Bandpass Frequency-Selective Surface With Stable Transmission Amplitude and Insertion Phase Delay

This article investigates the insertion phase delay (IPD) stability of bandpass frequency-selective surfaces (FSSs) to further enhance the signal transmission accuracy through radomes and proposes an IPD-stable FSS. The dual-square-slot and folded Jerusalem cross structures contributing to the IPD stability for TE and TM polarizations, respectively, are analyzed and designed. To improve the high-angle stability of the transmission amplitude, four identical square slots and folded Jerusalem cross cells are spliced by metallic strips, respectively. Then, stable transmission amplitude and IPD can be achieved by combining these two interconnected structures at the top and bottom layers of the substrate, respectively. Simulation results show that the proposed FSS achieves dual-polarized IPD stability at 15 GHz with a significantly improved IPD compared to a reference slab of 6.35 mm thickness, while maintaining the transmission amplitude stable under oblique incidence up to 70°. A prototype of the proposed interconnected FSS is fabricated, and measured results agree well with the simulated ones.