In-Band SCS Reduction of Microstrip Phased Array Based on Impedance Matching Network

A novel method to reduce in-band scattering cross section (SCS) of a phased array while maintaining high radiation performance is proposed in this paper, by using a special impedance matching network. The optimum load impedance curves of a phased array element are theoretically analyzed according to antenna scattering mechanism firstly, and they are approximated by an impedance matching network cascaded to the element afterwards. Then, an E-plane 1 × 32 linear microstrip array antenna operating in 8 ~ 10GHz is designed to validate the proposed idea, and a parallel RLC circuit is adopted to match the optimum element impedance curves in the operating band, whose R, L, C values are determined by minimum mean square error criterion. Practically, the RLC circuit is implemented simply by strip lines with open-circuited and short-circuited shunt stubs, as well as an impedance transformer. According to numerical and experimental studies, the proposed array antenna features an obvious in-band SCS reduction of typically above 6dB compared to its conventional counterpart without the impedance matching network, while maintaining high radiation, aperture efficiencies and reflection coefficient around -10dB.