Comtech EF Data DD2401 User Manual

DD2401 VME

L-Band Demod Card

Installation and Operation Manual

MN-VME2401

Revision B

Comtech EF Data • 2114 W 7th St. • Tempe, AZ 85281 • [phone] • Fax: [phone] • www.comtechefdata.com

DD2401 VME L-Band Demodulator Card Installation & Operational Manual Warranty Policy

WP

Warranty Policy

Comtech EF Data products are 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 owner is responsible for freight to Comtech EF Data and all related
customs, taxes, tariffs, insurance, etc. Comtech EF Data is responsible for the freight charges only for return
of the equipment from the factory to the owner. 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.

All equipment returned for warranty repair must have a valid RMA number issued prior to return and be
marked clearly on the return packaging. Comtech EF Data strongly recommends all equipment be returned
in its original packaging.

Comtech EF Data Corporation’s obligations under this warranty are limited to repair or replacement of failed
parts, and the return shipment to the buyer of the repaired or replaced parts.

Limitations of Warranty

The warranty does not apply to any part of a product that has been installed, altered, repaired, or misused in
any way that, in the opinion of Comtech EF Data Corporation, would affect the reliability or detracts from the
performance of any part of the product, or is damaged as the result of use in a way or with equipment that
had not been previously approved by Comtech EF Data Corporation.

The warranty does not apply to any product or parts thereof where the serial number or the serial number of
any of its parts has been altered, defaced, or removed.

The warranty does not cover damage or loss incurred in transportation of the product.
The warranty does not cover replacement or repair necessitated by loss or damage from any cause beyond

the control of Comtech EF Data Corporation.
The warranty does not cover any labor involved in the removal and or reinstallation of warranted equipment

or parts on site, or any labor required to diagnose the necessity for repair or replacement.
The warranty excludes any responsibility by Comtech EF Data Corporation for incidental or consequential

damages arising from the use of the equipment or products, or for any inability to use them either separate
from or in combination with any other equipment or products.

A fixed charge established for each product will be imposed for all equipment returned for warranty repair
where Comtech EF Data Corporation cannot identify the cause of the reported failure.

Exclusive Remedies

Comtech EF Data Corporation’s warranty, as stated is in lieu of all other warranties, expressed, implied, or
statutory, including those of merchantability and fitness for a particular purpose. The buyer shall pass on to
any purchaser, lessee, or other user of Comtech EF Data Corporation’s products, the aforementioned
warranty, and shall indemnify and hold harmless Comtech EF Data Corporation from any claims or liability of
such purchaser, lessee, or user based upon allegations that the buyer, its agents, or employees have made
additional warranties or representations as to product preference or use.

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.

MN-VME2401 – Rev. B iii

Warranty Policy DD2401 VME L-Band Demodulator Card Installation & Operational Manual

Warranty Repair Return Procedure

Before a warranty repair can be accomplished, a Repair Authorization must be received. It is at this time
that Comtech EF Data will authorize the product or part to be returned to the Comtech EF Data facility or if
field repair will be accomplished. The Repair Authorization may be requested in writing or by calling:

Comtech EF Data Corporation

2114 W 7

th

Street.
Tempe, Arizona 85281 (USA)
ATTN: Customer Support
Phone: [phone]
Fax: [phone]

Any product returned to Comtech EF Data for examination must be sent prepaid via the means of
transportation indicated as acceptable to Comtech EF Data. Return Authorization Number must be clearly
marked on the shipping label. Returned products or parts should be carefully packaged in the original
container, if possible, and unless otherwise indicated, shipped to the above address.

Non-Warranty Repair

When a product is returned for any reason, Customer and its shipping agency shall be responsible for all
damage resulting from improper packing and handling, and for loss in transit, not withstanding any defect or
nonconformity in the product. By returning a product, the owner grants Comtech EF Data permission to
open and disassemble the product as required for evaluation. In all cases, Comtech EF Data has sole
responsibility for determining the cause and nature of failure, and Comtech EF Data’s determination with
regard thereto shall be final.

iv MN-VME2401 – Rev. B

DD2401 VME L-Band Demodulaotr Card Installation & Operational Manual Preface

P

Preface

This manual provides installation and operation information for the Radyne DD2401 VME L-Band
Demodulator Card. This is a technical document intended for use by engineers, technicians, and
operators responsible for the operation and maintenance of the DD2401 VME Demodulator Card.

