Reconfigurable Antenna Design

A novel technique to reconfigure the frequency range of a planar monopole antenna is presented. By adjusting the degree of spiral tightness, a shift of the well-matched operating frequency range is achieved. The proposed antenna is capable of covering the frequencies in the range from 2.9 to 15 GHz, depending on the degree of spiral tightness. The antenna yields a high-efficiency across the full operating bandwidth. Radiation patterns show good omnidirectional features in all primary cuts and remain relatively stable with the change of antenna configuration, so that it is a remarkable candidate for indoor or mobile applications where a large frequency range and omnidirectional radiation are required.

A compact multiband antenna has been redesigned to be reconfigurable with embedded switches to allow selective addressing of these bands. The concept, simulation, and implementation of developing these reconfigurable antennas using MEMS switches and their relevant experimental demonstrations will be discussed in this article. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1892–1896, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24474

Results for a reconfigurable PIFA using smart materials are presented. A novel approach is investigated by using PZT materials that switch into contact using a dc control voltage to reconfigure the PIFA structure and hence produce a tunable antenna.

A new CPW fed E-shaped reconfigurable Antenna with frequency diversity is designed and analyzed in this paper. The basic antenna consists of CPW fed E-shaped Patch antenna which operates at 5.8GHz which falls in IEEE 802.11 WLAN/RFID applications. The reconfigurability in frequency is obtained by connecting the switches in basic antenna by use of PIN diodes. By controlling the switches the antenna can be operated at three different frequencies namely 8.5GHz, 6.18GHz and 8.76GHz. The return loss of -28dB, -28.2dB,-33.07dB and -38.17dB are observed at 5.8GHz, 8.5GHz, 6.18GHz and 8.76GHz respectively. Two dimensional radiation patterns with elevation angles, gain, and efficiency of about 70% are also obtained. The compact aperture area of the antenna is 35mm X 30mm. The thickness of the substrate is 1.5mm. The proposed antenna is described and simulated results are illustrated. The results of antenna are simulated by using Zeeland's MOM based IE3D tool.

A multifunctional reconfigurable antenna (MRA) capable of operating in nine modes corresponding to nine steerable beam directions in the semisphere space is presented. The MRA consists of an aperture-coupled driven patch antenna with a parasitic layer placed above it. The surface of the parasitic layer has a grid of 3 3 electrically-small square-shaped metallic pixels. The adjacent pixels are connected by PIN diode switches with ON/OFF status to change the geometry of the parasitic surface, which in turn changes the current distribution on the antenna, thus provides reconfigurability in beam steering direction. The MRA operates in the IEEE 802.11 frequency band (2.4-2.5 GHz) in each mode of operation. The antenna has been fabricated and measured. The measured and simulated impedance and radiation pattern results agree well indicating an average of dB realized gain in all modes of operation. System level experimental performance evaluations have also been performed, where an MRA equipped WLAN platform was tested and characterized in typical indoor environments. The results confirm that the MRA equipped WLAN systems could achieve an average of 6 dB Signal to Noise Ratio (SNR) gain compared to legacy omni-directional antenna equipped systems with minimal training overhead.

In this paper, a frequency and radiation reconfigurable microstrip antenna design is proposed for Ultra Wide Band application (UWB). The radiating patch was an E-shaped microstrip printed over a FR-4 substrate with relative dielectric constant of 4.3, and thickness of 3 mm. A microstrip line feeds this proposed antenna. To satisfy the UWB frequencies the length ground plane has been reduced. The finite ground plane is printed on the lower side of dielectric substrate. The modeling process and performance estimation of the designed antenna was achieved by using the electromagnetic simulator, Computer Simulation Technology (CST) Software. Simulation results indicate that the designed antenna has an effective bandwidth, for-10 dB, extending from approximately 3 GHz to more than 16 GHz, which covers the entire UWB band of 3.1 GHz to 10.6 GHz.

