Abstract-A dual-band dual-element multiple-input-multiple-output (MIMO) antenna system with enhanced isolation is proposed. The MIMO antenna system is based on printed 4-shaped antenna elements. Dual band isolation is achieved by using an array of printed capacitively loaded loops (CLLs) on the top side of the board for high band isolation improvement and a complementary CLL structure on the GND plane of the antenna for lower band isolation improvement. The lower band of operation covers 827-853 MHz and the higher band covers 2.3-2.98 GHz. Two prototypes were investigated to access the effect of the isolation mechanism. Measured isolation improvement of 10 dB was observed in the lower operating band while the improvement in the higher band was approximately 2.5 dB. The isolation improvement was at the expense of 5% reduction in efficiency. The measured gain patterns as well MIMO figures of merits such as the correlation factor, TARC and MEG were investigated as well.

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Directional ultrawideband (UWB) antennas are popular in wireless signal-tracking and body-area networks. This paper presents a stacked microstrip antenna with an ultrawide impedance bandwidth of 114%, implemented by introducing defects on the radiating patches and the ground plane. The compact (20×34 mm) antenna exhibits a directive radiation patterns for all frequencies of the 3–10.6 GHz band. The optimized reflection response and the radiation pattern are experimentally verified. The designed UWB antenna is used to maximize the received power of a software-defined radio (SDR) platform. For an ultrawideband impulse radio system, this class of antennas is essential to improve the performance of the communication channels.

A novel W‐band arbitrary polarization compact radiating structure that can be used to design antenna arrays with wide angle beamforming and limited grating lobes is described in this article. The radiating element is a slot which can be oriented in any direction to achieve the desired polarization. This slot is placed on a rectangular cavity, which is operated in its fundamental mode to achieve compact size. The cavity is coupled with a substrate‐integrated waveguide feed line using a coupling slot. These radiating elements are series fed to form compact one‐dimensional arrays, which can be combined to design two‐dimensional arrays having field of view up to 120° and with limited grating lobes in the plane transverse to the one‐dimensional array axis. One‐ and two‐dimensional arrays for two orthogonal polarizations were fabricated and tested to validate the described structure.