R. Nilavalan

A Reconfigurable Wideband and Multiband Antenna Using Dual-Patch Elements for Compact Wireless Devices

A reconfigurable wideband and multiband C-Slot patch antenna with dual-patch elements is proposed and studied. It occupies a compact volume of 50 × 50 × 1.57 (3925 mm3), including the ground plane. The antenna can operate in two dual-band modes and a wideband mode from 5 to 7 GHz. Two parallel C-Slots on the patch elements are employed to perturb the surface current paths for excitation of the dual-band and the wideband modes. Two switches, implemented using PIN diodes, are placed on the connecting lines of a simple feed network to the patch elements. Dual-band modes are achieved by switching “ON” either one of the two patch elements, while the wideband mode with an impedance bandwidth of 33.52% is obtained by switching “ON” both patch elements. The frequencies in the dual-band modes can be independently controlled using positions and dimensions of the C-Slots without affecting the wideband mode. The advantage of the proposed antenna is that two dual-band operations and one wideband operation can be achieved using the same dimensions. This overcomes the need for increasing the surface area normally incurred when designing wideband patch antennas. Simulation results are validated experimentally through prototypes. The measured radiation patterns and peak gains show stable responses and are in good agreements. Coupling between the two patch elements plays a major role for achieving the wide bandwidth and the effects of mutual coupling between the patch elements are also studied.

Multiband Inverted-F Antenna With Independent Bands for Small and Slim Cellular Mobile Handsets

The design of a small ultra-thin printed inverted-F antenna (PIFA) with independent control on the resonant frequency bands is proposed. The antenna consists of a slotted radiator supported by shorting walls and a small ground plane. The structure is designed and optimized to operate at 2.09, 3.74 and 5 GHz with achievable bandwidths of 11%, 8.84% and 10%, respectively. These three bands cover the existing wireless communication frequency bands from 1.5-6.8 GHz. Each of the three bands can be controlled independently without affecting the other two bands. The 2.09 GHz band can be controlled to operate between 1.5-2.09 GHz (33.33%), the 3.74 GHz band can be controlled over the range of 3.57-4.18 GHz (15.76%) and the 5 GHz band can be controlled to cover the band from 5.00-6.80 GHz (30.50%). Results of intensive investigations using computer simulations and measurements show that the ground plane and the feed locations of the antenna have marginal effects on the performance of the antenna. The effects of the users hand and mobile phone housing on the return loss, radiation patterns, gains and efficiency are characterized. The measured peak gains of the prototype antenna at 2.09, 3.74 and 5 GHz are 2.05, 2.32 and 3.47 dBi, respectively. The measured radiation efficiencies for the corresponding three bands are 70.12, 60.29 and 66.24% respectively.

Multiband and Wideband Monopole Antenna for GSM900 and Other Wireless Applications

In this letter, the design of a compact monopole antenna for multiband and wideband operations is proposed. The antenna has three distinct frequency bands, centered at 0.94, 2.7, and 4.75 GHz. The antenna has a compact size of only 30 × 40 × 1.57 mm including the ground plane. The multiband and wideband operations are achieved by using an E-shaped slot on the ground plane. The design procedure is also discussed. The frequency bands can be independently controlled by using the parameters of the E-slot. The impedance bandwidth, current distributions, radiation patterns, gain, and efficiency of the antenna are studied by computer simulation and measurements.

Compact Printed Multiband Antenna With Independent Setting Suitable for Fixed and Reconfigurable Wireless Communication Systems

This paper presents the design of a low-profile compact printed antenna for fixed frequency and reconfigurable frequency bands. The antenna consists of a main patch, four sub-patches, and a ground plane to generate five frequency bands, at 0.92, 1.73, 1.98, 2.4, and 2.9 GHz, for different wireless systems. For the fixed-frequency design, the five individual frequency bands can be adjusted and set independently over the wide ranges of 18.78%, 22.75%, 4.51%, 11%, and 8.21%, respectively, using just one parameter of the antenna. By putting a varactor (diode) at each of the sub-patch inputs, four of the frequency bands can be controlled independently over wide ranges and the antenna has a reconfigurable design. The tunability ranges for the four bands of 0.92, 1.73, 1.98, and 2.9 GHz are 23.5%, 10.30%, 13.5%, and 3%, respectively. The fixed and reconfigurable designs are studied using computer simulation. For verification of simulation results, the two designs are fabricated and the prototypes are measured. The results show a good agreement between simulated and measured results.

