Abstract: A method and apparatus for hybrid analog-digital pulse compression, as well as, a method of use and manufacture includes an analog intermediate frequency filter, a converter, and a digital correlator. The analog intermediate frequency filter filters and weights returned echo signals, and the digital correlator compresses the filtered and weighted echo signals. The frequency or impulse response of the digital correlator is set based on the frequency or impulse response of the analog intermediate frequency filter to obtain a pulse compressor with minimal mismatch loss and improved sidelobe suppression. The invention provides for the lowest possible sampling rate of analog-to-digital convertors used with the apparatus; thus, minimizing the cost of this device and all subsequent digital processing.

Abstract: An enhanced performance Mode S interrogator that includes a matched channel receiver. The receiver includes equiripple-phase response filters with finite peaks of attenuation. This new class of filters provides a faster rise of attenuation than all-pole filter while extending the equiripple delay further into the stopband.

Abstract: A tunable narrow-band filter is described incorporating a phase-locked loop that includes a phase detector, amplifier, loop filter, and voltage controlled oscillator wherein the loop filter transfer function is derived or extracted from the desired closed-loop transfer function that is of order n=3 or greater. The loop filter may furthermore have finite transmission zeros or peak attenuation at specific frequencies close to the passband which also appear in the characteristics of the narrow-band filter.The invention overcomes the problem of providing peak attenuation close to the passband of an electronically tunable narrow-band filter.

Abstract: An intermediate-band, low-transient crystal filter utilizing standard components. The filter is characterized by improved response and temperature stability and a size which is smaller than presently used LC filters, helical filters and wide-band crystal filters. This is achieved by an unusual partitioning of a low-pass prototype ladder network which yields a cascade of symmetric lattice sections and, hence, a realizable crystal filter. The cascade is composed of only two fundamental sections.