In this communication, a millimeter-wave (MMW) pattern reconfigurable Vivaldi antenna utilizing graphene-based tunable resistor is proposed. First, a modified Vivaldi antenna with high front-to-back ratio is achieved by equal proportion slotting on the ground patch. Then, a pattern reconfigurable antenna consisting of a pair of back-to-back modified Vivaldi antennas with two graphene nanoplate pads symmetrically loaded on the feed line is proposed to realize dynamical manipulation of gain. By applying bias voltage from 0 to 4 V, the resistance of the graphene pad can be gradually reduced from 200 to 20Ω. Two slots located on the ground allow two graphene pads to be dc interruption for independent resistance control. By varying the resistance of two graphene pads, the radiation pattern of Vivaldi antenna can be manipulated from two opposite beams to a single beam. Finally, a prototype antenna centering at 30 GHz with a bandwidth of 16.6% is fabricated and measured, which realizes reconfigurable radiation beams at 90° and/or 270° with three states.

A double-layer wideband transmitarray antenna using two degrees of freedom elements is presented. The double-layer transmitarray antenna is composed of 441 elements. Each element includes four metal vias and two patches with two degrees of freedom (TDF) printed on both sides of the dielectric substrate. Four metal vias are used to achieve the maximum transmission magnitude and two patches with TDF are adopted to obtain a sufficiently large variation range of phase shift. A square transmittarray is designed, fabricated, and measured to validate the proposed design. Simulation and measurement results have good agreement. Experimental results show that the proposed antenna has high gain of 30.0 dBi at 21GHz, aperture efficiency of 40% and 1-dB gain bandwidth of 9.6% (20.1GHz-22.2GHz). The proposed double-layer transmittarray antenna greatly simplifies the design complexity and reduces the thickness, the mass, and the cost with respect to existing transmitarray antennas.

A wideband fourth-order filtering antenna consists of two substrate integrated waveguide (SIW) dual-mode cavities is presented in this letter. The first SIW cavity creates two resonant nodes and one radiation null (RN) located on the upper stopband. The second SIW cavity integrated with a slot cannot only achieve radiation function but also realize dual-mode resonance, which can produce another lower out-of-band RN. These two RNs can be controlled to improve frequency selectivity and design flexibility. The coupling matrix theory is adopted to guide the design of the filtering antenna, and the generation principle of these two RNs can be explained by cross coupling. Finally, such a filtering antenna operating at the center frequency of 5.4 GHz with a fractional bandwidth of 7.64% and a maximum gain of 5.3 dBi is fabricated and measured.

In this letter, a transparent ultra-wideband (UWB) halved coplanar Vivaldi antenna (HCVA) with metal mesh film (MMF) is proposed. Based on the equivalence principle, the halved type antenna is achieved by replacing a radiation fin with the ground plane. The proposed HCVA has the advantages of ultra-wideband impedance matching, miniaturized aperture size, high directivity, and simple feed structure. By employing MMF with a low sheet resistance of 0.35 Ω/sq and high optical transmittance above 72% in the radiation fin and ground plane, the antenna is entirely transparent. An example transparent HCVA is fabricated and measured. According to the simulated and measured results, most of the reflection coefficient is below -10 dB from 0.78 GHz to 20 GHz. Moreover, the peak realized gain reaches 10.4 dBi with the compact size of 0.32×0.47×0.052λL 3, where λL is the wavelength at the lowest operating frequency.

In this article, a novel class of dynamically tunable filtering attenuators with high selectivity and continuously tunable attenuation is proposed through the comprehensive design of graphene sandwiched structure (GSS), microstrip line, and half-mode substrate integrated waveguide (HMSIW). The GSSs are loaded on microstrip resonators to reduce the resonance intensity, which results in a valid attenuation in the passband. A co-design method of GSS, microstrip resonator, and HMSIW coupling structure based on the equivalent circuit model is proposed to minimize the impact of graphene on the selectivity of filtering attenuator. A transmission zero located on the upper band is also introduced to enhance the selectivity. By varying the bias voltage on GSSs, a controllable attenuation from 1.7 to 8.4 dB can be obtained over the operating bandwidth centering at 1.72 GHz while preserving good selectivity. It is worth mentioning that the out-of-band suppression of the proposed filtering attenuator is also reduced from 40 to 50 dB. Another tunable filtering attenuator based on microstrip short-ended resonators is also designed to verify the method. Finally, a prototype is fabricated and measured and the measured results are in good agreement with the simulation results.

In this communication, we propose glide-symmetric double-layer (D-L) spoof surface plasmon polaritons (SSPPs) structures for controlling the field confinement of SSPPs to achieve antenna beam manipulation with a large frequency-scanning angle. By changing the shape of the glide-symmetric D-L SSPPs, we can control the electric field confinement of the SSPPs to emerge symmetric or asymmetric distribution. Hence, the proposed SSPPs structure can produce electromagnetic (EM) leakage on both sides or single side, furtherly achieving dual-beam (D-B) or single-beam (S-B) radiation. Two SSPPs antennas with dual beams and single beam are designed, fabricated, and measured. Both the D-B antenna and S-B antenna operate from 9 to 24 GHz. Within the working band, the D-B antenna accomplishes 134.3° (−90° to +44.3°) beam-scanning angle with the realized gain of 8.03–12.17 dBi, while the S-B antenna achieves 119° (−77.9° to 41.1°) beam-scanning angle with 10.31–14.24 dBi realized gain. The simulated and experimental results verified the beam manipulation and large frequency-scanning angle in antenna design.