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In this paper, a compact super wideband annular ring antenna using 45° clock-wise square patch inclusions for super high frequency and polarization diversity applications is proposed. The inclusions consist of a combination of squares and circles into one another in the inner area of a main annular ring radiator. The antenna uses a partial ground plane having a stair-type defected ground structure, is designed on an FR-4 substrate, and has a total size of 25 × 26 × 1.6 mm3 (0.17λ × 0.18λ). The design was fabricated and experimental results fairly agreed with simulations and resulted in an antenna with an operating frequency from 2.07 to 30 GHz; that is, a large fractional bandwidth of 174.2$\%$ with a bandwidth (BW) ratio of 14.5:1 and a high BW dimension ratio, BW per unit electrical length of 5693, and a measured peak gain of 8 dBi with an average gain of 5 dBi for the overall operating frequency. For the polarization diversity, a 4 × 4 multiple input-multiple output configuration is additionally presented, offering an effective isolation of ≥ 22.5 dB between ports and corroborated by measurements.

This article presents a miniaturized three-dimensional super wideband antenna with filtering capabilities. A conventional rectangular patch antenna has been modified by truncating its corners with semi-circles and a trapezoidal shaped partial ground plane is utilized to achieve super wideband performance. The planar design is later extended to a 3D design with the addition of three dielectric cuboids in the radiator. The cuboids are inserted at low current density regions within the operating range to achieve miniaturization com-pared to the planar antenna. The impedance bandwidth of the 3D antenna is ~17.55 GHz, measured from 2.45 to 20 GHz. The filtering capabilities are achieved by means of an upside-down T-shaped resonator introduced in the center of the patch and two U-shaped slots etched from the patch. In total, three interfering communication bands are rejected, WiMAX (3.2–3.8 GHz),IEEE 802.11/WLAN (5.17–5.33 GHz), and ITU (7.7–8.5 GHz). The proposed antenna is miniaturized as it merely has an overall size of 0.20λl x 0.19λw x 0.011λh mm3 (corresponds to 2.45 GHz) compared to the relevant literature. The design has been analyzed using an equivalent circuit model, fabricated and measured for validation. The simulated and measured results are found well in agreement.

This paper presents an analysis of microstrip patch antennas with different dielec-tric/magnetic substrate profiles in an attempt to obtain operating frequency reduction. Initially, different ridge shapes in the substrate were examined. An in-depth investigation of the ridge shape and its dimensions on the antenna performance has been carried out. Subsequently an antenna with a magnetic-slab loaded in the prime magnetic-field region beneath the patch is proposed. The new magnetic loaded antenna design is aimed to reduce the resonant frequency of a conventional patch and reduce the profile of an earlier design with a substrate ridge. Various magnetic materials have been embedded within the original dielectric substrate of the patch antenna. Measured results validated the hypothesis that this frequency can be reduced by placing magnetic materials at the centre of the patch. The achieved gain is expected to be further enhanced by using forthcoming magnetic materials with improved performance.

Ultra-wide band (UWB) is an attractive technology for innovative in-vehicle wireless communications requiring high data rates and multiband orthogonal frequency division multiplexing (MB-OFDM) a suitable scheme for the accomplishment due to its high performance, low-power and low-cost characteristics. To contribute toward improved UWB MB-OFDM communications inside vehicles, a channel-based antenna synthesis technique to customise in-vehicle UWB antennas that reduce ‘blind spots’ in the communication channel is proposed and presented. For the realisation, a comprehensive analysis was utilised and comprised an in-car channel evaluation including bit-error-rate (BER) estimations and radiation pattern-and-source syntheses. The channel was measured using a standard antenna to set up the base of the experiments and the distribution of the impulse responses and signal-to-noise ratios in the vehicle's passenger plane shown. The currently available IEEE 802.15.3a channel models were perceived unrealistic for the in-vehicle application and the reason for measuring the channel practically. Using these specific channel measurements, the synthesised pattern is unveiled and consequently the channel-based antenna synthesis technique used to predict the antenna source. The antenna with optimised pattern-and-source showed an improved BER performance compared with the standard antenna in this application; that is, a figure of merit of 37.73% minimised ‘blind spots’.

