Effect of antenna peak sidelobe levels on L-band space-based GMTI radar performance

In this paper, we present simulation results that show the effect of the two-way peak sidelobe levels on the signal-to-interference-plus-noise ratio (SINR) loss curve, as a function of clutter-to-noise ratio, for a monostatic space-based ground moving target indicator (GMTI) radar operating at L-band in a low earth orbit. We perform space-time adaptive processing (STAP) using the joint domain localized (JDL) algorithm presented in H. Wang and L. Cai (1994) and examine the effect of two receive antenna weighting functions on the SINR loss curve: a) uniform weights, and b) Taylor array factor weights. When STAP is performed using the JDL algorithm, the number of required spatial degrees-of-freedom determine the number of beams that are formed. The large aperture antennas used in space-based radar (SBR) are often partitioned into subarrays, and JDL auxiliary beams are formed by steering the receive array factor. Steering the receive array factor gives a different peak sidelobe level for each beam. We show that when the transmit antenna is uniformly weighted, the two-way peak sidelobes which affect the SINR loss curve are due to the first few sidelobes of the transmit pattern. A uniformly weighted receives antenna results in a narrower mainlobe and, therefore, a narrower SINR loss notch. However, this comes at the expense of increased sidelobe clutter levels when operating in a strong clutter-to-noise environment. Simulations are used to show that the best receive antenna weighting scheme depends on the clutter environment in which the radar operates