The Network Customer Support Plan identifies the steps to be followed in resolving the
Customer’s concern.
The resolution efforts will follow these levels of contact:
• Level One Contact – Factory Authorized Service Center.
• Level Two Contact – Comtech EF Data Customer Support.
• Level Three Contact – Network Test and Field Support
Procedural Steps
Step Procedure
1
2
3
4
5
The Customer raises a concern with the Level One Contact.
The Level One Contact will perform Hardware repairs and Network Operations
troubleshooting in accordance with the Comtech EF Data Service Center
agreement.
If the Level One Contact is unable to resolve the concern, then the Level One Contact will inform the Level Two Contact of the concern in accordance with the
instructions found within the attached Comtech EF Data Customer Support
Department’s document.
The Level Two Contact will enter the concern into the Comtech EF Data database
and determine whether the concern is a Hardware concern or a Network Operations concern
The Level Two Contact will interface with the Level One Contact and provide
the appropriate hardware support and enter all correspondence into the Comtech EF
Data database.
6
7
8
If the Level Two Contact determines that the concern is a Network Operations
concern, then the Level Two Contact will inform the Level Three Contact.
The Level Three Contact will interface with the Level One Contact and provide
the appropriate support and enter all correspondence into the Comtech EF Data
database.
If the Level Three Contact determines that there is a Hardware failure then the
Level Three Contact will inform the Level Two Contact. Go to Step 5.
2.3.6AC Power Connector ............................................................................................................................ 2–9
2.3.7DC Power - Optional............................................................................................................................. 2–9
4.2.2Theory of Operation.............................................................................................................................. 4–6
4.2.3Theory of Modulation Types................................................................................................................. 4–7
4.3.2Theory of Operation.............................................................................................................................. 4–11
Figure 2-1. Installation of the Mounting Bracket.....................................................................................................2–3
Figure 2-2. View of Rear Panel................................................................................................................................2–7
Figure 3-1. Front Panel View...................................................................................................................................3–1
Figure 3-3. Main Menu.............................................................................................................................................3–5
Table 1-2. Environmental and Physical....................................................................................................................1–8
Table 2-2. Remote Connector and Pinouts (J6)........................................................................................................2–5
Table 3-1. LED Indicators........................................................................................................................................3–2
Table 5-1. Conversion to S/N and Eb/N0 Chart.........................................................................................................5–4
Table 5-2. SNM-1002 Fault Tree .............................................................................................................................5–9
This manual provides installation and operation information for the Comtech EF Data
SNM-1002 LinkSync™ Modem. This is a technical document intended for earth station
engineers, technicians, and operators responsible for the operation and maintenance of
the SNM-1002 LinkSync™ Modem.
Conventions and References
Cautions and Warnings
CAUTION indicates a hazardous situation that, if not avoided, may result in
minor or moderate injury. CAUTION may also be used to indicate other
CAUTION
WARNING
unsafe practices or risks of property damage.
WARNING indicates a potentially hazardous situation that, if not avoided,
could result in death or serious injury.
IMPORTANT indicates a statement that is associated with the task
IMPORTANT
being performed. .
Metric Conversion
Metric conversion information is located on the inside back cover of this manual. This
information is provided to assist the operator in cross-referencing English to Metric
conversions.
Recommended Standard Designations
Recommended Standard (RS) Designations have been superseded by the new designation
of the Electronic Industries Association (EIA). References to the old designations are
shown only when depicting actual text displayed on the screen of the unit (RS-232, RS485, etc.). All other references in the manual will be shown with the EIA designations
(EIA-232, EIA-485, etc.) only. For more information, refer to the Department of Defense
(DOD) MIL-STD-188-114A, “Electrical Characteristics of Digital Interface Circuits.”
Products names mentioned in this manual may be trademarks or registered trademarks of
their respective companies and are hereby acknowledged.
Reporting Comments or Suggestions Concerning this Manual
Comments and suggestions regarding the content and design of this manual will be
appreciated. To submit comments, please contact the Comtech EF Data Technical
Publications department: techpub@comtechefdata.com
Electrical Safety
The SNM-1002 LinkSync Modem has been shown to comply with the following safety
standard:
• EN 60950: Safety of Information Technology Equipment, including electrical business
machines.
The equipment is rated for operation over the range 85 to 264 volts AC. It has a maximum
power consumption of 60 watts.
Fuses
The SNM-1002 LinkSync Modem is fitted with two fuses, one each for line and neutral
connections. These are contained within the body of the IEC power connector, behind a small
plastic flap.
• For 230 volt AC operation, use T0.75A, 20mm fuses.
• For 115 volt AC operation, use T1.25A fuses, 20mm fuses.
IMPORTANT
Environmental
The SNM-1002 must not be operated in an environment where the unit is exposed to extremes of
temperature outside the ambient range 0 to 50°C (32 to 122°F), precipitation, condensation, or
humid atmospheres above 95% RH, altitudes (un-pressurised) greater than 2000 metres,
excessive dust or vibration, flammable gases, corrosive or explosive atmospheres.
Operation in vehicles or other transportable installations that are equipped to provide a stable
environment is permitted. If such vehicles do not provide a stable environment, safety of the
equipment to EN60950 may not be guaranteed.
For continued operator safety, always replace the fuses with the
correct type and rating.
The installation and connection to the line supply must be made in compliance to local or national
wiring codes and regulations.
The SNM-1002 is designed for connection to a power system that has separate ground, line and
neutral conductors. The equipment is not designed for connection to power system that has no
direct connection to ground.
The SNM-1002 is shipped with a line inlet cable suitable for use in the country of operation. If it
is necessary to replace this cable, ensure the replacement has an equivalent specification.
Examples of acceptable ratings for the cable include HAR, BASEC and HOXXX-X. Examples of
acceptable connector ratings include VDE, NF-USE, UL, CSA, OVE, CEBEC, NEMKO,
DEMKO, BS1636A, BSI, SETI, IMQ, KEMA-KEUR and SEV.
International Symbols:
Symbol Definition Symbol Definition
~
Alternating Current
Fuse
Telecommunications Terminal Equipment Directive
In accordance with the Telecommunications Terminal Equipment Directive 91/263/EEC, this
equipment should not be directly connected to the Public Telecommunications Network.
In accordance with European Directive 89/336/EEC, the SNM-1001 Network Modem has been
shown, by independent testing, to comply with the following standards:
Emissions: EN 55022 Class B - Limits and methods of measurement of radio interference
characteristics of Information Technology Equipment.
