Showing papers presented at "International Workshop on Antenna Technology in 2014"

Design of dual-band frequency selective surface with miniaturized elements

Abstract: A new dual-band frequency selective surface (FSS) is introduced in this paper. By having a miniaturized unit cell size, the proposed FSS transmission response shows minimal sensitivity to the angle of the incident electromagnetic wave. The two passband frequencies of the proposed configuration can be controlled independently by tunning the unit cell geometrical parameters appropriately. An equivalent circuit model analysis is presented to provide an insightful synthesis procedure for the filter. Full-wave numerical electromagnetic simulations are used to confirm the analysis and synthesis method presented based on the circuit model.

A spectrally efficient chipless RFID tag based on split-wheel resonator

Abstract: A completely passive, compact and fully printable chipless RFID tag is proposed. The tag utilizes the scattering from an array of orthogonally polarized split-wheel resonator pairs to achieve multi-bit data capacity. As split-wheel resonators of identical resonance frequency but with orthogonal polarizations do not interfere with each other in their first mode of resonance, this allows realization of the same frequency band twice, once for each polarization, to encode information, thus enhancing the overall spectral efficiency of the proposed tag. When interrogated with broadband plane wave signals of two orthogonal polarizations, the reader detects the RCS peaks generated by each of the resonator pairs in both x- and y-polarizations and with n resonator pairs, effectively 22n−1 items can be tagged and identified. As the tags require only single sided metallization, direct printing of such tags using conductive ink on paper or polymer substrate can yield a ubiquitous electronic tagging method which can replace optical barcode in the future.

Microstrip patch antenna array at 3.8 GHz for WiMax and UAV applications

Abstract: This paper presents the design of a rectangular microstrip line-fed patch antenna array with a centre frequency of 3.8 GHz for WiMAX and Unmanned Air Vehicle (UAV) applications. A single element, 1×2 and 2×2 microstrip rectangular patch antennas were designed and simulated in Computer Simulation Tool (CST) Microwave Studio environment. The results of designed antennas were compared in terms of Return Loss (S11 parameters), bandwidth, directivity, gain and radiation pattern. Compared to traditional microstrip antennas the proposed array structure achieved a gain and directivity of 13.2 dB and 13.5 dBi respectively. The antenna was fabricated using Rogers Duroid RT-5880 substrate with a dielectric constant e r of 2.2 and a thickness of 1.574 mm respectively. The array antennas were measured in the laboratory using Vector Network Analyser (VNA) and the results show good agreement with the array antenna simulation.

Optimal design of antenna arrays

Abstract: A universal method for the optimal design of antenna arrays is introduced in this paper. The method is based on the optimization of the power transmission efficiency between the antenna array to be designed and a test antenna array whose elements are placed in the desired directions in which radiations need to be maximized. The optimized distribution of excitations for the antenna array is determined by an eigenvalue equation derived from the Rayleigh quotient for the power transmission efficiency. The method is applicable to any type of antenna array. To demonstrate its validity, different antenna arrays for various applications have been designed using the proposed method.

Shorting strategies for a wearable L-slot planar inverted-F antenna

Abstract: Wearable antennas are one of the key technologies supporting wearable wireless communication systems. A wearable textile L-slot planar inverted-F antenna is investigated in this paper with different shorting methods, namely a folded strip of silver fabric, embroidered vias and eyelets. The performance of the proposed antenna with these three shorting methods is compared through simulations with realistic shorting models. According to the obtained numerical results, the antenna has three resonances at 4.5 GHz, 5.0 GHz and 6.6 GHz. In terms of gain and efficiency, the embroidered vias shorting method, which is the simplest and cheapest method to implement, has slightly lower performance than the silver fabric folded strip and eyelet shorting methods due to its higher resistance.

Design and measurement of W-band offset stepped parabolic reflector antennas for airport surface foreign object debris detection radar systems

Abstract: Debris on the airport surface may cause severe damage to aircraft. To detect these obstacles, foreign object debris (FOD) detection systems have been developed recently. By utilizing high-sensibility and weather robustness characteristics, the millimeter-wave radar is an essential sensor device for these systems. This paper discusses an offset parabolic reflector antenna for airport surface FOD detection radar systems. Firstly, the overview of the FOD detection radar systems, which employs a band of between 92 GHz and 100 GHz, is shown. For the azimuth beam scanning antenna, the antenna is required to achieve both a narrow azimuth beamwidth and a wide elevation beamwidth. Secondly, the stepped parabolic reflector is newly designed to obtain an 8 degree elevation -20 dB down power beamwidth. Finally, the designed reflector is fabricated based on chemical wood materials. The measured result shows the 38 dBi gain and the 8.4 degree beamwidth for the elevation plane.