A design study of coil antennas aimed to be used as Interrogators in high-frequency (HF) radio frequency identification (RFID) is presented. The magnetic field (H-field) of the coil is enhanced by defining optimally the number of turns of the antenna, and optimizing and exploiting the internal area of an initial coil. The distributed turns coil antennas are designed for highest possible H-field without compromising the Q-factor of the antenna with respect to an initial design. To achieve best solution, a non-uniformly distributed turns design is proposed and whose radiating elements are formulated accordingly. The analytical and simulated results show reasonable agreement to validate the designs. The enhanced H-field of the antenna shows an unconstrained Q-factor, indicates a potential rise to the interrogating coverage and as a result a higher efficient antenna.

This article presents a design study of a coil antenna with enhanced magnetic field (H-field), aimed to be used as an interrogator in high frequency radio frequency identification. To achieve this, the number of loops of the antenna are refined by optimizing and exploiting the inner area of an initial coil, using distributed loops, unconstrained inductance and comparable Q-factor (for a fair comparison) with respect to an initial design. The analytical and simulated results show reasonable agreement to validate the design. The enhanced H- field of the antenna shows an unconstrained Q-factor, indicates a potential rise to the interrogating coverage and hence, resulting in more efficient antenna. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:944–948, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27406

Ultra-wideband (UWB) is a very attractive technology for innovative in-car wireless communications requiring high data rates. A designated antenna, which presents a reflection coefficient (S11) matched band comparable to the band-pass filter (BPF) normally required at the transducers, plays a positive contribution in this in-car application and was validated for the scenario. The inherited BPF-like response of the antenna relaxes the specification of the front-end BPF components of the transceivers. The in-car propagation channel was modelled and used to validate the BPF-like antenna. For the modelling, a comprehensive set of well-defined measurements (using a standard antenna) were used to set-up the in-car channel simulator and simulated results were used to validate the BPF-like antenna. In addition, the performance of the UWB radio system is studied and the probability of errors over the communication channel compared using the standard and the BPF-like antenna by predictions. This work has been part-funded by the European Union.

A near-field highly focused circular phased-array antenna for 5.8-GHz radio frequency identification (RFID) applications is presented. The electric field (E-field) at the focus is enhanced by a constructive vector combination in a three-dimensional (3-D) coordinate system. The array dipoles of the antenna are oriented to enhance the energy confinement at the focus, and the radii of the circular array is optimized for lower sidelobe levels. As a result, the proposed design achieves an enhanced focalization of ≈ 4 dB with reduced sidelobe levels of ≈ 12 dB compared to earlier designs.

Dual-polarised microstrip flat panel antennas suited for radio-over-fibre (RoF) micro-cellular distribution systems are presented. The antenna units are intended to be low-cost and compact, provide reasonable gain, and serve the 4G-long term evolution (LTE) wireless band in a Manhattan scenario. A design study has been carried out to assess the effects of mutual coupling between the required sectors for the scenario. Return loss, isolation on dual ports, and radiation patterns are shown. Improved matching lines for optimum optical fibre link gains using cost/performance units are also introduced.

Given the constrained geometry of modern mobile equipment, the design of small volume antennas such as planar inverted-F Antennas (PIFAs) is of great interest. In devices such as laptops, PDAs, and phones, antennas must be low profile and compact by Huynh, M.-C and Stutzman (2004). Here a novel low cost, easily fabricated, miniaturized multiband PIFA antenna with a frequency selective surface (FSS) as a bottom layer is presented. The miniature PIFA is designed for GSM 900, GSM1800, DECT, DCS, UMTS, Bluetooth (WLAN) and HiperLAN 1&2.

A compact, flexible, long-range, and impedance transformer balun-like integrated UHF RFID tag antenna is proposed for the detection of water bottles. To alleviate the performance of a tag antenna in close proximity to a high dielectric material such as water, the radiating element of the tag antenna uses folded, unbalanced strips made of balun-like arms wrapped around the tag’s body. As a result, a wide bandwidth with reasonably good radiation resistance is achieved. The tag’s body comprises dual-loops for the impedance matching to the tag chip. This leads to a long read range of 13.33 m; > 5.83 m compared to other state-of-the-art designs. The proposed tag antenna conforms to a small footprint by wrapping the balun-like arms around the tag’s body, which results in a compact form. The tag is fabricated, and the results reasonably agree with simulations.