A review of hybrid couplers:state-of-the-art, applications, design issues and challenges

Abstract In recent years, the hybrid branch-line coupler has attracted much attention due to its appealing features such as of low cost and ease in fabrication for wireless communications. The fifth-generation cellular networks promise to support several wireless technologies by capitalizing a multitude of frequencies and increase data rates. To achieve that, the butler matrix technique can be used to enhance both bandwidth and data rate with the implementation of beamforming. Conventional hybrid couplers are the main component to build a butler matrix, but they are generally bulky in size and narrow in bandwidth. Moreover, requirements imposed by newer wireless technologies makes the efforts in improving size compactness and bandwidth even more challenging. On the other hand, several techniques have been proposed in literature to solve both issues. This study focuses on the design challenges and issues of hybrid coupler designs and technologies, besides underlining their promising potential. In this context, several techniques for hybrid coupler to achieve the required bandwidth and size reduction are highlighted, such as the T-shape, meander line, two sections, three-section, and parallel couple lines

Single-layer planar monopole antenna-based artificial magnetic conductor (AMC)

Abstract In this paper, a coplanar waveguide (CPW)-fed patch antenna is fabricated on a layer of metasurface to increase gain. The antenna is fabrication on Roger substrate with a thickness of 0.25 mm, with the overall dimension of the proposed design being 45 × 30 × 0.25 mm³. The size of the patch antenna is 24 × 14 × 0.25 mm³, and the AMC unit cell is 22 × 22 × 0.25 mm³. This metasurface is designed based on the split-ring resonator unit cells forming an array of the artificial magnetic conductor (AMC). Meanwhile, the antenna operation on 3.5 GHz is enabled by etching a split-ring resonator slot on the ground plane with a small gap to enhance antenna gain and improve impedance bandwidth when integrated with a metasurface. This simulation planer monopole antenna is applied for 5G application. The experimenter test is applied for the antenna performance in terms of return loss, gain, and radiation patterns. The operating frequency range with and without MTM is from 3.41 to 3.68 GHz (270 MHz) and 3.37 to 3.55 GHz (180 MHz), respectively, with gain improvements of about 2.7 dB (without MTM) to 6.0 dB (with MTM) at 3.5 GHz. The maximum improvement of the gain is about 42% when integrated with the AMC. The AMC has solved several issues to overcome the typical limitation in conventional antenna design. A circuit model is also proposed to simplify the estimation of the performance of this antenna at the desired frequency band. The proposed design is simulated by CST microwave studio. Finally, the antenna is fabricated and measured. Result comparison between simulations and measurements indicates a good agreement between them