Doppler frequency compensation circuit
First Claim
1. A doppler frequency compensation circuit for a data link system comprising:
- a moving airborne station source of coherent downlink R.F. signals comprising a fixed frequency carrier signal and a modulating data signal,a ground station for receiving said coherent R.F. signals,means in said ground station for recovering an I.F. carrier signal from said received coherent signal which is shifted by the downlink doppler frequency effect,a scaling phase-locked loop coupled to said shifted I.F. carrier signals for producing a deviation frequency signal at said ground station which is inversely proportional to an uplink doppler frequency, andan inverting phase-locked loop coupled to said deviation frequency signal for producing uplink I.F. doppler frequency compensated signals.
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Accused Products
Abstract
In a communications data link network of the type having a plurality of ground stations and a single moving airborne station, there is provided a doppler frequency compensation circuit in each of the ground stations. The downlink carrier frequency is fixed and continuously broadcast to the receiving ground station which continuously receive the doppler shifted carrier signal. The ground stations are provided with coherent demodulators which provide a coherent I.F. recovered carrier signal that is applied to a scaling phase-locked loop to provide a deviation frequency signal that is applied to an inverting phase-locked loop which provides a pre-compensated uplink R.F. carrier signal. The uplink R.F. carrier signal has a compensated uplink doppler frequency component which equals the inverted and scaled doppler frequency of the received downlink carrier.
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Citations
16 Claims
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1. A doppler frequency compensation circuit for a data link system comprising:
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a moving airborne station source of coherent downlink R.F. signals comprising a fixed frequency carrier signal and a modulating data signal, a ground station for receiving said coherent R.F. signals, means in said ground station for recovering an I.F. carrier signal from said received coherent signal which is shifted by the downlink doppler frequency effect, a scaling phase-locked loop coupled to said shifted I.F. carrier signals for producing a deviation frequency signal at said ground station which is inversely proportional to an uplink doppler frequency, and an inverting phase-locked loop coupled to said deviation frequency signal for producing uplink I.F. doppler frequency compensated signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification