S.R. Pennock

Site Assessment of Multiple-Sensor Approaches for Buried Utility Detection

The successful operation of buried infrastructure within urban environments is fundamental to the conservation of modern living standards. Open-cut methods are predominantly used, in preference to trenchless technology, to effect a repair, replace or install a new section of the network. This is, in part, due to the inability to determine the position of all utilities below the carriageway, making open-cut methods desirable in terms of dealing with uncertainty since the buried infrastructure is progressively exposed during excavation. However, open-cut methods damage the carriageway and disrupt societys functions. This paper describes the progress of a research project that aims to develop a multi-sensor geophysical platform that can improve the probability of complete detection of the infrastructure buried beneath the carriageway. The multi-sensor platform is being developed in conjunction with a knowledge-based system that aims to provide information on how the properties of the ground might affect the sensing technologies being deployed. The fusion of data sources (sensor data and utilities record data) is also being researched to maximize the probability of location. This paper describes the outcome of the initial phase of testing along with the development of the knowledge-based system and the fusing of data to produce utility maps.

Very wideband operation of twin-layer inset dielectric guide

An inset dielectric guide (IDG) with a multilayer dielectric filling is studied, using the transverse resonance diffraction, technique. The convergence and numeric efficiency of the analysis are good, and comparisons with experimental measurements of phase constant show the validity of the data produced. Those aspects of the IDG structure that limit its monomode bandwidth when it is filled with a single dielectric are investigated. It is shown how the monomode bandwidth of such an IDG may be made greater than that of rectangular metal waveguide by appropriate choice of aspect ratio. It is also shown how the simple use of two dielectric layers in the IDG slot can yield a guide whose monomode bandwidth is 66%, which is much greater than the typical operating bandwidth of a standard double ridge waveguide (40%). In the maximum bandwidth configuration, variation in the position of the boundary between the dielectrics produces little change in bandwidth. Hence, it appears that multilayer IDG is an attractive transmission media for wideband applications at both microwave and millimeter-wave frequencies. >

Analysis of coupled inset dielectric guides under LSE and LSM polarization

The inset dielectric guide (IDG) represents an easy-to-fabricate alternative to the image line that is also less sensitive to loss radiation at discontinuities. Two IDG geometries were analyzed, the so-called deep and shallow IDG structures, operating in the LSE and LSM polarizations, respectively. The propagation constants of single and coupled symmetrical IDGs have been calculated as well as the coupling coefficients of coupled guides. The transverse resonance diffraction method with variational formulation was used. Measured values show very good agreement with predicted values for the propagation constants of coupled deep slot IDGs. The information is a prerequisite for the design of directional couplers in IDG. >

Dispersion Characteristic of Coupled Inset Dielectric Guides

The inset dielectric quide (IDG) represents an easy-to-fabricate alternative to image line that is also less sensitive to loss by radiation at discontinuities. The propagation constants of single and coupled identical IDGs have been calculated under the LSE approximation. The Transverse Resonance Diffraction (TRD) method with variational formulation for impedance operators is used. Measured values show very good agreement with predicted values for the propagation constant of a single IDG and for the coupling coefficient of coupled IDGs.

A novel OFDM based ground penetrating radar

This paper proposes a novel GPR system based on the Orthogonal Frequency Division Multiplexing (OFDM) technique. The selection of the major system parameters for the OFDM based GPR are considered. An example system configuration is simulated. Target positions can be determined with high accuracy, even when in the presence of noise. Finally, the potential benefits of using OFDM for GPR are presented.

Space domain analysis of micro-IDG structures

The microstrip loaded inset dielectric waveguide has been proposed as a transmission medium alternative to microstrip, and as a useful antenna medium at X-band and millimetric frequencies. In the present analysis we consider the case where a multi-layer, multi-conductor microstrip circuit may be housed within inset dielectric waveguide. A generalised transverse resonance diffraction method is developed in the space domain for analyzing such structures. Experimental and theoretical results for the propagation characteristics of the fundamental and first higher order mode of a few different configurations are presented showing good agreement. >

Broadside coupled strip inset dielectric guide and its directional coupler application

A theoretical and numerical method is presented for the analysis of broadside-coupled strip inset dielectric guide. The method of analysis is based on an integral equation formulation and Galerkins procedure. Besides propagation constants for two fundamental and higher order modes, the characteristic impedances for the two fundamental modes are calculated using the total propagating power and the longitudinal strip currents. The propagation characteristics of the two fundamental modes are then used to compute 4-port circuit parameters that are essential for accurate analysis and design of coupled line circuits. The effects of various structural parameters on the S-parameters are investigated and it is found that this broadside coupled strip IDG structure is useful for the realization of the directional couplers. Examples of strong and weak directional couplers are given. Furthermore, the propagation constants and S-parameters of coaxially excited coupled strips are measured, and are in good agreement with the theoretical analysis. >

Effects of iron pipe corrosion on GPR detection

Many studies into the use of GPR to detect targets assume that the targets are ideal reflectors. In reality most targets have been in the ground for many years and have settled and suffered some contamination or corrosion. Iron pipe in particular can be hard to find with GPR. Some possible corrosion processes suggest that a varying conductivity and permittivity profile may be established around a pipe. The consequences of such corrosion induced profiles are that the radar return may be greatly diminished in the classic look-down GPR mode of operation. The analysis shows that the novel look through GPR mode of operation is affected far less by the corrosion induced profiles.

TDOA/AOA Data Fusion for Enhancing Positioning in an Ultra Wideband System

This paper considers a new location scheme for ultra wideband (UWB) positioning system. The newly adopted scheme combines the time difference of arrival (TDOA) and the angle of arrival (AOA) positioning techniques in order to enhance the accuracy of the positioning system compared to the classical technique (TDOA). The new technique is simulated in a sports tracking application in a football field. Results are compared with results from a similar system using classical TDOA technique in order to establish a proof-of-concept. Simulation shows that the new technique is actually giving better performance with an acceptably longer processing time. This technique has the promise of boosting positioning accuracy with a relatively low level of complexity.

Design of Multiple Array Flat Millimetric Antennas in IDG

IDG (Inset Dielectric Guide) has proved an excellent antenna medium for linear arrays. The low coupling in the near field between lines, small dimensions, pure polarization properties and the ease of manufacture make it suitable for two dimensional flat arrays which are strongly demanded. We present a 7-array prototype realized on IDG operating at 30 GHz.