As a selleckbio result, their implementations on those traditional in-service stepped-frequency radars were restrained.A new motion compensation algorithm, selleck chemical based on the maximum likelihood (ML) estimation, is provided in this paper. It will be shown that this algorithm can estimate the target’s radial velocity accurately and reconstruct the distorted HRRP successfully. Inhibitors,Modulators,Libraries Without altering the conventional waveforms, the new algorithm can be implemented on the in-service stepped-frequency radars.The remainder of this paper is organized as follows. Inhibitors,Modulators,Libraries In Section 2, the signal model of moving targets in stepped-frequency radar systems is formulated. In Section 3, the ML estimator of the radial velocity is derived.

Then, using the fast Fourier transforms to reduce the computational load, the new algorithm is proposed.

In Section Inhibitors,Modulators,Libraries 4, some numerical examples Inhibitors,Modulators,Libraries are given to demonstrate the performance of the proposed algorithm. Section 6 presents the conclusions drawn from this work.2.?Signal ModelA stepped-frequency Inhibitors,Modulators,Libraries pulse train is a series of pulses modulated with different carrier frequencies. The carrier frequency of the first pulse is fc and those of the rest N?1 subsequent pulses are fc+n��f, n=1,2,��,N?1, where N is the number of pulses and ��f is the frequency step size. Then, the nth transmitted Inhibitors,Modulators,Libraries pulse issn(t)=rect(t?nTrT)?ej2��(fc+n��f)t,n=0,1,��,N?1,(1)where rect(?) is the rectangular function, T is the pulse width, Tr is the pulse repetition interval (PRI) and the amplitude of the transmitted pulse is supposed to be 1.

Supposing that the target is an ideal point-like scatterer, and disregarding both the energy divergence on wave propagation paths and the variation of target’s reflection factor, the nth received Inhibitors,Modulators,Libraries pulse isrn(t)=��?rect(t?2(R0+VRnTr)/c?nTrT)?ej2��(fc+n��f)[t?2(R0+VRnTr)/c]+wn(t),(2)where Anacetrapib �� is the amplitude of the received signal, c is the speed of light, wn(t) is the additive noise, Inhibitors,Modulators,Libraries R0 and VR are the initial range and radial velocity of the target. As in most studies on the stepped-frequency waveforms, it is assumed that VR is constant in the whole coherent processing interval (CPI), Dacomitinib and the target range migration does not exceed cT/2, which is the rough resolution determined by a single pulse.

Each pulse is demodulated with its corresponding carrier frequency, thus the baseband signal of the nth pulse isxn(t)=��?rect(t?2(R0+VRnTr)/c?nTrT)?e?j4��(fc+n��f)(R0+VRnTr)/c+wn(t).

The sample of the received baseband www.selleckchem.com/products/Imatinib(STI571).html signal isxn=��?e?j4��(R0fc+R0��fn)/c?e?j4��(fcVRTrn+VRTr��fn2)/c+wn.(3)The first phase term of the right side of (3) is caused by the initial range of the target, and the second phase term VX-770 is the additional phase term caused by the radial velocity. When the target and the radar are relatively stationary, i.e., VR=0, one can use the IDFT to estimate the target’s range and to generate the HRRP.