(Also tested to FCC Part 15 Class B)
Immunity: EN 50082 Part 1 - Generic immunity standard, Part 1: Domestic, commercial and light
industrial environment. Additionally, the SNM-1001-has been shown to comply with the
following standards:
EN 61000-3-2 Harmonic Currents Emission
EN 61000-3-3 Voltage Fluctuations and Flicker
EN 61000-4-2 ESD Immunity
EN 61000-4-4 EFT Burst Immunity
EN 61000-4-5 Surge Immunity
EN 61000-4-6 RF Conducted Immunity
EN 61000-4-8 Power frequency Magnetic Field Immunity
EN 61000-4-9 Pulse Magnetic Field Immunity
EN 61000-4-11 Voltage Dips, Interruptions, and Variations Immunity
EN 61000-4-13 Immunity to Harmonics
In order that the Modem continues to comply with these standards,
observe the following instructions:
IMPORTANT
• Connections to the transmit and receive IF ports (BNC female connectors) should
be made using a good quality coaxial cable - for example RG58/U (50 Ω or
RG59/U (75 Ω).
• All 'D' type connectors attached to the rear panel must have back-shells that
provide continuous metallic shielding. Cable with a continuous outer shield
(either foil or braid, or both) must be used, and the shield must be bonded to the
back-shell.
• The equipment must be operated with its cover on at all times. If it becomes
necessary to remove the cover, the user should ensure that the cover is correctly
re-fitted before normal operation commences.
This Comtech EF Data product is warranted against defects in material and workmanship for a
period of two years from the date of shipment. During the warranty period, Comtech EF Data
will, at its option, repair or replace products that prove to be defective.
For equipment under warranty, the customer is responsible for freight to Comtech EF Data and all
related custom, taxes, tariffs, insurance, etc. Comtech EF Data is responsible for the freight
charges only for return of the equipment from the factory to the customer. Comtech EF Data will
return the equipment by the same method (i.e., Air, Express, Surface) as the equipment was sent
to Comtech EF Data.
Limitations of Warranty
The foregoing warranty shall not apply to defects resulting from improper installation or
maintenance, abuse, unauthorized modification, or operation outside of environmental
specifications for the product, or, for damages that occur due to improper repackaging of
equipment for return to Comtech EF Data.
No other warranty is expressed or implied. Comtech EF Data specifically disclaims the implied
warranties of merchantability and fitness for particular purpose.
Exclusive Remedies
The remedies provided herein are the buyer's sole and exclusive remedies. Comtech EF Data shall
not be liable for any direct, indirect, special, incidental, or consequential damages, whether based
on contract, tort, or any other legal theory.
Disclaimer
Comtech EF Data has reviewed this manual thoroughly in order that it will be an easy-to-use
guide to your equipment. All statements, technical information, and recommendations in this
manual and in any guides or related documents are believed reliable, but the accuracy and
completeness thereof are not guaranteed or warranted, and they are not intended to be, nor should
they be understood to be, representations or warranties concerning the products described.
Further, Comtech EF Data reserves the right to make changes in the specifications of the products
described in this manual at any time without notice and without obligation to notify any person of
such changes.
If you have any questions regarding your equipment or the information in this manual, please
contact the Comtech EF Data Network Customer Support Department.
This chapter provides an overview of the SNM-1002 LinkSync Modem, referred to in
this manual as “the modem” (Figure 1-1).
Figure 1-1.
SNM-1002
LinkSync
Modem
1.1 Overview
The SNM-1002 LinkSync™ modem is a high performance, digital modem designed to
provide LinkSync™ functionality for Comtech EF Data ' s Bandwidth-on-demand (BOD)
Multimedia Integrated Digital Access System (MIDAS).
• 2.4 kbit/s to 4.375 mbit/s continuous modulator.
• 50/180 MHz operation.
• Extensive online monitoring.
• Built in Self-test.
1–1
SNM-1002 LinkSync™ Modem Revision 2
V
A
V
A
A
ALA
A
A
A
Introduction MN/SNM1002.OM
1.2 Mode of Operation
The SNM-1002 is an integral component of the MIDAS Network Management System
(NMS), providing the LinkSync™ monitor and control communication between the NMS
and the MIDAS network.
LinkSync™ provides three key functions for the MIDAS network.
• Automatic Frequency Control (AFC) for all modems within the network.
• Power Management for all active traffic circuits within the network.
• Circuit Disruption capability which allows the NMS to terminate circuits
between any two internal traffic nodes (SNM-1010/1010L)in the network.
The SNM-1002 performs a critical roll for each of these three LinkSync™ capabilities
under the direct control of the MIDAS NMS. Refer to Chapter 4. Theory of Operation.
Built-in scramblers/descramblers TX and RX frequency synthesizers
Differential encoder/decoder Multi-rate FEC convolutional Viterbi Decoder
The modem is a complete, self-contained unit in a standard, one-rack unit (1 RU), 19inch (48 cm), rack-mountable enclosure weighing approximately 9 lbs. (4 kg). The unit
was constructed using modular design (Figure 1-4), and consists of from two to five
Printed Circuit Boards (PCBs), depending on the configuration. The modem consists of
two, major, replaceable assemblies as follows:
• Rear panel, main PCB, and power supply
• Upper and lower enclosures (chassis) and the front panel
The front panel of the modem contains all Monitor and Control (M&C) function
indicators used for operating the modem. The modem can be operated remotely via the
M&C connection on the rear panel. Refer to Chapter 2 for connector information and
Appendix A for remote control operation information.
Operating Frequency Range 50 to 180 MHz, in 1 Hz steps
Modulation Type QPSK
BPSK
Operating Channel Spacing Less than 0.5 dB degradation operating with 2 adjacent-like channels,
each 10 dB higher at 1.3 times the symbol rate.
Digital Interface EIA-422/449 on 37-pin D
Digital Data Rate QPSK, R=1/2, 2.4 kbps to 4.375 Mbps
Scrambling/Descrambling CCIT INTELSAT V.35
Forward Error Correction Viterbi, K=7, Rate 1/2, 3/4, 7/8
Filter Mask Types Closed net (Comtech EF Data)
Modulator
Output Power -5 to –30 dBm, adjustable in 0.1 dB steps
Output Spurious < -55 dBc, 0 to 500 MHz
Output Impedance
Output Return Loss 20 dB
Data Clock Source
Demodulator
Input Power:
Desired Carrier
Adjacent Carriers
Maximum Total
Input Impedance
Input Return Loss 20 dB
Carrier Acquisition Range
Clock Acquisition Range
AGC Output 0 to 10V at 10 mA maximum
75Ω (Optional: 50Ω)
-5
Internal , ± 1 x 10
-30 to –55 dBm
+30 dBc total power within 10 MHz from desired carrier
+40 dBc in-band (0 to 500 MHz)
-5 dBm
75Ω (Optional: 50Ω)
± 35 kHz maximum
± 100 PPM
Default Levels: 0V for –60 dBm
10V for –25 dBm
Levels can be programmed in 0.5V increments.
