Multi-Layer PCB Bow-Tie Antenna Array for (77–81) GHz Radar Applications

In this article, a new wideband cavity-backed bow-tie microstrip antenna is presented for short-range 77-81 GHz radar applications. The design is based on a subarray consisting of two single elements. Each element consists of a multilayer bow-tie patch antenna surrounded by a metallic cavity to suppress the surface waves and parallel plate modes. The subarray elements are fed through a laminated waveguide with 180° phase shift. An eight-layer build-up and a new advanced multilayer PCB technology, the so-called any-layer PCB technology, is used for the fabrication. The performance of this antenna has been verified by both simulations and measurements. A bandwidth of more than 8% is achieved. The gain is 7.9 dBi, and the radiation efficiency is 70% at 79 GHz. Beam widths of 84° in the E-plane and 48° in the H-plane are obtained, which are compatible with radar requirements for short-range applications.