Muhammad U. Khan

A Dual-Element Dual-Band MIMO Antenna System With Enhanced Isolation for Mobile Terminals

A novel dual-band 4-shaped printed multiple-input-multiple-output (MIMO) antenna system of two elements is designed and fabricated for Long Term Evolution (LTE) wireless handheld and portable terminals. The low frequency band covered is 803-823 MHz, and the high frequency band covered is 2440-2900 MHz. The isolation between the two elements was more than 17 dB in the low band after using a defected ground plane structure (DGS) between the two antenna elements. The overall size of the printed MIMO antenna system was 50× 100×1.56 mm3.

A CSRR Loaded MIMO Antenna System for ISM Band Operation

A 2 × 2 (four-element) multiple-input multiple-output (MIMO) patch antenna system is designed and fabricated for a 2.45-GHz ISM band operation. It uses complementary split-ring resonator (CSRR) loading on its ground plane for antenna miniaturization. This reduces the single-element antenna size by 76%. The total board size of the proposed MIMO antenna system, including the GND plane is 100 × 50 × 0.8 mm3, while the single-patch antenna element has a size of 14 × 18 mm2. The antenna is fabricated and tested. Measured results are in good agreement with simulations. A minimum measured isolation of 10 dB is obtained given the close interelement spacing of 0.17λ. The maximum measured gain for a single operating element is -0.8 dBi.

RF Energy Harvesting for Ubiquitous, Zero Power Wireless Sensors

This paper presents a review of wireless power transfer (WPT) followed by a comparison between ambient energy sources and an overview of different components of rectennas that are used for RF energy harvesting. Being less costly and environment friendly, rectennas are used to provide potentially inexhaustible energy for powering up low power sensors and portable devices that are installed in inaccessible areas where frequent battery replacement is difficult, if not impossible. The current challenges in rectenna design and a detailed comparison of state-of-the-art rectennas are also presented.

A Frequency Reconfigurable MIMO Antenna System for Cognitive Radio Applications

Abstract In this paper, a two element frequency reconfigurable multiple-input-multiple-output (MIMO) antenna system is presented. The proposed antenna consists of miniaturized patch antenna elements, loaded with varactor diodes to achieve frequency reconfigurability. The antenna has bandwidth of 30 MHz and provides a smooth frequency sweep from 2.12 GHz to 2.4 GHz by varying the reverse bias voltage of varactor diode. The antenna is designed on an FR4 substrate and occupies a space of 50×100 × 0.8 mm3. The antenna is analyzed for its far-field characteristics as well as for MIMO performance parameters. Designed antenna showed good performance and is suitable for cognitive radios (CR) applications.

A multi-band 2×1 MIMO antenna system consisting of CSRR loaded patch elements

A miniaturized printed 2×1 MIMO antenna system is designed and fabricated. The antenna has resonant frequencies at 750 MHz, 1.18 GHz, 1.7 GHz and 2.26 GHz. The elements of the MIMO antenna system are patch antennas loaded with CSRR. The CSRR loading is used for patch antenna miniaturization and to obtain multiple resonant frequencies. The overall dimensions of the MIMO antenna system are 120×60×0.8 mm3 while the area of individual patch element is 44×35 mm2. The bandwidth, isolation and correlation coefficient of the MIMO antenna system are evaluated from its measured s-parameters while the MEG of the antenna elements are evaluated from the radiation pattern of the antenna elements.

Compact UWB-MIMO antenna with band-rejection in WLAN

A compact multiple-input-multiple-output (MIMO)/ diversity ultra-wideband (UWB) antenna with planar structure is presented in this paper. It comprises of two modified rectangular slot antennas excited by microstrip transmission lines. An inverted U-shaped slot is inserted in the feeding transmission line to create a band-rejection at WLAN band (5.15-5.825 GHz). The mutual coupling between the two antenna elements is decreased by introducing T-shaped slot and a rectangular slot between them. The rectangular slot reduces the coupling at lower frequencies i.e. 3-5 GHz while T-shaped slot maintains good isolation at higher frequencies i.e. 5-10.6 GHz. The proposed antenna has a bandwidth of 7.5 GHz and operates at 3.1-10.6 GHz. It occupies a space of 22 × 26 mm2 and achieves minimum isolation of 20 dB between its antenna elements over the whole operating band. The small size, good isolation and stable radiation patterns of the proposed antenna make it suitable candidate for UWB diversity applications.

Analysis of miniaturized MPA design using theory of characteristic modes

A miniaturized microstrip patch antenna (MPA) design is analyzed using the theory of characteristic modes. The miniaturization is achieved by using an annular slot in the ground plane of the MPA. The theory of characteristic modes is applied to understand the resonant behavior of the antenna and to find the optimal location for the excitation of the antenna. Using this method, a 46% miniaturization in the size of MPA is achieved.

Annular slot based printed MIMO antenna system design

A 3-element printed MIMO antenna system operating in the 2.45 GHz band is presented. The antenna is made up of three annular slot antenna elements. The antenna shows good isolation characteristics between closely spaced antenna elements. A minimum measured isolation of 11 dB is found between its antenna elements. The antenna has a bandwidth of 100 MHz. It is evaluated for MIMO antenna performance matrices where it shows good performance.

Channel capacity analysis of a novel printed MIMO antenna system in a wireless mobile environment

In this paper, novel highly compact 4-element and 8-element printed MIMO antenna systems are designed to operate in the 5 GHz 802.11ac WLAN band. The dimensions of both antennas are 100×50×0.8 mm3 including the ground plane. From the radiation patterns of the antenna elements, a stochastic model is used to analyze the channel capacity of both the elements in a wireless mobile channel. Due to non-zero correlation coefficient between the MIMO antenna elements, the achieved capacity at 20 dB SNR in the 4-element MIMO antenna system is 6 bits/sec/Hz less than the corresponding ideal 4-element MIMO antenna system with uncorrelated elements. Measured performance metrics for both antennas are presented.

A compact broadband circularly polarized WSS antenna for future 5G communication systems

This paper presents a small broadband circularly polarized square slot antenna for future 5G communication systems. The proposed antenna has a compact size of 5.5×5.5 mm2 and consists of a wide square slot (WSS) and a T-shaped stub in the ground plane. The WSS structure is fed through a microstrip transmission line designed on the other side of the substrate. Symmetric and asymmetric fractals are made with in the WSS structure to achieve wide CP bandwidth. The impedance and 3dB axial ratio (AR) bandwidth of the proposed antenna is 72.15% (21.6–41.8 GHz) and is 67.17% (25.69–44.5 GHz) respectively. The simulated peak gain of 4.85 dBic is achieved with in the AR band.