Geoff Hilton

Numerical and experimental evaluation of phantoms for off-body wireless communications

The effects of a numerical and a physical phantom on different antenna configurations are evaluated. Input response, radiation patterns and efficiency are considered in the presence of the phantoms. In order to validate the phantoms as a substitute for human tissue, these effects are compared to those experienced due to the proximity of the human body. The detuning effects on a patch antenna due to the phantom were demonstrated and shown to match the effects of the human body. The radiation pattern of a loop antenna was measured on and off the phantom. The presence of the phantom was found to reduce the efficiency of the loop antenna by 88%.

The effect of antenna position and environment on MIMO channel capacity for a 4 element array mounted on a PDA

The properties of a four element slot antenna array mounted on a PDA for a MIMO system are investigated by means of a finite difference time domain analysis and a multipath channel model. The effects of changing the positions of the antenna elements on the PDA box and the effect of the box being held in a human hand are investigated

Optimising radio coverage for wireless media servers

A three element patch antenna array is designed for a 2×3 802.11n wireless home media server application for highdefinition video streaming at 2.4GHz. An efficiency comparison shows that the use of the RT/Duroid substrate results in a 3dB improvement in performance over the cheaper FR4 substrate. The RT/Duroid patches are characterised in terms of input responses, full (3D) radiation patterns and directivities, including mounting on the terminal and local environment. The performance of the MIMO system is evaluated in an office environment in terms of received power, data throughput, datagram error rate, coverage area, and delay jitter. Results are compared with commercial omnidirectional antennas. Although high performance is possible (data rate at least 40Mbps), it depends heavily on the orientation of the box due to the directional radiation of the patches. An antenna selection scheme may therefore prove beneficial in future designs.

Towards a hardware implementation of ultra-wideband beamforming

This paper discusses and analyses the hardware implementation of an ultra-wideband (UWB) beamformer for UWB Impulse Radio data transmission. We use a Complex Programmable Logic Device (CPLD) acting as the binary baseband information source. The CPLD provides input to a pulse shaper and subsequently to a four-element array of UWB antennas. This smart antenna system comprises the digital baseband part, the radio-frequency frontend, and the antenna array. For this contribution, we discuss the design, implementation, and UWB measurement results obtained in an anechoic chamber.

Electronic beam squint tracking for land mobile satellite terminals

Preliminary results from an investigation of the applicability of the electronic beam squint (EBS) tracking technique to land mobile satellite terminals. Two systems are described, based on the EBS technique, which use both conventional waveguide and phased-array technology. Results are presented covering the error-detection capabilities of the systems, along with some operational analysis to illustrate the dynamic capabilities of the performance of such schemes. The systems described are intended for use at L-band and Ku-band. Both techniques appear to offer a simple, and hence cost-effective, alternative to the current terminal arrangements.<<ETX>>

Variable Geometry Conformal Antenna Array for Element Comparison

The design of conformal antenna arrays has historically been carried out by warping suitable planar antenna arrays to the desired radius of curvature. There has been little investigation into the effects of characteristic antenna performance on conformal array performance as the radii of curvature is varied. This paper presents a Variable Geometry Conformal Antenna Array Test Rig, designed to allow the investigation of the performance of a variety of antenna types (cavity slot, patch, etc) in a controlled environment. This approach allows direct comparisons to be drawn between each set of antenna elements in the test rig, and also simplifies the model space for Finite Difference Time Domain (FDTD) modelling, allowing an additional comparison between measured antenna pattern and coupling measurements and modelled results. In this paper measurements of Conformal Cavity Slot antenna elements and Dual Feed Dual Patch antenna elements are presented.

The analysis of a printed dipole antenna array using an enhanced Finite Difference Time Domain method

The Finite Difference Time Domain method is well suited for the solution of complex electromagnetic problems, such as antenna array characterisation, but it can suffer from the requirement of large amounts of computer resources. In this contribution, a number of enahncements to the FDTD method are applied to the analysis of an array of printed dipole antenna elements leading to a reduction in computer resources by an order of magnitude compared to standard approaches while achieving similar accuracy.