This paper proposes a synthesis method of orthogonal beamforming networks (BFNs) with arbitrary ports. The proposed method is based on matrix decomposition theory and breakthrough the synthesized BFN number to arbitrary. It has been theoretically demonstrated that the BFN with cascading 180° hybrid couplers can synthesize shaped beams. Therefore, a BFN synthesis method that combines the QR decomposition theory and the optimization algorithm is introduced. With the help of an optimization program, a specific power ratio of each 180° hybrid coupler in the BFN is determined. The proposed synthesis method is verified by experiments with an orthogonal 6 × 2 BFN with flat-topped radiation patterns. Through optimization, five 180° hybrid couplers with different power ratios synthesize the proposed BFN. Results show that two flat-topped beams with a beam-width of (32±0.3)°, gain ripples less than 2.5 dB, and a side-lobe level less than 12 dB are achieved. The proposed method has the advantages of high accuracy and efficiency and a simple structure, which makes it convenient for multi-beam antenna arrays in multiple-input multiple-output (MIMO) systems.

A synthesis method for orthogonal beam-forming networks (BFNs) with arbitrary N inputs and N outputs is presented. Compared to those formerly developed, the new method allows the design of a BFN in order to not only generate arbitrary N orthogonal beams and N inputs but also make the 180° hybrids less. This skill is obtained by means of a new approach to decompose the matrix Q1 and Q2 which are mentioned in “Method of Synthesizing a Beam-Forming Device for the N-Beam and N-Element Array Antenna, for any N” IEEE Trans. Antennas Propagat., vol. 60, no. 4, pp. 1771-1776, Apr. 2012. The solution of such a design problem can be carried out by applying QR decomposition based on Givens transformations. Such a design method also takes into account the computer programming realization. Numerical results are obtained through the commercial simulator to prove the correctness of the method. The ease, accuracy, and efficiency of this synthesis method for the design of BFN make it very useful in modern applications of multi-beam antenna arrays.

This letter presents the new concept and method of feed line resonator (FLR). Unlike the conventional filter feed lines, which serve solely for external coupling, the proposed feed line resonators can not only introduce additional transmission poles within the passband, but also generate transmission zeros at both sides of the passband, thereby significantly augmenting the filter’s performance without enlarging its physical dimensions. A novel and systematic method for constructing multimode resonators, called the connected line resonator (CLR) method has been proposed, two parallel lines are connected to obtain three resonant modes for filter design. The key advantage of this proposed CLR is its ability to exhibit a substantial attenuation slope at the higher band edge. To demonstrate the FLR and CLR method, two wideband filters were designed based on the high-temperature superconducting film, with the center frequency at 7.3 GHz, and the fractional bandwidth of about 59%. The measured results agree well with the simulation ones.

A slim dual‐polarised antenna with omnidirectional patterns is proposed for wireless local area network (WLAN) applications. The antenna is a composition of a modified J‐type antenna for vertical polarisation and two crossed‐loop antennas for horizontal polarisation. For improving the isolation between the two polarisations, a rectangular loop is partially added in the middle of one of the loop antenna, connecting the end of the J‐type antenna. The rectangular loop also acts as tuning the impedance of the antenna. For achieving omnidirectional patterns of the horizontal polarisation, a series circular feeding network is designed to excite the loop antennas. The antenna is fabricated by copper and the circular network is printed on a substrate. Measurement results show the 10 dB return losses of the two ports are covering the whole 2.4 GHz WLAN band, with the isolation better than 20 dB. The gains vary <2.2 dB in the horizontal plane for both the polarisations. With the advantages of slim structure, lightweight, and easy fabrication, the proposed antenna is convenient to use in the WLAN routers.

摘要

Fully-connected beamforming networks (FCBNs) can provide better performance in a hybrid beamforming (HBF) architecture for massive multiple-input-multiple-output (MIMO) systems. The traditional FCBN adopts the “splitters + phase shifters + attenuators + combiners” architecture, which has a huge intrinsic loss by the theoretical analysis. The network loss and topology complexity pose challenges for its engineering applications. To address the aforementioned issues, this article proposes a new efficient FCBN architecture, eliminating the intrinsic loss of the network. The proposed new FCBN architecture consists of tunable and fixed directional couplers and phase shifters in cascading, achieving both amplitude and phase adjustments. For synthesizing such a tunable network with arbitrary I/O ports, the complete QR factorization synthesis method with the corresponding tunable complex Givens rotation matrix has been proposed and proved. To demonstrate the proposed synthesis method, a $2\times 4$ FCBN network has been synthesized, fabricated, and measured. Concentrating on the characteristics of the FCBN, an optimization process has been introduced to simplify hardware topology complexity. The results show that the proposed FCBN architecture has advantages in no intrinsic loss, simple topology, and low cost, making it widely applied in wireless communication systems to improve the system efficiency.