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A novel windmill‐shaped metasurface (MTS) structure is firstly presented and applied to realise broadband antennas with stable radiation patterns. Different from conventional square MTS structure, the proposed windmill‐shaped MTS structure is formed by etching several triangular sawtooth slots instead of rectangular slots on the radiating square patch. Through the characteristic mode analysis, it can be found that the proposed MTS structure exhibits a much stable broadside radiation within a large bandwidth of 45.9%. Besides, the tapered edges resulted from the sawtooth slots can be regarded as smoother transitions, which would bring a better impedance matching. Based on above analysis, two antennas with different aperture sizes using the proposed windmill‐shaped MTS are well designed accordingly. Both antennas demonstrate the capability to achieve large impedance bandwidths over 40% and stable radiations (2‐dB gain bandwidth >33%). Compared with the conventional MTS‐based antenna, these proposed antennas improve the bandwidth and radiation performances effectively, showing great promises for modern wireless communication systems. [ABSTRACT FROM AUTHOR]

A novel 24 GHz circularly polarised metasurface rectenna for wireless power transmission is designed in this study. Based on experimental measurements and retro‐simulation, an effective approach is proposed to extract the parasitic parameters of a Schottky diode. A highly efficient millimetre wave rectifier with a measured efficiency of 63% is constructed based on the exact equivalent circuit parameters of a diode. A circularly polarised metasurface antenna is adopted as the receiving antenna, and the gain is enhanced by introducing metal vias around the metasurface. The antenna and the rectifier are connected directly via a microstrip line. Measurements show that the metasurface antenna has a gain of 11.3 dBic and an axial ratio of 2.5 dB at 24 GHz. The measured conversion efficiency of the rectenna reaches 63% at 300 Ω load when the input power is 15.2 dBm. The rectenna has the advantages of low profile, which can be conformal to the electrical equipment. [ABSTRACT FROM AUTHOR]

This study proposes a compact structure of the three‐way Gysel power divider with arbitrary power dividing ratio, which has a significant difference from existing N‐way ones with a common node in the centre of the circuit. First, existing equations are reviewed, and new analytical closed‐form equations are derived according to the proposed structure. The frequency bandwidths, affected by the parameters of isolation networks are investigated in detail and optimised for performance balance. For verification, the proposed three‐way Gysel power dividers are calculated, optimised and fabricated at the centre frequency of 3.5GHz with different dividing ratios of 1:1:1 and 1:2:3, respectively. Moreover, the equations are derived to design the N‐way Gysel power divider. [ABSTRACT FROM AUTHOR]

This study develops a differential‐fed filtering patch antenna, which features superior frequency selectivity, compact size, low cross‐polarisation, and symmetrical radiation patterns. The proposed antenna consists of a rectangular patch on the top layer, which is differentially fed by a balun bandpass filter on the bottom layer. A pair of rectangular coupling slots were etched on the middle layer for energy coupling. The patch antenna performs not only as the radiator but also as the last resonator of the whole filter circuit for compactness. A prototype of the proposed filtering antenna operating at 2.45 GHz was fabricated and tested. The measured in‐band peak gain is 5.9 dBi with steep roll‐off at band edges, and the out‐of‐band gain is less than − 25 dBi. Moreover, symmetrical radiation patterns and low cross‐polarisation levels of − 22 dB are also realised for the proposed filtering antenna. [ABSTRACT FROM AUTHOR]

Two compact dual-wideband bandstop filters based on open-coupled lines and transversal signal-interaction concepts are proposed in this study. Two transmission paths with a half-wavelength open stub and two open-coupled lines are used to realise two wide stopbands for WLAN bands. Second/third-order stopbands with transmission poles near each stopband can be easily achieved by the two transmission paths. Two planar dual-wideband bandstop filters with 10 dB fractional bandwidths of 40 and 18.2, 61 and 26.8% are designed and fabricated. The theoretical and measured results are in good agreement and show good in-band filtering performance and high selectivity. [ABSTRACT FROM AUTHOR]