Recent Advances in Reconfigurable Antennas at University of Technology Sydney

This paper presents an overview of the recent advances in reconfigurable antennas for wireless communications at University of Technology Sydney.In particular,it reports our latest progress in this research field,including a multi-linear polarization reconfigurable antenna,a pattern reconfigurable antenna with multiple switchable beams,and a combined pattern and polarization reconfigurable antenna.

Reconfigurable Pattern Patch Antenna for Mid-Band 5G:A Review

New requirements in communication technologies make it imperative to rehash conventional features such as reconfigurable antennas to adapt with the future adaptability advancements.This paper presents a comprehensive review of reconfigurable antennas,specifically in terms of radiation patterns for adaptation in the upcoming Fifth Generation(5G)New Radio frequency bands.They represent the key of antenna technology for materializing a high rate transmission,increased spectral and energy efficiency,reduced interference,and improved the beam steering and beam shaping,thereby land a great promise for planar antennas to boost the mid-band 5G.This review begins with an overview of the underlying principals in reconfiguring radiation patterns,followed by the presentations of the implemented innovative antenna topologies to suit particular advanced features.The various adaptation techniques of radiation pattern reconfigurable planar antennas and the understanding of its antenna design approaches has been investigated for its radiation pattern enhancement.A variety of design configurations have also been critically studied for their compatibilities to be operated in the midband communication systems.The review provides new insights on pattern reconfigurable antenna where such antennas are categorized as beam steering antenna and beamshaping antennas where the operation modes and purposes are clearly investigated.The review also revealed that for mid-band 5G communication,the commonly used electronic switching such as PIN diodes have sufficient isolation loss to provide the required beam performance.

Researches on Reconfigurable Antenna in CEMLAB at UESTC

This paper summarizes the achievement and progress in the research on reconfigurable antenna since 2001, in Computational Electromagnetics Laboratory （CEMLAB） at University of Electronic Science and Technology of China （UESTC）. Several typical reconfigurable antennas are introduced, which can realize frequency, pattern or frequency-pattern reconfigurability by electrically controlling methods. Some techniques involved in the design and analysis of reconfigurable antennas are reported. At last, the development trend of reconfigurable antenna is predicted in the conclusions.

A Planar 4-Bit Reconfigurable Antenna Array Based on the Design Philosophy of Information Metasurfaces

Inspired by the design philosophy of information metasurfaces based on the digital coding concept,a planar 4-bit reconfigurable antenna array with low profile of 0.15λ0(whereλ0is the free-space wavelength)is presented.The array is based on a digital coding radiation element consisting of a 1-bit magnetoelectric(ME)dipole and a miniaturized reflection-type phase shifter(RTPS).The proposed 1-bit ME dipole can provide two digital states of"0"and"1"(with 0°and 180°phase responses)over a wide frequency band by individually exciting its two symmetrical feeding ports.The designed RTPS is able to realize a relative phase shift of 173°.By digitally quantizing its phase in the range of 157.5°,additional eight digital states at intervals of 22.5°are obtained.To achieve low sidelobe levels,a 1:16 power divider based on the Taylor line source method is employed to feed the array,A prototype of the proposed 4-bit antenna array has been fabricated and tested,and the experimental results are in good agreement with the simulations.Scanning beams within a±45°range were measured with a maximum realized gain of 13.4 dBi at12 GHz.The sidelobe and cross-polarization levels are below-14.3 and-23.0 dB,respectively.Furthermore,the beam pointing error is within 0.8°,and the 3 dB gain bandwidth of the broadside beam is 25%.Due to its outstanding performance,the array holds potential for significant applications in radar and wireless communication systems.

Frequency Reconfigurable Antenna for Multi Standard Wireless and Mobile Communication Systems

In this paper,low profile frequency reconfigurable monopole antenna is designed on FR-4 substrate with a compact size of 30 mm^(3)×20 mm^(3)×1.6 mm^(3).The antenna is tuned to four different modes through three pin diode switches.In Mode 1(SW1 to SW3=OFF),antenna covers a wideband of 3.15–8.51 GHz.For Mode 2(SW1=ON,SW2 to SW3=OFF),the proposed antenna resonates at 3.5 GHz.The antenna shows dual band behavior and covers 2.6 and 6.4 GHz in Mode 3(SW1 and SW2=ON,SW3=OFF).The same antenna covers three different bands of 2.1,5 and 6.4 GHz when operating in Mode 4(SW1 to SW3=ON).The proposed antenna has good radiation efficiency ranges from 70%∼84%,providing adequate average gain of 2.05 dBi in mode 1,1.87 dBi in mode 2,1.4–1.75 dBi in mode 3 and 1.05–1.56 dBi in mode 4.The achieved impedance bandwidths at respective frequencies ranges from 240 to 5000 MHz.The Voltage Standing Waves Ratio(VSWR)of less than 1.5 is achieved for all operating bands.To validate the simulation results,the proposed antenna is fabricated and experimentally tested in antenna measurement laboratory.Due to its reasonably small size and support of multiple bands operation,the proposed antenna can be used in modern communication systems for supporting various applications such as fifth generation(5G)mobile and wireless local area networks(WLAN).

