Reconfigurable antennas, with the ability to radiate more than one pattern at different frequencies and polarizations, are necessary in modern telecommunication systems. The requirements for increased functionality (e.g., direction finding, beam steering, radar, control, and command) within a confined volume place a greater burden on today's transmitting and receiving systems. Reconfigurable antennas are a solution to this problem. This paper discusses the different reconfigurable components that can be used in an antenna to modify its structure and function. These reconfiguration techniques are either based on the integration of radio-frequency microelectromechanical systems (RF-MEMS), PIN diodes, varactors, photoconductive elements, or on the physical alteration of the antenna radiating structure, or on the use of smart materials such as ferrites and liquid crystals. Various activation mechanisms that can be used in each different reconfigurable implementation to achieve optimum performance are presented and discussed. Several examples of reconfigurable antennas for both terrestrial and space applications are highlighted, such as cognitive radio, multiple-input-multiple-output (MIMO) systems, and satellite communication.

Reconfigurable Antennas for Wireless and Space Applications

The advancement in wireless communications requires the integration of multiple radios into a single platform to maximize connectivity. In this paper, the design process of reconfigurable antennas is discussed. Reconfigurable antennas are proposed to cover different wireless services that operate over a wide frequency range. They show significant promise in addressing new system requirements. They exhibit the ability to modify their geometries and behavior to adapt to changes in surrounding conditions. Reconfigurable antennas can deliver the same throughput as a multiantenna system. They use dynamically variable and adaptable single-antenna geometry without increasing the real estate required to accommodate multiple antennas. The optimization of reconfigurable antenna design and operation by removing unnecessary redundant switches to alleviate biasing issues and improve the system's performance is discussed. Controlling the antenna reconfiguration by software, using Field Programmable Gate Arrays (FPGAs) or microcontrollers is introduced herein. The use of Neural Networks and its integration with graph models on programmable platforms and its effect on the operation of reconfigurable antennas is presented. Finally, the applications of reconfigurable antennas for cognitive radio, Multiple Input Multiple Output (MIMO) channels, and space applications are highlighted.

Reconfigurable Antennas: Design and Applications

Three types of ultrawideband (UWB) antennas with triple notched bands are proposed and investigated for UWB communication applications. The proposed antennas consist of a planar circular patch monopole UWB antenna and multiple etched slots on the patch and/or split ring resonators (SRRs) coupled to the feed line. Good agreement is achieved between the simulated and measured results. These techniques are significant for designing UWB antennas with multiple narrow frequency notched bands or for designing multiband antennas.

Planar Ultrawideband Antennas With Multiple Notched Bands Based on Etched Slots on the Patch and/or Split Ring Resonators on the Feed Line

A planar polarization-reconfigurable metasurfaced antenna (PRMS) designed using metasurface (MS) is proposed. The PRMS antenna consists of a planar MS placed atop of and in direct contact with a planar slot antenna, both having a circular shape with a diameter of 78 mm (0.9 $\lambda_{0}$ ), making it compact and low profile. By rotating the MS around the center with respect to the slot antenna, the PRMS antenna can be reconfigured to linear polarization, left-hand and right-hand circular polarizations. An equivalent circuit is used to explain the reconfigurability of the antenna. The PRMS antenna is studied and designed to operate at around 3.5 GHz using computer simulation. For verification of simulation results, the PRMS antenna is fabricated and measured. The antenna performance, in terms of polarization reconfigurability, axial-ratio bandwidth, impedance bandwidth, realized boresight gain and radiation pattern, is presented. Results show that the PRMS antenna in circular polarizations achieves an operating bandwidth of 3.3–3.7 GHz (i.e., fractional bandwidth 11.4%), a boresight gain of above 5 dBi and high-polarization isolation of larger than 15 dB. While the PRMS antenna in linear polarization achieves a gain of above 7.5 dBi with cross-polarization isolation larger than 50 dB.

Design of Polarization Reconfigurable Antenna Using Metasurface

A polarization reconfigurable E-shaped patch antenna with wideband performance is proposed in this communication. The antenna is capable of switching its polarization from right hand circular polarization (RHCP) to left hand circular polarization (LHCP) and vice versa. Its structure is simple and consists of a single-layer single-feed E-shaped patch and two RF switches placed at appropriate locations in the slots. The design targets the WLAN IEEE 802.11 b/g frequency band (2.4-2.5 GHz) being used in various wireless communication systems. Full wave simulation is used for the antenna analysis, and a prototype of the antenna with an integrated DC biasing circuit has been fabricated and tested. Good agreement is obtained between simulated and measured results. The antenna exhibits a 7% effective bandwidth from 2.4 GHz to 2.57 GHz with a 8.7 dBic maximum gain. The antenna radiation symmetry is maintained upon switching between the two circular polarization modes.

