Combiner with phase and delay correction
AssigneeLockheed Martin Corporation
InventorsDennis L. Wilson, Frank Chethik
Life of this patent
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Abstract
A combining technique for coherently combining signals transmitted from a moving satellite that are received by separate antennas. The combining technique corrects for differential delays that are large enough to cause misalignments in the symbols of the communication signal as well as the phase of the signal. Further the combining technique tracks changes in the differential delay, keeping the phase and the symbols properly aligned for combining.
Claims15
A combiner for combining signals received from a moving satellite using a plurality of antennas, said combiner comprising:
- a variable delay for inserting delays that matches a received signal from a first antenna with a reference signal from a second antenna;
- a delay discriminator for determining whether the received signal is early or late compared to the reference signal and for controlling the delays that are inserted by the variable delay;
- phase processing circuitry for measuring the phase error between the delayed received signal and the reference signal and for adjusting the phase of the received signal to remove the phase error;
- and
- combiner circuitry for combining the received signal with the reference signal to form a composite signal that is selectively demodulated.
A method of combining signals received from a moving satellite using a plurality of antennas, said method comprising the steps of:
- inserting delays that will match a received signal from an antenna with a reference signal from another antenna;
- determining whether the received signal is early or late compared to the reference signal and controlling the delays that are inserted by the variable delay;
- measuring the phase error between the delayed received signal and the reference signal and for adjusting the phase of the received signal to remove the phase error;
- and
- combining the received signal with the reference signal to form a composite signal that is selectively demodulated.
Apparatus for inserting delays that will match a received signal from an antenna with a reference signal from another antenna, said apparatus comprising:
- a downconverter for shifting the received signal to in-phase and quadrature baseband signals;
- a pair of light modulators at different light frequencies for changing the in-phase and quadrature baseband signals to light signals at optical frequencies;
- a light combiner for combining the outputs of the modulators onto one fiber;
- optical switches for routing the light signals through different lengths of fiber comprising different delays for the signals;
- a pair of light demodulators for recovering the baseband signals at the output of the variable delay;
- an upconverter for shifting the recovered baseband signals back to the IF frequency;
- and
- an oscillator coupled to the downconverter and the upconverter to maintain the same frequency in both converters.
Dependencies are inferred from the claim text.