Terence S. P. See

Small Printed Ultrawideband Antenna With Reduced Ground Plane Effect

A small printed antenna is described with a reduced ground-plane effect for ultrawideband (UWB) applications. The radiator and ground plane of the antenna are etched onto a piece of printed circuit board (PCB) with an overall size of 25mmtimes25 mmtimes1.5 mm. A notch is cut from the radiator while a strip is asymmetrically attached to the radiator. The simulation and measurement show that the miniaturized antenna achieves a broad operating bandwidth of 2.9-11.6 GHz for a 10-dB return loss. In particular, the ground-plane effect on impedance performance is greatly reduced by cutting the notch from the radiator because the electric currents on the ground plane are significantly suppressed at the lower edge operating frequencies. The antenna features three-dimensional omni-directional radiation with high radiation efficiency of 79%-95% across the UWB bandwidth. In addition, a parametric study of the geometric and electric parameters of the proposed antenna will be able to provide antenna engineers with more design information

A UWB Dipole Antenna With Enhanced Impedance and Gain Performance

A planar dipole antenna is proposed with enhanced impedance and gain performance across an ultrawideband (UWB) operating bandwidth of 3.1-10.6 GHz. The proposed antenna consists of two semi-elliptical-ended arms connected by a shorting bridge. With the shorting bridge, the length of the antenna is reduced and the radiation performance in terms of gain is improved especially at higher frequencies. The performance of the proposed antenna is validated experimentally using a wideband balun to realize the microstrip-co-planar strip transition. The results show that the proposed antenna can achieve a gain of 2.4-6.2 dBi across a VSWR=2 impedance bandwidth of 118% (2.8-10.9 GHz). The time domain responses of pulsed UWB signals through conventional and proposed antennas are compared. Furthermore, a parametric study is performed to provide antenna engineers with the information about the design.

Small planar UWB antennas in proximity of the human head

The effects of a human head on the performance of small planar ultra-wideband (UWB) antennas in proximity of the head are investigated numerically and experimentally. In simulation, a numerical head model is used in the XFDTD software package. The head model developed by REMCOM is with the frequency-dependent dielectric constant and conductivity obtained from the average data of anatomical human heads. Two types of planar antennas printed on printed circuit board (PCB) are designed to cover the UWB band. The impedance and radiation performance of the antennas are examined when the antennas are placed very close to the human head. The study shows that the human head slightly affects the impedance performance of the antennas. The radiated field distributions and the gain of the antennas demonstrate that the human head significantly blocks and absorbs the radiation from the antennas so that the radiation patterns are directional in the horizontal planes and the average gain greatly decreases. The information derived from the study is helpful to engineers who are applying UWB devices around/on human heads.

A Printed Ultra-Wideband Diversity Antenna

A printed ultra-wideband (UWB) antenna operating at a frequency range of 3.1-5.8 GHz is proposed for diversity applications. The antenna consists of two orthogonal half circles with the radiators placed symmetrically with respect to a protruded T-shaped ground plane, which has a slot at the upper centre portion of the ground plane. The simulated and measured results show that across the operating bandwidth, the antenna can achieve spatial diversity with good isolation. In addition, a parametric study has been conducted to investigate the effects of the slot and ground plane size on the impedance matching and isolation

Small ground-independent planar UWB antenna

In this paper, a small ground-independent planar UWB antenna is proposed. It is designed to cover the UWB band of 3.1 - 10.6 GHz. The antenna is etched onto a piece of PCB. A notch is cut from the radiator to reduce the size of the planar antenna. The simulations and measurements show that its impedance characteristics are ground-plane independent. The performance of the antennas is tested in time and frequency domains

Proximity effect of UWB antenna on human body

In this paper, two types of UWB antennas, with and without band-notched characteristics were placed in proximity of the human body. The effects of the human body on the impedance and gain are investigated. The transmission performance is also analyzed for the different body orientations. Generally, the impedance is sensitive to the presence of the body, although the band-notched characteristic is retained. The RF transmission is dependent on the body orientation and antenna separation from the body. At certain orientations, the attenuation due to the absorption by the body can actually be reduced when the reflection by the human body becomes dominant.

Performance benchmarking for wireless body area networks at 2.4 GHz

This paper investigates wireless body area network (WBAN) performance to capture packet reception ratio (PRR) and its correlation with received signal strength indicator (RSSI), and the minimum transmission powers required for the targeted performance. We design and carry out experiments on IEEE 802.15.4 based WBAN prototype to measure the performance metrics in different activities and environments. It is observed that RSSI values for a given on-body link has radical variation in a minute-scale period in a realistic environment. This observation implies that a few of RSSI samples cannot be used as an estimate of the average RSSI over many packets transmitted over an on-body link. In postural mobility, the periodicity pattern of link property is more obviously observed at links with clearer line-of-sight and at higher transmission powers. The objective of the performance benchmarking is to provide insights and guidelines for the design of resource management schemes for WBANs.

Ultra-Wideband Antennas with Miniaturized Size, Reduced Ground Plane Reliance, and Enhanced Diversity

This paper reports the techniques applied in developing high performance UWB antennas with miniaturized size, reduced ground plane reliance, and enhanced diversity. The fundamental idea about the design with reduced ground plane reliance is first reviewed. Next, the miniaturized antenna design with less ground plane effect is introduced. Last, the antenna which features the small size, less ground plane dependence, and also capable of providing enhanced diversity performance is presented.

Analysis and Optimization of Compact Suspended Plate MIMO Antennas

This paper presents the analysis and optimization of compact suspended plate antennas for multiple-input-multiple-output (MIMO) wireless local area network (WLAN) applications. First, instead of using the conventional average envelope correlation coefficients, a performance metric using the two- and three-dimensional patterns of the envelope correlation coefficients are proposed to evaluate the diversity performance of antennas in MIMO systems. Following this, a compact three-element suspended plate antenna array with a bent ground plane is presented for WLAN MIMO applications. The diversity performance of the design is experimentally and numerically analyzed. Last, the design guidelines for the optimization of multiple suspended plate antennas in terms of their orientation and feed configuration is provided for achieving the upper bound of the diversity performance with minimum inter-element mutual coupling.

Experimental Study on the Dependence of Antenna Type and Polarization on the Link Reliability in On-Body UWB Systems

An experimental study on the use of ultra-wideband antenna systems (3.5–4.5 GHz) on the human body for wireless body area network (WBAN) applications is conducted. It has been found that the link reliability can be improved and transmit power can be reduced by properly selecting the transmit and receive antennas with different radiation properties (omni-directional, directional, pattern diversity) and polarizations (vertical and horizontal) at each location on the body. Moreover, when there is blockage by the body, it may be possible to achieve better transmission when the antennas are horizontally polarized. Also, antennas with pattern diversity can be used to enhance the overall reliability of the communication system. In order to eliminate the use of cables in the measurements, an on-body UWB system has been developed and the reliability can be assessed more practically in terms of the peak amplitude of the received waveform and the bit error rate. It has been observed that when the link quality is improved, the transmit power can be reduced by more than 20 dB without compromising on the reliability, which will conserve the battery power.