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In this letter, a design of broadband microstrip three‐way directional coupler (TWDC) is presented. The broadband performance of the microstrip TWDC is realized by the method of cascading multi‐section. The broadband TWDC is designed to achieve equal power division and −120°, 0°, and +120° phase differences between output signals. To verify the broadband design, a prototype of three‐section microstrip TWDC operating at C‐band is designed, fabricated and measured. The measured results show that the power division error of the designed broadband TWDC is less than ±0.7 dB and phase error is less than ±12° at a relative bandwidth of 16%. To verify its performance in multibeam application, the designed TWDC is used as a beamforming network for multibeam antenna array to generate three orthogonal beams. [ABSTRACT FROM AUTHOR]

Adaptive beamformers at the element level usually require a great number of training samples and the computational cost for calculating the weight vector for large phased array antennas is very high, which make it difficult for real-time applications. To address this problem, a two-dimensional (2-D) adaptive beamformer applicable to large planar array antennas that have low computational complexity and low training sample requirement is proposed. In the proposed method, the weight matrix is first reconstructed as a matrix that has the same or close columns and rows by utilising the special Kronecker property of the array steering matrix. Then, the weight vector is determined by adopting a bi-quadratic cost function and a bi-iterative algorithm. Experimental results show that the proposed method can achieve fairly good performance even when the training samples are small. [ABSTRACT FROM AUTHOR]

ABSTRACT A high gain dual-polarized wideband Fabry-Perot (FP) antenna fed by 1 × 2 antenna array is proposed. A metasurface consisting of patch and mesh array is employed as a partially reflective surface, which produces a reflection phase with a positive slope over a wideband frequency range for increasing antenna's gain bandwidth. To obtain dual polarizations and further improve the gain of antenna, a 1 × 2 patch array coupled by two orthogonal slots is designed as the feed of the FP antenna. A prototype is fabricated and measured. The measured results demonstrate that this proposed antenna has a 3-dB gain bandwidth of 22.2% in both polarizations. The peak gain of 15.7 dBi and 15.2 dBi is obtained at two polarization ports, respectively. Within the 3-dB gain bandwidth, good impedance matching with high isolation over 35 dB between the two ports is achieved as well. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2316-2321, 2016 [ABSTRACT FROM AUTHOR]