Transmit beampattern design for coherent FDA by piecewise LFM waveform.

• We quantitatively derive the relationship between spatial angle and frequency points. The transmit beampattern design problem can be transformed into the simple spectral shaping issue in coherent FDA. • We devise the piecewise LFM waveform to synthesize the desired beampattern. It enjoys the advantage of constant modulus, reduced computation complexity and low sidelobe level. • We derive the transmit beampattern response and the multi-dimensional ambiguity function to evaluate relevant properties in range and angle domain. In transmit beampattern design, it is desirable to maximize the power around locations of interest. Multiple-input multiple-output (MIMO) radar transmits orthogonal waveforms, which is hardly achievable in practical applications. Moreover, the constant modulus constraint and the computational burden limit the system performance. In this paper, we propose an effective piecewise linear frequency modulation (PLFM) waveform for coherent frequency diverse array (FDA) radar to synthesize the desired transmit beampattern. By deriving the relationship between the beam direction and the transmit signal frequency, we find that different sub-band of transmitted signal corresponds to different angular sector. With the relationship between frequency band and mainlobe of beampattern, the beampattern synthesis is transformed into the design of waveform spectrum which is realized by designing the PLFM waveform in this paper. Compared with the state-of-the-art technique, the proposed PLFM waveform in coherent FDA enjoys the advantage of the constant modulus, low sidelobe level and reduced computation complexity. In addition, the multi-dimensional ambiguity function and the transmit beampattern response are derived to examine the properties. Numerical results are presented to validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]