Circular Polarization Reconfigurable Wideband E-Shaped Patch Antenna for Wireless Applications

A single-feed circular microstrip antenna with reconfigurable polarization capability is proposed. This antenna has a simple structure, which consists of a radiating circular patch, five switches (PIN diode), three matching stubs, and a 50 microstrip feed line. It can be switched between 4 different states: two states (low-frequency and high-frequency) for linear polarization (LP), one state for left hand circular polarization (LHCP) and one for right hand circular polarization (RHCP) by controlling the bias voltage of two PIN diodes. At the same time, three switchable matching stubs are used for matching every polarization state. Simulation results and experimental results show that the proposed antenna demonstrates a low cross polarization level, good impedance bandwidth, and a very good axial ratio in the circularly polarized states.

/pdf/a-novel-single-feed-circular-microstrip-antenna-with-2jinbxcliv.pdf

A Novel Single-Feed Circular Microstrip Antenna With Reconfigurable Polarization Capability

Two CPW-fed compact elliptical monopole UWB antennas are introduced with band rejection characteristic at the band used for wireless LAN applications. The antennas are fabricated on ultra thin (100 mum) liquid crystal polymer (LCP) and the band notch is caused by the presence of a resonating slot within the elliptical radiator. The two investigated antennas have a U-shaped slot and a C-shaped slot respectively. From the presented return loss and VSWR measurements, the C-shaped slot causes a wider rejection band compared to the U-shaped slot that could be used for the design of UWB antennas with reconfigurable sub bands. Both designs present almost identical radiation pattern behavior with the design without any slot with the exemption of the gain in the frequency notch band, which is maintained negative.

/pdf/cpw-fed-ultra-wideband-uwb-monopoles-with-band-rejection-53lbl8emyw.pdf

CPW-fed ultra wideband (UWB) monopoles with band rejection characteristic on ultra thin organic substrate

Cognitive radios seem to provide an answer to the problem aroused from the continuously increasing wireless applications that result in the congestion of the spectrum and the increase of interference. Cognitive radios require agile components and therefore antennas with reconfigurable characteristics. The current paper presents three antennas that use PIN diodes to achieve frequency, pattern and polarization reconfigurability respectively. An annular slot microstrip-fed antenna (ASA) is matched at three different frequencies and the reconfigurable matching network results in a reconfigurable operation frequency. The same radiator is used to achieve radiation pattern reconfigurability by integrating two PIN diodes on the slot circumference. Lastly a microstrip-fed circular patch antenna is presented which with the appropriate use of PIN diodes it can switch between left hand circular polarization (LHCP) and right hand circular polarization (RHCP).

Reconfiguring antenna characteristics using PIN diodes

This paper describes a novel and low-cost technique for detecting process-related interconnect faults in MCMs. This method is an alternative to existing test methods such as TDR, TDT electron beam, and capacitance techniques which are either expensive in terms of test equipment, are cumbersome due to the requirement of multiple probes, or provide poor fault coverage. The proposed technique applies a stimulus through a tuned load and a single probe at one end of the interconnect. By measuring the attenuation of the test stimulus due to pole movement relative to known attenuation measurements, interconnect faults such as near-opens, near-shorts, opens, and shorts can be detected. The total test time is small and the hardware cost of test equipment is low. Extensive simulations have been performed to show the validity of the method.

http://ieeexplore.ieee.org/iel3/4046/11600/00529832.pdf

A novel low-cost approach to MCM interconnect test

A curvature CPW-fed ultra-wideband monopole antenna on LCP substrate is proposed. The proposed antenna has good performance over the entire UWB frequency range (3.1 - 10.6 GHz), which enhanced the impedance bandwidth by adding four notches on rectangular patch. It can be easily mounted in conformal shapes (e.g. cylindrical), because LCP substrate have many attractiveness, especially flexible characteristic, for use in many mm-wave areas. The radiation patterns for both structures have similar performance to the conventional monopole antenna, because the antenna is flexed along its radiating side. The simulated peak-gain variation is less than 5 dBi for both structure, which cover UWB frequency range.

/pdf/a-curvature-cpw-fed-ultra-wideband-monopole-antenna-on-5g8va8q89i.pdf

Boyon Kim

Papers

A Novel Single-Feed Circular Microstrip Antenna With Reconfigurable Polarization Capability

CPW-fed ultra wideband (UWB) monopoles with band rejection characteristic on ultra thin organic substrate

Reconfiguring antenna characteristics using PIN diodes

A novel low-cost approach to MCM interconnect test

A curvature CPW-fed ultra-wideband monopole antenna on liquid crystal polymer substrate using flexible characteristic