In this paper, a wideband circularly polarized (CP) antenna with low radar cross-section (RCS) and high gain properties is investigated. The proposed antenna is based on a combination of the Fabry-Perot cavity (FPC) and sequential feeding technique. The purpose of this antenna is to produce CP with high directive gain over a wide bandwidth, whilst preserving low RCS. The principle of the FPC and resonance is achieved by applying one frequency selective surface (FSS) metasurface. A microstrip slot array operating at the Ka-band, excited by a sequentially rotated feeding network is designed and fabricated. It is indicated that all the merits mentioned above can be obtained over a broad frequency band by designing a suitable FSS metasurface and modifying the feeding lengths to adjust desirable phase. RCS reduction is realized by 180° + 37° reflection phase variations between adjacent FSS unit cells on the metasurface. The experimental results show that the gain of the antenna with the metasurface is at least 7 dB greater than that of the primary antenna with a peak value approximately 20 dB at 28.5 GHz. In addition, bandwidths of 3-dB gain, impedance (|S11| ≤ -10 dB), and axial ratio (AR) ≤ 3 dB are ranged from 27.5 to 33.5 GHz (19.7%), 26.7 to 34.2 GHz (24.6%) and 26.8 to 33.1 GHz (21%), respectively. The monostatic RCS reduction for a normal incidence is effectively suppressed from 28 to 48 GHz (52%).

This manuscript focuses on the design of a transparent circularly polarized (CP) antenna subarray integrating with CubeSat’s solar panels. The sub-array antenna employs two techniques including the Fabry_Perot cavity (FPC) and sequential rotation-feeding network. These techniques are used to generate CP along with a high level of directivity over a broad bandwidth. The main aim here is to propose a multi-functional antenna with the high radiation properties as well as the capability of power harvesting, simultaneously. To harvest power using a solar panel the transparency requirement should be satisfied. Hence, the proposed design is sputtered with the thin layer of indium-tin-oxide (ITO) with a thickness of 200nm. However, it seems to be sacrificed a large amount of conductivity at the frequency band of interest (x-band). Correspondingly, the performance of conductivity and transparency both the materials of ITO and copper as coated on the proposed design is determined. Alternatively, as an optically transparent conductor (OTC), a combination of both coating layers, including ITO and copper with thicknesses of 200nm and 5nm, respectively, are applied. In the scattering point of view, the proposed design is also capable of suppressing the radar cross section (RCS) for the space missions with the aim of space-based observations.

This paper proposed a wideband, efficient and high gain circularly polarized (CP) array antenna based on gap waveguide technology for 30 GHz frequency band applications. The antenna sub-array is a 2 ×2-slot groove gap waveguide (GGW)-based cavity-backed antenna. The antenna is fed by a ridge gap waveguide (RGW). Two corners of the radiating slots are truncated to obtain CP radiation and some corrugations are introduced to the radiating layer to suppress the surface waves between neighbor sub-arrays. The planar 16-way feeding network based on RGW is utilize to feed the sub-arrays. The feeding network is multi-level sequential phased with a quadrature phase shift. To validate the array antenna performance, a prototype of the antenna has been manufactured using standard milling technology. The measured reflection coefficient bandwidth is about 22 % covering from 28.3 to 35.3 GHz and a measured 3-dB axial ratio bandwidth of about 21.8 % is achieved from 27.8 to 34.6 GHz. The maximum measured gain is 23.5 dBi which is occurred at 30.75 GHz.

In this paper, a 2-D scanning magnetoelectric (ME) dipole antenna array fed by printed ridge gap waveguide (PRGW) Butler matrix is proposed. The ME dipole antenna is designed to achieve a bandwidth wider than 20% at 30 GHz and stable gain of 6.5 ± 0.8 dB over the operating frequency bandwidth. A $4\times 4$ planar PRGW Butler matrix is designed and constructed using a four PRGW hybrid couplers having a wide bandwidth performance. The overall performance of the Butler matrix exhibits about 5° phase error over the operating frequency bandwidth. The integration of ME dipole antennas with the designed Butler matrix results in four fixed beams, one in each quadrant at an elevation angle of 35° from the broadside to the array axis. The proposed passive beam switching network (BSN) has a wide bandwidth of 20% with radiation efficiency higher than 84% over the operating bandwidth. The proposed BSN shows a stable radiation pattern with a stable gain of 10.3±0.2 dB, where the sidelobe level is less than −15 dB over the whole operating frequency band. The fabricated prototype of the proposed BSN is tested, where the measured and simulated results show an excellent agreement.

A single-layer right-angle broadband transition between the substrate-integrated waveguide and air-filled standard rectangular waveguide is proposed and demonstrated at the V-band. An aperture coupled patch with two pairs of inductive posts is employed to form the transition. An impedance bandwidth wider than 48% for return loss less than -10 dB is achieved. The proposed back-to-back transition is fabricated on a single layer substrate using the printed circuit board technology. The measured results of back-to-back prototype show that the insertion loss of a single transition is less than 0.5 dB. The measured results show a good agreement with HFSS simulation results. This transition with compact size, wide bandwidth, and low cost can be used for a variety of millimeter-wave circuits and systems.