Coherence Performance Analysis On Distributed Radar

As the next generation of novel radar system,distributed coherent radar aims to use sub-unit radars located at different positions in space to carry out coherent processing of radar signals to improve the signal-to-noise ratio of radar.Compared with a single sub-unit radar,distributed full coherent radar can obtainN^?18?signal-to-noise ratio gain without designing large aperture radar system with complex structure and high cost,where N is the number of sub-unit radars,thus it now becomes the popular research of radar technology.In this thesis,coherent performance of distributed radar operating in narrow-band and broad-band modes is analyzed.The specific work is as follows:1.For narrow-band distributed receiving radar system,taking the distributed radar scene of"one transmitter and two receivers"as an example,the narrow-band receiving coherent gain is defined based on electromagnetic scattering mechanism.Secondly,by expanding the incident and scattering plane waves into the sum of Bessel series,the expression of scattering electric field?E-field?with respect to the mode scattering response matrix of a target is obtained.Thirdly,under the condition of small scattering angular interval,by expanding the exponential function into the sum of Taylor series,theoretical analysis of scattering angular interval based on narrow-band receiving coherent gain is presented.Fourthly,the conversion model from plane coordinate system with scattering angle to geodetic coordinate system is established.Then,simulation experiments of narrow-band receiving coherent gain with respect to scattering angular interval are analyzed from three aspects:?1?for targets of random shapes with random incident angles and random scattering angles,when mode scattering response matrix of targets,incident angles and scattering angles are assumed random variables,statistical characteristics of narrow-band receiving coherent gain varying with scattering angular interval are analyzed;?2?for a given target with the given incident angle and given scattering angle,the variation of narrow-band receiving coherent gain with respect to the scattering angular interval is analyzed,and under the condition of the given scattering angular interval,narrow-band receiving coherent gain with respect to incident angle,scattering angle and frequency is analyzed.?3?for a given target with random incident angles and random scattering angles,assuming incident angle and scattering angles are random variables,statistical characteristics of narrow-band receiving coherent gain with respect to scattering angular interval are analyzed.Finally,the spatial distribution range of receiving sub-unit radar is given when a certain coherent gain is satisfied.2.For broad-band distributed radar,taking the scene of"one transmitter and two receivers"as an example,coherent performance of distributed radar in frequency domain is analyzed firstly.Then,in order to analyze coherent performance of distributed radar in broad-band mode,broad-band receiving coherent gain is defined.Similar to the analysis of coherent performance in narrow-band mode,the simulation of broad-band receiving coherent gain with respect to scattering angular interval is also analyzed from three aspects.Then,the spatial range of broad-band distributed radar is given when a certain coherent gain is satisfied.3.The coherent condition and coherent performance of narrow-band and broad-band distributed radar are compared and analyzed.The results show that receiving coherent gain of distributed radar is sensitive to the changes of scattering angular interval and frequency.Therefore,choosing a suitable scattering angular interval in the low frequency band will ensure a high coherent gain of distributed radar.At the same time,comparing narrow-band receiving coherent gain with broad-band receiving coherent gain,it can be seen that under the same condition of coherent processing,coherent performance of broad-band distributed radar will be better than that of narrow-band distributed radar;under the same condition of coherent gain,the spatial range of broad-band distributed radar will be greater than that of narrow-band distributed radar.