{'fraction_non_alphanumeric': 0.02848575712143928, 'fraction_numerical': 0.010494752623688156, 'mean_word_length': 5.068181818181818, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Small-Size Shielded Metallic Stacked Fabry–Perot Cavity Antennas With Large Bandwidth for Space Applications

New configurations of small-size shielded metallic Fabry-Perot (FP) antennas with improved performance over a large frequency band are presented in S-band for space missions. The bandwidth enlargement is obtained by stacking two FP cavities of different size, each of them presenting a low quality factor. Their radiating apertures measure around λ0 and 2 × λ0, respectively. Concentric corrugations are also introduced between both cavities to control the higher-order modes that are excited systematically in shielded small-size FP antennas due to lateral resonances. The obtained results are compared to those of a single-stage FP cavity antenna with the same aperture size. Several prototypes have been fabricated and measured. An aperture efficiency higher than 70%, a reflection coefficient smaller than -15 dB, and sidelobe levels lower than -20 dB have been obtained experimentally, over a wide frequency band (2.4-2.66 GHz). These characteristics make stacked FP cavity antennas very attractive to replace global coverage horn antennas, or to be used in feed clusters of multiple-beam antennas, especially in C- and S-bands, where they lead to more compact and less bulky solutions compared to classical feed horns.