Tech Notes
PSM-512/1500/2100/2100L/4900 and M4000/M5000
Carrier Frequency Doppler Tracking Capabilities
Datum Systems satellite modems have been tested to determine the maximum Doppler rate they can tolerate and maintain lock and performance. The Doppler rate is the rate that the receive carrier changes frequency due to any cause. This is usually due to Doppler effect caused by movement of the satellite.
Tables of Eb/No verses Doppler Rate for Different Modem Modes.
|
BPSK, Rate 1/2, 32 kbps |
|
|
4.0dB |
2.5 kHz/sec |
|
5.0dB |
2.5 kHz/sec |
|
6.0dB |
2.5 kHz/sec |
|
8.0dB |
2.5 kHz/sec |
|
10.0dB |
2.5 kHz/sec |
|
QPSK, Rate 1/2, 32 kbps |
|
|
4.0dB |
19 Hz/sec |
|
5.0dB |
31 Hz/sec |
|
6.0dB |
156 Hz/sec |
|
8.0dB |
313 Hz/sec |
|
10.0dB |
391 Hz/sec |
|
QPSK, Rate ¾, 32 kbps |
|
|
5.0dB |
75 Hz/sec |
|
6.0dB |
200 Hz/sec |
|
7.0dB |
300 Hz/sec |
|
9.0dB |
300 Hz/sec |
|
11.0dB |
300 Hz/sec |
|
QPSK, Rate ¾, 128 kbps |
|
|
5.0dB |
1.2 kHz/sec |
|
6.0dB |
3.2 kHz/sec |
|
7.0dB |
4.8 kHz/sec |
|
9.0dB |
4.8 kHz/sec |
|
11.0dB |
4.8 kHz/sec |
|
BPSK, Rate 1/2, 256 kbps |
|
|
4.0dB |
160 kHz/sec |
|
5.0dB |
160 kHz/sec |
|
6.0dB |
160 kHz/sec |
|
8.0dB |
160 kHz/sec |
|
10.0dB |
160 kHz/sec |
|
QPSK, Rate 1/2, 256 kbps |
|
|
4.0dB |
1.2 kHz/sec |
|
5.0dB |
2.0 kHz/sec |
|
6.0dB |
10 kHz/sec |
|
8.0dB |
20 kHz/sec |
|
10.0dB |
25 kHz/sec |
|
QPSK, Rate 3/4, 64 kbps |
|
|
5.0dB |
300 Hz/sec |
|
6.0dB |
800 Hz/sec |
|
7.0dB |
1.2 kHz/sec |
|
9.0dB |
1.2 kHz/sec |
|
11.0dB |
1.2 kHz/sec |
Notes:
These are maximum rates for reliable acquisition and < 0.2 dB BER degradation.
The tracking range is equal to the programmed sweep range, up to +/- 1.250 MHz.
Rapidly changing carrier levels and converter phase noise will degrade the above table values.
For applications requiring fast tracking, the modem should be tested in a representative system under actual working conditions for final approval.
MAB 5/99