Low-loss bandpass antenna-filter-antenna arrays for applications in quasi-optical systems

A new type of 3-pole frequency selective surface (FSS) is proposed as a low-loss bandpass filter for quasi-optical applications. This FSS is realized as a uniform array of antenna-filter-antenna (AFA) elements. Each AFA element is a three layer structure consisting two slot antennas and a stripline resonator. A Chebyshev bandpass AFA with 9.5% bandwidth was designed for 32 GHz and fabricated on two layers of Teflon substrates (ε_r=2.2, tan δ=0.0009). The maximum measured in-band insertion loss for this design is <0.5 dB, which is limited by the in-band ripple of the Chebyshev response.