Baseband Loopback
Buffer Clock TX/RX/INT
Buffer Size
Code and decode Rate
Data Rate Select
Descrambler On/Off
Descrambler Type
Differential Encoding and Decoding
IF Loopback
Interface Loopback
MOD/DEMOD Spectrum Normal/Invert
Rev Emulation Current/Function
RF Loopback
RX Clock Normal/Invert
RX Frequency
Scrambler On/Off
Scrambler Type
Self Test
Transmitter On/Off
TX Frequency
TX Power
TX/RX Filter Mask
Signals Monitored Corrected BER
Fault Status
Power Supply Voltage
Raw Error Rate
RX Carrier Detect
RX Eb/No
RX Signal Level
Stored Fault Status
Configuration Retention Will maintain current configuration for at least 1 year without power.
Addressing Programmable from 1 to 255 possibilities
Address 0 is reserved for global addressing.
Diagnostic
Diagnostic Features BER Monitoring
Buffer Fill Status Monitoring
Fault Monitoring (include current and stored faults)
1.75" H x 19.0" W x 14" D (4.4 H x 48 W x 36 D cm)
Power Prime power 90 to 264 VAC, 47 to 63 Hz,
40W maximum, fused at 2A
Optional: 38 to 64 VDC
Operating Temperature
Storage Temperature
Humidity 0 to 95% non-condensing
Mounting Standard 19-inch (48.3 cm) rack mounts
Operational Shock When any one corner of the modem is dropped from 1 cm
Survivability Shock and Vibration MIL-STD-810D Method 514.4, Procedure 8, 1 hour/axis
Weight 9 lbs. Maximum
Shipping:
Weight
Size
0 to 50°C (32 to 122° F)
-55 to +70° C (-67 to 158° F)
Note: Front and rear accepts standard rack mount slides
onto a hard surface, the modem will not take any errors or
faults
MIL-STD-167-1
(4 kg Maximum)
15 lbs. (7 kg)
20 x 21 x 9 inch (51 x 53 x 23 cm)
1.5 Bit Error Rate Performance
The following specifications for the Eb/N0 required to achieve 10-3 to 10
different coding configurations. All values are for operating in QPSK mode. Without
coding, the modem provides QPSK operation within 0.8 dB of theoretical for BER in the
range 10
connected back-to-back through an additive white Gaussian noise channel. Refer to
Figure 1-6 for the performance BER curves.
-1
to 10-6. Performance measurements were recorded with transmit and receive IF
The modem arrives fully assembled from the factory. After unpacking the modem, install
the modem as follows:
1. If required, install the mounting bracket in equipment rack (Figure 2-1). Install
and tighten the bracket bolts.
2. Loosen the screw with flat washer located on the left side of modem chassis.
Mount the modem chassis into the equipment rack and slide the screw with flat
washer through the slot of the mounting bracket. Tighten the screw sufficiently to
allow the modem chassis to slide in the bracket.
3. Connect the cables to the proper locations on the rear panel. Refer to Section 2.3
for connector pinouts, placement, and function.
4. Connect the primary power cable to the power source. Before turning on the
power switch, become familiar with the front panel operation in Chapter 3.
5. If problems exist with the installation, refer to Chapter 5 for troubleshooting
information.
Note: Cables may be procured from Comtech EF Data by contacting Comtech EF Data
Network Customer Support department for information.
1. Connect supplied Y-Cable (Figure 2-2) as follows:
a. Connect the supplied-cable base connector to the FASTCOM card.
b. Connect supplied-cable Port 1 connector to the Comtech EF Data
supplied EIA-422 cable from SNM-1001 Modem.
c. Cable Port 2 connector is not connected.
2. Connect 9-pin EIA-232 cable from Controller Server COM 1 port to SNM-1001
Remote port (J6).
a. If non-redundant SNM-1001, the following remote settings are required:
• EIA-232
• 19.2 Baud rate
• 8N1
3. Connect 9-pin EIA-232 cable from Controller Server COM 2 port to SNM-1002
Remote port (J6).
4. Connect 25-pin pre-programmed dongle (security key) to Controller Server
25-pin I/O port.
A typical redundant wiring schematic is included to assist the user in establishing a
redundant configuration. The following table can assist the user in cable selection and
location. One or both of the 1:1 redundant configurations can be installed in a MIDAS
System. Figure 2-3 shows both Network Control Modem and LinkSync Modem
Redundancy.
The remote connector is a 9-pin female D connector (J6) located on the rear panel of the
modem. Screw locks are provided for mechanical security of the mating connector.
The remote connector interfaces the M&C functions to the MIDAS Controller. This is an
EIA-232 DCE interface. Refer to Appendix A for a description of the remote interface.
Refer to Table 0-2 for pinout information.
Table 0-2. Remote Connector and Pinouts (J6)
EIA-232
Pin # Name
1
2 RD (RX)
3 TD (TX)
4
5 GND
6 DSR
7 RTS
8 CTS
9
2.3.2 Data I/O Interface Connector (J8)
This connector is only utilized when the modem is operating in a Redundant LinkSync
Configuration. In a Redundant LinkSync Configuration, the Data I/O cable connects
between an SNM-301 1:1 Switch and J8 of the LinkSync modem. Refer to Chapter 1,
Figure 1-3.
2.3.3 RF Output Connector (CP1)
CP1 is a BNC connector for the transmit IF signal. The standard output impedance is 75Ω,
and the output power level is -5 to -30 dBm. In normal operation, the output will be a
QPSK- or BPSK-modulated signal between 50 and 180 MHz, in 1 Hz steps.
2.3.4 RF Input Connector (CP2)
CP2 is a BNC connector for the receive IF signal. The standard input impedance is 75. For
normal operation, the desired carrier signal level should be between -30 and -55 dBm.
Signals between 50 and 180 MHz are selected and demodulated to produce clock and data
at the Data I/O connector.
CP3 is a BNC connector for an external reference. The input impedance is 75Ω. For
normal operation, the reference signal is
≥ 0 dBm.
2.3.6 AC Power Connector
The AC power is supplied to the SNM-1002 by a standard, d etachab le, non-locking,
3-prong power cord. Refer to the following listing for AC power specifications.
Input power
Input voltage
Connector type
Fuse protection
50W max.
90 to 264 VAC, 47 to 63Hz.
Note: Unit switches ranges automatically.
IEC
1A slo-blo line and neutral fusing 5 mm type fuses.
2.3.7 DC Power - Optional
For DC supplied units, the DC Power is supplied by terminal lugs installed on the back
panel. Refer to the following table for specifications
Input power
Input voltage
Connector type
Fuse protection
50W max.
38 to 64 VDC.
Terminal Lug
1A slo-blo 5 mm type fuses.
2.3.8 Ground Connector (GND)
A #10-32 stud on the rear panel of the modem is used for connecting a common chassis
ground among all equipment.
Note: The AC power connector provides the safety ground.
Note: Front panel operation of the LinkSync modem is only required for initial
installation for setting the remote communication parameters. Under normal operation,
the MIDAS NMS configures and controls the LinkSync for all of the functions it
provides. A complete menu tree is shown for navigational purposes only.
The modem front panel (Figure 3-1) enables control of modem configurations parameters
and displays the modem status.
