Satellite communication system
AssigneeThe United States of America as represented by the Secretary of the Army
InventorFrank S. Gutleber
Life of this patent
Estimating the term…
Abstract
A loop-around doppler canceling loop is employed between a master ground minal or node and a slave ground terminal or node for translating a doppler-free reference to the slave terminal by having a local voltage controlled oscillator (VCO) of frequency f at the master terminal lock to a frequency f.sub.o =f.sub.d where f.sub.o is frequency of the primary standard reference clock 8 at the master terminal and f.sub.d is the two-way doppler frequency that exists during transmission between the master and slave ground terminals by way of satellite.
Claims8
A frequency division multiple access satellite communication system having a master ground node and at least one slave ground node, each of said nodes comprising
- a primary frequency standard at said master node for supplying a precisely maintained standard frequency clock f.sub.o ;
- a phase lock loop at said master node including a voltage controlled oscillator of frequency f which establishes the pulse repetition interval during which message information occurs,
- means for transmitting from said master node by way of said satellite on a suitable radio frequency carrier the video signal of frequency f from said voltage controlled oscillator to said slave node which arrives at said slaved node shifted in frequency by f.sub.d where f.sub.d is the doppler shift encountered during the transmission of energy between said nodes owing to the relative motion between said satellite and said nodes,
- means at said slave node for retransmitting on said same carrier by way of said satellite to said master node the doppler-shifted video signal received at said slave node which arrives at said master node with the frequency f+2f.sub.d,
- said phase lock loop responding to the received doppler-shifted timing control signal of frequency f+2f.sub.d on said radio frequency carrier and to the frequency-doubled output of said primary frequency standard for locking the frequency of said voltage controlled oscillator to a value f.sub.o -f.sub.d, and
- means for transmitting by way of said satellite from said master node to said slave node the video signal of pulse repetition frequency f.sub.o -f.sub.d which arrives doppler-shifted at said slave node as a timing signal at the standard frequency f.sub.o.
Dependencies are inferred from the claim text.