Novel Dual-Mode Retrodirective Array Using Synthesized Microstrip Lines

In this paper, an innovative architecture for realizing a dual-mode retrodirective array (RDA) is proposed and experimentally validated. The new design functions as a reflection-type RDA in one frequency band and features the characteristics of a Van Atta array in the other band. A unique 50-Ω synthesized microstrip line is applied to fulfill the core building blocks of this RDA, i.e., the dual-mode quadrature hybrids and crossovers. Both couplers show equivalent responses to their conventional counterparts in the low-frequency band, but enable direct-thru transmission properties in the high band. To validate this innovative architecture, a four-element dual-mode RDA is fabricated and experimentally verified. The measured bistatic radiation patterns provide supportive evidence to the dual-band self-steering capability of the proposed array. The circuit topologies, design approaches, system considerations, and simulated and measured results are investigated in detail throughout this paper. Suggestions to improve the system performance are discussed as well.