{'fraction_non_alphanumeric': 0.04212299915754002, 'fraction_numerical': 0.037910699241786014, 'mean_word_length': 4.5, '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}}
A novel wideband reflectarray using sub-wavelength Archimedes spiral unit cell

ABSTRACT A novel wideband reflectarray antenna based on a sub-wavelength Archimedes spiral unit cell is proposed in this paper. The size of the unit cell is fixed to ( -the free space wavelength at 5.8 GHz), and the reflection phase variation can be obtained by changing the inward extension length of the arms. After the element simulation analysis, a smooth and almost linear reflection phase curve is achieved. The phase range can reach more than 500°, which is enough to meet the phase shift requirement of the reflectarray. Based on the proposed unit cell, a 10 × 10-element reflectarray with the size of 220 mm×220 mm is designed, fabricated, and measured. The measured result agrees well with the simulations, which show relatively wide 1- and 3-dB gain bandwidths of 20.7% (5.57–6.77 GHz) and 31.4% (5.31–7.13 GHz), respectively. The measured gain at its working frequency of 5.8 GHz is 18.9 dBi with an aperture efficiency of 34.2%. Furthermore, the cross-polarization levels of the proposed antenna are less than −25 dB, which attributes to all the elements that are arranged mirror symmetrically.