Clive Parini

Study of a printed circular disc monopole antenna for UWB systems

This paper presents a study of a novel monopole antenna for ultrawide-band (UWB) applications. Printed on a dielectric substrate and fed by a 50 /spl Omega/ microstrip line, a planar circular disc monopole has been demonstrated to provide an ultra wide 10 dB return loss bandwidth with satisfactory radiation properties. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated. A good agreement is achieved between the simulation and the experiment. In addition, the time domain performance of the proposed antenna is also evaluated in simulations.

Antennas and propagation for body centric wireless communications

Research in antennas and propagation for body centric wireless communications continues to grow, in response to increasing demands for body area networks (BANs) for healthcare, defence and personal communications and entertainment. This paper will briefly review recent international work, and then report on advances in three UK BAN research centres, Birmingham, Queen Mary and Queens Belfast. The demand for greater security in BAN links could be met by the use of 60GHz channels, and the likely channel characteristics will be discussed and initial results given. New insights into surface wave excitation on the human body has enabled a novel low profile antenna to be designed that maximises link performance where very thin antennas are necessary. Finally advances in the numerical computation are reported, in which the importance of relating phantoms directly to patients to give subject specific simulations and to allow improved modelling of internal organs.

Antennas and propagation for on-body communication systems

On-body communication channels are of increasing interest for a number of applications, such as medical-sensor networks, emergency-service workers, and personal communications. This paper describes investigations into channel characterization and antenna performance at 2.45 GHz. It is shown that significant channel fading occurs during normal activity, due primarily to the dynamic nature of the human body, but also due to multipath around the body and from scattering by the environment. This fading can be mitigated by the use of antenna diversity, and gains of up to 10 dB are obtained. Separation of the antennas performance from the channel characteristics is difficult, but results show that for many channels, an antenna polarized normal to the bodys surface gives the best path gain. Simulation and modeling present many challenges, particularly in terms of the problems scale, and the need for accurate modeling of the body and its movement.

Comparison between two different antennas for UWB on-body propagation measurements

The effect of two different antenna types on radio propagation in ultrawideband (UWB) on-body channel measurement are analyzed. Statistical path loss parameters and time domain channel characteristics [mean delay and root mean square (rms) delay spread] are extracted from measurement data. Reduction in rms delay spread is experienced when using printed horn shaped self-complementary antennas (HSCA) for specific body area links in comparison to monopole-like omnidirectional antennas, e.g., planar inverted cone antennas (PICA). Results show that the hybrid use of different type UWB antennas can effectively improve channel behavior in body-centric wireless networks.

Statistical Analysis and Performance Evaluation for On-Body Radio Propagation With Microstrip Patch Antennas

On-body propagation channel measurements using two microstrip patch antennas for various links are presented and statistically analyzed. The attenuation attributed to factors such as the body, head and clothing are: 19.2, 13.0, and 1.7 dB, respectively, when measurement performed in the anechoic chamber. Measured cumulative distribution function (CDF) of data in the chamber and lab fits to lognormal distribution with deviation factors comparable in both cases. The results demonstrate that the human body is a major shadowing contributor in body area network (BAN) radio systems. The performance of potential radio systems under the measured channel variations is also investigated. Excellent system performance is achievable with power levels as low as 0.01mW. These results support the significance of channel characterization and modelling in producing suitable wireless systems for ultra low power BANs

UWB on-body radio channel modeling using ray theory and subband FDTD method

This paper presents the ultra-wideband on-body radio channel modeling using a subband finite-difference time-domain (FDTD) method and a model combining the uniform geometrical theory of diffraction (UTD) and ray tracing (RT). In the subband FDTD model, the frequency band (3-9 GHz) is uniformly divided into 12 subbands in order to take into account the material frequency dispersion. Each subband is simulated separately and then a combination technique is used to recover all simulations at the receiver. In the UTD/RT model, the RT technique is used to find the surface diffracted ray path, while the UTD is applied for calculating the received signal. Respective modeling results from two- and three-dimensional subband FDTD and UTD/RT models indicate that antenna patterns have significant impacts on the on-body radio channel. The effect of different antenna types on on-body radio channels is also investigated through the UTD/RT approach.