The indicators are defined in Table 3-1 as follows:
Table 3-1. LED Indicators
Name LED Meaning
Faults
Transmit Red A fault condition exists in the transmit chain.
Receive Red A fault condition exists in the receive chain.
Common Red A common equipment fault condition exists.
Stored Yellow A fault has been logged and stored.
The fault may or may not be active.
Status
Power On Green Power is applied to the modem.
Transmitter On Green Transmitter is currently on.
This indicator reflects the actual condition of the transmitter, as
opposed to the programmed condition.
Carrier Detect Green Decoder is locked.
Test Mode Yellow Flashes when the modem is in a test configuration.
Alarms
Transmit Yellow A transmit function is in an alarm condition.
Receive Yellow A receive function is in an alarm condition.
Use the Main menu in Figure 3-3 as a quick reference for accessing the modem functions.
When the modem power is applied, the base level of the menu system displays the
sign-on message:
• Line 1 of the sign-on message is the modem type.
• Line 2 is the node address.
The main level of the menu system is Function Select. To access this level from the
sign-on message, press the [←] or [→] keys. From the Function Select menu, select one
of the functional categories:
• Configuration
• Monitor
• Faults/Alarms
• Stored Faults/Alarms
• Utility
Press [←] or [→] to move from one selection to another. When line 2 displays the desired
function, select that level by pressing [ENTER]. After entering the appropriate functional
level, press [←] or [→] to move to the desired function.
To view the modem’s configuration, enter the Configuration level from the Function
Select menu. Once in the Configuration menu, press [←] or [→] to scroll through the
Configuration menu selection:
• Modulator
• Demodulator
• Interface
• Save
• Recall
Press [ENTER] to select the desired Configuration menu option. To view the options for
the selected configuration parameters, press [←] or [→].
Notes:
1. Menus or commands that are specific to certain modem configurations are only
accessible after selecting the appropriate modem configuration. This prevents
incompatible parameters from accidentally being selected.
3. All of the windows are accessible in the Custom mode. Take caution not to select
incompatible parameters, as the modem does not shut out incompatible command
choices in the Custom mode.
ASSIGNED FILTERS
MOD POWER OFFSET
MODULATOR TYPE
ENCODER TYPE
TX BPSK OREDERING
MOD SPECTRUM
TX SYMBOL RATE
ASSIGNED FILTERS
DEMODULATOR TYPE
DECODER TYPE
RX BPSK ORDERING
DEMOD SPECTRUM
RX SYMBOL RATE
TX OVERHEAD TYPE
RX OVERHEAD TYPE
TX TERR INTERFACE
RX TERR INTERFACE
BUFFER PROGRAM
FRAMING STRUCTURE
RTS TX-IF CNTRL
TX DATA PHASE
RX DATA PHASE
CTS DELAY
TIME/DATE
REMOTE BAUD RATE
REMOTE ADDRESS
REMOTE TYPE
OPERATION MODE
YEAR DISPLAY
TEST MODE STATUS
LAMP TEST
SELF TEST
DISPLAY CONTRAST
M&C FIRMWARE
BOOT FIRMWARE
FPGA FIRMWARE
DEMO MODE
EXT AGC: MAX PWR
EXT AGC: MIN PWR
MASTER RESET
MODEM TYPE
MODEM EMULATION
REV EMULATION
MODEM OPTIONS
LOCAL MODEM AUPC
MODEM SERIAL
CONFIGURATION CODE
Note: The following menus tree shows the modem functions available for an SNM-1002
LinkSync Modem. The defaulkt settings used when deployed in a MIDAS Network are
underlined.
3.4 OPENING SCREEN
SNM 1002
Ver:X.X.X
3.4.1 FUNCTION SELECT:CONFIGURATION
FUNCTION SELECT
CONFIGURATION
The main level of the menu system is Function Select. To access this level from the
sign-on message, press the [←] or [→] keys. From the Function Select menu, select one
of the functional categories:
• Configuration
• Monitor
• Faults/Alarms
• Stored Faults/Alarms
• Utility
Press [←] or [→] to move from one selection to another. When line 2 displays the desired
function, select that level by pressing [ENTER]. After entering the appropriate functional
level, press [←] or [→] to move to the desired function.
To view the modem’s configuration, enter the Configuration level from the Function
Select menu. Once in the Configuration menu, press [←] or [→] to scroll through the
Configuration menu selection:
• Modulator
• Demodulator
• Interface
• Save
• Recall
Press [ENTER] to select the desired Configuration menu option. To view the options for
the selected configuration parameters, press [←] or [→].
Displays the modulator TX IF frequency between 50 and 180 MHz, in 1 Hz steps.
Upon entry, the current transmitter frequency is displayed with the flashing cursor on the
first character. Press [← ] or [→] to move the flashing cursor, and [↑ ] or [↓ ] to increase
or decrease the digit at the flashing cursor. Press <ENTER> to execute the change.
3.4.1.1.3 MODULATOR:TX-IF OUTPUT
TX-IF OUTPUT
ON
Displays the modulator output status, either On
Upon entry, the current TX-IF output is displayed with the flashing cursor on the first
character. Press [↑ ] or [↓ ] to On or Off. Press <ENTER> to execute the change.
or Off.
3.4.1.1.4 MODULATOR:TX POWER LEVEL
TX POWER LEVEL
-10.0 dBm
Displays the modulator output level from:
• -5.0 to –30.0 dBm (Normal Range)
Upon entry, the current TX power level is displayed with the flashing cursor on the first
character. Press [← ] or [→] to move the flashing cursor, and [↑ ] or [↓ ] to increase or
decrease the digit at the flashing cursor. Press <ENTER> to execute the change.
Upon entry, the current scrambler is displayed with the flashing cursor on the first
character. Press [↑ ] or [↓ ] to change the carrier mode. Press <ENTER> to execute the
change
or Off.
3.4.1.1.6 MODULATOR:DIFF. ENCODER
DIFF. ENCODER
ON
Displays the differential encoder status, either On
Upon entry, the current differential decoder is displayed with the flashing cursor on the
first character. Press [↑ ] or [↓ ] to change the carrier mode. Press <ENTER> to execute
the change.
Displays the carrier mode of operation as follows:
Normal-Modulated
Center-CW
Offset-CW
Dual-CW
Upon entry, the current carrier mode is displayed with the flashing cursor on the first
character. Press [↑ ] or [↓ ] to change the carrier mode. Press <ENTER> to execute the
change.
The carrier mode in normally in this Modulated position.
Generates a carrier at the current modulator frequency. This can be used to
measure the output frequency.
Generates a single, upper, side-band-suppressed carrier signal. The upper sideband is at one-quarter of the symbol rate from the carrier. When inverted
spectrum is selected, this generates a single, lower, side-band-suppressed
carrier.
Generates a dual side-band suppressed carrier signal. Side-bands are at one-half
of the symbol rate from the carrier. This is used to check the channel balance and
carrier null.