Cautions and Warnings

A caution icon indicates a hazardous situation that if not avoided, may result in minor or moderate
injury. Caution may also be used to indicate other unsafe practices or risks of property damage.

A warning icon indicates a potentially hazardous situation that if not avoided, could result in death
or serious injury.

A note icon identifies information for the proper operation of your equipment, including helpful
hints, shortcuts, or important reminders.

Trademarks

Product names mentioned in this manual may be trademarks or registered trademarks of their
respective companies and are hereb y acknowledged.

MN-VME2401 – Rev. B v

Preface DD2401 VME L-Band Demodulaotr Card Installation & Operational Manual

Revision

Level

Copyright

2009, Comtech EF Data This manual is proprietary to Comtech EF Data and is intended for the
exclusive use of Comtech EF Data’s customers. No part of this document may in whole or in
part, be copied, reproduced, distributed, translated or reduced to any electronic or magnetic
storage medium without the express written consent of a duly authorized officer of Comtech EF
Data

Disclaimer

This manual has been thoroughly reviewed for accuracy. All statements, technical information,
and recommendations contained herein 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 t o be, represe nt at ions or war ranti es
concerning the products described. Comtech EF Data assumes no responsibility for use of any
circuitry other than the circuitry employed in Comtech EF Data systems and equipment.
Furthermore, since Comtech EF Data is constantly improving its products, reserves the right to
make changes in the specifications of products, or in this manual at any time without notice and
without obligation to notify any person of such changes .

Record of Revisions

Date Reason for Change

1.0 04-01-98 New Release.
A 12-16-08 Updated Terrestrial Interfaces.
B 2-23-09 Clarified use of 8PSK. Technical specifications made to match other product

lines

Comments or Suggestions Concerning this Manual

Comments or suggestions regarding the content and design of this manual are appreciated.
To submit comments, please contact the Comtech EF Data Corporation Customer Service
Department.

vi MN-VME2401 – Rev. B

DD2401 VME L-Band Demodulaor Card Installation & Operational Manual Table of Contents

ToC

Table of Contents

Section 1 - Introduction ............................................................................................. 1-1

1.0 Description ______________________________________________________ 1-1

1.1 DD2401 VME Demodulator Card Available Options _______________________ 1-2

1.1.1 Reed-Solomon Codec (Optional) ____________________________________ 1-2

1.1.2 Turbo Codec (Optional)_ __________________________________________ 1-2

1.1.3 8PSK (Optional) ________________________________________________ 1-2

Section 2 - Installation ............................................................................................... 2-1

2.0 Installation Requirements ___________________________________________ 2-1

2.1 Unpacking _______________________________________________________ 2-1

2.2 Removal and Assembly ____________________________________________ 2-1

2.3 Mounting Considerations ___________________________________________ 2-1

2.4 Demodulator Checkout _____________________________________________ 2-1

2.4.1 Initial Power-Up _________________________________________________ 2-1

2.4.2 Factory Terminal Setup (Refer to Section 4.4) __________________________ 2-2

2.4.3 Remote Protocol Factory Default Setup _______________________________ 2-2

2.5 Storage ________________________________________________________ 2-2

Section 3 - Theory of Operation ................................................................................ 3-1

3.0 Theory of Operation _______________________________________________ 3-1

3.1 Applications ______________________________________________________ 3-2

3.1.1 SCPC Point-to-Point Links _________________________________________ 3-2

3.1.2 SCPC Point to Multi–Point Links in a Broadcast Application _______________ 3-2

3.1.3 DAMA (Demand Assigned Multiple Access) ___________________________ 3-3

3.1.4 TDMA (Time Division Multiple Access) Remote Site Application ____________ 3-3

3.2 VME Demodulator Card Reed-Solomon ________________________________ 3-3

3.2.1 Reed-Solomon Codec ____________________________________________ 3-3

3.2 Clocking Options __________________________________________________ 3-4

3.2.1 RX Buffer Clock Options __________________________________________ 3-4

MN-VME2401 – Rev. B vii

Table of Contents DD2401 VME L-Band Demodulator Card Installation & Operational Manual

