Discrete phase modulator
AssigneeHughes Electronics Corporation
InventorsHoward S. Nussbaum, William P. Posey, Steve I. Hsu, Stephen D. Taylor
Life of this patent
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Abstract
Discrete phase modulation for modulating the transmit and receive radar signal waveforms in order to control distortion. The signal is modulated by discrete phases which change from pulse-to-pulse. A digital frequency division circuit accurately generates the modulation signals, and allows the discrete phases to be generated with precise accuracy. The discrete phase changes can be a quadratic phase progression for target Doppler and range detection.
Claims15
A radar system, comprising:
- a radar transmitter system for transmitting a sequence of pulses to form a transmit pulse train, said pulse train including pulse repetition intervals between pulses;
- a receiver system for receiving return signals from said transmitted pulse train and producing receive antenna signals;
- and
- means for modulating said received antenna signals with a constant frequency modulating signal with step changes of phase from pulse to pulse.
A radar system, comprising:
- a radar transmitter system for transmitting a sequence of pulses to form a transmit pulse train, said pulse train including pulse repetition intervals between pulses, said transmitter system including means for modulating said pulses with a constant frequency modulating signal with transmit step changes of phase from pulse to pulse;
- and
- a receiver system for receiving return signals from said transmitted pulse train and producing received signals.
A modulator for modulating an RF signal with fixed frequency modulation with step changes of phase, comprising:
- a modulating circuit for modulating said RF signal with a modulating signal;
- and
- a signal generator for generating said modulating signal, said generator including:
- (a) means for providing a constant frequency signal;
- and
- (b) means for shifting the phase of said constant frequency signal by a sequence of discrete phase changes to produce said modulating signal, said means for shifting the phase of said constant frequency signal including:
- (i) means for converting said constant frequency signal into a pulse train waveform of periodicity corresponding to the periodicity of said constant frequency signal,
- (ii) means responsive to said pulse train waveform for dividing the frequency of said pulse train waveform by a factor of N, thereby increasing its period by said factor of N, said means including a counter clocked by said pulse train for counting N pulses and then resetting, said counter having N states, and
- (iii) means for resetting said counter to commence counting from an incremented start count state for a single cycle of division of said frequency division means, said incremented start state being incremented by M states from the counter nominal start state, thereby providing a phase change of (M/N) 360 degrees.
A modulator for modulating an RF signal with fixed frequency modulation with step changes of phase, comprising:
- a modulating circuit for modulating said RF signal with a modulating signal;
- and
- a signal generator for generating said modulating signal, said generator including:
- (a) means for providing a constant frequency signal;
- and
- (b) means for shifting the phase of said constant frequency signal by a sequence of discrete phase changes to produce said modulating signal, said means for shifting the phase including a band pass filter centered at said constant frequency.
Dependencies are inferred from the claim text.