Low sidelobe interleaved transmit-receive antennas for FMCW radar applications

In this paper a design strategy for the reduction of the SLL of the antenna system is presented. The reduced SLL, below - 40 dB for the two-way radiation pattern, is obtained by firstly employing a statistical interleaving placement strategy on a uniform lattice yielding a quasi-50% partitioning of the aperture between the transmit and receive functions, and then by thinning the resulting arrays according to a Taylor illumination function. The array thinning implements a density taper of equally excited elements. The performance of the density tapering has been demonstrated to compare well with the amplitude tapering, while resulting in a much simpler implementation of the beam forming network and in a substantial reduction in the number of elements, this being a desired feature in modern array antennas for radar applications. The thinning strategy affects the antenna gain (about - 3dB), but it is extremely beneficial in terms of peak SLL reduction (between - 10 and - 15dB), this compromise being considered convenient and sustainable in FMCW radar systems for coastal surveillance applications.