Dual Circularly Polarized Planar Four-Port MIMO Antenna with Wide Axial-Ratio Bandwidth

Abstract

A broadband compact-sized planar four-port multiple-input–multiple-output (MIMO) antenna with polarization diversity is presented. The proposed dual circularly polarized (CP) MIMO antenna consists of four G-shaped monopole elements, two of which are left-hand CP and the other two are right-hand CP. A vertical line strip in the G-shaped radiating element acts in balancing the vertical and horizontal electric field components to obtain 90° phase difference between them for circular polarization. Also, an I-shaped strip is incorporated between the ground planes of the G-shaped antenna elements to obtain equal voltage level in the proposed MIMO configuration. The dual circular polarization mechanism of the proposed MIMO/diversity antenna is analysed from the vector current distributions. The impedance bandwidth (S11 ≤ –10 dB) of the MIMO antenna is 105.9% (4–13 GHz) and the 3 dB axial ratio bandwidth (ARBW) is 67.7% (4.2–8.5 GHz), which is suitable for C-band applications. The overall size of the MIMO antenna is 70 × 68 × 1.6 mm3, and the minimum isolation between the resonating elements is 18 dB. The envelope correlation coefficient is less than 0.25, and the peak gain within the resonating band is 6.4 dBi.

Quad-Port Multiservice Diversity Antenna for Automotive Applications

“…The total active reflection coefficient (TARC) is the square root of the summation of outgoing powers divided by the summation of incident powers at any port of an N-port antenna [35]. TARC is estimated using the Equation (7), where ai is the incident signal Diversity gain (DG) is defined as an increase in signal-to-interference ratio without compromising quality [34]. It also demonstrates how much transmission power can be saved by employing a diversity scheme.…”

“…The total active reflection coefficient (TARC) is the square root of the summation of outgoing powers divided by the summation of incident powers at any port of an N-port antenna [35]. TARC is estimated using the Equation (7), where a i is the incident signal and b i is the received signal. TARC of the proposed antenna is less than −10 dB, shown in Figure 16.…”

“…Diversity techniques such as spatial, pattern, and polarization are used to encounter multipath interference. Therefore, a multiple-inputmultiple-output (MIMO)/diversity antenna could be advantageous for vehicular communications [6][7][8][9]. But, the main problem with MIMO antennas is high coupling between resonating elements.…”

Dual-Frequency Linear-to-Circular Polarization Converter for Ka-Band Applications

“…In recent years, wireless sensor networks (WSN) have attracted attention in the wireless communication domain for several applications such as medical and military surveillance, localization, smart homes, smart cities and monitoring. Circularly polarized (CP) antennas are often used in these applications [ 1 , 2 , 3 , 4 ] due to their ability to improve channel performance through alleviating multipath interference, low absorption losses and signal attenuation. CP can be generated in different ways depending on the kind of antenna.…”

Periodically-Stub-Loaded Microstrip Line Wideband Circularly Polarized Millimeter Wave MIMO Antenna

“…The other part at the bottom is an interdigital radiator, which introduces a linear polarization (LP). A triple-port MIMO antenna comprised of two LP dipoles and one CP chamferededge square patch antenna was proposed for WLAN systems [10]. In [11], inverted-L strips were used in the ground plane to achieve a wide axial ratio bandwidth (ARBW).…”