Tech Note 4
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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

 

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  Last modified: September 04, 2008