In this paper, a W-band single-layer reflectarray antenna is proposed with the advantages of broadband and high aperture efficiency. A novel dual rotation-symmetry windmill element is designed in the W-band, which consists two layers of copper patches printed on a Rogers RT5880 substrate. Based on the analysis of the proposed metasurface element, a square reflectarray with 13.85λ ₀ (44.2 mm) aperture diameter at 94 GHz center frequency was designed, fabricated and measured. The designed reflectarray antenna shows a 1-dB gain bandwidth of 25.5% (89-113 GHz) in the W-band. Moreover, the measured gain is 31.1 dBi at 94 GHz and the maximum aperture efficiency is 53.4%. The result shows that the proposed design has prospects in wireless communication applications.

We propose a W-band circularly polarized reflectarray antenna in this article, which contains a single-layer reflectarray and a linearly polarized horn feed. To realize the proposed antenna, we designed a novel W-band multi-resonant element containing a Rogers RT5880 substrate with copper patches printed on its both surfaces. Then, a circular reflectarray with 12.25 λ₀ (39.1 mm) aperture diameter was designed based on the proposed multi-resonant element, whose center frequency is 94 GHz. We further fabricated the proposed circular reflectarray and tested its performance. In the measured results, we can see that the obtained 1 dB gain bandwidth is 19.1% (91~109 GHz) and the obtained 2 dB gain bandwidth can reach as wide as 27.6% (89~115 GHz). Moreover, the 3 dB axial ratio bandwidth is 13.8% (89~102 GHz). The measured gain of our proposed reflectarray antenna at 94 GHz is 29.1 dBi and the corresponding aperture efficiency can reach as high as 52.0%. Those results show that our proposed antenna may be prospective in wireless communication applications due to its strengths in broadband and high aperture efficiency.

ABSTRACT In this paper, a flat-top metasurface broadband mushroom antenna for microwave power transmission (MPT) is proposed. It has a 4×4 array of patches that are connected to the ground through vias to form a mushroom structure to reduce back lobe radiation. The antenna is fed by a microstrip, with the feeding slot located just underneath the central gap between the mushroom cells. This configuration enables the simultaneous excitation of dual resonance modes, resulting in aperture radiation and a wide impedance bandwidth. The final design has an overall dimension of 1.96 λ ₀ ×1.96 λ ₀ ×0.09 λ ₀ at 5.4 GHz. After simulation and measurement, The final impedance bandwidth is 4.2-7.0GHz (50%), the flat-top bandwidth is 4.2-6.3GHz (40%), the peak gain is 8.4dBi, and the stable 1dB flat-top beam bandwidths of the E-plane and H-plane from 4.2GHz to 5.4GHz are both greater than 67° and 38°, and the 3dB flat-top beam bandwidths of the E-plane and H-plane are both stably greater than 85 ° and 24 ° at 5.6-6.3GHz. The stable flat-top radiation pattern makes it more popular in microwave radio transmission. Compared with other works, this antenna has the advantages of broadband, compactness, and wide beamwidth.

The miniaturization and high power of klystron are the main concerns of accelerators. Multi-beam klystron (MBK) can accommodate higher power and a lower operating voltage than single-beam klystrons, significantly reducing volume and weight. This paper introduces the design and simulation of the beam-wave interaction system and multi-beam electron gun for S-band compact MBK. The 3-D particle simulation results show that the output power of the MBK is 12.6 MW, driven by an input signal with a frequency of 2856 MHz and a power of 13 W. The corresponding efficiency is 70%. In addition, the gain of the MBK is 59.9 dB. The design goal of S-band miniaturized high-power MBK is realized.