Measurement setups for millimeter-wave antennas at 60/140/270 GHz bands

Abstract: Antenna development at millimeter-wave (mmW) bands has many unique challenging issues wherein the measurement is one of the toughest one because of the expensive testing setup, limited system dynamic range, complicated and tedious calibration as well as measurement procedures. Furthermore, cable, connector or probe used in the measurement shows non-ignorable effect on the measurement results of the antenna under test (AUT), which must be considered carefully in the measurement system configuration. In this paper, we present three measurement setups for mmW antennas at 60 GHz, 140 GHz and 270 GHz bands, respectively. The detailed setup configurations are addressed to achieve the maximum system dynamic range with the available commercial accessories. The setups are successfully used to characterize a number of antennas at 60/140/270 GHz bands with different feeding connections (coax, waveguide and probe). The measured radiation patterns show very good agreement with the simulations.

A low-profile single-layer UWB polarization stable FSS for electromagnetic shielding applications

Abstract: A low-profile frequency selective surface (FSS) exhibiting effective shielding over a large bandwidth is presented. The FSS unit-cell consists of a cross-dipole and a ring printed over the opposite surfaces of a low-cost FR-4 substrate. The design demonstrates a wide 7.5 GHz stopband and provides necessary shielding in both X- and Ka- bands simultaneously. The numerical investigations confirm the shielding behaviour of this FSS with more than 20 dB attenuation and 74% bandwidth in 6.5–14 GHz. Moreover, it shows angular stability for both TE and TM polarization at various angles of incidence up to 45°.

Reconfigurable deployable antennas for space communications

Abstract: This paper discusses the merging of reconfigurable and deployable antennas for satellite and space communications. Reconfigurable antennas, normally proposed for terrestrial applications, allow deployable antennas to be more adaptive and more capable to perform additional functions. In this paper, various antenna concepts that can deploy and at the same time possess frequency tuning capability are proposed for space communications. The addition of tuning ability allows a more efficient, selective and cognitive communication schemes.

Multi-band, dual polarization, dual antennas for beam reconfigurable antenna system for small cell base Station (Invited paper)

Abstract: Multiband, dual polarization dual antennas for beam reconfigurable antenna system suitable for small cell indoor wireless base stations is proposed. The whole design consists of horizontal and vertical antennas on a PCB board. Both the antennas are printed monopole type. The antenna supports LTE (1.7-2.1 GHz) and WLAN (2.5 GHz and 5.75 GHz) band frequencies. The simulated reflection coefficients |S 11 | of the proposed antenna shows that at operating frequencies undergo sufficient bandwidth lower than -7dB. Additionally, radiation characteristic of the presented antenna shows dual polarization behavior and switching states of the beam.

Diffraction loss and phase modulation of terrestrial radio-link by wind turbine

Abstract: Coexistence of wind farms and terrestrial radio links require the investigation of suitable exclusion zones. A proper analysis of this interference including the effect of diffraction is very difficult by numerical field simulation as the problem is electrically extremely large. We propose and analyze a simple diffraction model for a wind turbine (WT) based on a one-dimensional Fresnel diffraction approach applied to tower and rotor. For the first time the dynamic behavior of the diffraction caused by the rotor blades has been investigated.

A printed dual band antenna with a ground plane and electromagnetically-coupled feed for wireless body area networks

Abstract: This paper presents a printed dual band antenna with a full ground plane and electromagnetically coupled feed for body area network devices operating in the industrial, scientific, and medical (ISM) band at 2.45 GHz and 4.9GHz public safety Wireless Local Area Networks (WLAN) band (4.94–4.99GHz). Performance along with parametric analyses are presented. Investigations have been carried out to assess its performance for body centric wireless communication. The electromagnetically-coupled feed is tuned to fill a null in the radiation pattern and to achieve impedance matching. The proposed antenna exhibits a wide radiation pattern along the body surface to provide maximum coverage and its narrow width (14mm) makes it suitable for on-body applications.

