A sector-shaped compact π/8 partial substrate-integrated waveguide cavity antenna from the TM220 diagonal mode of the SIW cavity is presented. A 61% size miniaturization is achieved compared to the SIW rectangular cavity in its complete mode configuration. The compact cavity radiator is used as an element of a compact 8-port multiple-input multiple-output (MIMO) antenna. The 8-port MIMO antenna occupies the entire full cavity with slots loaded on the top and bottom layers. The fabricated prototype has a -10 dB impedance bandwidth (BW) from 6.006-6.143 GHz. The mutual coupling within the BW is less than -21 dB. The presented MIMO antenna has an envelope correlation coefficient (ECC) less than 0.0027, and a percentage diversity gain reduction below 1.73%, which makes it a suitable candidate for use in MIMO-based wireless communications (This paper has been accepted for publication in  IEEE Antennas and Wireless Propagation Letters )

A low mutually coupled multiple-input multiple-output (MIMO) antenna is designed for on-chip millimetre-wave (mm-Wave) application. Two circularly polarized (CP) cylindrical dielectric resonator antennas (CDRA) with polarization diversity are placed over a double substrate silicon layer. Herein, a simple decoupling approach is applied to inhibit mutual coupling by introducing a metal plate in the substrate between the two DRAs. According to the simulation results, the inserted metallic plate improved isolation by 4-5 dB in the desired CP bandwidth. This is achieved while maintaining excellent radiation efficiency and gain, making the suggested antenna appropriate for mm-wave on-chip MIMO applications. (This paper has been submitted to  Asia-Pacific Microwave Conference 2022 (APMC 2022) )

The multiplexing gain for multiple-input multiple-output (MIMO) antenna for both multi-user and single-user MIMO and sum rate loss for MIMO antenna for multi-user MIMO are introduced. Several case studies for finding these new performance metrics of MIMO antennas are also discussed. Unlike existing MIMO antenna performance metrics in the literature, these new parameters had ensured proper characterization of MIMO antenna performance with respect to MIMO wireless communications. This paper is submitted to  2022 IEEE Microwaves, Antennas, and Propagation Conference (MAPCON) .

The performance analysis of hard-switching based mixed free space optical (FSO)/ intelligent reflecting surface (IRS)-aided radio frequency (RF) communication system is carried out in terms of outage probability (OP). The FSO link with larger bandwidth is considered as primary link, it is active for transmission when the FSO channel condition is good enough. The RF link referred to as the back-up link is activated for transmission whenever the FSO link is poor. Further, the transmission via RF link is assisted by an IRS consisting of reflecting elements that are programmable and passive in nature. For this setup, the OP is evaluated for different numbers of reflecting elements at the IRS. In order to obtain 0:001 OP with 28 dB transmit SNR of the RF link, the required transmit SNR of the FSO link with 90 elements at the IRS in the RF link is 27 dB whereas, with 100 elements at the IRS, the required SNR is 18 dB. Thus, it has been observed that the use of 10 IRS elements can reduce the required SNR of FSO link by 9 dB while keeping the OP fixed. The impact of the IRS on the OP is significant specifically when the FSO link is weak. Further, the OP performance of hard-switching scheme based mixed IRS-aided RF/FSO system has been analyzed considering both strong and moderate atmospheric turbulences, and different link distances. (This paper has been submitted to IEEE GLOBECOM Workshop 2022)

In this paper, the diversity order (DO) and the diversity measure (DM) of multiple-input multiple-output (MIMO) antennas in generic single-user, multi-user and massive MIMO wireless communications are calculated for several practical case studies. These performance metrics are calculated from the antenna correlation coefficient (ACC) matrix. The DO is calculated from the rank of the ACC matrix, and the DM is obtained from the trace and Frobenius norm of the ACC matrix. Numerical results are provided. In particular, it is shown that though the DM is always less than the DO, it incorporates the effect of antenna correlation on the diversity gain in a better way.  (This paper has been submitted to  IEEE Antennas and Wireless Propagation Letters )