Three-Frequency Nonlinear Heterodyne Detection. 1: cw Radar and Analog Communications

摘要: Though heterodyne detection provides a valuable technique for detecting small signals, the conventional system has several inherent disadvantages. In applications such as communications and radar, obtaining reasonably high signal-to-noise ratio (SNR) requires (1) good knowledge of velocity transmitter or target, (2) stable yet tunable local oscillator, (3) target source that presents minimum frequency broadening. These conditions are frequently not adhered to by real systems, particularly in ir optical, giving rise capabilities far below optimum. Calculations presented use operation three-frequency nonlinear eliminates many stringent required detection, while maintaining its near-ideal SNR. The technique, which is similar principle radiometry, makes two-frequency second detector useful signal acquisition; signals unknown Doppler shift, fact, performance generally superior system. Although primary emphasis on optical because large shifts encountered there, application microwave radiowave also discussed. For cw radar analog communications, SNR, power spectral density (PSD), detectable (MDP) obtained compared with standard configuration. Both sinewave Gaussian input treated. A variety specific cases discussed including optimum case, typical AM FM case. Evaluation pulsed digital (both absence presence lognormal atmospheric channel) reserved Part 2 this paper [Appl. Opt. 14, 680 (1975)].