A 3×3 Antenna Beamforming Network Based on Waveguide Nolen Matrix for Ka-Bands

Abstract

The Fifth generation (5G) wireless communication system aims to provide high bandwidth, high sensitivity, high gain and power capability. Millimeter wave technology then proposed for these demands with various range of features such as higher bandwidth, low interference, and frequency reuse. However, millimeter wave technology has a key disadvantage of high path loss due to small wavelength in the channel of high attenuation coming from the atmosphere, in addition to the very small wavelength that produces an unwanted crosstalk between the transmission lines. Thus, beamforming network and waveguide-based structures such as Nolen matrix was proposed to overcome these problems. The objective of this research is to design a low loss and high-performance Nolen beamforming network based on waveguide technology. Taking in consideration is the advantage of flexible number of beam ports in Nolen matrix using single layer technique. This work aims to design a $3\times 3$ Nolen matrix with main beam directions of 0, 30° and −30° at 26 GHz. The $3\times 3$ Nolen matrix is designed using low loss hollow waveguide single layer technique. Then, the proposed Nolen matrix is fed three-waveguide slotted antenna. The proposed $3\times 3$ Nolen matrix has measured phase differences at port 1 (35.40°), port 2 (156.43°) and port 3 (−93.57°) in the x-y plane. Waveguide slotted antenna has designed at 26 GHz with tilted slots at broad wall of the waveguide structure. This tilted technique has the benefit of increasing the bandwidth up to 50% of FBW. A simulation and measurement using CST software is performed for the proposed antenna. A return loss of −15 dB with wideband of 2.08 GHz are obtained. A gain of 14 dB is observed at broad wall respectively. Waveguide antenna has been integrated with Nolen matrix to build Nolen beamforming; the measured beamforming network has a good return loss of less than - 10 dB with phase error of −8 degree at outputs. Three beams are achieved with beam scanning of $\pm ~30$ degree. The beam from port 1 is radiated in the direction of −26°. The beams from port 2 and port 3 are radiated in the directions of +27° and +6° respectively. Therefore, this beamforming has a greater impact on the mm wave beamforming networks and applications.

Keywords

• Nolen matrix
• direct coupling
• beamforming network
• millimeter wave