3D printed orthomode transducer (OMT) integrated with a 3D printed lens antenna is presented in this work. The OMT integrated with the lens antenna covers the range of 54–80 GHz, the radiator can handle a fractional bandwidth of 38%. Fused filament fabrication printing process is used for the domed elliptical profile lens antenna and polyjet printing process is used for fabrication of the OMT. The simulated radiation efficiency of the antenna remains above 90% for the entire bandwidth and the structure shows a gain of above 16 dBi.

In this paper, a high-order-mode (HOM) (TE330) cavity-fed 45° linear polarized 6×6 slot array antenna is proposed. The 45° linear polarization is achieved by introducing asymmetric cross slots on the HOM cavity, resulting in low profile and wide bandwidth. The antenna array was verified using standard printed circuit board technology. Measured results show that the impedance bandwidth ( $|S_{11}|\le$ −10 dB) is 13.9% (36.98–42.92 GHz), and the peak gain is 19.3 dBi with a 3-dB gain bandwidth of 13.6%. Attributed to its simple structure, low profile, and wide bandwidth, the presented antenna is a good candidate for 5G applications.

A wideband tunable balanced phase shifter is achieved by utilizing varactor-loaded coupled lines (VLCLs)-embedded multistage branch-line structure. The tunable phase shift with low in-band phase deviation is attributed to the regulation in phase shift of the VLCLs and the horizontal microstrip lines in series. The wideband differential-mode (DM) impedance matching and common-mode (CM) suppression are due to multiple DM transmission poles and CM transmission zeros, which are brought about by the cascade of VLCLs and a microstrip line with short-circuited stubs in the DM-equivalent circuit and open-circuited stubs in the CM-equivalent circuit, respectively. Compared with the state-of-the-art tunable balanced phase shifters, the proposed design not only has the advantages of wide operating bandwidth (BW) with low in-band phase deviation but also has low insertion loss and easily fabricated structure. Theoretical analysis and design procedure were conducted, resulting in a prototype covering the frequency of 1.8 GHz. This prototype offers a tunable phase shift capability ranging from 0° to 90°. The prototype exhibits an operating BW of 45%, with a maximum phase deviation of ±6°. It also achieves a 10 dB DM return loss and CM suppression, while maintaining a maximum insertion loss of 2.5 dB.

A metasurface reflector-backed wideband planar antenna is designed for millimeter-wave (mmWave) applications. A simple meandering structure is used for radiation element design, while the back side consists of a partial ground plane and parasitic elements. The utilization of meander-shaped element led to small antenna dimensions. The partial ground plane is used to achieve wide bandwidth, while the parasitic elements are used to improve the impedance matching toward higher frequency bands. To achieve high gain and directional radiation characteristics, an array of metasurfaces is placed behind the radiating element. It is observed from the simulated results that the proposed antenna system offers 17.72 GHz of impedance bandwidth in the operating range of 22.28–40 GHz, while the measured impedance bandwidth is noted to be 15.8 GHz, ranging from 23 to 38.8 GHz. Furthermore, it is observed that a metasurface-based planar antenna tends to achieve a peak gain of ≈9 dBi in the band of interest.

This paper presents the design of an elliptical shape ultra-wide band antenna for imaging of wood. The antenna is constructed comprising an elliptical shape of patch loaded by a stub to resonate at lower bands, strip loading at the back, and chamfered ground. Despite having miniaturized dimensions of 20 mm × 20 mm, the proposed antenna shows better results compared to recent studies. The simulation results depict a good ultra-wide bandwidth from 2.68 to 16 GHz, and 18.2–20 GHz. Besides, the proposed antenna has two low-frequency bands at 0.89–0.92 and 1.52–1.62 GHz, maximum gain of 5.48 dB, and maximum directivity of 6.9 dBi. The measurement outcomes are performed in air, plywood, and high-density wood and show a good agreement with the simulated results done using electromagnetic simulator CST. In addition to that, the measurement results of S-parameters, transmitted and received signals show a good agreement with the simulated results. Besides, the measured results illustrate a good isolation and uniform illumination among arrays as well as the received signals' shapes do not change in different environments, but only the amplitude. Hence, the proposed antenna seems to be adequate for microwave imaging of wood.

Novel designs of a circularly polarized 2 × 2 and 4 × 4 slot array antennas (CPSAAs) are proposed. Sequential phase feed network composed of a section of 270° and four strips is utilized to feed the array structures. Array elements are simple linearly polarized wide slot antennas (WSAs) composed of simple radiating patches with truncation on four corners and slotted ground plane on substrate backside. Each WSA operates over the UWB frequency band of 3.1–10.6 GHz. When the WSAs are arranged in the form of 2 × 2 and 4 × 4 CPSAAs, frequency bands of 3–13.1 and 1.4–12.3 GHz are covered, respectively. More importantly, CP is generated at 4.5–8 and 4.6–8.8 GHz for 2 × 2 and 4 × 4 CPSAAs, respectively. This is while; the WSAs are linearly polarized elements. Higher gain values and wider bandwidths are obtained with respect to single WSA. Design process and performance analysis of the single and array antennas are discussed through the paper.