Method and apparatus for reduction of the subpulses reciprocal intermodulation in a complex electromagnetic pulse

摘要

The invention relates to a method and an apparatus finding application in radar systems, in particular those generating and processing broadband radar pulses of constant amplitude with linear and nonlinear frequency modulation. A complex radar pulse consists of a number of subpulses of different carrier frequencies ’ C1 , ’ CN and in case of insufficient frequency separation the subpulses reciprocal intermodulation occurs limiting detection range and causing false detections. Method consists in determining the low-pass representation (4) of a plurality N of radar subpulse signals wherein each radar subpulse signal is processed simultaneously; and then in time-multiplexing (5); limiting (6) amplitude fluctuations; shifting (8) frequency spectrum into original carrier frequencies and band-pass filtering (9) of the complex radar pulse modified according to preceding steps. Determining the low-pass representations of a plurality N of radar subpulse signals further comprises steps of sharing radar subpulse signals processing channel into a plurality N of processing channels, mixing the subpulse signal with a heterodyne generator signal and eliminating undesired results of signal mixing and reducing frequency spectrum of subpulses. The step of shifting the frequency spectrum comprises steps of selecting an adequate carrier frequency waveform, reading from mass data storage means the selected carrier frequency waveform and mixing the carrier waveform signal with low-pass representation of a radar subpulse signal. The step of time-multiplexing, limiting amplitude fluctuations and shifting the frequency spectrum are performed sequentially under a supervision of control means, and repeated so many times as the number of subpulses.