In this paper, an effective method to suppress mutual coupling between two substrate integrated waveguide (SIW) slot antenna arrays is presented. To achieve that, a decoupling feed network is used. The feed network is composed of a two-layer directional coupler that is connected to two SIW-slot antenna arrays directly to establish an indirect coupling with controlled magnitude and phase, which can effectively reduce the direct coupling generated by surface waves between the array elements. A 2×4 array of slot antenna as well as the proposed decoupling network is designed, fabricated, and measured to illustrate the effectiveness of the proposed technique. The measured and simulated results verified the good decoupling performance. The measured mutual coupling is about -35 dB at the center frequency without negatively affecting the return loss and radiation patterns. The proposed mechanism of the decoupling network is simple and successfully used in SIW slot antenna arrays.

In this paper, a new class of circularly polarized (CP) antennas is presented. It is based on the utilization of stacked printed circuit boards (PCBs) in order to realize a quasi-helix. An end-cap disk is used to optimize the axial ratio. Good impedance matching and low axial-ratio (AR) in a wide frequency band make the proposed antenna an excellent candidate for satellite communication systems and Wi-Fi applications. The structure is composed of eight PCB layers, where each layer is processed using regular single-layer PCB technology. The lowest PCB laminate is used for the feed network, while the higher stacked PCB laminates form the helical radiating element section. seven microstrip 120-degree arcs are used on PCB laminates to form a quasi-helix structure, which, with the help of the end-cap disk, can generate electromagnetic CP radiation. A prototype of the proposed antenna for 5.8-GHz WLAN was fabricated and measured to validate the proposed concept. The measured operating bandwidth for |S ₁₁ |<-10 dB is 33% (5.05–7.05 GHz). The measured 3-dB AR bandwidth covers a frequency band from 5.45 and 6.6GHz (19.25%). Unidirectional radiation patterns with excellent performance in terms of CP and high front-to-back ratio were obtained over the operating bandwidth.

A new class of multi-layer microstrip patch antenna (MPA) array fed by substrate integrated waveguide (SIW) cavities is presented for Ku-band applications. An efficient compact multi-layer SIW feeding network is designed, which has lower losses than the conventional corporate feeding network based on microstrip lines or coplanar waveguides. A 4 × 4 array consists of four stacked layers, including three based on the SIW technology as a feeding network and one layer for the radiating antenna array. Each layer can easily be fabricated from a dielectric substrate and processed using the printed circuit board (PCB) technology. Afterward, all the PCB laminates are stacked together and tied by screws. The measured antenna operates from 11.2 to 13.6 GHz achieving 19.35% bandwidth. The measured peak gain at 12.5 GHz is 17.1 dBi, equivalent to 71.47% aperture efficiency. The fabricated array exhibits several advantages: broadband, low cost, compactness, high radiation efficiency, high aperture efficiency, and lightweight, which makes it a candidate for Ku-band satellite applications.

A stacked multi-layer substrate integrated waveguide (SIW) microstrip patch antenna with broadband operating bandwidth and low cross-polarization radiation is provided. A complete study on the propagating element bandwidth and cross polarization level is presented to demonstrate the importance of the design. The proposed antenna includes three stacked printed circuit board (PCB) layers, including one layer for the radiating 2 × 2 rectangular patch elements and two SIW PCB layers for the feeding network. There are two common methods for excitation in cavity-backed patch antennas: probe feeding (PF) and aperture coupling (AC). PF can be used to increase the bandwidth of the antenna. Although this method increases the antenna’s bandwidth, it produces a strong cross-polarized field. The AC method can be used to suppress cross-polarized fields in microstrip patch antennas. As microstrip patch antennas are inherently narrowband, the AC method has little effect on their bandwidth. This paper proposes an antenna that is simultaneously fed by AC and PF. As a result of this innovation, the operating bandwidth of the antenna has increased, and cross-polarization has been reduced. Actually, the combination of probe feeding and aperture coupling schemes leads to achieving a broadband operating bandwidth. The arrangement of radiator elements and cavities implements a mirrored excitation technique while maintaining a low cross-polarization level. In both numerical and experimental solutions, a less than −30 dB cross-polarization level has been achieved for all of the main directions. A fractional impedance bandwidth of 29.8% (10.55–14.25 GHz) for ${\mathrm{S}}_{11}$ < −10-dB is measured for the proposed array. Simulated and measured results illustrate good agreement. Having features like low cost, light weight, compactness, broadband, integration capabilities, and low cross-polarization level makes the designed antenna suitable for remote-sensing and satellite applications.