Specifications

Trojan Interface SDM-650B Satellite Modem
G–6 Rev. 5
G.3 Specification
G.3.1 MIL-STD-188-114 Parameters
Circuit Supported SD, ST, TT, RD, RT, DM, RR, MC, MOD FAULT,
DEMOD FAULT.
Amplitude (RD, RT, ST, DM, RR)
4, ± 2V differential into 100Ω.
DC Offset (RD, RT, ST, DM, RR) ± 0.4V.
Impedance (RD, RT, ST, DM, RR)
Less than 100Ω, differential.
Impedance (SD, TT, MC)
100, ± 20Ω, differential.
Polarity True when B positive with respect to A.
False when A positive with respect to B.
Phasing (TT, RT) False-to-true transition nominally in center of data bit.
Symmetry (ST, TT, RT) 50%, ± 5%.
Frequency Stability (ST) ± 100 ppm.
Modulator Fault Open collector output, 15V max, 20 mA max current
sink. Fault is open circuit.
Demodulator Fault Open collector output, 15V max, 20 mA max current
sink. Fault is open circuit.
G.3.2 Clock Synthesizer/Dejitter Circuit
Reference Clk Sources Transmit Clk
Receive Data Clk
External Reference Clk (MC)
Modem Internal Clk (SCT)
Reference Clk Input 32 kHz to 10 MHz, in 8 kHz steps
Synthesized TX Clock 56 to 2048 kHz, in 8 kHz steps
Synthesized RX Clock 56 to 2048 kHz, in 8 kHz steps
Jitter Gain Synth Clk Freq/Ref Clk Freq, modified by a 1-pole
(20 dB/decade) low-pass response corner at 0.4 Hz
G.3.3 Doppler Buffer Parameters
Buffer Size (bits) 512, 1024, 2048, 4096, 8192, 16384, 32768
Clock Source Synthesized RX Clock
Data Rate 56 to 2048 kbit/s
Indicators Buffer Overflow (stored fault)
Buffer Underflow (stored fault)
Controls Reset Buffer to Center
Buffer Depth
Misc. Buffer automatically recenters on Over/Underflow,
power-on, or start of service