3.2.1.1 RX SAT Clock _________________________________________________ 3-5

3.2.1.2 SCT: Serial Clock Transmit _______________________________________ 3-5

3.2.2 EXT REF: External Reference, J2 ___________________________________ 3-5

3.2.3 Reed-Solomon Operation in the DD2401 VME Demodulator Card __________ 3-5

3.2.4 Reed-Solomon Code Rate _________________________________________ 3-5

3.2.5 Interleaving_____________________________________________________ 3-6

Section 4 - User Interfaces ........................................................................................ 4-1

4.0 User Interfaces ___________________________________________________ 4-1

4.1 Remote Port Control (J3) ___________________________________________ 4-1

4.2 Terminal Mode Control (J1) _________________________________________ 4-1

4.3 Terminal Port User Interface _________________________________________ 4-2

4.3.1 Connecting the Terminal __________________________________________ 4-2

4.3.2 Terminal Screens ________________________________________________ 4-3

4.4 Remote Port User Interface _________________________________________ 4-6

4.4.1 Protocol Structure _______________________________________________ 4-6

4.4.2 Protocol Wrapper ________________________________________________ 4-6

4.4.3 Frame Description and Bus Handshaking _____________________________ 4-8

4.4.4 Global Response Operational Codes _________________________________ 4-8

4.4.5 Collision Avoidance _____________________________________________ 4-10

4.4.6 Software Compatibility ___________________________________________ 4-11

4.4.7 Flow Control and Task Processing _________________________________ 4-11

4.4.8 RLLP Summary ________________________________________________ 4-12

4.4.9 DD2401/DD2401L Opcode Command Set ___________________________ 4-13

4.4.11 Module Command Set __________________________________________ 4-14

4.4.12 Detailed Command Descriptions __________________________________ 4-14

4.4.12.1 DMD2401 Demodulator _______________________________________ 4-14

4.4.12.2 Module Queries & Commands __________________________________ 4-35

4.4.12.3 Default Values Demodulator ____________________________________ 4-39

Section 5 - Rear Panel Interfaces .............................................................................. 5-1

5.0 DD2401 VME Demodulator Card Connections ___________________________ 5-1

5.1 Power ________________________________________________________ 5-2

5.1.1 Diagnostic LED's ________________________________________________ 5-2

5.2 Terrestrial Data I/F ________________________________________________ 5-3

viii MN-VME2401 – Rev. B

DD2401 VME L-Band Demodulaor Card Installation & Operational Manual Table of Contents

5.3 EXT REF ________________________________________________________ 5-4

5.4 SERIAL CONTROL I/F _____________________________________________ 5-4

5.5 RX IN ________________________________________________________ 5-4

5.5.1 L-Band ________________________________________________________ 5-4

5.6 Remote Port _____________________________________________________ 5-4

5.7 Remote Addresses ________________________________________________ 5-5

Section 6 - Maintenance and Troubleshooting ........................................................ 6-1

6.0 Periodic Maintenance ______________________________________________ 6-1

Section 7 - Technical Specifications ......................................................................... 7-1

7.0 Introduction ______________________________________________________ 7-1

7.1 Receive Data Rates _______________________________________________ 7-1

7.2 Demodulator Specifications _________________________________________ 7-1

7.3 Options ________________________________________________________ 7-1

7.4 Environmental ____________________________________________________ 7-1

7.5 Physical ________________________________________________________ 7-2

7.6 BER Charts ______________________________________________________ 7-3

7.7 AGC Curve _____________________________________________________ 7-12

Glossary ..................................................................................................................... G-1

MN-VME2401 – Rev. B ix

Table of Contents DD2401 VME L-Band Demodulator Card Installation & Operational Manual

x MN-VME2401 – Rev. B

DD2401 VME L-Band Demodulator Card Installation & Operational Manual Introduction

1

Introduction

1.0 Description

The Radyne DD2401 VME L-Band Demodulator is intended for use as apart of the receiving
ground equipment in a satellite communication system. The card based unit is designed to
receive a single carrier up to 5 MBits/s throughput on the RS422 synchronous interfaces. The
DD2401 VME card is compatibility with all Radyne's DMD products including the DMD20, DMD50
and OM20.

Figure 1-1. DD2401 VME L-Band Demodulator Card

The DD2401 VME Demodulator Card is designed to perform at one end of the satellite Single
Channel Per Carrier (SCPC) Link receiving the carrier. The VME can be used in a Mesh or Star
Topology Network. The Demodulator supports BPSK, QPSK, OQPSK or 8PSK demodulation.

