Nonlinear Heterodyne Detection

摘要: Conventional heterodyne detection is useful in a number of configurations, including the scattered or reflected radiation from moving target (Doppler radar), communications, spectroscopy, and radiometry. Its use has been demonstrated many regions electromagnetic spectrum radiowave, microwave, infrared, optical. advantages as technique are well known: high sensitivity, frequency selectivity, strong directivity. For radar applications, it provides major method recovering desired signals removing clutter. The significant improvement sensitivity that over direct arises knowledge Doppler (also called intermediate (IF)) which permits narrow receiver bandwidth centered about IF. In such obtaining reasonably signal-to-noise ratio (SNR) requires 1) good velocity source target, 2) stable yet tunable local oscillator, 3) presents minimum broadening 4) at least several photons per measurement interval. These conditions frequently not adhered to by actual systems, particularly infrared optical, giving rise capabilities below optimum. this chapter, we study performance requirements alternative configurations. particular, consider two basic systems intrinsically nonlinear, first virtue multiple-quantum process itself, second mixing configuration electronics following detector.