based on the
detector tracking and the stability of the resistors in the power splitter.

To set the 5400Afor ratio measurement of insertion loss and return loss,
select m for channel 1 and u for channel 2. Calibrate as before. DispIay 9
shows the amplifier gain and return loss after the source power was varied
over a 30 dB range.

Trace Functions

: TRANSMSSN (A/RI 1.0 dB/DIV OFFSET +33.0 dB
: RETN LOSS (B/R) 10.0 dB,DIY

_

_

Display 9

I:

+33.50 d8

!:

-16.58 dB

2.4684 GHz

PRESS SELECT

FOR

CURSOR MEN"

START: 0.7000 GHz

401 pts

500 MHz/DIV

STOP: 4.0000 GHz

LEVEL:- dBm

The w function captures the change in gain due to the increasing
power. The vertical width of the gain band indicates the amount of gain com­pression at that frequency. Notice that the gain compression varies significantly
with frequency.

The 5400A Series also measures absolute power in dBm. On channel 2
press

rP*]

under the @ front panel key and

[SELECTINPUTA].

Gain

at a specified output power can be easily measured using the cursor.
Of course, any loss between the amplifier output and the measurement

detector must be added to the readings.

6

Trace

Memory

The 54OOA Series Trace Memory function can automatically add the loss
between the amplifier and the A detector to the power reading. The loss
can be measured in Transmission measurement mode and stored into
Trace Memory by pressing the
the

/TRACE

MEMORY STORAGE HENq

1

LOAD MEMORY WITH TRACE DATA/

under

and (MENU1 front panel key. The Trace
Memory may also be loaded with a Complex Limit line whose value
equals the Ioss of the attenuator.

Press

[COMPLEX LIMITS]

under the WI front panel key and

ENTER AHlG4

,._.__ __ _.__

limit
equal to the attenuator loss. This value may then be stored into Trace Memory.
When

@w DATA-MEMORY]

is chosen the display will indicate the power from the
amplifier in dBm, corrected for the attenuator loss. Display 10 shows this
measurement.

1:

TPANSHSSN (A/R) 1.0 dB/DIV

2: PWRi-MEM) (A)= 1.0 dB/DIV OFFSET t30.B dB

START: 0.7000

401 pts

500 MHZ/DIV

OFFSET +32.0 dB

STOP: 4.0000 GHr

LEYEL: +9.0 dBm

CURSOR

1:+X,.06 dB
2:+30.02 dBn

I.8044 GHz

PRESS SELECT

FOR

CURSOR MEN"

Display70

Display 11 shows the WAX] variation in gain and output power after an input
power change of 20 dB.

1: TRANSMSSN (A/R)
2: POWER (Al 1.0 dB/OIV

I.0 dB/DIV

t

START: 0.7000 GHz

401 pts

500 MHz/OIV

OFFSET +32.0 d6
OFFSET t10.0 dB

STOP: 4.0000 GHz

LEVEL- dBm

1:

+33.24 dB

PRESS SELECT

FOR

CURSOR MENU

Display 11

All of the above setups have a constant or Ieveled input power to the amplifier.
Since the output power from the amplifier is the input power plus the gain, any
gain variations cause output power variations. This can be seen in Displays 10
and 11.

n

_

Amplifiers are generally specified to provide a minimum output power over a
specified frequency range. A better way to measure characteristics such as gain at
a specified output power and output power at 1 dB gain compression is to vary
the input power, with frequency, to compensate for gain variations. This can
easily be done by leveling the output power with an external leveling loop.
The 5400A Series supports this measurement capability.

7

External Leveling

Figure 4 shows the setup for gain and output power with external leveling.

54ODASCALARMEASUREME

Figure 4
Setup for

amplifier
measurements using
exfernal bve/ing

Display 12 shows the gain variations with a constant output power of +22.6 dBm.
The minimum output power over the specified frequency range with just 1 dB
gain compression can be easily measured.

1: TRANWSSN (A/R) 5.0 dB/DIV OFFSET +35.0 dB
2: P&W-MEHI IA)

I

10.0 $_j/DlV

OFFSET +60.0

dB

CURSOR

1 1:+34.14dS

2:+22.5840m

2.3429GHZ

Disdav

12

PRESS SELECT

FOR

CURSOR MENU

START: 0.7000 GHz

401 pts

500 MWDIV

Store the gain display with a low input power into Trace Memory by
pressing
and

1 LOAD

TRACE MEMORY WITH TRACE DATA~

VIEW (DATA-YEM)

under the m front panel key

.