Reconfigurable wideband patch antenna for cognitive radio

Cognitive radio communication is envisaged to be a new paradigm of methodologies for enhancing the performance of radio communication systems through the efficient utilization of radio spectrum. A key enabler for realization of a cognitive communication system is the capability of re-configurability in the underlying hardware and the associated protocol suite. Reconfigurable double C-slot microstrip patch antenna fed by 50 Ω microstrip line is proposed in this paper. The frequency tuning is performed by switching on and off two patches. The antenna can operate in dual-band or in very wide band mode in 5, 6 and 7 GHz bands. The wide-band mode can be obtained when both switches are in the ON state with impedance bandwidth of 33.52 % from 4.99 to 7 GHz. The total size of the ground plane is 50 × 50 mm2. The proposed antenna verified through both numerical simulation and measurement of an experimental prototype. The antenna achieves a gain of 5 to 8 dBi and radiation efficiency about 80%.

Experimental investigation of real aperture synthetically organised radar for breast cancer detection

Breast cancer is the most common cancer in woman, and early detection increases the likelihood of successful treatment and long-term survival screen film mammography is currently the most effective method for detecting breast tumours, however this technique suffers from relatively high false negative and positive detection rates, and it involves uncomfortable compression of the breast. This paper presents the experimental investigation of real aperture synthetically organised radar for breast cancer detection. The work presented herein originated as a theoretical study employing FDTD models. This contribution presents subsequent experimental validation using a mechanically-scanned 2 element antenna array and a breast phantom consisting of synthetic biological materials

A Novel Technique and Soldering Method to Improve Performance of Transparent Polymer Antennas

A novel technique and a nonthermal soldering method to improve the performance of AgHT-8 transparent polymer antennas are proposed in this letter. The proposed technique involves the removal of the coating layer at areas on the coplanar waveguide (CPW) ground and feed line where the connectors of the coaxial feed or legs of the SMA connectors will be attached and applying a coat of silver paint on the exposed areas before cold-soldering the coaxial connections or SMA connector legs. The nonthermal or cold soldering using electrically conductive paste enables direct soldering of the coaxial feed points or connector legs, which cannot otherwise be done with hot or thermal soldering. This type of connection greatly enhances the performance of the AgHT-8 polymer antennas compared to coaxial feed point connections through hot-soldered copper pads glued to the surface of the polymer coating. The proposed technique also gives a stronger connection bond than directly cold-soldering the feed points or connectors to the smooth surface of the AgHT-8 material. Furthermore, the copper pad connection technique also introduces additional losses contributed by the adhesive properties of the glue used. This proposed novel technique and soldering method may be extended to enhance antenna performance made from other similar transparent conductive polymers like ITO.

A Novel Transparent UWB Antenna for Photovoltaic Solar Panel Integration and RF Energy Harvesting

A novel transparent ultra-wideband antenna for photovoltaic solar-panel integration and RF energy harvesting is proposed in this paper. Since the approval by the Federal Communications Committee (FCC) in 2002, much research has been undertaken on UWB technology, especially for wireless communications. However, in the last decade, UWB has also been proposed as a power harvester. In this paper, a transparent cone-top-tapered slot antenna covering the frequency range from 2.2 to 12.1 GHz is designed and fabricated to provide UWB communications whilst integrated onto solar panels as well as harvest electromagnetic waves from free space and convert them into electrical energy. The antenna when sandwiched between an a-Si solar panel and glass is able to demonstrate a quasi omni-directional pattern that is characteristic of a UWB. The antenna when connected to a 2.55-GHz rectifier is able to produce 18-mV dc in free space and 4.4-mV dc on glass for an input power of 10 dBm at a distance of 5 cm. Although the antenna presented in this paper is a UWB antenna, only an operating range of 2.49 to 2.58 GHz for power scavenging is possible due to the limitation of the narrowband rectifier used for the study.

Miniature transparent UWB antenna with tunable notch for green wireless applications

In this paper, the design of a UWB antenna using a transparent AgHT-8 material is proposed for green wireless applications. Computer simulation is used for studies. For verification of the design, the proposed antenna is fabricated on an AgHT-8 film and measured. Results show that the antenna has better radiation efficiency relative to its size than the previous designs, good omni-directional radiation patterns throughout the FCC bandwidth of 3.1–10.6 GHz and a comparable gain. To filter out the unwanted signals in the WLAN band, two vertical slots are introduced to produce a tuning notch in the 5 GHz frequency band. For demonstration of green wireless applications, the transparent antenna is incorporated with a solar panel for harnessing solar energy. Results show that the transparency of the antenna makes it a good candidate for future green wireless applications.

Study on the performance deterioration of flexible UWB antennas

A flexible transparent film uwb antenna for curved surfaces has been designed and developed for wireless communications. The antenna has demonstrated good performance over the entire UWB bandwidth. It can be mounted on any conformal shape by virtue of the film properties of both the antenna as well as the substrate. The radiator and ground are both designed using AgHT-8 while the substrate is of a polymer. The antenna is shown to be able to maintain its performance below the 10dB level throughout the entire UWB bandwidth of 7.5GHz i.e from 3.1 GHz to 10.6 GHz as it is flexed through various radius of curvature thus providing an insight into how to overcome performance deterioration in wearable antennas.