3.4.1.1.8 MODULATOR:MODEM REFERENCE
MODEM REFERENCE
INTERNAL
Displays the following references to the modulator:
• INTERNAL
• EXT1, EXT5, EXT10, and EXT20 MHz
Note: If any EXT REF is selected for the modem reference and there is no input to CP3,
the modem will detect an alarm and switch to the INTERNAL clock.
Upon entry, the current modem reference is displayed with the flashing cursor on the first
character. Press [↑ ] or [↓ ] change the modem reference. Press <ENTER> to execute the
change.
Displays the IF loop back status, either On or Off
Upon entry, the current IF loop back is displayed. Press [↑ ] or [↓ ]. Press <ENTER> to
execute the change.
.
3.4.1.2.7 DEMODULATOR:BER THRESHOLD
BER THRESHOLD
NONE
Displays the BER threshold .
If the BER threshold set is exceeded, a receive fault will be indicated by the modem
status indicators. BER threshold may be set from 1.0 E-3 to 1.0 E-8, or may be disabled
by specifying NONE
Upon entry, the current BER threshold is displayed. Press [↑ ] or [↓ ]. Press <ENTER> to
execute the change.
.
3.4.1.2.8 DEMODULATOR:SWEEP CENTER
SWEEP CENTER
+ 0 HZ
Displays the sweep center frequency for the directed sweep function. When in directed
sweep, the value from the sweep monitor screen (when the modem was last locked)
should be entered for the sweep center frequency. The sweep center frequency can be set
in the range from –35000 to +35000 Hz. Default: 0 Hz
Upon entry, the current sweep center frequency is displayed with the flashing cursor on
the first character. Press [← ] or [→] to move the flashing cursor, and [↑ ] or [↓ ] to
increase or decrease the digit at the flashing cursor. Press <ENTER> to execute the
change.
Displays the overall travel of the sweep width range during acquisition in the directed
sweep mode. The sweep width may be set from 0 to 70000 Hz. Default: 60000 Hz
When set at 70000 Hz, the modem is in Normal acquisition mode. The smaller the range,
the faster the modem will lock, provided the receive carrier center frequency is within the
RX-IF frequency sweep range.
.
3.4.1.2.10 DEMODULATOR:REACQUISITION
REACQUISITION
0 SECONDS
Displays the sweep reacquisition mode time duration. This is the time that the modem
will remain in a narrow sweep after loss of acquisition. After this timer runs out, the
modem will return to the normal acquisition sweep. The reacquisition time is 0 to 999
seconds. Default: 0 seconds
Programs the clock source for the modem transmitter clock to the following
configurations:
TX TERRESTRIAL
SCT (INTERNAL)
RX (SATELLITE)
EXT CLOCK
Upon entry, the current TX clock source is displayed. Press [↑ ] or [↓ ] to make the
selection. Press <ENTER> to execute the change.
Sets the TX clock to recover timing from the incoming clock/data.
Sets the TX clock to operate from the modem internal clock (this also is the
fallback clock).
Note: When loop timing is enabled, SCT (LOOP) is displayed instead of SCT
(INTERNAL).
Sets the RX clock to recover timing from the output clock/data.
Sets the TX clock to operate from the EXT-CLK clock. Transmit clock source
must be phase/frequency locked to the data that is being transmitted. The
correct frequency must be programmed into EXT-CLK FREQ.
Programs the TX clock phase to AUTO, NORMAL, INVERT
Upon entry, the current TX clock phase is displayed. Press [↑ ] or [↓ ] to make the
selection. When AUTO is s elected, the modem will automatically select NORMAL or
INVERT to properly phase the TX clock with the TX data. Press <ENTER> to execute
the change.
.
3.4.1.3.3 INTERFACE:EXT-CLK FREQ
EXT-CLK FREQ
1544.000 KHZ
Programs the external reference clock input frequency between 8.0 kHz and 10.0 MHz.
Default: 1544 kHz
Note: The clock rate must be equal to the data rate unless the asymmetrical loop timing
option is present.
This clock frequency can be any multiple of 600 Hz from 2.4 to 64 kHz, and can be any
multiple of 8 kHz from 64 kHz to 4.376 MHz.
This can be used for the Doppler/plesiochronous buffer reference. It can be a reference to
SCT. Use the master clock input on J8 for the external master reference. The EXT REF
on CP3 only allows for 1, 5, 10, and 20 MHz external reference input.
Upon entry, the current setting for the external reference is displayed. Press [←] or [→]
to increment or decrement the digit at the flashing cursor. Press [ENTER] to execute the
change.
Programs the interface buffer output clock to one of the following modes:
RX (SATELLITE)
SCT (INTERNAL)
EXT. CLOCK
TX TERRESTRIAL
INSERT CLOCK
Upon entry, the current setting of the plesiochronous buffer clock is displayed. Press [↑] or
[↓] to make the selection. Press [ENTER] to execute the change.
Sets the output buffer clock to the satellite clock. (This is a Bypass.)
Sets the buffer clock to operate from the modem internal clock. This is
also the fallback clock.
Sets this clock source to the external clock.
Sets the buffer output clock to recover timing from the incoming TX data
clock.
Selects the recovered clock from the insert send data input received from
the terrestrial equipment.
3.4.1.3.5 INTERFACE:RX CLOCK PHASE
RX CLOCK PHASE
NORMAL
Programs the RX clock phase to Normal
Upon entry, the status of the RX Clock is displayed. Press [↑] or [↓] to make the selection.
Press [ENTER] to execute the change.
or Inverted.
3–17
SNM-1002 LinkSync Modem Revision 2
/
Operation MN/SNM1002.OM
3.4.1.3.6 INTERFACE:B-BAND LOOP BACK
B-BAND LOOP BACK
OFF
Programs the modem for baseband loopback operation, On or Off
When baseband loopback is turned on, the data and timing signals are switched from the
demodulator to the modulator on the modem side of the interface. The DTE baseband
signals are also looped back from the transmitter data and clock to receiver data and clock
on the customer side of the interface. This is a bi-directional loopback of the baseband data.
Refer to figure 3-4 for a block diagram of baseband loopback operation.
Upon entry, the status is displayed. Press [↑] or [↓] to make the selection. Press [ENTER] to
execute the change.
.
CUSTOMER
DATA
REMOTE SERIAL
INTERFACE
FAULT INDICATORS
IBSORIDR
INTERFACE
SATELLITE MODEM
ENCODER/
MODULATOR
MICRO-
COMPUTER
DEMODULATOR
DECODER
POWER SUPPLY
TRANSMIT RF
EQUIPMENT
AC POWER
RECEIVE RF
EQUIPMENT
Figure 3-4. Baseband Loopback
Note: When baseband loopback is turned on, data is looped back on the customer side of the
interface. This is a bi-directional loopback of the baseband data. This test mode will verify the
customer equipment and cabling between the modem and the customer equipment. The baseband
loopback is not bi-directional in D&I.
