Abstract
In this work, two configurations (Config.-A and Config.-B) of planar four-port dual circularly-polarized (CP) multiple-input-multiple-output (MIMO) antenna are proposed for sub-6 GHz (3.4-3.8 GHz) applications. The MIMO antennas are designed on the FR-4 substrate with size of $60\times 60\times 1.6$ mm 3 . Each radiating element (unit cell) of the MIMO antenna is comprised of a microstrip feed line and an open slot ground plane integrated with two rectangular arms for realizing circular polarization. An I-shaped metallic strip is used in the proposed four-port MIMO Config.-A and Config.-B antennas for obtaining common voltage level in the ground plane. Both MIMO antenna configurations exhibit good impedance matching in the band of interest. In the MIMO Config.-A antenna, all ports provide the same CP band, while in the Config.-B antenna the ports-1/-2 and -3/-4 radiate at different CP bands. The proposed MIMO Config.-A and Config.-B antennas support both types of polarization (left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP)). With the Config.-B antenna, the maximum 3-dB axial-ratio (AR) beamwidths of 118.9° and 92.7° are obtained at 3.536 GHz in the xz- and yz-planes, respectively. Furthermore, the I-shaped strip helps in improving 3-dB AR beamwidth in the MIMO Config.-B antenna. Inter-element isolation greater than 19 dB and envelope correlation coefficient (ECC) less than 0.12 (far-field) are achieved between the ports of the fabricated MIMO antenna prototype.
Highlights
The multiple antenna elements at the transmitter and receiver end upsurge the channel capacity, data transmission rate, and quality of the wireless communication system
FABRICATED MIMO ANTENNA (CONFIG.-A) It can be seen from Fig. 9(a) that the MIMO Config.-A antenna shows good impedance matching in the operating band of 3.4–3.8 GHz
The MIMO Config.-A antenna can be used when there is a requirement of the same CP band from all the unit cells with polarization choice (LHCP/right-hand circularlypolarized (RHCP))
Summary
The multiple antenna elements at the transmitter and receiver end upsurge the channel capacity, data transmission rate, and quality of the wireless communication system. The aperture radius (equal to x5) of the wide slot affects the current path, which changes the resonating frequency band of the antenna An I-shaped metallic strip is used for connecting the ground planes of unit cells without disturbing the radiation characteristics of the unit cells This step ensures an equal reference voltage level in both four-port MIMO configurations, making it integrable with other MMICs. In Section IV, it is shown that the I-shaped strip helps in improving the 3-dB AR beamwidth of the MIMO Config.-B antenna. The gain and AR of the fabricated antenna are measured inside an anechoic chamber using the method given in [24]
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