The display now shows changes in gain from the low

power condition over the specified frequency range. See Display 13.

1:

TRN(-"EM) (A/R)

2:

PWR(-"EM) (A)

t

START: 0.7000 GHZ

401 pts

5.0 dB/DIV

10.0 dBlOIV

500 MHZ/D,"

OFFSET

D.y~

OFFSET

60. dB

j CHANNEL 1
/ TRACE MEMORY

USE :THEN

ST&: 4.0000 iz'v,

LEVEL: EXT t-22.0) ' +" 71dEm

PRESS SELECT

.

DispIay 13

As the power is increased the gain drops due to gain compression. Once 1 dB
compression is observed, the output power for 1 dB compression can be read
from the Channel 2 cursor. A Pass/Fail indication may be used to indicate 1 dB
compression by setting a

,. -.. _~_^_

LOW LIMIT

of --I dB.

t

Systems Applications

Fast Sweep for Tuning

The 54OOASeries offers even more automation of the gain compression
measurement with a built-in

SYSTEM APPLICATIONS

function which automates

the above sequence. This function can be found under the -1
front panel key See DispIay 14.

1: TRN(-MEMI (A/RI 1.0 dB/DIV OFFSET 0.0 dB
2: PWRMEM) (Al

START: 0.7000 GHz

401 pt6 LEVEL: EXT (+4.41

lO.O~B/D'V OFFSET 60.0 dB

500 MHz/DIU

AMPLIFIER

FUNCTION

HAY POWER

9.0 dBn

' INCREASE

POWER "NTlL
LIMITS FAlL

Display 14

For applications where the test amplifier must be adjusted while monitoring the
5400A display, faster update speeds may be obtained by reducing the number of
horizontal data points taken. Selecting :-I under the -1 front
panel key allows selecting u, 1201, or m data points. Display 15 shows this
menu. Best cursor resolution is obtained with

401

points. Fastest update rate is

obtained with 101 points.

TRANSMSSN (A/RI
OFF

I

START: 0.7000 GHz

101 pt5

5.0 dB/DlV

500 MHZIDIU

OFFSET t35.O dt

STOP: 4.0000 GHI

LEVEL: +2.3 dBm

5417A

FREOUENCY

DATA POINTS

USE :THEN

'RESS SELECT

1

Display 15

Continuous

and Markers

cursor

As described earlier, the 5400A Series offers cursor and reIative cursor
functions to measure amplifier characteristics. The cursor frequency infor­mation is based on the number of points of displayed data. The 5400A Series
also offers markers, based on the source frequency information, however,
they aIso indicate the trace amplitude at each frequency. Markers can be
selected under the -1 front panel key. A display of both markers
and cursors is available by selecting
the

[ANALYZER CONFIGURE)

menu, under the 1-1 front panel key.

: CONTINUOUS CURSOR READOUT /

under

Display 16 shows both markers and continuous cursors readouts.

1: TRANSMSSN (AIR)
2: OFF

t

START: 0.7000 Gb

101

!a

5.0 dB/OiY

500 HHz/DIY

OFFSET +35.0 d@

I

!

!
1
I
I
I
I
!
i
I
I

:

STOP: 4.0000 GH.

LEYEL: +2.3 dBln

5417A j

MARKERS 1-4

Ill:_

1:+32.33 dB

HZ: 2.0000

1:+33.79 d0

H3: 3.0000
1:+33.60 dB

H4: 3.9998
1:+32.75 dB

MARKERS S-8

PRESS SELECT

FOR ON/OFF

Display 16

10

Automated Setup

Figure 5 shows an automatic setup for amplifier measurements.
The Wiltron 360CC MS-DOS@ computer automates all of the
measurements
discussed in this
application note.
Results, both from
the 54OOA And
the computer,
are viewed on
the color VGA

monitor.

Figure 5

MS-DOS’ is a registered trademark of Microsoft Corporation.

Printed in

USA

June 1991;Rev: A

Wiltron Company l 490 Jarvs Drive l Morgan Hill, CA 9.5037-2809

Tel.

[phone] l Telex 285227 WILTRON MH 0 FAX [phone]

11410-cm31

ANWOA-I