Sets the size of the buffer, 32 to 262144 bits, 1 to 99 mS , or 0 (Bypass)
Upon entry, the current buffer length is displayed. Press [↑] or [↓] to select the desired
buffer size. The buffer size is displayed in seconds or bits. Enter the Utility Interface menu
to change the buffer units to seconds or bits.
• If selecting seconds, choose from 1 to 99 ms, in increments of 1 ms,
or 0 (Bypass).
• If selecting bits, choose from 32 to 262144 bits, in increments of 16 bits.
• Press [ENTER] to execute the change.
Note: To have the modem calculate the plesiochronous shift, set the buffer units to ms.
When a specific buffer depth is desired, set the buffer units to bits. Select bits or ms from
the Utility Interface menu.
3.4.1.3.8 INTERFACE:BUFFER CENTER
BUFFER CENTER
YES/NO
This configuration function is used to center the buffer. Choosing YES centers the buffer.
The SCT output will become phase-locked to the RX satellite clock.
TX and RX data rates must be equal unless the asymmetrical loop timing option is On or
.
Off
Upon entry, the status is displayed. Press [↑] or [↓] to make the selection. Press [ENTER]
to execute the change.
3.4.1.4 CONFIGURATION:SAVE
CONFIGURATION
SAVE
The Configuration Save menu allows programming of configuration parameters into
memory on the M&C. There are five memory locations that may be used to store specific
configuration setups that are used frequently. After changing the configuration
parameters to the desired settings, enter the Configuration Save menu and select memory
location 1 through 5.
Press [ENTER] to execute the save.
3.4.1.5 CONFIGURATION:RECALL
CONFIGURATION
RECALL
The Configuration Recall menu allows the user to recall a previously saved configuration
setup. Upon entry, select memory location 1 through 5 by pressing [↑] or [↓].
The Faults/Alarms menu is accessible from the Function Select menu. The Faults/Alarms
are similar to monitor functions, as they display the current fault status of the group being
displayed.
Press [←] or [→] to move between the following Faults/Alarms groups:
• Modulator
• Demodulator
• Transmit Interface
• Receive Interface
• Common Equipment
Line 2 of the display shows the current Faults/Alarms status in real time. For each
parameter monitored, fault status is displayed as one of the following:
• “–” indicates that no fault or alarm exists.
• “+” indicates that a fault exists, and will cause switching in a redundant system.
• Reversed contrast “+” indicates an active alarm.
Unlike faults, alarms do not cause switching to occur. To display labels for individual
faults or alarms, press [ENTER].
Press [←] or [→] to move the flashing cursor to make the selection. The label for that
Fault/Alarm is then displayed on line 1 of the display. Press [CLEAR] to exit this level of
operation and return to the previous level.
The following sections outline the faults and alarms monitored and displayed in each
group.
Data or AIS. When data fault is selected in the Interface
Configuration menu, the fault indicates a data stable condition. This
indicates the data is all 1s or 0s (i.e., data is not transitioning). When
AIS is selected, the alarm indicates the data is all 1s from customer
data input to the modem. When None is selected in the Interface
Configuration menu, the TX Data/AIS Fault/Alarm is not activated.
Note: AIS is an alarm, not a switching fault.
Transmitter phase-locked loop fault. Indicates the transmitter
Phase-Locked Loop (PLL) is not locked.
Activity detector alarm of the selected interface transmit clock.
The interface will fall back to the internal clock when this alarm
is active.
Not Applicable.
Not Applicable.
TX interface configuration fault.
Indicates the TX interface cannot execute a programmed
configuration parameter.
Buffer underflow alarm. Indicates that a buffer underflow has
occurred.
Buffer overflow alarm. Indicates that a buffer overflow has
occurred.
Data or AIS. When data fault is selected in the Configuration
Interface menu, the fault indicates a data stable condition. This
indicates the data coming from the satellite is all 1s or 0s (i.e.,
data is not transitioning). When AIS is selected, the Alarm
indicates the data is all 1s from the satellite. When None is
selected in the Configuration Interface menu, the RX Data/AIS
Fault/Alarm is not activated.
Note: AIS is an alarm, not a switching fault.
Frame BER fault. Indicates that the frame BER exceeds 1-3.
Not Applicable.
Buffer clock phase-locked loop fault. Indicates the buffer clock
PLL is not locked.
Activity detector alarm of the selected interface receive clock.
The interface will fall back to the satellite clock when this fault is
active.
DEMUX lock fault. Indicates that the DEMUX is not locked.
RX 2047 lock alarm. Indicates the RX 2047 data pattern is not
locked.
Note: This alarm is only active if RX 2047 is ON.
Buffer full alarm. Indicates the buffer is less than 10% or greater
than 90% full.
Not Applicable.
Not Applicable.
Not Applicable.
Configuration alarm.
The modem stores the first 10 (Flt0 through Flt9) occurrences of fault status changes in
each of the following major fault categories:
• Modulator
• Demodulator
• Transmit Interface
• Receive Interface
• Common Equipment
Each fault status change is stored with the time and date of the occurrence of the fault.
Stored faults may be viewed by entering the stored faults level from the Select menu.
Stored faults are not maintained through controller power-on reset cycle. However, the
last known time is maintained in nonvolatile Random Access Memory (RAM). On
power-up, a common equipment fault is logged (Flt0) with that last known time and date.
In addition, on power-up, an additional common equipment fault is logged (Flt1) to
indicate the power-up time and date. The power-down and power-up times are logged as
common equipment fault 0 and common equipment fault 1, respectively.
On entering the stored faults level, press [←] or [→] to move between the fault groups
and the “Clear Stored Faults ?” selections. The time and date of the first stored fault
status (Flt0) for the selected group will be displayed alternately on line 2 of the display.
Press [↑] or [↓] to cycle through the selected group has stored fault status (Flt0 through
Flt9). To display the fault status associated with the displayed time and date, press
[ENTER]. To identify the fault, press [←] or [→] to move the flashing cursor. To clear
the currently logged stored faults, press [ENTER] when the “Clear Stored Faults/Yes?”
selection is displayed.
Note: Faults are stored in time sequence, with the oldest fault status change stored in
Flt0, and the most recent in Flt9. Only the first 10 fault status changes are stored. All
stored faults, which have not been used, indicate “No Fault” on the display.
The Function Select Utility menu is divided into the following categories:
• Modulator
• Demodulator
• Interface
• Network
• System
• Modem Type
• Factory Setup
The menu information includes:
• Filter Types
• Terrestrial Interface Types
• Mod/Demod Types
• Time/Date
• Encoder/Decoder Types
• Modem Types
• Current Firmware
• Test Mode Status
• Overhead Type
• Revision Emulation
• Lamp Test
Provisions are also made for assigning data and code rates to the modulator and
demodulator.
After entering the Utility menu, press [←] or [→] to select the desired sub-menu, and
press [ENTER].
