Tracking receiver for broadband chirp emissions

Abstract

Abstract A tracking receiver is disclosed which utilizes optical processing for detecting and tracking input broadband chirp like emission signals. The tracking receiver includes a scanning local oscillator, the output signal of which is caused to be scanned in frequency. A mixer mixes the unknown input signal and the local oscillator output signal to produce an intermediate frequency (IF), frequency difference signal. The IF signal is analyzed in an optical spectrum analyzer which includes an acoustooptical modulator for modulating a beam of radiation, as a laser beam, with the intermediate frequency signal, and optical means, as a lens, for producing a spatial frequency distribution of the intermediate frequency spectrum in a Fourier plane. A photodetector array is provided in the Fourier plane for detecting the spatial spectrum. A processor processes the output of the photodetector for temporally stable grouped intensity patterns caused by an input spectra signal varying in frequency near the scan rate of the local oscillator. The processor is responsive thereto to control a programmer which controls the frequency of the local oscillator to cause it to approach and become equal to the frequency of the input spectra signal. A recorder is provided for recording the output of the scanning local oscillator, and the scanning local oscillator is controlled to proceed through a programmed frequency scan pattern.

Inventors

• 👤 Robert W. Brandstetter

Bibliographic Details