Consequently, the purpose of this paper is to compensate this space-variant selleckchem JQ1 phase error.With respect to the azimuth dimension, Pacritinib clinical trial high resolution is obtained by coherent integration over a large aperture. The generally linear radar flight trajectory assumption, which is the basis of frequency domain image formation algorithm, is deviated, especially when nonplanar motion (NPM) occurs. Polar format algorithm (PFA) [7-8] is a popular high resolution spotlight SAR algorithm Inhibitors,Modulators,Libraries due to its efficient NPM compensation capability. However, due to the planar wavefront approximations made in PFA, the data exhibits space-variant phase errors and migration errors, which limit the focused scene size. Then, subaperture algorithm [9] is proposed.
Due to its space-variant phase correction capability, fine resolution imaging of large scene becomes available.
In Inhibitors,Modulators,Libraries this paper, a new image formation algorithm which incorporates the synthetic bandwidth technique with subaperture processing is proposed. Instead of traditional pulse synthesis preprocessing, it integrates the pulse synthesis into range subaperture processing. Meanwhile, it is able to compensate the space-variant Inhibitors,Modulators,Libraries phase errors caused by the radar motion during the pulse cluster.2.?SAR Signal Inhibitors,Modulators,Libraries ModelingConsider Inhibitors,Modulators,Libraries a spotlight SAR operating in the geometry of Figure 1, for simplicity, we only examine the case in which the sensor travels in a straight line at constant velocity. The central point of the scene is defined as the origin of the coordinate system, and radar Inhibitors,Modulators,Libraries antenna phase center (APC) is identified by coordinates (x, y, z).
The variable ��n and Inhibitors,Modulators,Libraries n are the APC’s instantaneous squint angle and grazing angle, respectively, at the nth Anacetrapib LFM pulse. They equal ��0 and 0 at the center of the aperture. The distance from the APC to the scene center is rcn. In this paper, we account for the broadside mode only, then ��0 = 0. A target scatter is located at (sx, sy, 0), and the range from APC to this Inhibitors,Modulators,Libraries target is measured by rsn. After performing dechirp and residual video phase (RVP) elimination on the echo signal of the nth pulse, we can express the Doppler phase history as [7]f(n,i)=expj4��c(f0+��Tsi)R��(1)where R�� = (rcn?rsn) is the differential range, c is the velocity of light, f0 is the carrier frequency of the transmitted signal, �� is the chirp rate, Ts is the sample interval in fast time, Dacomitinib i is the range sample index with ?I/2��i�� I/2 ? 1, and n is the index value of pulse number with ?N/2 �� n �� N/2 ?1.
Figure 1.SAR geometry.The http://www.selleckchem.com/products/Bosutinib.html differential range ruxolitinib structure R�� can be expressed as [7]R��=sxcos��nsin��n?sycos��ncos��n+re=cos��ncos��n(sxtan��n?sy+��(n))(2)where ��(n)=recos��ncos��n, which is caused by the assumption of planar wavefront. By using the Taylor expansion, ��(n) can be expressed as �� (n) �� ��0 + ��1n + ��2n2 when the cubic and higher order terms are ignored. Since the coefficients of this polynomial are dependent on the target position, this error is space-variant.