Authors: Muhammad Umar Khan
Source: FERMAT, Volume 7, Communications 1, Jan Feb.,2015
Abstract: Fourth generation (4G) wireless communication standards have adopted multiple-input-multiple-output (MIMO) systems to cater for high data rate requirements. For a successful implementation of these standards, the antenna of MIMO systems is an important design consideration. The MIMO systems require that their antenna with multiple elements should have high port isolation and low correlation between it elements. The wireless devices, where these systems are implemented require that their antenna must be low-profile and fit within the enclosing of the device. Together, these restrictions make the design of antennas for the MIMO systems a challenging task. Antenna is still one of the largest parts of any communication device. A standard antenna dimension correspond to half wavelength of its operating frequency. Decreasing the size of antenna beyond this limit severely degrades its radiation characteristics. For MIMO systems, accommodating multiple antenna elements in a limited space is therefore a serious issue which require that the novel antenna miniaturization techniques be developed. These techniques should try to reach the best possible practical limit of small antennas while maintaining reasonable radiation characteristics. In this work, antennas for MIMO systems are designed for various standards between 0.7 GHz to 6 GHz. All the designed antennas are planar, low-profile and uses modified microstrip patch antennas (MPAs) as the elements. A metamaterial (MTM) inspired technique is proposed which uses the complementary split-ring resonator (CSRR) for MPA miniaturization. We first thoroughly investigate the miniaturization technique and then develop design procedures based on it. An 80% miniaturization in the patch area is achieved using the proposed method in the 700 MHz band and 65% miniaturization is achieved in the 5GHz band. The miniaturized MPA thus developed are used to design 2-element MIMO antenna systems in the lower LTE band, 4-element MIMO antenna systems in the ISM band and 8-element MIMO antenna systems in the WiFi band. All the designs are highly compact and conform to the dimensions of a standard wireless device.
Keywords: Metamaterial, Inspired Antenna ,Miniaturization, MIMO System Applications
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