A low-profile planar multiple-input multiple-output (MIMO) antenna consisting of four elements with isolation improvement is proposed for 5G mm Wave (24–40) GHz applications. Each radiating element of the MIMO antenna comprises of a microstrip-fed tilted spade-shaped radiator with four asymmetrical slots and a partial ground plane. The antenna is optimized to resonate at 35 GHz covering a wide impedance bandwidth from 23.9 to 40.1 GHz. Two cross lines are then loaded between the antenna elements to improve the isolation > − 30     d B . The MIMO structure with the decoupling lines is fabricated and tested. The measured results are in good correlation with the simulated results. Other MIMO performance metrics such as the envelope correlation coefficient (ECC), channel capacity loss (CCL), diversity gain (DG), and total active reflection coefficient (TARC) are examined, and the results are found to be satisfactory for the device to be used for mm-wave 5G MIMO applications. Also, the antenna’s performance metrics such as radiation efficiency, gain, and radiation patterns over the operating band are presented.

<span>This article represented a heart shape reconfigurable monopole antenna with polarization diversity. The proposed antenna is fed by a 50 Ω microstrip feed line that is printed on a flexible FR-4 (εr=4.4) substrate. The antenna comprises a ring-slot, a cross slot and four positive-intrinsic-negative (PIN) diodes that are soldered on ring slot. Four PIN diodes act as a switch and by controlling these PIN diodes effective current direction is changed hence four various states of polarization are achieved. Four states of polarization such as horizontal linear polarization (H-LP), vertical linear polarization (V-LP), right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) can be switched easily with the help of these PIN diodes and achieved an efficiency of more than 90%. Proposed antenna shows voltage standing wave ratio (VSWR)&lt;2 at all working frequency and -10 dB reflection coefficients (RC) bandwidths (BW) (i.e., S11≤-10 dB) about 32.86% for linear polarization (LP) states while RHCP and LHCP states possess BW of about 31.61% and 31.67% respectively. It also shows axial ratio (AR) BW of 3.41% and 2.44% for RHCP and LHCP, respectively. Besides, the antenna has a well-suited omnidirectional pattern with a positive gain of all working frequency of interest where cross-polarization level is much lower than that of antenna gain.</span>

No abstract

No abstract

In this article, an array antenna possessing linear polarization switchable ability with enhanced gain is proposed by employing 4‐patch elements in square shape. The 4‐elements were arranged on the upper plane of the antenna where edge to edge distances were set to be 0.8λ of its operating frequency. The radio frequency signal was fed to energize the patch elements by means of a feed circuit which was realized by the both‐sided microwave integrated circuit technology. In addition, polarization switching is done by simply utilizing diode at the corner of the elements as switching elements to perform beam tilting. The incorporation of extra Magic‐T circuit to feed dc bias signal to the diodes helps to achieve improved isolation between feeding signal and the isolation was found to be less than −25 dB. The array antenna was designed to operate at 10.2 GHz and the dimensions of the patch elements was chosen to be 9.4 × 9.4 mm2. A Teflon glass fiber of 0.8 mm was used as the dielectric substrate having dielectric constant 2.15 while simulation. Later the proposed antenna was fabricated performance is validated experimentally. The measured S11 was found to be less than −15 dB at operating frequency with a neat measured gain of 13.1 dBi, higher compared with 7.1 dBi gain of single antenna, with minimized sidelobe levels of less than −10 dB. The crosspolarization for the radiation pattern was found better than 20 dB which was an excellent result. The measured polarization angle was found to be −44.24° and +46.20° for negative and positive bias respectively at operating frequency with a neat efficiency of more than 80% in its operating bandwidth. The proposed array antenna is a suitable candidate for the application in polarimetric Radar, X‐band radar, and polarization diversity applications for being lightweight in structure which was made possible using this novel technology. The antenna simulation is done by the advanced design system and the optimized along with experimental data are discussed in this article.