A compact quad band slot antenna with high isolation suitable for multiple-input–multiple-output (MIMO) applications is developed. The quad bands are achieved by introducing slots in a modified, size reduced circular patch antenna. The single-antenna element consists of a substrate sandwiched between a modified circular patch with F shape slot, a feeder line and a via running between the radiating patch and the feeder line. The proposed design resonates at the frequencies of 1.8 GHz (1.7–1.88 GHz), 3.6 GHz (3.50–3.76 GHz), 5.4 GHz (5.25–5.38 GHz), and 7.2 GHz (7.15–7.35 GHz) covering the GSM II, WIMAX, wireless local area network (WLAN), and C-band applications, respectively. The independent tuning of frequency bands is achieved by varying the length of the slots. Orthogonally placed two- and four-element MIMO antenna system are fabricated, tested, and the measurement results are presented. The separation between each element is reduced to 0.085λ while introducing slotted and pulsed stubs to improve isolation between elements. A detailed analysis, including mutual coupling, low correlation, diversity gain, and total array reflection coefficient had been reported. The two- and four-element MIMO antennas achieved correlation as low as 0.005, mutual coupling ≤−15 dB, and diversity gain nearly 10 dB.

Compact modified T-slot circular patch antenna for multiple input multiple output (MIMO) applications, which has good response for four operating frequency bands is developed. Here the design consists of a circular patch with a new slot loaded T- shape on one side of the substrate and a feeder line on the other side of the substrate. A shorting pin is located between the patch and the feeder line. This proposed antenna resonates at the frequencies of 2, 4.8, 5.4, and 6.2 GHz covering the S-band, C-band, and LTE applications. The independent tuning of frequency bands is achieved by varying the length of the slots. By independent tuning of frequency bands, the selection of interested frequency band is achieved. The single element with miniaturized size of 1.945λ × 1.945 λ (30 × 30 mm2) is achieved including the feed line. The antenna has been tested for MIMO applications. The measured envelope correlation coefficient between the two elements, which are spaced 0.139 λ is <0.1(low correlation) and mutual coupling is found to be in the range of −20 dB to −80 dB. The simulation and measurement results of reflection coefficient, mutual coupling, and radiation pattern are presented.

A novel modified elliptical patch antenna is designed to provide performance diversity for c‐band wireless applications. Initially antenna A and antenna B are designed to enhance the radiation efficiency and bandwidth, respectively. With the similar patch and substrate size of both antennas by controlling the length of the slots and width of the feed antenna C is designed to yield unique performance in a single element. Antenna C achieves the performance of enhanced radiation efficiency and bandwidth with the reconfigurable mechanism. When antenna C switch to antenna A configuration, it resonates in the frequencies of 3.7, 5.1, and 6.35 GHz have the radiation efficiency of 82.55, 83.3, and 87.09%, respectively and whenever it turns to antenna B configuration it resonates at the bands of 4, 4.8, and, 6.7 GHz have the bandwidth of 260, 300, and 240 MHz, respectively. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:408–415, 2017