In order to improve the channel capacity of communication equipment and reduce the size of antenna, an asymmetric coplanar strip (ACS) fed four-element UWB MIMO antenna with dual band notches is proposed in this paper. The antenna has a simple structure and a compact size of 37×37 mm². The antenna consists of four modifled staircase-shaped radiation elements and four floor on the same side. The antenna elements are placed vertically without additional decoupling structure, and the isolation less than -15 dB
in the working bandwidth of 2.9-10.6 GHz can be obtained by using polarization diversity. In addition, the antenna has the notched characteristic of WiMAX and WLAN band. The antenna has good gain and low envelop correlation coefficient (ECC), and the simulation results agree with the measured results, which indicates that the antenna is suitable for UWB system.
A dual‐band patch antenna with diverse radiation patterns is presented in this paper. Circular patch and turnstile‐shaped patch are placed up and down to obtain dual band characteristic. Two surface current loops on the circular patch and turnstile‐shaped patch work like equivalent magnetic dipole. Four rectangle slots and four PIN diodes are loaded on the circular patch to readjust the surface current. Due to the changed current path, an equivalent electric dipole is introduced and two dipoles with phase difference of 180° are combined with each other to achieve directional radiation pattern. By switching the states of the diode to control the connection states of the rectangle slot on the circular patch, then a dual‐band antenna with diverse patterns is designed. The measured results show that the overlapping bandwidths of lower band f1 is 2.9% (2.42‐2.49 GHz) and over 2.9 dBi gain, the overlapping bandwidths of upper band f2 is 2.0% (4.87‐4.97 GHz) and over 4.8 dBi gain. The measured patterns of f1 show that the proposed antenna can not only omnidirectional radiation but also directional radiation with a scan angle of 90°. Meanwhile, the measured patterns of f2 remain omnidirectional radiation.
The terahertz communication system with traditional hybrid precoding structure has the problem of beam diffusion. This problem leads to the serious loss of achievable rate and offsets the performance gain caused by bandwidth increase, so a broadband hybrid precoding scheme based on cyclic delay is proposed in this paper. Firstly, a broadband hybrid precoding framework based on cyclic delay is constructed. A delay element is placed at each antenna of the traditional full-connected hybrid precoding structure. Thus, a frequency-dependent phase shift is accomplished to compensate the beam diffusion. Then, the unit delay of delay element at each antenna is determined by maximizing the array gain of the subcarriers, but there is a problem that the unit delay is not uniform. Finally, through the design of analog precoding, the unity of the unit delay can be realized, while maximizing the array gain of each sub-carrier. The simulation results show that the proposed scheme can achieve 100% array gain at any sub-carrier, and is suitable for solving the problem of beam diffusion under different bandwidth and different number of transmit antennas. Compared with the existing schemes, the achievable rate of the proposed scheme is very close to that of the full-digital precoding scheme, and has the advantage of high energy efficiency.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.