In this paper, several designs of micorstip arrays antennas, suitable for wireless communication applications, are presented. This paper demonstratesseveral shapesof microstrip array antennas, such as rectangular and circular patch antennas array. Specifically, 4x1, 2x1, and single element of both shapes are designed and simulated bya full wave simulator(IE3d). Moreover, this paper presents acomparison between both rectangular and circular antenna arrays.Since, the resonance frequency of these antennas is 2.4 GHz, these antennas are suitable for ISM band and WLAN.

An approach for transmitting multiple signals using a single switched parasitic antenna (SPA) has been recently reported. The idea there is to map the signals to be transmitted onto a set of basis functions that serve as 'virtual antennas' in the beamspace (i.e. wavevector) domain. In this work, we generalize the derivation of the antenna pattern basis functions regarding a 3-element SPA of arbitrary radiating elements, within a symmetric array topology, for multiplexing signals in the wavevector domain (using different beampatterns) rather than in the hardware antenna domain with multiple feeding ports. A fully operational antenna system example is modeled, optimized regarding its return loss and the power imbalance between the basis functions, and finally realized. The measurements of the SPA show good agreement with the simulated target values, revealing an accurate design approach to be adopted as a fast SPA prototyping methodology. The SPA has been successfully employed for multiplexing two BPSK datastreams over-the-air, thus paving the way for practically compact and highly efficient MIMO transceiver designs.

Continuous electrowetting (CEW) is demonstrated to be an effective actuation mechanism for reconfigurable radio frequency (RF) devices that use non-toxic liquid-metal tuning elements. Previous research has shown CEW is an efficient means of electrically inducing motion in a liquid-metal slug, but precise control of the slug's position within fluidic channels has not been demonstrated. Here, the precise positioning of liquid-metal slugs is achieved using CEW actuation in conjunction with channels designed to minimize the liquid-metal surface energy at discrete locations. This approach leverages the high surface tension of liquid metal to control its resting position with submillimeter accuracy. The CEW actuation and fluidic channel design were optimized to create reconfigurable RF devices. In addition, solutions for the reliable actuation of a gallium-based, non-toxic liquid-metal alloy (Galinstan) are presented that mitigate the tendency of the alloy to form a surface oxide layer capable of wetting to the channel walls, inhibiting motion. A reconfigurable slot antenna utilizing these techniques to achieve a 15.2% tunable frequency bandwidth is demonstrated.

ABSTRACT Tunable reflective elements based on graphene patches are proposed for reconfigurable-beam reflectarray antennas. The complex conductivity of graphene can be dynamically varied when an electric field is applied, allowing to control the phase of the reflected wave at each element of the reflectarray. The proposed patches support plasmonic slow wave propagation at THz frequencies, drastically reducing the physical dimensions of the cell. Here, an element which provides a dynamic phase range of more than 300° is demonstrated with moderate losses in a wide band. The scattering matrix of the element has been obtained by full-wave electromagnetic simulations and also by a circuit approach accurately modeling the graphene cell response.

A planar substrate-superstrate configuration loaded by a graphene sheet is proposed as a novel reconfigurable antenna for THz applications. The effects of the introduction of graphene on the dispersion and radiation properties of the fundamental leaky modes supported by the structure are analyzed in detail, with the aim of investigating the possibility of beam scanning at a fixed frequency by varying the graphene chemical potential via an electrostatic bias. After optimizing the graphene position inside the antenna substrate for achieving maximum directivity at broadside, large scanning ranges are obtained in which the normalized attenuation constants of the fundamental TE/TM leaky-mode pair exhibit small values and reduced variation, thus producing a scanning process with an essentially-constant narrow beamwidth. In the same ranges, the phase constants of the TE/TM-mode pair are shown to be equalized, thus opening the possibility of designing fixed-frequency scanning antennas with conical beams and reconfigurable dual polarization.

