[amsat-bb] Automatic doppler tracking of DSB

James Whitfield n5gui at cox.net
Fri Feb 1 08:46:34 PST 2008

I am trying to find out if there has been any development of a frequency tracking system to compensate for doppler shift, or at least find a person or organization with which to discuss concepts.  I tried to contact AMSAT about this more than a week ago, but there has been no response.  I have tried to contact AMSAT again, and decided to try this bulletin board as well.

It started when I read that AO-16 had been placed in a test mode with an FM uplink and DSB downlink.  I remembered a diagram of a double sideband suppressed carrier ( DSB ) demodulation technique that used a variation of a phased locked loop to recover the frequency and phase of the original carrier.  I realized that it should be able to track the "original carrier" through the doppler shift caused by the relative motion between the satellite and the receiving station.

I decided to find out more about the concept.  I was not able to find any reference to the technique having been used with satellites, but I believe the system is called a Costas Receiver, or perhaps is refered to as a Costas Loop.

If someone knows if this was used for doppler frequency tracking, please let me know where I can get more information.  If there is a person or organization that would be better suited to my inquiry,  I would like to know that as well.

Thank you.

James Whitfield

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