A compact passive retrodirective antenna array with SIW phase shifters integrated

A compact millimeter-wave passive retrodirective antenna (RDA) array with substrate integrated waveguide (SIW) phase shifters integrated is presented in this paper. The primary function of the passive RDA array is to enhance the monostatic radar cross section (RCS) of the metal plate. SIW phase shifters are utilized to realize the phase criterion of the passive RDA array instead of only changing the length of the transmission lines, resulting in a compact size and less scattering influence from the SIW structure. Alternating longitude SIW slots array antenna is adopted as radiation element and SIW transmission lines integrated with SIW phase shifters are used to form the feeding network. To validate the design method, a prototype passive RDA array with 8 radiation elements using the single-layer printed circuit board (PCB) process is designed and fabricated at 35 GHz. Experimental results agree well with simulation results, validating that the prototype RDA array can achieve an enhancement of more than 10 dB on the monostatic RCS compared to the metal plate with same size.