The demodulator can be accessed via a single RS485 serial link system for complete remote
monitor and control (M&C) capability and offers the terminal control via an RS232 connection.

Selection of any data rate is provided over the following ranges:

BPSK: 9.6 Kbps to 1200 Kbps
QPSK: 9.6 Kbps to 4.375 Mbps
OQPSK: 9.6 Kbps to 4.375 Mbps
8PSK: 64.0 Kbps to 5.0 Mbps

The VME Demodulator Card can track and acquire a carrier over a programmable range of ± 1
kHz to ± 42 kHz. Acquisition times of less than three seconds are typical at data rates greater
than 64 Kbps over a range of ± 25 kHz.

To facilitate link testing, the VME Demodulator Card incorporates a built-in ‘2047’ tes t patter n with
BER measurement capability.

MN-VME2401 – Rev. B 1-2

Introduction DD2401 VME L-Band Demodulator Card Installation & Operational Manual

1.1 DD2401 VME L-Band Demodulator Card Available Options

Various options are available for the DD2401 VME L-Band Demodulator Card:

1.1.1 Reed-Solomon Codec (Optional)

The VME Demodulator Card is equipped w ith an Intelsat Reed-Solomon Outer Codec with an
interleaver as an optional enhancement for applications requiring Bit Error Rates (BER) of 10
The encoder and decoder are completely independent and meet the IESS-308/309 Specification.

-10

.

1.1.2 Turbo Codec (Optional)

The VME Card is equipped with Turbo Product Code (TPC) Codec. TPC Codes include 0.495
and 0.793, 21/44, 1/2, 3/4 and 7/8 Rate.

1.1.3 8PSK (Optional)

The VME Card offers in addition to the standard B/O/QPSK waveforms an 8PSK optional high
order waveform capable of either Trellis 2/3 or any TPC 0.495, TPC0.793, TPC 3/4 and TPC 7/8
when purchased wit the Turbo option.

1-2 MN-VME2401 – Rev. B

DD2401 VME L-Band Demodulator Card Installation & Operational Manual Introduction

MN-VME2401 – Rev. B 1-2

DD2401 VME L-Band Demodulator Card Installation & Operational Manual Installation

2

Installation

This section provides unpacking and installation instructions, and a description of external
connections.

2.0 Installation Requirements

The VME2401 demodulator card is designed to be installed within any standard VME-compliant
cabinet.

2.1 Unpacking

The VME Demodulator Card was carefully packaged to avoid damage and should arrive
complete with the following items for proper installation:

1. VME L-Band Demodulator Card

2. Installation and Operation Manual

2.2 Removal and Assembly

If using a knife or cutting blade to open the carton, exercise caution to insure that the blade does
not extend into the carton, but only cuts the tape holding the carton closed. Carefully unpack the
unit and ensure that all of the above items are in the carton.

2.3 Mounting Considerations

When mounted in an equipment cabinet, ad equ ate ve nti lat ion m ust be prov ided. T he am bient
temperature in the cabinet should preferably be between 10° a nd 35° C, and held constant for
best equipment operation. The air available to the cabinet should be clean and relatively dry. The
unit should not be placed immediately above a high heat or EMF generator to ensure the output
signal integrity and proper receive operation.

2.4 Demodulator Checkout

The following descript ions assume that the VME Demodulator Card is installed in a suitable
chassis.

2.4.1 Initial Power-Up

The VME Demodulator Card is shipped from the factory with preset factory defaults. upon initial
power-up, a user check should be performed to verify the shipped demodulator configuration.

The following are standard VME Demodulator Card Factory Configuration Settings:
Data Rate: 2,048 Kbps

Forward Error Correction (FEC): 1/2 Rate Viterbi
Frequency: 950 MHz (L-Band)
Interface: RS422

MN-VME2401 – Rev. B 2-1

Installation DD2401 VME L-Band Demodulator Card Installation & Operational Manual

Position

Position

Position

Position

on

The connector definitions and pinout tables are shown in secti on 5.0. Any connection interfacing
to the modem must be the appropriate mating connector.

Shielded cables with the shield terminated to conductive backshells are required in

order to meet EMC directives. Cables with insulation flammability ratin g s of 94 VO or

better are required in order to meet Low Vo ltage Directives.