With the headway in the growth of the wireless communication over the past few years, there lies the increase of miniaturization, multiband and cost effective. So as to meet all these requirements, Fractal antenna design is preferred. With these advantages, performance of the fractal antenna can be enhanced with the concept of reconfiguration. In this paper the Reconfiguration is achieved with the help of varactor diodes being placed in the patch with the electronic dc biasing provided at the right part of the patch and the left part of the patch is loaded with the fractals so as to obtain the multiband and miniaturization. The Proposed antenna is being designed and simulated using Ansoft-High Frequency Structure Simulator (HFSS). The proposed antenna is being operated at 2.45GHz yielding after simulation four resonant frequency that are nearly constant covering band of 2.26-2.31GHz,5.0251GHz,7.06-7.15GHz,9.54-9.59GHz.The Gain obtained is 7.63dB.The Proposed antenna can be used in applications such as WiMax, WLAN, Satellite etc

Procedures using neural networks are developed for characterizing multiband reconfigurable antennas. A multilayer perceptron (MLP) is used to locate the operational frequency bands of the antenna at different reconfigured conditions. Another self-organizing map (SOM) neural network accomplishes the task of locating the switches to be turned ON for a desired frequency response. The developed formulation is tested on a laboratory prototype antenna.

Results for a reconfigurable PIFA using smart materials are presented. A novel approach is investigated by using PZT materials that switch into contact using a dc control voltage to reconfigure the PIFA structure and hence produce a tunable antenna.

This letter investigates a new reconfigurable antenna technique based on the rotation of a slot. The surface currents are redistributed for each slot position. The antenna is simulated, fabricated, and tested. The return loss frequency tuning matches the simulated data. The antenna radiation pattern remains unchanged for different slot positions. Finally, the process for automatic rotation and control of the slot is investigated using graph models.

This paper presents the concept of using a harmonic trap to design a wideband reconfigurable antenna. The reconfigurable antennas can be used to select one of a number of operating frequency bands. If these bands cover a very wide frequency range, then one of the higher-frequency bands can be a harmonic of a lower band. When the antenna operates at the lower band, it can have a good match at the high frequency. This paper proposes a technique for designing a wideband reconfigurable printed dipole antenna so as to select only one of the operating frequency bands by using a harmonic trap. The antenna is designed, fabricated, and measured. It is shown that by using switches and harmonic traps, a reconfigurable printed dipole antenna can be designed over a frequency range of 3:1. The antenna is thus suitable for frequency switching in the FCC ultra-wideband allocation. Figure 6 Measured radiation patterns of reconfigurable printed dipole at the resonance frequency of the bands in the E-plane (solid line: copolarization; dashed line: cross-polarization) Figure 7 Measured radiation patterns of reconfigurable printed dipole at the resonance frequency of the bands in the H-plane (solid line: copolarization; dashed line: cross-polarization)

ABSTRACT A reconfigurable twin inverted-F monople antenna has been developed to cover various services including (GSM/DCS/UMTS/IMT-2000/WLAN). These services operate at seven different frequency bands (800 MHz, 900 MHz, 1.8 GHz, 2.1 GHz, 2.4 GHz WLAN, and 5.2 GHz frequency bands). The developed antenna is compact and has a low profile which makes it optimum for laptop implementation (103 mm times 12 mm times 3 mm). It utilizes two-branches, and each branch has more than one-resonance. The twin PIFA antennas are switchable to collectively provide wider range of operating frequencies, i.e. services. The embedded switches, however, are strategically located next to the ground plane to ease their implementation, and reduce parasitics. The implemented design is aimed at simultaneously providing fixed service like Bluetooth at 2.4 GHz, and switchable services (like GSM or PCS for example) at all other frequencies.

This letter presents a Vivaldi antenna having the capability of dynamically rejecting interferers, mainly aiming at multistandard communication with dynamic frequencies allocation. Only half of the Vivaldi is used and placed over a ground plane, which is suitable to vehicular communication. The rejection filter is integrated to the antenna real estate and consists of two microstrip resonators and two varactor diodes coupled to the slot of the Vivaldi. It is simply biased by applying the control voltage at the antenna RF port. Good matching is achieved from 2.5 to 8 GHz while rejecting a band whose central frequency can be tuned from 1.8 to 5.8 GHz. Simulated and measured return loss, gain, and radiation patterns are presented. The measured gain rejection in the direction of the radiation maximum is about 20 dB or better in the entire tuning range.