Secondary radar digital monopulse receiving apparatus and method
First Claim
1. A digital monopulse radar receiving apparatus, comprising:
- first means for generating complex phasor components from radar frequency (RF) sum (Σ
) and difference (Δ
) signals received by an antenna from an aircraft including,first down conversion means for down converting the received sum and difference RF signals to a first relatively lower intermediate frequency,second down conversion means for down converting the received sum and difference RF signals at the first relatively lower intermediate frequency, to a second relatively lower intermediate frequency to permit conversion to digital form, andanalog to digital conversion (ADC) means for sampling the twice down converted sum and difference RF signals to generate digital signals; and
second means for determining an azimuth angle, indicating an angle of the detected aircraft in relation to a boresight of the antenna, from the digital signals including,demodulating means for demodulating the digital signals at an intermediate frequency derive from the twice down converted sum RF signal, to generate complex inphase and quadrature components at baseband, andmeans for generating the azimuth angle from the generated complex inphase and quadrature components.
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Abstract
A secondary radar uses monopulse reception techniques to improve the estimate of the aircraft position and to improve the reliability of the reply decoding process. Digital signal processing techniques are utilized to replace the analog circuit used in the prior implementations. The secondary radar implements monopulse processing using a half angle phase method wherein the sum and difference signals are encoded in a complete phasor. The detection of the signal and extraction of the azimuth angle data is implemented using a digital receiver concept. The complex phasor is sampled at an intermediate frequency, down converted to baseband and detected. The azimuth angle is computed using arithmetic methods implemented by digital signal processing circuitry.
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Citations
11 Claims
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1. A digital monopulse radar receiving apparatus, comprising:
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first means for generating complex phasor components from radar frequency (RF) sum (Σ
) and difference (Δ
) signals received by an antenna from an aircraft including,first down conversion means for down converting the received sum and difference RF signals to a first relatively lower intermediate frequency, second down conversion means for down converting the received sum and difference RF signals at the first relatively lower intermediate frequency, to a second relatively lower intermediate frequency to permit conversion to digital form, and analog to digital conversion (ADC) means for sampling the twice down converted sum and difference RF signals to generate digital signals; and second means for determining an azimuth angle, indicating an angle of the detected aircraft in relation to a boresight of the antenna, from the digital signals including, demodulating means for demodulating the digital signals at an intermediate frequency derive from the twice down converted sum RF signal, to generate complex inphase and quadrature components at baseband, and means for generating the azimuth angle from the generated complex inphase and quadrature components. - View Dependent Claims (2, 3, 4, 5)
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6. A digital monopulse radar receiving method, comprising the steps of:
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(a) down converting radar frequency (RF) sum (Σ
) and difference (Δ
) signals received by an antenna from an aircraft to a first relatively lower intermediate frequency;(b) down converting the received sum and difference RF signals at the first relatively lower intermediate frequency, to a second relatively lower intermediate frequency to permit conversion to digital form; (c) sampling the twice down converted sum and difference RF signals to generate digital signals representing complex phasor components of the received sum and difference signals; (d) demodulating the digital signals at an intermediate frequency derived from the twice down converted sum RF signal, to generate complex inphase and quadrature components at baseband; and (e) generating an azimuth angle, indicating an angle of the detected aircraft in relation to a boresight of the antenna, from the generated complex inphase and quadrature components. - View Dependent Claims (7, 8, 9, 10, 11)
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Specification