2.4.2 Factory Terminal Setup (Refer to Section 4.4)

The factory terminal setup is as follows:
Emulation Type: VT-100 (can be changed)

Baud Rate: 19200
Data Bits 8
Parity: No Parity (Fixed)
Stop Bits: 1

2.4.3 Remote Protocol Factory Default Setup

Demodulator will be configured with default settings when they are shipped from factory. Refer to
Section 5-6 to Defaults setting can be modified may be the default settings for the RS485
Communication port are:

Table 2-1. S1 DIP Switches

Demodulator

Demodullator

1

2

off off off 33

3

4

Address in

Decimal

2.5 Storage

It is recommended that the unit be stored in its original sealed packaging. The unit should be
stored in a dry location where the temperature is stable, away from direct contact with rain, snow,
wind, sun or anything that may cause damage.

2-2 MN-VME2401 – Rev. B

DD2401 VME L-Band Demodulator Card Installation & Operational Manual Installation

MN-VME2401 – Rev. B 2-3

DD2401 VME L-Band Demodulator Card Installation & Operational Manual Theory of Operation

3

Rx
Baseband
Processing

Terminal

Remote

Port

M&C

Remote

Serial

Interfaces

Demodulator

RX RF

Equipment

Power Supply

+5 VDC
+12VDC

-12VDC

Terrestrial Data

Interface

Customer

Data

Terrestrial I/O

Modulator

Interconnect

Antenna

Demodulator Card

External

Referance

DD2401 VME Block Diagram

IF Input 950-1750 MHz

-25 to -55 dBm

Reference

Theory of Operation

3.0 Theory of Operation

The VME L-Band Demodulator Card is capable of receiving four L-Band signals between 950­1750 MHz. The IF signals are then converted into data. The data is digitally filtered, passed
through the Viterbi FEC, differentially decoded and descrambled before it is sent to the RS422
terrestrial interface. The RS422 data from each demodulator can be retrieving from the rear
panels of each demodulator.

Figure 3-1. DD2401 VME Demodulator Block Diagram

MN-VME2401 – Rev. B 3-1

Theory of Operation DD2401 VME L-Band Demodulator Card Installation & Operational Manual

Figure 3-2. DD2401 VME L-Band Demodulator Block Diagram

3.1 Applications

Following are just a fe w representative forms of satellite c ommunications links and networks in
which the DD2401 VME Demodulator Card may be used.

3.1.1 SCPC Point-to-Point Links

The most straightforward application for a Satellite Demodulator is to serve as the Data
Communications Equipment (DCE) for a Point-to-Point Data Link. When used in this mode, two
demodulators located at two different sites are tuned to complementary transmit and receive
frequencies. Each direction of the communications link may have the same or entirely different
transmission parameters. In this application, it is typical that the link is established and
maintained on a continuous basis, although a special “on demand” case is described later.

3.1.2 SCP C Point to Multi–Point Links in a Broadcast Application

A broadcast application might involve the necessity of sending continuous or intermittent data
from one source and “broadcasting” the information to many remote locations. For instance,
constant pricing information and updates may be sent by a central location to many store
locations. There may be minor return information from the remotes acknowledging receipt.

Another broadcast application could be transmitting background music from a central location to
many store sites. In this case, there would be no return path.

The topology of the network in both of these broadcast examples would typically be called a
“Star” Network. As shown in Figure 3-3, the shape of the configuration is drawn with the central
“Hub” as the center of the star and the remotes as points of the star. In both cases the transmit
frequency and other parameters are shared by the receiver of all the remotes.

3-2 MN-VME2401 – Rev. B

DD2401 VME L-Band Demodulator Card Installation & Operational Manual Theory of Operation

Figure 3-3. Star Network Configuration

3.1.3 DAMA (Demand Assigned Multiple Access)

If a telephone network is to be simulated with a virtual switch between demodulators carrying
digitized voice information. A central computer might be used to assign a pair of frequencies for
any conversation and send this connection information to the proper sites to set up the
connection. In this application, a new network called a “Mesh” Network is required. Any of the
voice demodulators at any site can be programmed to link with any other demodulator. The
resulting link diagram looks like a mesh of interconnects.

Since the frequencies can be assigned on demand, the network is called “Demand Assigned,
Multiple Access,” or DAMA.