Design and Performance Investigation of a Dual-Element PIFA Array at 2.5 GHz for MIMO Terminal

A study is described of a modified planar inverted-F antenna (PIFA) operating in 2.5 GHz band on a printed circuit board (PCB) of a mobile phone handset. The antenna dimension is reduced substantially with a miniature ground plane and capacitive loading. While inheriting the attractive features of PIFAs, such as low profile, easy fabrication and low cost, the proposed antenna exhibits low coupling to the PCB. A dual-element PIFA array is implemented on a mobile handset PCB and the diversity performance of the dual-element PIFA array is evaluated in both simulation and measurement.

Single Feed Stacked Patch Circular Polarized Antenna for Triple Band GPS Receivers

A novel design of a circular polarized antenna for multiband GPS receivers is presented. The design employs the concept of multistacked patches fed through a single coaxial probe. Three patches being stacked together with a slit and symmetry I-slot are used to achieve triple operating frequency bands for GPS including L1 (1.575 GHz), L2 (1.227 GHz) and L5 (1.176 GHz). The proposed antenna has achieved a bandwidth of 2.0%, 1.5%, and 1.7% at GPS L1, L2, and L5 bands, respectively. It exhibits a minimum axial ratio of 0.51 dB with broad beamwidth in the upper hemisphere required for the GPS applications. The design of the proposed antenna is verified in the experiment. In addition, a detailed analysis has been carried out to study the effects of different geometrical parameters on the performance of the antenna.

Reconfiguring UWB Monopole Antenna for Cognitive Radio Applications Using GaAs FET Switches

A novel ultrawideband (UWB) microstrip monopole antenna with reconfigurable multiband function is presented. Reconfigurability is achieved by using GaAs field effect transistor (FET) switches to connect multiple stubs of different lengths to the main feed line of the monopole. The antenna is compact and flexible in terms of the availability of different reconfiguration bands and, most importantly, the simple biasing of the GaAs FET switches will not have a severe effect on the antenna performance. Using GaAs FET switches did not degrade the antenna radiation patterns due to the simple biasing technique and the few external biasing components needed, besides these switches did not degrade the antenna gain and efficiency due to their low insertion loss and low on resistance. When the antenna was reconfigured from UWB to work into multiple frequency bands, the total peak gain improved by 20% compared to the UWB case. In addition, the total efficiency of the antenna has not been significantly reduced in any reconfigured band, whereas the out-of-band total efficiency is hugely reduced, which highlights the filtering role of the reconfiguration process. The total dc power consumption of the antenna switches is still very low (<; 33 μW), and this will lead to simple integration of the antenna in some portable communication systems or future cognitive radio front ends.

Experimental Characterization of UWB On-Body Radio Channel in Indoor Environment Considering Different Antennas

An experimental investigation to characterize the transient and spectral behavior of the ultrawideband (UWB) on-body radio propagation channel for body-centric wireless communications is presented. The measurements were performed considering over thirty on-body links in the front of human body in the anechoic chamber, and in indoor environment. Two different pairs of planar antennas have been used, namely, CPW-fed planar inverted cone antennas (PICA), and miniaturized CPW-fed tapered slot antennas (TSA). A path loss model is extracted from measured data, and a statistical study is performed on the time delay parameters. The goodness of different statistical models in fitting the root mean square (RMS) delay has been evaluated. Results demonstrate that the TSA, due to its more directive radiation behavior is less affected from the reflections from body parts and surrounding environment. The antenna shows significant size reduction and improved time delay behavior, and hence is an ideal candidate for UWB body area networks (BAN).