Frequency Reconfigurable Antenna for Portable Wireless Applications

In this paper,the design and experimental evaluation of a hexagonalshaped coplanar waveguide(CPW)-feed frequency reconfigurable antenna is presented using flame retardant(FR)-4 substrate with size of 37×35×1.6 mm3.The antenna is made tunable to three different modes through the status of two pin diodes to operate in four distinct frequency bands,i.e.,2.45 GHz wireless fidelity(Wi-Fi)in MODE 1,3.3 GHz(5G sub-6 GHz band)in MODE 2,2.1 GHz(3G Long Term Evolution(LTE)-advanced)and 3.50 GHz Worldwide Interoperability for Microwave Access(WiMAX)in MODE 3.The optimization through simulation modeling shows that the proposed antenna can provide adequate gain(1.44∼2.2 dB),sufficient bandwidth(200∼920 MHz)and high radiation efficiency(80%∼95%)in the four resonating frequency bands.Voltage standing wave ratio(VSWR)<1.5 is achieved for all bands with properly matched characteristics of the antenna.To validate the simulation results,fabrication of the proposed optimized design is performed,and experimental analysis is found to be in a considerable amount of agreement.Due to its reasonably small size and support of multiple frequency bands operation,the proposed antenna can support portable devices for handheld 5G and Wireless LAN(WLAN)applications.

RF MEMS Based Reconfigurable Rectangular Slotted Self Similar Antenna

Wireless communication systems which require flexibility and reconfigurability in antenna systems faces main problems like antenna performance, size, weight and cost. A wide band Frequency Reconfigurable Rectangular Slotted Self Similar Antenna has been proposed in this paper. The rectangular slotted patch is repeated for two iterations at different scales and is separated by means of Radio Frequency Micro Electro Mechanical Systems (RF MEMS) switches in order to provide reconfigurability. The antenna can operate in three frequency bandsi.e. K-band, Ku-band and Ka-band by altering the states of RF MEMS switches. To avoid fringing effects and to improve antenna performance, quarter wavelength (λ/4) spacing is required between the antenna and the ground plane. However, a Reconfigurable Antenna requires different λ/4 spacing which is difficult to achieve using a common ground plane. So the Frequency Reconfigurable antenna is integrated with high impedance surface (HIS) like Electronic Band Gap (EBG) structures to suppress standing waves and surface waves with a unified profile thickness of 1.75 mm. The overall dimension of the proposed antenna along with RF MEMS Switch, feed element and HIS is about 8 mm × 8 mm × 1.75 mm. The simulated results of the proposed antenna reveal enhancement in antennas performance like Voltage Standing Wave Ratio (VSWR), Front to Back Ratio (FBR) and bandwidth when it is placed over HIS EBG. Also the radiation patterns of the proposed antenna when placed over EBG shows the suppression of side lobe and backward radiation.

Th-Shaped Tunable Multi-Band Antenna for Modern Wireless Applications

A compact,reconfigurable antenna supporting multiple wireless services with a minimum number of switches is found lacking in literature and the same became the focus and outcome of this work.It was achieved by designing a Th-Shaped frequency reconfigurable multi-band microstrip planar antenna,based on use of a single switch within the radiating structure of the antenna.Three frequency bands(i.e.,2007–2501 MHz,3660–3983MHz and 9341–1046 MHz)can be operated with the switch in the ON switch state.In the OFF state of the switch,the antenna operates within the 2577–3280MHz and 9379–1033MHz Bands.The proposed antenna shows an acceptable input impedance match with Voltage Standing Wave Ratio(VSWR)less than 1.2.The peak radiation efficiency of the antenna is 82%.A reasonable gain is obtained from 1.22 to 3.31 dB within the operating bands is achieved.The proposed antenna supports UniversalMobile Telecommunication System(UMTS)-1920 to 2170 MHz,Worldwide Interoperability and Microwave Access(WiMAX)/Wireless Broadband/(Long Term Evolution)LTE2500–2500 to 2690 MHz,Fifth Generation(5G)-2500/3500 MHz,Wireless Fidelity(Wi-Fi)/Bluetooth-2400 to 2480 MHz,and Satellite communication applications in X-Band-8000 to 12000 MHz.The overall planar dimension of the proposed antenna is 40×20mm2.The antennawas designed,along with the parametric study,using Electromagnetic(EM)simulation tool.The antenna prototype is fabricated for experimental validation with the simulated results.The proposed antenna is low profile,tunable,lightweight,cheap to fabricate and highly efficient and hence is deemed suitable for use in modern wireless communication electronic devices.