Notes:
1. The Utility Factory Setup menu is for Comtech EF Data service personnel only.
Entering this menu without authorization may cause the modem to operate
incorrectly.
2. Changes in the Utility menu may cause changes in other front panel menus.
Upon entry, the current transmitter rate is displayed.
3.4.5.1.2 MODULATOR:MOD POWER OFFSET
MODEM POWER OFFSET
+ 0.0 DB
Modulator power offset adjust. Offsets the modulator output power readout in the
Configuration menu. This feature does not actually change the modulator power level, but
displays an offset value in the monitor.
The modulator power offset range is -99.9 to +99.9 dB, in 0.1 dB steps.
Note: Anything except 0.0 dB will cause ADJ to be displayed for the TX power level.
Displays the TX interface type RS-232, RS-422, or V.35.
3.4.5.3.4 INTERFACE:RX TERR INTERF ACE
RX TERR INTERFACE
RS422
Displays the RX interface type RS-232, RS-422, or V.35.
3.4.5.3.5 INTERFACE:BUFFER PROGRAM
BUFFER PROGRAM
BITS
Buffer unit program function. Select MILLI-SECONDS or BITS
Note: To have the modem calculate the plesiochronous shift, set the buffer units to MILLISECONDS. For a specific buffer depth, set the buffer units to BITS.
Displays the currently selected framing type and structure of the data. This function is used
with the buffer program in ms for plesiochronous buffer slips.
Upon entry, the framing type (T1 or E1) is displayed on Line 1. The framing structure of
each type (None or G.704) is displayed on Line 2. Press [←] or [→] and [↑] or [↓] to select
framing structure and type. Press [ENTER] to execute the change.
3.4.5.3.7 INTERFACE:RTS TX-IF CNTRL
RTS TX-IF CNTRL
OFF
Programs the modem to allow a Request To Send (RTS) signal to On or Off
when data is ready for transmission.
Press[←], [→], [↑], or [↓] to move the flashing cursor. Press [ENTER] to execute the
change.
Select OFF, AUTO, or RUN. After completion of the test, SELF TEST (“PASSED” or
“FAILED”) is displayed.
• OFF bypasses built-in self test
• AUTO initiates built-in self test when turning on modem
• RUN initializes self test
3.4.5.4.10 SYSTEM:DISPLAY CONTRAST
DISPLAY CONTRAST
LEVEL: 64
Sets the contrast setting of the Front Panel menu.
Press [ENTER] to begin. Press [↑] or [↓] to increment or decrement the number at the
flashing cursor, from 0 to 100. Press [ENTER] to execute the change.
3.4.5.4.11 SYSTEM:M&C FIRMWARE
M&C FIRWARE
FW/NNNNNN-DDR
Displays the M&C module firmware version. The display includes the month, day, and
year.
3.4.5.4.12 SYSTEM:BOOT FIRMWARE
BOOT FIRWARE
FW/NNNNNN-DDR
Displays the boot module firmware version. The display includes the month, day, and y ear
Turn all FAST features ON that are installed in the modem for 60 minutes.
During this time period, the operator is encouraged to implement the features
and discover the capablilites of the different options. After the 60-minute
time limit, the modem resets to its previous configuration.
3.4.5.4.15 SYSTEM:EXT AGC: MAX PWR
EXT AGC: MAX PWR
0.0 VOLTS
Sets the AGC voltage for a receive signal level of -60.0 dBm. The voltage range is 0.0
10.0V, in 0.5V steps.
Upon entry, the current external AGC voltage level is displayed. Press [↑] or [↓] to
increment or decrement the AGC voltage level in 0.5V steps. Press [ENTER] to execute the
change.
Note: For any receive signal level between -25.0 and -60.0 dBm, the software will
interpolate the required AGC voltage.
Sets the AGC voltage for a receive signal level of -25.0 dBm. The voltage range is 0.0 to
, in 0.5V steps.
10.0V
Upon entry, the current external AGC voltage level is displayed. Press [↑] or [↓] to
increment or decrement the AGC voltage level in 0.5V steps. Press [ENTER] to execute the
change.
Note: For any receive signal level between -25.0 and -60.0 dBm, the software will
interpolate the required AGC voltage.
3.4.5.4.17 SYSTEM:MASTER RESET
MASTER RESET
HARD/SOFT
Initiating a hard reset will reset the modem and place the
default configuration settings in ROM. Initiating a soft reset
CAUTION
Select [ENTER] once to access HARD or SOFT.
Press [←] or [→] to make the selection. Press [ENTER].
Press [→] five times to move the cursor to YES. Select YES and press [ENTER] again.
Note: The following parameters do not revert to default settings after a hard reset:
will reset the modem hardware, but saves the current
configuration settings
When the modem is changed from one type of operation to another, the modem will be
reset to the default configurations of the new modem type. The RF-IF Output must be
turned on to get the modem to lock.
• If the existing modem type is the same as the type entered, the modem will not
change any parameters.
• If the modem type is changed to Custom, no parameters will be changed.
• If the modem will not allow the modem type selection, that type of operation
may not be an available option.
• Select MODEM OPTIONS and OVERHEAD OPTIONS to see which modem
operations are allowed.
1. Programming a current version (default) allows all features and options (if
installed) to operate normally.
2. Programming a FUNCTIONAL version (X) eliminates any changes that affect
the later version. Only functional changes are affected by the revision emulation
feature.
3. A correction change (e.g., VER 3.1.2) remains fixed in accordance with the latest
version. Since the revision emulation default is the current version, program the
functional version at the start of each operation.
4. The revision emulation feature does not affect some interface changes for the
direct operation of the modem (Configuration save/recall, test mode screen in the
Utility/System, all factory setup modes, etc.).
3.4.5.5.4 MODEM TYPE:MODEM OPTIONS
MODEM OPTIONS
--------------
Displays the installed modem options.
If the option is installed, a “+” symbol is displayed. To view the available options press
[ENTER]. Observe for the flashing cursor. Press the [←] [→] arrows to move from one
symbol to the next. The first line will display the option. The second line will display the
status:
HIGH POWER ( 0 ) 0 = Not Installed, Not Upgradeable
HIGH STABILITY ( 0 ) - = Not Installed
ASLT ( - ) + = Installed
VITERBI ( + ) X = Not Installed, Field Upgradeable
SEQUENTIAL ( - )
SINGLE RATE ( - )
LOW RATE VAR ( - )
FULL RATE VAR ( + )
CARD #1 PCB ( x )
CARD #2 PCB ( x )
CARD #3 PCB ( x )
8PSK 2/3 ( - )
TX ONLY ( - )
RX ONLY ( - )
• Uplink Power Control (UPC) at the MIDAS Controller
• Circuit Power Management (Option)
! Site level call blocking based on HPA power
4.1.1 Automatic Frequency Control
OPERATION
MIDAS provides automatic frequency control (AFC) to reduce the traffic modem
acquisition time for continuous mode operation and to improve the burst acquisition
performance of the SNM-1000/1001 Network Control Modem and the Node Control
Modems
The outbound control channel is used as the system-wide reference, which is
continuously monitored by the LinkSync™ Modem at the MIDAS Controller site and all
the Node Control Modems
in any part of the system.
