Abstract
The use of passive radar for detection of targets of different type has gained considerable popularity in past few years. This radar uses the so-called the "signals of the opportunities" which are already in the environment. These opportunistic signals can be of different types, both in terms of frequency and modulation type. Therefore, instead of designing a separate hardware receiving system, a better approach will be design a single software defined receiver having capability to capture any signal of interest by just changing antenna system. Also to obtain various signals of interests, a multi-channel receiver system is desired so that advance array processing algorithms like digital beamforming can be utilized. Therefore, a state of the art software defined, multi-band, and a multi-channel passive radar system has been designed and being tested. One important step in the processing of signals for final target detection is the cancelation of direct path signal coming from main transmitter. Usually this is done by a combination of digital beamforming and adaptive filters based interference cancelation algorithms. An improved digital beamformer is designed with complete control of side-lobes to suppress the direct path signal. Also improved interference cancelation is done by using a cascade (two-stage) of adaptive filters. By using the combination of these techniques it will be shown that a considerable weak target can be detected.