Effect of Antenna Bandwidth and Placement on the Robustness to User Interaction

Abstract: Modern smart phones require antenna systems that can deal with an ever-growing number of bands. This study compares two different approaches to the coverage of large bandwidths: Wide-band (WB) antennas covering a whole band at once and tunable narrow-band (NB) antennas covering only one channel at a time but tunable to all channels within the band of interest. To investigate the effect of antenna placement the antennas are placed both at the top and the bottom of the phone. All antenna configurations are simulated in talk position with a head and hand included. The hand is constructed with a movable index finger and the index finger is swept at 6 positions on the backside of the phone. The study shows that WB antennas detune a lot more than NB antennas and that top-mounted antennas are experiencing more than 6 dB higher losses than bottom-mounted antennas. It is proposed to expand this study with more antenna types and placements as both of these parameters are known to influence the immunity to the user. It is also proposed to compare the simulation results to measurements to increase the confidence in the results.

Dual-band MIMO antenna using double-T structure for WLAN applications

Abstract: A dual-band multiple-input-multiple-output (MIMO) antenna is proposed for the wireless-local-area-network (WLAN) applications in the 2.4-GHz and 5.2-GHz bands. The antenna consists of two double-T monopole elements with microstrip-fed and symmetrically placed on a substrate. To enhance isolation between the two monopole elements, three slots are cut on the ground plane on the other side of the substrate. The longer slot is used for better isolation in the 2.4-GHz band, while the two shorter slots are used for the 5.2-GHz band. Simulation and measurement are used to study the antenna performance in terms of S parameters, radiation patterns, realized gain, efficiency, and envelope correlation coefficient. Results show that the MIMO antenna has the two operation bands (2.20-2.75 GHz and 5.09-5.50 GHz) with mutual coupling of less than -15 dB and envelope correlation coefficient of less than 0.1, making it a good candidate for WLAN applications.

Low-cost smart antennas for advanced wireless systems

Abstract: Smart antenna is a key technology for mobile communications, satellite communications, radar and sensors as it can enable the wireless systems to achieve the optimum performance by electronically steering its maximum radiation towards the desired directions while forming nulls against interfering sources. Traditional smart antennas are, however, complicated in structure, bulky, power hungry and costly. For commercial applications, it is important to reduce the size, mass, power consumption and cost of smart antennas. Firstly, this paper presents an introduction to smart antennas, followed by a brief review of various types of low-cost smart antennas. Then, several recent examples of low-cost smart antennas reported by the author's group are presented and discussed. These antennas are capable of achieving electronic beam steering within a wide angular range, while having compact sizes, low power consumption and low cost. A detailed list of references is given in the end of this paper.

Time domain analysis of a miniature tapered-slot UWB antenna

Abstract: This paper presents the time domain study of a miniature tapered-slot ultra-wideband antenna. Firstly, the antenna geometry and frequency domain performance are briefly discussed. Subsequently, a detailed analysis of the time domain behavior of the antenna has been provided. Through the measurements, the transfer function and group delay of the antenna system are obtained. Then, using the convolution approach, the impulse response has been investigated. The antenna is shown to have good performance in time domain as well as frequency domain.

Applications of circularly polarized crossed dipole antennas

Abstract: Circularly polarized crossed dipole antennas are presented in this paper. A compact crossed dipole is realized with the use of a meander line and a barbed end in each dipole arm. A vacant-quarter printed ring is used as a 90° phase delay line to achieve circularly polarized radiation. For multi-band applications, each dipole arm is divided into multi-branches with different lengths to obtain multiple resonances. These radiators can be equipped with different reflectors, such as a finite planar metallic conductor, a cavity-backed metallic conductor, and a finite artificial magnetic conductor to obtain the desired antenna radiation characteristics. These antennas are quite practical for many wireless communication systems, such as satellite communications, global positioning systems, wireless local area networks, and radio-frequency identification devices.