1
Includes SNM-1000 and the integrated traffic/control modem s (SNM -1010 and SNM-1010L).
2
The integrated traffic/control modems and the network te rm inals i n a standard configurat ion
monitor the outbound control channel in the “control m ode”.
4–1
1
, by keeping the frequency drift to within ± 500 Hz.
2
. The AFC process does not depend on the absolute accuracy
SNM-1002 LinkSync Modem Revision 2
Theory of Operation MN/SNM1002.OM
The AFC process consists of three steps:
1. Removing the receive offset of the Network Control Modem at the MIDAS
Controller.
2. Removing the receive offset of the Node Control Modems and the traffic
modems at the traffic sites.
2. Removing the transmit offset of the Node Control Modems and the traffic
modems at the traffic sites.
These three steps are performed as follows:
1. The LinkSync™ Modem measures the receive frequency of the outbound
control channel and provides this information to the MIDAS Controller
periodically, the period being user-configurable. The MIDAS Controller then
calculates the offset from the nominal, which is used to correct the Network
Control Modem’s TX frequency.
2. The Node Control Modem determines the receive offset by measuring the
receive frequency of the outbound control channel.
a. This offset is used to calibrate the RX frequency of the Node Control
Modem and all the traffic modems (during call setup) at the node.
b. The traffic modems that have active calls are not adjusted. Calibrations
are periodically performed where the period is user –configurable.
3. MIDAS Controller periodically polls a Node Control Modem to transmit
exclusively, and measures the receive frequency for the incoming bursts from
the Node Control Modem on the inbound control channel.
a. It then estimates the offset and provides this information to the Node
Control Modem.
b. The Node Control Modem then applies this offset to correct its TX
frequency and that of all the traffic modems (during call setup).
c. The traffic modems that have active calls are not adjusted. This process
is repeated periodically, the period being user-configurable.
4–2
SNM-1002 LinkSync Modem Revision 2
Theory of Operation MN/SNM1002.OM
4.1.2 Uplink Power Control
Uplink Power Control at the MIDAS Controller site compensates for outbound control
channel uplink degradation so that it always downlinks at a constant power at the
satellite.
A reference E
is calculated for the received outbound control channel at the MIDAS
b/No
Controller site for clear sky conditions. The LinkSync™ Modem, at the MIDAS
Controller site, measures the received outbound control channel E
on a continuous
b/No
basis.
• If the measured E
differs from the calculated reference, the MIDAS
b/No
Controller calculates the offset to be applied to the transmit power level of the
outbound control channel to achieve the desired reference E
b/No
.
• The transmit power is adjusted only when the difference exceeds a threshold,
which is configurable.
4.1.3 Circuit Power Management (Option)
Circuit power management is provided as an option. It includes:
• Circuits at setup.
• Site level call blocking based on available High power Amplifiers (HPA) power.
4.1.3.1 Site Level Call Blocking
The MIDAS Controller supports dynamic site level call blocking based on the available
HPA power. The MIDAS Controller keeps track of the HPA power for each site. A call
originating from a site is blocked if it would cause the total transmit power for that site to
exceed the recommended HPA power (less backoff). This leads to improved system
stability.
4.2 Monitor and Control (M&C)
The M&C monitors the modem and provides configuration updates to other modems
within the modem when necessary.
The modem configuration parameters are maintained in battery-backed RAM, which
provides total recovery after power-down situation. The M&C functions include
extensive fault and status reporting. All modem functions are accessible through a remote
communications interface. A block diagram of the M&C is shown in Figure 4-1.
4–3
SNM-1002 LinkSync Modem Revision 2
Theory of Operation MN/SNM1002.OM
4.2.1 Theory of Operation
The M&C card is composed of the following subsections:
• Microcontroller with Universal Asynchronous Receiver/Transmitter (UART)
• Digital-to-Analog Converter (DAC)
• Read Only Memory (ROM)
• Analog-to-Digital Converter (ADC)
• Read Access Memory (RAM)
• Universal ASYNC
• User Interface
• Fault and Alarm Relays
FAULT
MODEM
AND ALARM
RELAYS
11 MHz
CLOCK
DAC
ADC
MICRO-
2
IC BUS
CONTROLLER
EIA-232
OR
EIA-485
Figure 4-1. M&C Block Diagram
ROM
(M&C,
BULK,
BOOT)
RAM AND
REAL
TIME
CLOCK
9-PIN
REMOTE
4–4
SNM-1002 LinkSync Modem Revision 2
Theory of Operation MN/SNM1002.OM
The heart of the M&C card is the Dallas 80C310 microcontroller operating at 11 MHz.
This microcontroller contains 256 kbytes of internal RAM. The ROM at U8 is 29F040
(512 kbytes).
ROM access times must be equal to or greater than 150 ns. The RAM can be 8 or
32 kbytes in size. This RAM chip is internally battery-backed and contains a real time
clock used by the M&C.
The non-volatile RAM on the M&C module allows the module to retain configuration
information without prime power for 1 year (approximately). If the modem is powered
down, the following sequence is carried out by the M&C microcontroller.
1. When power is applied to the M&C, the microcontroller checks the non-volatile
memory to see if valid data has been retained. If valid data has been retained, the
modem is reconfigured to the parameters maintained by the RAM.
2. If the non-volatile memory fails the valid data test, a default configuration from
ROM is loaded into the system.
The UART supports serial ASYNC communications channels (remote port) with a data
rate of 19200 bit/s. The UART is a built-in peripheral of the microcontroller. The
communications type is EIA-232.
The DAC supplies a voltage that controls the contrast of the display. The ADC monitors
all the voltages from the power supply. The DAC and ADC are mapped to the
microcontroller with an Integrated Circuit (IC) bus.
All functions are memory-mapped to the micro-controller.
4.3 Modulator
The modulator provides PSK modulated carriers within the 50 to 180 MHz range. The
types of modulation that encode the transmitted baseband data from the interface PCB
are:
• BPSK
• QPSK
Refer to Section 4.2.3 for a description of each modulation type.
A block diagram of the modulator is shown in Figure 4-2.
4–5
SNM-1002 LinkSync Modem Revision 2
Theory of Operation MN/SNM1002.OM
MONITOR
SCT
REFERENCE
SCT
PLL
OPTIONAL
CONVOLUTIONAL
ENCODER
&
CONTROL
LO
BPF
BPF
DIGITAL
SIGNAL
PROCESSING
POWER LEVEL
CONTROL
Figure 4-2. Modulator Block Diagram
LPF
RF LOOPBACK
OUTPUT
RF
OUTPUT
4–6
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