Comtech EF Data CDM-625 - Page 55

CDM-625 Advanced Satellite Modem Revision 13
Introduction MN-CDM625
1–15
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 (nominal 50/75
Ω
, BNC female connector)
As an output: 10MHz, 2.7 volts peak-to-peak ± 0.4 volts, 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 to 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 to 35
o
C
±1.0 dB over frequency, data rate, modulation type and temperature range 0 to 50
o
C
50-180 MHz band:
±0.5dB over frequency, data rate, modulation type and temperature range 15 to 35
o
C
±0.8dB over frequency, data rate, modulation type and temperature range 0 to 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 maximum, 100W
• 48VDC, 3.125 Amps maximum, 150W @ 50
o
C (180 watts @ 30
o
C)
• Supplied through Tx IF center conductor and selectable ON/OFF via M&C control.
BUC Current Monitor
Min/Max 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.