3.1.4 TDMA (Time Division Multiple Access) Remote Site Application

In a TDMA Network, the central Hub continually transmits a stream of outbound data containing
information for multiple remote sites, while the remote sites transmit back to the Hub on a timed
basis. Each of these remotes is said to “burst” its information back on a specific frequency. This
may be the same inbound frequency for all sites.
Each of the remotes is responsible for accessing its own information from the outbound data
stream by reading the address assigned to specific parts of the data. The TDMA Network usually
looks like the Star network described above.

The DD2401 VME Demodulator Card is specifically designed to be usable as the remote site
Demodulator of a TDMA network when coupled with a proper “Burst” Demodulator at the hub site.

3.2 VME Demodulator Card Reed-Solomon

3.2.1 Reed-Solomon Codec

Utilizing a Reed-Solomon (RS) Outer Codec concatenated with a convolutional inner codec is an
effective way to produce very low error rates even for poor signal-to-noise ratios while requiring
only a small increase in transmission bandwidth. Typically, concatenating an RS Codec requires
an increase in transmission bandwidth of only nine to twelve percent while producing a greater
than 2 dB improvement in Eb/No. RS is a block codec where K data bytes are fed into the

MN-VME2401 – Rev. B 3-3

Theory of Operation DD2401 VME L-Band Demodulator Card Installation & Operational Manual

EXT REF

EXTERNAL

INTERNAL

SCT CLK

REF FREQ

SRC

RECEIVE

CLOCK & DATA

RECOVERY

SCT

RX SAT

RT

RD

BUFFER CLK

SRC

DEMODULATION

J19

J10

DATA POLARITY

BUFFER CLK POL

NORMAL
INVERTED

INVERT NONE

INV. BASEBAND

INV. TERR DATA

encoder which adds 2t = (N - K) check bytes to produce an N byte RS Block. The RS Decoder
can then correct up to “t” erred bytes in the block (refer to Figure 3-4 and Table 3-1).

3.2 Clocking Options

The Demodulator supports a number of different clocking options that can be recovered
from the satellite or the terrestrial links. The various clocking options allow users to
determine which clock will best fit their applications. Figure 3-7 gives an overview on
how the modem processes the various clocks for the Rx Buffer Clock source.

Figure 3-4. Clocking and Polarity Diagram

3.2.1 RX Buffer Clock Options

The modem supports a number of RX Buffer clock options that can be recovered from the
satellite, terrestrial links, internally or externally. The various clocking options allow users to
determine which clock will best fit their applications. Figure 3-7 gives an overview on how the
modem processes the various clocks for the Tx Clock and the Rx Buffer Clock. The modem
allows users to select clock polarity and Rx Clocks may be independently locked. The following
RX Buffer clock selections are available:

3-4 MN-VME2401 – Rev. B

 Rx Satellite Clock (Recovered from Satellite)

DD2401 VME L-Band Demodulator Card Installation & Operational Manual Theory of Operation

 SCT (Internal Oscillator)

3.2.1.1 RX SAT Clock

The RX Sat clock is recovered from the satellite that is received from the distant end. If selected
the Buffer Clock is lock to the RX sat clock.

3.2.1.2 SCT: Serial Clo ck Tran sm it

If SCT clock is selected as the RX Buffer clock source, then it should be configured for internal.
SCT is sometimes referred to as Internal Timing or Send Timing (ST).

3.2.2 EXT REF: External Reference, J2

This is not actually a clock, but does have some clocking implications. When the external
reference is used, the master oscillator within the modem is locked to the external reference, and
the internal accuracy and stability of the unit assumes that of the External Reference. Therefore,
not only are the transmit frequencies locked to the external reference, but the modem’s internal
SCT Oscillator is locked to the external reference as well.

External reference port input is specified at 0 to +6 dBm.

3.2.2 Reed-Solomon Operation in the DD2401 VME Demodulator Card

When the Reed-Solomon Decoder is enabled, the signal is received and demodulated by the
receiving unit, fed to a Viterbi Decoder for the first layer of error correction. After error correction
by the Viterbi Decoder, the unique words are located and the data is deinterleaved and reformed
into blocks. The R-S Decoder then corrects the leftover errors in each block. The data is then
descrambled and output from the R-S Section.

