Ultra-wideband Passive radars Fundamental Theory and Applications

Abstract

Passive radars are such radars that record and process signals of the objects own radiation within the radio wave band. They are used to solve a wide range of remote sensing problems. The observations registered by such radars are a mixture of stochastic signals of the investigated and interfering objects, as well as the internal noise of the receiver. Signals and noise are completely random, and their statistical characteristics are the same. Another feature of the transmitting radio thermal signals is that their emission spectrum is ultra-wideband (UWB) (except for polyatomic gases, which are characterized by discrete absorption and emission lines). Therefore, it is expedient to provide wide- or UWB for the passive radars operating frequencies band. Transition to UWB signal processing requires the improvement of the passive UWB radars theory. This theory should be able to synthesize new algorithms for signal processing and reveal the physical essence of parameter estimates at the output of the radar. This will allow solving the inverse problems of estimating the parameters and characteristics of the objects. Results of many years of research are summarized in this paper, a logical connection is formed between the key elements of the microwave radiation theory, the mathematical apparatus for processing UWB signals and the fundamentals of the optimal signal processing algorithms synthesis. Examples of the signal processing algorithm synthesis in a single- and a multichannel passive radar are also given.