A Cylindrical Conformal Miniaturised Element Frequency Selective Surface with Unusual Resonance for Electromagnetic Shielding

ABSTRACT This paper introduces a Miniaturised Element Frequency Selective Surface (MEFSS) with unusual resonance characteristics that the longer loop determines the higher‐frequency resonance, whereas the short loop supports the lower‐frequency resonance, which provides electromagnetic shielding for the high‐sensitivity Intermediate‐Frequency (IF) receiver on the remote‐sensing module of a radiometer and is transparent at the data‐link frequency of 5.8 GHz. The MEFSS isolates the signals at 2.4 and 3.5 GHz, avoiding the crosstalk with IF signal. The longer metallic strip increases the equivalent inductance and improves resonance stability, as illustrated by an equivalent circuit model based on the field distribution. The planar and curved prototypes are fabricated and tested. The transmission coefficients of the planar Frequency Selective Surface (FSS) at different incident angles agree well with the simulation. In the test, MEFSS exceeds 17.3 dB in average shielding performance under normal incidence in two stopbands for both polarisations, with a maximum insertion loss of less than 1 dB over an incident angle range of 0°–70° in passband. The far‐field patterns, gains, and insertion losses of conformal MEFSS are measured in Compact Antenna Test Range (CATR). The far‐field patterns are consistent with the simulations. The measured insertion losses of conformal MEFSS in the passband are 0.60 and 0.47 dB under TE and TM polarisations.