3.2.3 Reed-Solomon Code Rate

The R-S Code Rate is defined by (N, K) where N is the total R-S block size in bytes (data + check
bytes) and K is the number of data bytes input into the R-S Encoder. The transmission rate
expansion required by the R-S Codec is then defined by N/K. The DD2401 VME
DEMODULATOR CARD allows any N or K setting up to N = 255, and K = 235 to allow tailoring of
the code rate to meet system requirements, with the following restrictions:

1. N/K must be less than 1.25 (25% maximum overhead).

2. N-K must be between 2 and 20, and must be even.

3. Maximum N = 255, Minimum N = 25.

4. Maximum K = 253, Minimum K = 23.

MN-VME2401 – Rev. B 3-5

Theory of Operation DD2401 VME L-Band Demodulator Card Installation & Operational Manual

Small IDR

IDR

3.2.4 Interleaving

The DD2401 VME DEMODULATOR CARD allows for interleaving depths of 4 or 8 R-S blocks.
This allows burst errors to be spread over 4 or 8 R-S blocks in order to enhance the error
correcting performance of the R-S Codec.

Figure 3-4. Reed Solomon Decoder Functiona l Block Diagram

Table 3-1. Reed-Solomon Codes for IDR

Type of Service Data

Rate

(Kbps)

R-S Code

(n, k, t)1

Bandwidth
Expansion

[ (n/k) -1 ]

Interleaving

Depth

Maximum
R-S Codec
Delay (ms)

2

(with 16/15 O/H)

(with 96 Kbps O/H)

64
128
256
384
512
768

1024
1536

1544
2048

(126, 112, 7)
(126, 112, 7)
(126, 112, 7)
(126, 112, 7)
(126, 112, 7)
(126, 112, 7)
(126, 112, 7)
(126, 112, 7)

(225, 205,10)

(219, 201, 9)

0.125

0.125

0.125

0.125

0.125

0.125

0.125

0.125

0.0976

0.0896

4
4
4
4
4
4
4
4

4
4

115

58
29
19
15
10

8
5

9
7

n = code length, k = information symbo ls and t = symbol error correcting capability.

Design objective

For the DD2401 VME Demodulator Card, the IDR Deframing must be supplied externally.

3-6 MN-VME2401 – Rev. B

DD2401 VME L-Band Demodulator Card Installation & Operational Manual User Interfaces

4

User Interfaces

4.0 User Interfaces

There are two user interfaces available for DD2401 VME Demodulator Card. These are:

a. Remote Port – (J5) Access to all available demodula tors
b. Terminal – (J1) Independent connection to each demodulator

4.1 Remote Port Control (J3)

All demodulators can be controlled by an external Monitor & Control (M&C) system through a
single Remote Port connection. Communication between the unit and the external system control
computer is via a binary protocol. The Remote Port provides RS-485 capability and thus is used
as a multi-drop control bus allowing a single external M&C computer to control all demodulators.
The Remote Port Data is outlined starting with Section 4.4 below.

4.2 Terminal Mode Control (J1)

Characters contained within the brackets < and > indicate pressing the appropr iate key.

The unit can be interactively monitored and controlled in the Terminal Mode, with a full screen
presentation of current settings and status. Programming is accomplished by selecting the item
to be modified and pressing the terminal key of the option number. For example, to change the
Receive Data Rate, enter “33” at the terminal. The DD240/VME2401/MD2401 DEMODULATOR
will respond by presenting the options available and requesting input. Two types of input may be
requested. If the input is multiple choice, the desired choice is selected by pressing <Space>.
When the desired option is displayed, press <Enter> to select that option. The other possible
input type requires a numerical input (such as entering a frequency or data rate). This type of
input is followed by pressing <Enter> or the carriage return key. An input can be aborted at any
time by pressing <ESC>. Invalid input keys cause an error message to be displayed on the
terminal.

The Terminal Control Mode supports a serial baud rate of 19200. The connection must be set for
8 data bits, 1 stop bit and no parity (8, N, 1). Three terminal emulations are supported: VT100,
WYSE 50, and ADDS. The emulation type can be changed by pressing <$> (dollar sign) on the
terminal keyboard.

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User Interfaces DD2401 VME L-Band Demodulator Card Installation & Operational Manual

4.3 Terminal Port User Interface

Each demodulator has a Terminal Port Connection (J1) that allows for complete control and
monitoring of the demodulator parameters and functions via an RS-232 Serial Interface.