Ultrahigh frequency tunability of aperture-coupled microstrip antenna via electric-field tunable BST

A composite ceramic with nominal composition of 45.0 wt%（Ba0.5Sr0.5）TiO3–55.0 wt%MgO（acronym is BST–MgO） is sintered for fabricating a frequency reconfigurable aperture-coupled microstrip antenna. The calcined BST–Mg O composite ceramic exhibits good microwave dielectric properties at X-band with appropriate dielectric constant εr around85, lower dielectric loss tan δ about 0.01, and higher permittivity tunability 14.8% at 8.33 k V/cm. An ultrahigh E-field tunability of working frequency up to 11.0%（i.e., from 9.1 GHz to 10.1 GHz with a large frequency shift of 1000 MHz）at a DC bias field from 0 to 8.33 k V/cm and a considerably large center gain over 7.5 d B are obtained in the designed frequency reconfigurable microstrip antenna. These results demonstrate that BST materials are promising for the frequency reconfigurable antenna.

A Polarization Programmable Antenna Array

Reconfigurable antennas are becoming a major antenna technology for future wireless communications and sensing systems.It is known that,with a single linear polarization(LP)reconfigurable antenna element,a preferred polarization can be produced from a set of multiple polarization states,thus improving the quality of the communication link.This paper presents a new concept of a polarization programmable reconfigurable antenna array that consists of a number of polarization reconfigurable antenna elements with a finite number of possible polarization states.By employing a new optimization strategy and programming the polarization states of all the array elements,we demonstrate that it is possible to realize any desired LP in the vectorial array radiation pattern with accurate control of sidelobe and crosspolarization levels(XPLs),thereby achieving the desired polarization to perfectly match that of the required communications signal.Both numerical and experimental results are provided to prove the concept,and they agree well with each other.

Frequency reconfigurable antenna actuated by inflated triangular structure:Design and analysis

This paper proposes a frequency reconfigurable triangular antenna actuated by an inflated triangular structure.The open path antenna is transformed from an open type to a closed structure by inflating.Inflatable structures are easy to manufacture by fusing 2 inextensible membranes together along a defined pattern of lines.However,the prediction of their deployed shape remains a challenge.To solve the pattern changed problem,guided by geometric analyses and local buckle characteristics,the inflated triangular structure has been designed and verified by experiment and simulation.In the process of transformation of the antenna,the resonant frequency of the antenna is changed because this frequency is determined by the conformational change.The resonant frequency changes from GHz to kHz when the design of initial structure sizes is from millimeter to meter.The measured peak gains,the frequency,and the radiation direction are also reconfigurable by the initial size.Finally,the reconfigurable resonator array is presented,which is coupled to electric fields to absorb all incident radiation.In this work,the changed pattern design by inflating is applied to the antenna design,and its frequency reconfigurability is achieved.Through the electricity performance analysis of the reconfigurable antenna,precise manufacturing will be possible and provide guidance for manufacturing frequency reconfigurable antennas.

Mutual information assessment of LOS MIMO systems with reconfigurable antenna arrays

In presence of line-of-sight （LOS） propagation, multiple-input multiple-output （MIMO） systems can achieve maximum capacity over the whole signal-to-noise ratio （SNR） region by deploying reconfigurable antenna arrays. In this paper, the moment generating function （MGF） formulas of the mutual information （MI） is obtained for LOS MIMO systems with reconfigurable arrays. Then the exact expression of the mean MI is derived in an easily evaluated form. The results show an excellent match between the theoretical curves and the Monte-Carlo simulations.

A novel broadband and high-gain microstrip reflectarray antenna with variable polarization

This article proposes a new kind of microstrip reflectarray antenna,of which the polarization could be reconfigured among all the polarization states instead of some fixed states in a dual-or multi-polarized antenna.The mechanism for polarized variability is so simple that only mechanical rotation is needed.Theoretical analysis shows that the reflected polarization covers all states and that the dual-or multi-layered unit structure sandwiched with air-gaps can broaden the bandwidth efficiently.Moreover,it is demonstrated that adopting more elements can enhance antenna gain.With these advantageous features,this kind of antenna has the potential significance for engineering applications in radar,communication,etc.In this article,a complete theoretical analysis as well as a specific design sample is given to verify this method.

Performance Evaluation of a Four-Element Antenna Array with Selection Circuits for Adaptive MIMO Systems

Reconfigurable antenna arrays increase the flexibility of adaptive MIMO systems. At present, most designs have adopted antenna arrays with reconfigurable elements. However, antenna selection is also an effective method, which has not been fully investigated. In this paper, the potential benefits of a four-element antenna array with selection circuits in the UMTS band （1920-2170 MHz） are explored. The array has eight pin-diodes embedded in the feeding network to select any sub-set of elements. For evaluation, an adaptive MIMO system was set up and a measurement campaign was taken in an indoor multi-path environment. The measurements were performed over a 300 MHz bandwidth centered at 2.05 GHz, covering the UMTS band. The results show that different channel conditions prefer different antenna array configurations. Therefore, in varying channel conditions the antenna array can support antenna selection algorithms to select the best sub-set of elements to increase channel capacity.