Low-profile antennas for on-body surface communications

Abstract: In this paper, low-profile antennas for on-body surface communication are introduced. A circular-ring patch antenna with TM 31 higher order mode for monopole-like radiation characteristic with low-profile in ISM 2.45 GHz band is proposed. A center-fed circular patch antenna with corrugated ground for surface wave guide in ISM 5.8 GHz band is also proposed.

60GHz pattern reconfigurable quasi-Yagi antenna — Proof through computational design

Abstract: The paper demonstrates the possibility of designing pattern reconfigurable quasi-Yagi antenna. Adjusting the length of dipole arms and delay line, the E-plane radiation direction is steered from -20° to +20°, in 5° steps, without compromising the realized radiation gain or shifting the operating spectrum as high as 60 GHz band. In this work, nine individual Yagi antennas with different beam directions are designed. They all have bands centered at 60 GHz, with wide bandwidths covered from 55 GHz to 65 GHz.

Ultra-wideband conformal apertures with digital beamforming for UHF to millimeter-wave applications

Abstract: This paper presents a reconfigurable low profile ultra-wideband (UWB) phased array, having as much as 14.1:1 instantaneous bandwidth suitable for UHF to millimeter wave applications, with unprecedented integrated digital beam-forming capability across the entire bandwidth. To realize spectrum efficiency, aperture reconfiguration is also proposed. That is, the system is tuned at the feed network rather than the aperture of the antenna by introducing switches and LC loads. Further, the proposed UWB phased array significantly reduces cost due to its novel on-site encoding for tracking individual array element signals to eliminate hardware phased shifters, a primary cost component of the phased arrays.

Compact UWB power divider with unequal distribution ratio

Abstract: A compact ultra-wideband (UWB) power divider with unequal distribution ratio is proposed in this paper. The UWB power divider is based on the conventional unequal Wilkinson power divider with two folded shunt quarter-wavelength short-circuited stubs separated by quarter-wavelength connecting lines at each output ports. The unequal distribution ratio is achieved by adjusting impedance ratio of two output ports. In addition, a single resistor is properly placed between two output ports for improving isolation. Finally, the simulated results are presented, which are in good agreement with the measured ones.

Bandpass filters based on coupled split ring resonators for surface waves on planar Goubau lines

Abstract: This paper demonstrates a method for enhancing the performance of recently introduced compact bandpass filters for terahertz surface waves on single wire waveguides, the so-called planar Goubau lines (PGLs). It is firstly shown numerically and validated experimentally that a gapped PGL loaded with a pair of split ring resonators (SRRs) acts as a bandpass filter. The concept and simulation result are validated through experiment. Furthermore, in order to achieve an improved frequency response, a third-order filter based on coupled SRRs is proposed. It is shown that while the size of the proposed filter is further reduced, it additionally benefits from a higher inband transmission, improved selectivity, and a controllable wide bandwidth.

Phase-gradient metasurfaces for beam steerable antennas

Abstract: Metasurfaces presenting a phase-gradient are designed at 10 GHz and are proposed to steer an antenna's radiated beam from broadside towards endfire direction. The metasurfaces are composed of both inductive and capacitive grids and the phase-gradient is achieved by modifying the elements in the inductive grid. Such phase-gradient metasurfaces are utilized as Partially Reflecting Surfaces (PRS) in Fabry-Perot (FP) leaky- wave antennas (LWAs). Depending on the gradient used, beam steering up to 60° has been observed numerically and verified experimentally.

Broadband zigzag corrugated taper slot antenna for heart failure detection systems

Abstract: A broadband unidirectional zigzag corrugated taper slot antenna for heart failure detection system is presented. A novel type of corrugation is used to keep the taper slot compact and provide a broad operating bandwidth. The antenna, which has the compact size of 0.22 λ × 0.26 λ (λ is the wavelength of the first resonance of the antenna, covers the band 650–916 MHz which is used in microwave-based heart failure detection. The antenna provides a stable gain of 1.6 dBi over its bandwidth with a stable unidirectional and symmetrical radiation pattern.

