ANGLE DISCRIMINATION RADAR RECEIVING SYSTEM HAVING SUBSTANTIAL SIDE LOBE CANCELLATION

• US 3,568,193 A
• Filed: 11/29/1967
• Issued: 03/02/1971
• Est. Priority Date: 11/29/1967
• Status: Expired due to Term

• Current Assignee: David K. Barton, Eric W. Beasley
• Original Assignee: David K. Barton, Eric W. Beasley
• Inventors: Barton, David K., Beasley, Eric W.
• Application Number:
  US04/686,678
• Time in Patent Office: 1,189 Days
• US Class Current: 342/156
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: H01Q 3/2617 Array of identical elements

Abstract

The receiving system comprises an antenna array of m elements spaced at discrete points for obtaining Shannon samples over an arc of an incident signal phase front, the arc center being taken at the antenna array. The phase front signals from the m elements are distributed onto n reception channels, n being less than m. Each phase front signal present in a given rank ordering of reception channels is multiplied by a sampling signal. This multiplication results in a time domain weighted analogue of the received signal space of the phase front along the arc. A summing network extracts the angle of incidence information from the time domain weighted analogue signal.

Claims

1. An angle discriminating radar receiving system comprising:

an antenna array of m elements spaced at discrete points for obtaining Shannon samples over an arc of an incident signal phase front, the arc center being taken at the antenna;

n reception channels, n being less than m ;

means for distributing the phase front signals from the m antenna elements onto the n reception channels;

a source of sampling signals;

means for successively modulating each phase front signal present in a given order of reception channels by a sampling signal; and

a summing network for extracting target radar signal and corresponding angle of incidence information from the successively modulated phase front signals.

2. An angle discriminating radar receiving system according to claim 1, characterized in that the arc of incident signal phase fronts subtends the elevation angles.

3. An angle discriminating radar receiving system according to claim 1, characterized in that the successively modulated phase front signals represent a time Domain analogue of the incident phase front signals distributed as a function of angle.

4. An angle discriminating radar receiving system comprising:

an antenna having an arbitrary aperture illumination function and beam patterns approximating the form (sin theta )/ theta , where theta is any angle intersecting an arc of an incident signal phase front, the arc center being taken at the antenna;

a plurality of reception channels;

means for distributing the antenna signals as a function of the angle theta among the reception channels;

a source of sampling signals, each signal being a function in time t approximating the from (sinkt)/kt where k is a constant coefficient and the function exhibits a minimal negative excursion;

means for sequentially multiplying the antenna signals present at a given rank ordering of reception channels by each sampling signal; and

a summing network for extracting target radar signal and corresponding angle of incidence information from the sequentially multiplied antenna signals.

5. An angle discriminating radar receiving system comprising:

an antenna array of m elements generating beams spaced at discrete angles theta constituting a Shannon sample of an arc of an incident phase front having its center at the antenna array, the antenna array having an arbitrary aperture illumination and beam patterns approximating the form (sin theta )/ theta ;

n reception channels, n being less than m;

means for distributing the phase front signals from the m elements onto the n reception channels;

a source of sampling signals, each signal being a function in time t approximating the form (sinkt)/kt , where k is a constant coefficient and the function further exhibiting minimal negative excursion;

means for sequentially multiplying each phase front signal present in a given order of reception channels by the sampling signal; and

a summing network for extracting target radar signal and corresponding angle of incidence information from the sequentially multiplied phase front signals.

6. An angle discriminating radar receiving system according to claim 5, characterized in that:

the antenna array comprises a planar array of linear conducting elements;

the means for distributing the phase front signals comprises n pickup horns; and

a metal lens interposed between the planar array and the pickup horns for focusing phase front signals incident upon the array into beams upon each of the respective pickup horns.

7. An angle discriminating radar receiving system according to claim 5, characterized in that each reception channel comprises:

a wide band radiofrequency amplifier responsive to distributed phase front signals for providing isolation and gain; and

a heterodyne mixer terminating the radiofrequency amplifier for translating the phase front signal to the lower intermediate frequency range.

8. An angle discriminating radar receiving system according to claim 5, characterized in that the means for sequentially multiplying each phase front signal comprises a wide band intermediate frequency balanced modulator intercoupling each reception channel and the source of sampling signals to the summing network.

9. An angle discriminating radar receiving system according to claim 5, characterized in that the source of sampling signals comprises:

a sampling waveform trigger generator synchronized by a signal at the radar repetition rate for generating pulses at a frequency of Delta f;

a filter arrangement responsive to the trigger pulses for shaping said pulses into the desired sampling waveform; and

a delay line having a delay equal to (1/ Delta f) with n taps spaced equally apart, the delay line being responsive to the filter arrangement output signal for providing n time displaced sampling waveforms.

10. An angle discriminating radar receiving system comprising:

a planar array of m antenna elements spaced at discrete points over an arc of an incident signal phase front, the arc center being taken at the array;

n pickup horns spaced apart and located at a distance from the planar array;

a beam-forming lens for focusing upon the pickup horns the phase front incident upon the planar array;

n heterodyne mixers terminating in corresponding pickup horns for translating the phase front signals to the intermediate frequency range;

a sampling waveform generator with each sampling signal being a function in time t approximating the form (sinkt)/kt, where k is a constant coefficient and the function further exhibits a minimal negative excursion, the waveform generator providing n time displaced sampling waveforms;

n wide band balanced modulators, each modulator terminating a corresponding heterodyne mixer and responsive to a distinct one of the n time displaced sampling waveforms; and

a resistive adder terminating respective ones of the balanced modulators.