Cavity-Backed Broadband Microstrip Antenna Array for Photonic Beam Steering at W Band

Abstract

We present here the design of a broadband antenna array for photonic beam-steering at W-band. The array unit-cell consists of two stacked microstrip patches that are cavity backed, and fed by aperturecoupling using an hourglass slot. The unit-cell shows a simulated impedance bandwidth of 37% for SWR<2 from 77 GHz to 112 GHz, thus covering most of the W band. The feeding network is designed using a low-loss Substrate Integrated Waveguide (SIW) and respects nearly the same bandwidth as the unit cell for a total SWR<2. Therefore, the structure is well-suited for fabrication by PCB technology. The final array is composed of 4 sub-arrays of 2×8 unit cells and exhibits a broadside directivity of 26 dBi. Each sub-array is expected to be fed by a Uni-Traveling-Carrier (UTC) photodiode, which enables power combining to overcome the low emitted power at mm-waves and also the use of optical phase shifters in the antenna architecture to achieve a +/-5° beam steering with reasonable grating lobes.

Modulated metasurface array for photonic beam steering at W band

“…This transition can be used to feed multiple types of antenna structures, from single layer PCB to more complex stack-ups [6], [7]. It is designed on a 254um thick Astra® MT77 (εr = 3.0 ± 0.1, tanδ = 0.0015 ± 0.0005 up to 100 GHz).…”