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Comtech EF Data CDM-625 User Manual

Page 50

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CDM-625 Advanced Satellite Modem

Revision 15

Introduction

MN-CDM625

1–14

Transmit filtering

Firmware prior to 1.4.0: Root-Raised Cosine, alpha = 0.35 (fixed)

Firmware 1.4.0 or later: Root-Raised Cosine, alpha = 0.35 and 0.25 – front panel/software selectable

See graph of output spectrum provided at the end of this section

Scrambling

IDR Mode, no RS, – per ITU V.35 (Intelsat variant)

IBS mode, no RS – per IESS-309, externally frame synchronized

Transparent Closed Network mode, no RS or Turbo coding – per ITU V.35 (Intelsat variant)

EDMAC mode, no RS coding – externally frame synchronized – proprietary

Turbo Product Code/LDPC/VersaFEC modes – externally frame synchronized – proprietary

All RS modes – externally frame synchronized per IESS-308/309/310

External Reference

As an input: 1, 2, 5 or 10MHz –6dBm to +10dBm (nom. 50/75 Ω, BNC female connector)

As an output: 10MHz, 2.7V peak-to-peak ±0.4V, low impedance output

(The Ext. reference phase locks Tx and Rx synthesizers, and all baseband clock generation)

Harmonics/spurious

Better than –60 dBc/4 kHz (typically <-65 dBc/4kHz)

measured from 1-500 MHz (50-180 MHz band)

measured F

0

±500 MHz (950-2000 MHz band)

Transmit on/off ratio

-60 dBc minimum

Output phase noise

< 0.48

0

rms double sided, 100 Hz to 1MHz (minimum of 16 dB better overall than the INTELSAT IESS-308/309 requirement)

dB/Hz

Frequency Offset

-63.0

100 Hz

-73.0

1 kHz

-83.0

10 kHz

-93.0

100 kHz

Fundamental AC line spurious is –42 dBc or lower

The sum of all other single sideband spurious, from 0 to 0.75 x symbol rate, is –48 dBc or lower

Output power

950-2000 MHz band: 0 to –40 dBm, 0.1 dB steps – manual mode. See AUPC section also

50-180 MHz band: 0 to –25 dBm, 0.1 dB steps – manual mode. See AUPC section also

Power accuracy

950-2000 MHz band:

±0.7dB over frequency, data rate, modulation type and temperature range 15-35

o

C

±1.0 dB over frequency, data rate, modulation type and temperature range 0-50

o

C

50-180 MHz band:

±0.5dB over frequency, data rate, modulation type and temperature range 15-35

o

C

±0.8dB over frequency, data rate, modulation type and temperature range 0-50

o

C

Output impedance

950-2000 MHz band: 50Ω, 19 dB minimum return loss (21 dB typical)

50-180 MHz band: 50Ω, or 75Ω 16 dB minimum return loss (18 dB typical)

Output connector

950-2000 MHz band: Type N female

50-180 MHz band: BNC female

Clocking options

Internal, ±0.06 ppm (SCT)

External, locking over a ±100 ppm range (TT)

Loop timing (Rx satellite clock) – supports asymmetric operation – Rx and Tx data rates need not be identical

External Clock

G.703 Clock Extension mode – internal ST clock can be slaved to an external T1 or E1 G.703 signal, and a G.703 timing

signal re-constituted at the distant end of the link, regardless of the actual link data rate

External TX Carrier Off

By TTL 'low' signal or external contact closure – hardware function automatically over-rides processor

BUC Reference

(10 MHz):

Phase Noise

On center conductor of L-Band output connector; 10.0 MHz ± 0.06 ppm (internal reference selected)

0.0 dBm, ± 3 dB; programmable ON/OFF

Source: either Internal Modem Reference or External Reference (10 MHz)
dB/Hz

Frequency Offset

-105

10 Hz

-125

100 Hz

-138

1 kHz

-148

10 kHz

-150

100 kHz

BUC Supply Voltage

Standard unit has no BUC supply.

Optional BUC Supply:

24VDC, 4.17 Amps max., 100W

48VDC, 3.125 Amps max., 150W @ 50

o

C (180W @ 30

o

C)

Supplied through Tx IF center conductor and selectable ON/OFF via M&C control.

BUC Current Monitor

Minimum/maximum programmable current alarm thresholds.

Tx Carrier ON Delay

Selectable feature power on to allow internal ovenized reference to stabilize before turning on Tx carrier. Intelligent algorithm

minimizes delay time based on internal temperature at power-up.

BUC Monitoring

Power level, temperature, power class, PLL lock.

Uses ND Satcom/Global VSAT Forum specification for FSK control and monitoring.