Range resolution improvement in passive bistatic radars using deconvolution
Author
Arslan, Musa Tunç
Advisor
Çetin, A. Enis
Date
2015-11Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Passive radar (PR) systems attract interests in radar community due to its lower
cost and power consumption over conventional radars. However, one of the main
disadvantages of a PR system is its low range resolution. The reason for this
is, the range resolution depends on the bandwidth of the transmitted waveform
and in a PR scenario, it is impossible to change transmitted waveform properties
of a commercial broadcast. In this thesis, a post processing scheme is proposed
to improve the range resolution of an FM broadcast based PR system. In the
post processing scheme, the output of the ambiguity function is re-expressed as
convolution of the autocorrelation of the transmitted signal and a channel impulse
response. Therefore, it is shown that it is possible to use deconvolution
methods to compute the channel impulse response using the output of the ambiguity
function and the autocorrelation of the transmitted signal. Thus, using
deconvolution to solve the channel impulse response provides an increase in the
range resolution of the PR system. The method successfully increases the target
separation distance and range resolution of a PR system using single FM channel
signal. The conventional ambiguity function is able to separate two targets when
the targets have about 17 km between each other where as the deconvolution
based post processing method can decrease this to about 10 km. The deconvolution
based post processing methods also decreases the side lobes around the
target when the system uses multi channel FM signals. For a scenario in which
three FM channels are employed, the highest side lobe is 1.2 dB below the main
target peak and after deconvolution, this highest side lobe decreases to about 10
dB below the main target peak.