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Human body tissues have a strong effect on the antenna operation in wireless body area networks (WBANs). In this study, the authors present the deep investigations of the effect of body tissue thicknesses on the performance of an ultra wideband (UWB) loop antenna by simulations when the antenna is operated on contact with tissues. The planar UWB loop antenna is designed for the examinations, which is targeted to be used in UWB WBAN applications. The effect of tissue thicknesses on the antenna performance is analysed and characterised in the terms of reflection coefficient S11, gain and total antenna efficiency, group delay, radiation patterns and specific absorption rate by simulations. A parametric layered human body tissue model with the frequency-dependent behaviour is exploited in the investigations. Further, the reflection coefficient of the presented antenna is measured in the different locations of the author's body. The main aim of these investigations is to demonstrate how the thickness of outermost body tissues affects the antenna performance.

The paper studies the design of ultra-wideband printed loop antenna based on the characteristic mode manipulated in a large frequency band. The structure of this antenna is very simple. The wide impedance bandwidth of 60% with |S11| < –10 dB (2.76–5.16 GHz) is obtained due to a simultaneous excitation of the significant antenna modes. A stable radiation pattern is also achieved within the frequency bandwidth. The antenna is designed on FR4 substrate and fed with 50 Ω coupled tapered transmission line.

Proposed is a simple technique to enhance the bandwidth of a planar monopole antenna with overall dimensions of 30 × 10 mm2. With the proposed method, based on a modified ground plane and a loop feeding structure, the −6 dB bandwidth can be enhanced by ∼50% compared to the basic structure. Based on the simulation results, the antenna achieved a total efficiency higher than 70% on the entire band and the maximum realised gain varied between 2 and 4.8 dB. A prototype has been realised, and good agreement has been obtained between the measured and simulated results.

A rectangle-shaped aperture antenna for ultra-wideband (UWB) applications which can prevent the interference problems is presented. By attaching a hollow-cross-loop resonator (HCLR), triple-notched frequency bands centred at 3.5, 5.7 and 8.2 GHz are obtained. The HCLR is loaded in the aperture over the microstrip feedline. The proposed antenna has been successfully simulated and measured. Based on the results, it is shown that the proposed antenna yields an impedance bandwidth of 2.55–12 GHz with a voltage standing wave ratio (VSWR) < 2, except for the triple-notched bands of 3.15–3.85 GHz (WiMAX band), 5.4–6.1 GHz (WLAN band) and 7.8–9.3 GHz (X-band satellite communication).

A novel planar non-dispersive antenna for ultra-wideband radar applications is introduced. The antenna concept is based on the combination of the electromagnetic characteristics of a loop and a planar monopole. A detail discussion on the proposed antenna topology and architecture is presented, and a dedicated backfeeding technique that shows a low transmission loss over a very wide frequency band is suggested. A frequency-independent equivalent circuit of the proposed antenna, useful in the codesign and optimisation of the relevant radio frequency front end is also extracted. It is experimentally demonstrated that the considered radiating element features a fractional bandwidth of 67%, good impedance matching, reasonably constant group delay and uni-directional stable over frequency radiation patterns with front-to-back isolation of about 12 dB.

In this work, a low profile ultra-wideband (UWB) antenna is designed and investigated using a novel loop-based wideband artificial magnetic conductor (WB-AMC) for gain enhancement. Initially, a compact loop antenna is designed using stub loading and further optimized for the UWB range by applying curve ground methodology. The average gain of the proposed antenna without WB-AMC is 2.7 dBi. To enhance the gain of the entire UWB range, loop-based WB-AMC in [2 × 2] forms is integrated. WB-AMC is used as a ground plane beneath the antenna. To validate the performance, the UWB antenna and WB-AMC are fabricated and tested. The measured results confirm the entire UWB range. Proposed antenna provides a peak gain of 9.4 dBi and an average gain of 5.8 dBi. Vertical profile reduction of 50% is achieved compared to perfect electric conductor ground. The proposed UWB antenna is a potential candidate for UWB wireless applications due to its attractive features such as low profile, wide bandwidth coverage, omnidirectional pattern, constant high gain, and group delay.

To design high-sensitivity sensors is one of the critical issues to be solved for ultra-high-frequency (UHF) partial discharge (PD) detection in substations. Commonly-used UHF sensors usually use ultra-wideband antennas for the frequency bands ranging from 300 MHz to 1.5 GHz. To avoid interference in the frequency bands, such as signals generated from mobile phones, a new multi-band UHF sensor is proposed based on the loop antenna theory and meandering technique, which reduces the sensor size, provides high sensitivity and exhibits omnidirectional performance. The sensor works in the bandwidth ranges of 480–520, 800–850 and 1100–1200 MHz, and has sensitivity of more than 10 mm. The PD detection platform was set up, three typical insulation defects, such as corona discharge, surface discharge and free metal particle discharge, were designed, and then the tests were performed to compare the performance of the multi-band sensor and broadband sensor. The results show that the multi-band sensor's bandwidth covers the main spectra of PD signals, thereby can be used for detecting most kinds of PD signals. The sensor's sensitivity is higher than that of the broadband sensor with its size occupying only 5% of the latter, meeting the requirements for detection of PD sources in substations.

The proposed antenna in this paper is compact UWB monopole antenna with a rectangular patch consists of stepped cuts and triangular slot. A two open loop resonators are designed and added near microstrip feed line to achieve sufficient band rejection from 5.1 GHz to 6.5 GHz for avoiding interference with WLAN frequency bands. The proposed antenna has low profile and compact size, its size equals 3.2 x 3.2 cm2. It has bandwidth from 3.1 GHz to 19.3 GHz with voltage standing wave ratio (VSWR) < 2, except the undesired band of 5.1–6.5 GHz. Two-lumped capacitors are inserted in order to investigate the ability of tuning the resonance frequency of the band-notched structures from 5.6 GHz to 3.5 GHz. Finally, the layout of the proposed UWB monopole antenna with the notched band is experimentally fabricated and measured to verify the simulation results. Furthermore, the return loss and far-field measurements of the fabricated antenna exhibit good match with simulation predictions.

A contactless scribe-line channel-leakage monitor with relaxed alignment requirement is described. It comprises photovoltaic converters for powering from indoor illumination, a visible light communication downlink for selecting one among multiple monitors, and an ultra-wideband impulse-radio uplink for transmitting the measured leakage data in the form of impulse repetition frequency. Readout is accomplished with an external loop antenna loosely aligned to the scribe-line transmitter antenna. The proposed monitor was implemented in 0.18-μm CMOS with a footprint 4960 μm × 160 μm including the transmitter antenna. It deploys a novel leakage sensor of ring-oscillator topology. All circuit blocks, except for the transmitter, are power-supplied directly by photovoltaic converters without regulation, and consume 64 nW. Transmitter is powered by an integrated storage capacitor charged to 1.8 V by a photovoltaic-powered voltage booster.

An ultra-wideband loop antenna is proposed, that is based on a wavelength loop antenna and a slot antenna. The self-complementary principle is applied to the designed ultra-wideband antenna. The antenna operates as a loop antenna in the low frequency band (0.3-1 GHz) and as a slot antenna in the high frequency band (1-14.2 GHz). The measured 210 dB bandwidth is 47.3:1 (0.3-14.2 GHz), and the size of the antenna is 220(0.22γ^sub L^) x 220(0.22γ^sub L^) x 177(0.18γ^sub L^) mm^sup 3^, where γ^sub L^ is the wavelength of 0.3 GHz.