The factory default setup parameters are as follows:
Emulation Type: VT100 (can be changed)

Baud Rate: 19200
Data Bits: 8
Parity: No Parity (Fixed)
Stop Bits: 1 stop bit

4.3.1 Connecting the Terminal

1. Connect the computer to the Remote Connector (J5) on the rear of the unit using
the RS-232 Cable.

2. Enable the terminal by selecting Terminal Mode (located under the System ­Control Mode Menu) from the front panel.

3. Verify that your emulation software is set to the following:

 8 data bits
 no parity
 1 stop bit

Modify the selection, if necessary, to match the settings (the Front Panel
‘SYSTEM’ Sub-Menu contains all the Terminal Emulation Controls).

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DD2401 VME L-Band Demodulator Card Installation & Operational Manual User Interfaces

4.3.2 Terminal Screens

Figure 4-1. Main Menu

Figure 4-2. Demodulator Menu

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User Interfaces DD2401 VME L-Band Demodulator Card Installation & Operational Manual

Figure 4-3. Event Buffer Menu

Figure 4-4. Alarm/Status Menu

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DD2401 VME L-Band Demodulator Card Installation & Operational Manual User Interfaces

Figure 4-5. Latched Alarm Status Menu

Figure 4-6. Interface Controls Menu

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User Interfaces DD2401 VME L-Band Demodulator Card Installation & Operational Manual

S1

S2

B0

B1

B2

B3

B4

B5

B6

B7

S1

S2, etc.

4.4 Remote Port User Interface

The Remote Port of the DD2401/DD2401L allows for complete control and monitor functions via
an RS-485 or RS-232 Internal Dip Switch Configurable Serial Interface.

Control and status m essages are conveyed between the DD2401/DD2401 L and the subsidiary
modems and the host computer using packetized message blocks in accordance with a
proprietary communications specification. This communication is handled by the Radyne Link
Level Protocol (RLLP), which serves as a protocol ‘wrapper’ for the M&C data.

Complete information on monitor and control software is contained in the following sections.

4.4.1 Protocol Structure

The Communications Specification (COMMSPEC) defines the interaction of computer resident
Monitor and Control software used in satellite earth station equipment such as Modems,
Redundancy Switches, Multiplexers, and other ancillary support gear. Communication is bi­directional, and is normally established on one or more full-duplex 9600-baud multi-drop control
buses that conform to EIA Standard RS-485. If a single device is placed on a single control bus,
then the control bus may conform to EIA Standard RS-232.

Each piece of earth s tation equipment on a c ontrol bus has a uni que physical addr ess, which is
assigned during stati on setup/config uration or prior t o shipm ent. Valid decim al addresses on one
control bus range from 032 to 255 for a tota l of up to 224 devices per bus. Addres s 255 of each
control bus is usually reserved for the M&C computer.

4.4.2 Protocol Wrapper

The Radyne COMMSPEC is byte-oriented, with the Least Significant Bit (LSB) issued first. Each
data byte is conveyed as mark/space information with one mark comprising the stop data. When
the last byte of data is transmitted, a hold comprises one steady mark (the last stop bit). To begin
or resume data transfer, a space (00h) substitutes this mark. This handling scheme is controlled
by the hardware and is transparent to the user. A pictorial representation of the data and its
surrounding overhead may be shown as follows:

The stop bit, S1 is a mark. Data flow remains in a hold mode until S1 is replaced by a space. If S1
is followed by a space, the space character is considered a start (ST ) and not part of the act ual
data (B

0 - B 7).

The above byte-oriented protocol is standard for UART based serial communication ports such as
Workstation or Persona l Computer (PC) COM por ts. COM ports should be conf igured for 8 data
bits, no parity, and one stop bit. For example, for 9600-baud operation, COM ports should be
configured as:

9600, 8, N, 1

The COMMSPEC developed for use with the Radyne Link Level Protocol (RLLP) organizes the
actual monitor and control data within a shell, or ‘protocol wrapper’, that surrounds the data. The
format and structure of the COMMSPEC message exchanges are described herein. Decimal
numbers have no suffix; hexadecimal numbers end with a lower case h suffix and binary values
have a lower case b suffix. Thus, 22 = 16h = 000010110b. The principal elements of a data
frame, in order of occurrence, are summarized as follows:

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