Rifaqat Hussain

A Cognitive Radio Reconfigurable MIMO and Sensing Antenna System

A planar, compact, single-substrate, multiband, frequency-reconfigurable multiple-input-multiple-output (MIMO) antenna system is presented. The proposed antenna elements are integrated with an ultrawideband (UWB) sensing antenna to develop a complete antenna platform for cognitive radio (CR) applications. The dual-element MIMO antenna is integrated with p-i-n and varactor diodes for frequency reconfigurability. Two modes of selection are used for the MIMO antenna system reconfigurability along with varactor tuning to sweep the frequency over a wide band especially below 1 GHz. The proposed sensing antenna is used to cover a wide range of frequency bands from 720 ~ 3440 MHz. The complete system comprising the multiband reconfigurable MIMO antennas and UWB sensing antenna for CR applications is proposed with a compact form factor. The antenna system is developed on a single substrate area of dimensions 65×120×1.56 mm3.

A compact reconfigurable multi-band MIMO antenna system

In this paper, PIN diode based reconfigurable mul- tiple input multiple output (MIMO) modified printed inverted F-shape antenna (PIFA) is presented. The proposed design is very versatile as it can be used to cover many frequency bands. The well known frequency bands covered are LTE 900 MHz, GSM 1800, WLAN 2450 MHz with several other bands as well. The proposed design provides at least 10 dB isolation between its antenna elements. The dimensions of the proposed design were 11×28 mm2 with a ground plane area of 60×120 mm2.

Compact 4-element MIMO antenna with isolation enhancement for 4G LTE terminals

In this work, a wide-band, planar, printed inverted-F antenna (PIFA) is proposed with multiple-input-multiple-output (MIMO) antenna configuration. The MIMO antenna system consists of 4-elements operating at 2.1 GHz frequency band for 4G LTE applications. The proposed design is compact, low profile and suitable for wireless handheld devices. The MIMO antenna is fabricated on commercially available FR4 substrate with εr equal to 4.4. The dimensions of single element are 26×6 mm2 with board volume equal to 100×60×0.8 mm3. Isolation is improved by 5 dB in the proposed design using ground slots. Characteristics mode analysis (CMA) is used to analyze the behaviour of the antenna system.

4-element planar MIMO reconfigurable antenna system for cognitive radio applications

In this paper, 4-element meandered dual mode meandered F-shape reconfigurable multiple-input multiple-output (MIMO) antenna is presented. The frequency reconfigurability is achieved using a combination of PIN diodes and varactor diodes. The proposed design is useful as it covers wide frequency bands below 1 GHz. The proposed design is compact and highly suitable to be used in cognitive radio based wireless handheld devices. Isolation enhancement between various antenna elements was achieved using a defected ground plane structure. The two modes cover the frequency bands 743~1240 and 2400 MHz with bandwidth of at-least 60 MHz.

Compact low frequency six-port design for wireless communication devices

In this paper, a compact wide-band direction finding system is proposed that is suitable for wireless handheld and mobile communication devices. The proposed six-port (SP) design covers a low frequency wide band ranging from 1.68 GHz to 2.25 GHz with a bandwidth of almost 570 MHz. This low frequency operation is unique to this design, as most of the available designs cover high frequency bands starting above 2 GHz. The frequency bands covered by this design are for commercially available wireless standards. This includes GSM-1800/GSM-1900/PCS (1850~1990 MHz) and UMTS(1885~2200 MHz) bands. A Major contribution of this optimized design results in 40% reduction in the total area comparing its size with the most relevant design. The dimensions of the optimized SP design are suitable to be accommodated within a software defined radio and cognitive radio platforms. Low frequency RF DF and compact size of this design are the key features. Moreover, the proposed system based on SP design can be extended to a variety of applications and other low cost microwave measurements as well. This SP design is realized on a dielectric substrate area of 65 × 65 × 0.64 mm3.

Reconfigurable MIMO Antennas for Cognitive Radios

The concept of cognitive radio (CR) is a new paradigm that autonomously discover the demographics of radio spectrum to get information about its utilization and determine the services being offered. The prospect usage of CR architectures in future generations of wireless communications is very promising. CR basically integrates machine learning algorithms into wireless devices and networks. It is evolving from self awareness stage to cognitive learning autonomously about its environment which would be helpful to adapt to new wireless standards, access users environment and behavior. A fundamental part in a CR is its front-end antenna system. The function of such antennas are self-awareness by scanning the entire spectrum of interest along with provides serving by reconfigurable antennas over several bands. In the near future, CR platforms will be integrated to become a part of wireless communication standards. The front end of a CR consists of a sensing antenna for spectrum scanning and a reconfigurable antenna or reconfigurable multiple-input-multiple-output (MIMO) antenna system for communication over several frequency bands. Reconfigurable antennas in CR applications are used to vary its fundamental properties to efficiently utilize the available bandwidth while MIMO antenna system based reconfigurable antennas are to be used to meet the high data rate requirements of future wireless terminals. This chapter will shine some light on the most recent CR front-end antennas focusing on MIMO based integrated architecture.

Low profile 6-element modified-monopole MIMO antenna system for mobile applications

In this paper, a printed, compact modified-monopole multiple-input-multiple-output (MIMO) antenna system is presented. The MIMO antenna system consists of 6-elements operating at 2 GHz for 4G applications. The proposed design is suitable for wireless handheld devices and mobile terminals. The MIMO antenna is fabricated on a commercially available FR4 substrate with εr equal to 4.4. The dimensions of the board are 115 × 65 mm2 representing a typical smart phone back plane size with a single element size of 16.5 × 7.42 mm2.

A dual six-port with two-angle resolution and compact size for mobile terminals

A compact, low frequency wide-band, dual-angle resolution dual six-port design for direction finding (DF) systems within mobile terminals is proposed. This system covers the frequency band from 1.68 GHz to 2.25 GHz with a minimum bandwidth of 570 MHz. This relatively low frequency operation is unique to this design for DF, as most of the available design covers high frequency bands above 2 GHz. In addition, a major contribution of this optimized design is 40% reduction in the total area compared with the closest design. Moreover, the proposed system is distinctive as it is capable of finding the direction in both elevation and azimuth planes. This six-port design is realized on a dielectric substrate area of 65 × 65 × 1.28 mm3.

A reconfigurable dual-band MIMO antenna system for mobile terminals

In this paper, a varactor diode based two element reconfigurable, dual-band, multiple input multiple output (MIMO) antenna is presented. The single antenna element is a modified printed inverted F-shape antenna (PIFA) with radiating lines and a folded patch. This proposed structure is grounded by a metallic wall for size optimization and compactness. The proposed design is very versatile as it can be used to cover wide frequency bands for dual-band operation. The well known frequency bands covered are GSM-750, GSM-870, LTE-900, LTE-1800, with several other bands as well. The proposed design provides at least -12 dB isolation between its antenna elements. The dimensions of the proposed single element design were 12×30 mm2 with a ground plane area of 65×120 mm2.

Characteristic modes of circular slot antennas etched on a finite ground plane

The theory of characteristic modes (TCM) is gaining momentum in the analysis of slot antennas, whose size is comperable to the metallic plane or chassis. In this paper, we will analyze the behavior of a circular slot on a fixed ground plane (GND). Circular slots having small dimensions compared to the GND do not alter the characteristic mode (CM) current distribution and the Modal Significance (MS) plots significantly but when the size of such slots increases, new slot modes are created. Some of the chassis modes are modified due to the presence of a slot at their current maxima. The generation of the slot mode depends on the size and the location of circular slot on the chassis.