Jia Yuan Yin

A circularly polarized (CP) beam-scanning leaky wave antenna (LWA) based on a slow-wave substrate integrated waveguide (SW-SIW) is presented in this paper. The SW effect is realized by introducing a spoof surface plasmon polariton (SSPP), excited by periodic etched 45° tilted slots on the top metallic layer of an SIW. With extra delta modulation, the electromagnetic waves radiate through the etched slots and scan continuously from a backward to forward direction as the frequency changes. Taking advantage of the tilted slots and relative displacement between the upper and lower slots, the direction of the electric field of the radiated waves and phase difference between them are adjustable, making a CP characteristic available. Both the simulated and measured results show the proposed LWA exhibits good performance. The total scanning angle reaches 70°, and the average gain is 8.9 dBi from 9.5 GHz to 11.7 GHz. The CP characteristic is verified through the axial ratio of less than 3 during the operating frequency range. A simple structure, compact size, and good performance make the proposed design promising for a compact wireless communication system.

Glide symmetry transmission line (TL) is a highly symmetric TL with characteristics such as reduced frequency dispersion and merged passband. The dispersion characteristics and field distribution of single-layer and double-layer spoof surface plasmon polaritons (SSPPs) unit with glide symmetry are studied in this paper. It is found that the double layer structure with stronger slow wave effect is more suitable for frequency scanning radiation with higher scanning rates. Thus, T-shaped glide symmetric double-layer unit is proposed. Such unit exhibits stronger field confinement and higher degrees of freedom in modulating dispersion characteristics. Besides the basic transmission characteristic, additional radiation characteristic based on such T-shaped glide symmetric double-layer units performs well with continuously beam scanning in a large frequency and angle range. Experimental results agree well with numerical simulations, demonstrating the superior performance of T-shaped glide symmetric double-layer SSPPs. The radiation method of such T-shaped glide symmetric double layer SSPPs can be applied to antenna design, which is conductive to the development of highly compact plasmonic integrated circuits and systems.

A differentially-fed dual-circularly polarized (CP) antenna using slow-wave delay lines is investigated in this communication. The antenna consists of two pairs of dipoles, one of which is fed by slow-wave feedlines and the other is fed by coplanar striplines (CPS). Based on the slow-wave effect, 90-degree phase difference can be realized between the two pairs of dipoles. To achieve dual-CP operation, two orthogonally placed differentially-fed baluns are employed to drive the feedlines. Subsequently, four parasitic loops are introduced, aiming to obtain high isolation over a wide operation band. Meanwhile, a metal reflector is loaded for unidirectional radiation. Finally, a prototype of the proposed antenna is fabricated and tested. The measurements indicate that the dual-CP antenna realized a port isolation of 38.4% (1.43–2.11 GHz) for |Sdd21| < -15 dB. Further, the measured -10 dB reflection coefficients bandwidth for the two ports is 1.36–2.40 GHz. Moreover, the dual-CP 3-dB axial ratio (AR) bandwidth is approximately 50.0% from 1.41 to 2.35 GHz. Owing to differential excitation, stable radiation patterns are obtained.

A filtering magnetoelectronic dipole antenna (MEDA) with quasi-elliptic gain response and wide operating band is investigated. Different from the conventional MEDA, the antenna studied here is fed by fork-shaped microstrip line aperture-coupled excitation. The intrinsic radiation null of the MEDA at the lower passband edge is utilized, and a mathematical model is firstly put forward to demonstrate its working mechanism. Four driven stubs connected to the shorted walls of MEDA are used to excite the planar dipole arms. The parasitic inductor and the coupling capacitor introduced by driven stubs form an equivalent low-pass filter network, leading to a radiation null at higher frequency. Furthermore, a third radiation null is generated by introducing two quarter-wavelength U-shaped shorted stubs to improve the out-of-band suppression. Besides, due to the introduction of multiple coupling structure, including the fork-shaped microstrip line coupling slot and driven stubs, a wide operating band can be realized while maintains a low profile of 0.15 wavelength. Experimental results show that an impedance bandwidth of 53.5% (2.95 to 5.1 GHz) is achieved and an out-of-band suppression level higher than 17.9 dB is obtained. What’s more, an average gain of 8 dBi and good radiation patterns are realized over the whole operating band.

We present a novel method to design a conventional Fabry-Perot (F-P) antenna but with low scattering. Combining a coding metasurface and an F-P antenna together could effectively reduce the scattering and keep high gain simultaneously. The coding element consists of two layers of square metallic patches printed on both sides of a dielectric substrate. The bottom metallic patch helps form a partially reflecting surface (PRS) for the F-P antenna, while the upper metallic patch is utilized to construct the coding metasurface with an optimized coding sequence, aiming to reduce the scattering of the F-P antenna by redirecting electromagnetic energies in all directions. Based on the specially designed coding metasurface, a good scattering reduction without degrading the radiation performance of the F-P antenna is achieved. Both simulated and experimental results demonstrate the excellent performance of the proposed antenna, with a peak measured gain of 19.8 dBi and a significant scattering reduction in the frequency range of 8-12 GHz.

Frequency-controlled broadband and broad-angle beam scanning is proposed using a circular-patch array fed by planar spoof surface plasmon polaritons (SPPs). Here, a row of circularly metallic patches is placed near an ultrathin planar spoof SPP waveguide. When the SPP wave is transmitted through the waveguide, the circular patches are fed at the same time. Because of the phase difference fed to the patches, the proposed structure can realize wide-angle beam scanning from backward direction to forward direction as the frequency changes, breaking the limit of traditional leaky-wave antennas. Both numerical simulations and measured results demonstrate good performance of the proposed structure. It is shown that the scanning angle can reach 55° with an average gain level of 9.8 dBi. The proposed frequency scanning patch array is of great value in planar integrated communication systems.