Design and experimental verification of steerable reflect-arrays based on two-bit antenna-filter-antenna elements

This paper presents a novel beam-steerable reflectarray topology based on reflective type antenna-filter-antenna (AFA) unit cells. A two-bit phase control is realized by using multi-moded AFA elements with programmable 3-pole/4-pole bandpass frequency response. A switchable AFA element of this type is designed and verified using finite-element method simulations and used to demonstrate the proposed beam steering scheme. Four proof-of-concept reflect-arrays with fixed preconfigured AFA elements have been fabricated for output beams scanned at 0deg, 15deg, 30deg and 45deg in the H-plane. The measurement results show that up to plusmn45deg of scan is possible at 35 GHz with a scan loss of less than 2.3 dB and a sidelobe level of <-11.2 dB. The average insertion loss measures at 1.4 dB at the center frequency assuming ideal switches.