Quadratic detectors for noise-immune detection of modulated signals

Quadratic detectors have been shown to have good frequency selectivity, short transient response, and effective noise suppression. We demonstrate how phase shifts in phase-shift-keyed signals are easily detected even in strong background noise, and how short-duration frequency variation can be accurately evaluated. Moreover design constraints of quadratic detectors are discussed and trade-offs are presented. Our simulations showed that the quadratic detector provides a simple method for the detection of phase shifts and frequency shifts in clean or noisy environments. These detectors and the design technique also have general signal processing applications.<>