3D frequency selective surfaces with wideband response

Abstract: A novel 3D Frequency Selective Surface (FSS) with horn shaped resonators is proposed which exhibits a very wide stop band. This new horn shaped resonator is a modification from a 3D FSS consisting of square cylinder unit elements. This feature introduces frequency-selective surfaces with the added advantage of lowering the sensitivity of the FSS frequency response with respect to the incidence angle. Simulation results prove that the FSS can realize broad selectivity of waves with the bandwidth more than 57%. The wideband transmission behavior is stable under oblique TM incidence angles from 0 to 80 degrees. The influence of various key parameters on 3D Horn Shape FSS characteristics has been investigated using the CST simulation software tool. By understanding the effect of each parameter, a comprehensive study for a better design of 3D Horn Shape FSS with wideband response is presented.

Metamaterial arrays and applications: FSS, EBG & AMC structures

Abstract: Over the past decade, interest in applications metamaterials has grown explosively. The potential take-up of these structures in communication and sensing systems is primarily due to the control of the amplitudes, frequencies and wave-numbers of propagating and non-propagating electromagnetic modes to an extent that was not previously possible. The control of electromagnetic modes in various application fields such as indoor and outdoor communication systems, communicating mobile objects, transport systems (cruise liners and high-speed trains), space/earth communication and microelectronics (at μ-wave and mm-wave frequencies), can include the following aspects: • controlling wave propagation • planar circuit miniaturization • waveguides/dispersive waveguides • enhanced filters • frequency selective reflection/transmission • antennas and antenna arrays • enhancing fields, near field imaging, high-Q cavities, • negative refraction • tuneable materials • high impedence layers/artificial materials.

Conformal load bearing antenna structure using Carbon Fibre Reinforced Polymer (CFRP)

Abstract: Modern aircraft communication systems are required to operate over a wide range of different frequency bands. Communication services can lead to the requirement for more than 15 different antenna structures. Modern examples of such antenna structures include blade antennas. Typically these antennas are mounted perpendicular to the skin of an aircraft in multiple positions to reduce interference and maintain aerodynamic performance. Blade antennas or those rigid antennas, which protrude from the exterior of an aircraft, can significantly increase parasitic drag. This in turn reduces aerodynamic performance affecting maximum airspeed, range, payload capacity and increase takeoff distances. Smart skin technology can be utilized to embed the antenna elements into the skin of aircraft wing or fuselage structures. The antenna would form a conformal, load bearing structure that can reduce aircraft weight, radar cross-section and aerodynamic parasitic drag [1]. This leads to a more efficient use of the existing aero-structure, providing a raft of benefits.

Near-field characteristics of a wideband travelling-wave antenna based on a tapered Half-Mode Substrate-Integrated Waveguide

Abstract: In this paper the near-field distribution of a travelling-wave antenna based on a Half-Mode Substrate-Integrated Waveguide (HMSIW) is investigated in order to verify the guided-wave characteristics and the radiation mechanism of this antenna type. Open-ended coaxial probes are utilized to capture the electromagnetic power density at different positions along the antenna aperture. The measurement and simulation results show a good correspondence which validates the measurement technique. The presented results show fundamental differences between the tapered HMSIW antenna and the traditional uniform leaky-wave antenna (LWA). Unlike the uniform LWA, the radiation of the tapered antenna mainly happens close to cut-off position, thus small radiating effective length and an omni-directional radiation pattern are obtained.

Movement based time division multiplexing for near real time feedback body area network applications

Abstract: A time division multiplexed coding system was designed and tested for a body-centric star network using a wireless node mounted in six different places in different time lots on the arm and leg and a central node (hub) on the chest during running. The proposed network allows a coordinated approach to gait analysis. The time sequence for communications between the wireless nodes and the hub is set during the first few steps as runners have different styles and can run at different speeds. After calibration the central unit sends a synchronization pulse during every running step and sets a unique transmission time window for each individual node. The time windows are scheduled when there is reliable communications between the hub and the sensor nodes around the body. Accelerometers on each node are used to identify these time windows for the diverse angles of rotation of the human limbs during running.

Four-branch microstrip leaky-wave antenna array for radiation towards broadside

Abstract: A half-width microstrip leaky-wave antenna (HW-MLWA) array for radiation towards broadside is presented. One of the main challenges of leaky-wave antennas is to radiate towards broadside. This can be achieved by a half-width MLWA array. Four uniform HW-MLWAs, terminated by 50O SMA coaxial loads, are used in the array. The full-wave numerical simulations show the ability of the proposed HW-MLWA array to radiate effectively towards broadside in a 200 MHz band around 4 GHz.