Abstract
This paper considers the design of a desired transmit beampattern under the good ambiguity function constraint using a correlated linear frequency modulation-phase coded (LFM-PC) waveform set in multiple-input-multiple-output (MIMO) radar. Different from most existing beampattern design approaches, we propose using the LFM-PC waveform set to conquer the challenging problem of synthesizing waveforms with constant-envelope and easy-generation properties, and, meanwhile, solve the hard constraint of a good ambiguity behaviour. First, the ambiguity function of the LFM-PC waveform set is derived, and the superiority of LFM-PC waveforms over LFM and PC waveforms is verified. The temporal and spatial characteristic analysis of the LFM-PC waveform set demonstrates that both the transmit beampattern and sidelobe level are mainly affected by the frequency intervals, bandwidths, and phase-coded sequences of the LFM-PC waveform set. Finally, the constrained beampattern design problem is formulated by optimizing these parameters for desired beampatterns and low sidelobes at different doppler frequencies, which is a bi-objective optimization problem. To solve this, we propose a joint optimization strategy followed by a mandatory optimization, where the sequence quadratic programming (SQP) algorithm and adaptive clonal selection (ACS) algorithm are exploited iteratively. The simulation results demonstrate the efficiency of our proposed method.
Highlights
A multiple-input-multiple-output (MIMO) radar has multiple transmit antennas to transmit multiple probing waveforms
Since we focus on the energy distribution on the θ-dimension in this paper, χ(τ, f d, θ ) can be turned into the transmit beampattern by setting τ = 0 and f d = 0, which describes the transmit power distribution in space
It is demonstrated that our synthesized transmit beampattern approaches the desired beampattern well, and the peak-to-sidelobe level (PSL) of angular waveforms within the predetermined doppler frequency range Fd reaches a low level at the first stage of optimization, which is below −16.28 dB
Summary
A multiple-input-multiple-output (MIMO) radar has multiple transmit antennas to transmit multiple probing waveforms. The method in [27] did not consider the range sidelobe level or the ambiguity function of the designed waveforms, while the method in [28] still suffered from the constraint of constant-envelope and easy-generation. We developed the transmit beampattern design problem with the constraint of the range sidelobe levels at different doppler frequencies by using the correlated LFM-PC waveforms. By optimally designing these three waveform parameters of the LFM-PC waveform set, the correlation properties of waveforms are controlled and adjusted, to match the desired beampattern with the constraints of range sidelobe levels at different doppler frequencies. We evaluate the performance of the proposed algorithm via numerical simulations in terms of the iteration process of optimization, synthesized transmit beampattern, range sidelobes, and the ambiguity function of designed waveforms.
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