Graham Parkinson

3D positioning using spherical location algorithms for networked wireless sensors deployed in grain

For the first time a novel ultra wideband positioning technique is demonstrated which can locate wireless sensor networks in grain silos and other lossy multi-path environments. Pulse edge detection and triggering are combined with classic ‘time of flight’ tri-lateration to yield time difference of arrival data with sub-nanosecond accuracies. Temporal positioning data is processed using spherical function construction to achieve position resolutions of 5 cm.

Bimodal Method of Determining Fat and Salt Content in Beef Products by Microwave Techniques

A bimodal microwave technique is presented as a rapid analytical method of estimating the fat and salt content of beef products. The dielectric properties of lean meat, fat, salt, and other nonmeat ingredients (dry and aqueous solutions) and meat blends of typical ingredients used in meat product manufacture are all separately investigated. A broadband coaxial probe technique is used to select frequencies of maximum sensitivity. The optimum frequency for fat determination lies between 8 and 20 GHz, and the optimum frequency for salt determination lies below 4 GHz. For example, by using a WR-90 cell, either the real or imaginary part of the complex permittivity can effectively resolve fat content, whereas the imaginary part of the permittivity correlates well with salt content when using a WR-284 cell. The technique is sufficiently robust to ensure that the dielectric effects of other nonmeat ingredients, temperature, and density do not adversely affect this measurement approach.

Environmental monitoring in grain

It is shown that Wireless Sensor Networks (WSNs) are capable of deployment in industrial processes which present particularly hostile RF environments. The techniques which have been developed have generic applicability, but in this work they are focused on the monitoring of grain storage. Determination of the environmental conditions in a grain silo is challenged by the dielectric properties of the grain and the multi-path nature of RF propagation in the silo. These challenges apply to both the inter-node WSN communication and node positioning. The methods adopted to meet these challenges and significant results achieved are presented.

An Instrument to Measure the Characteristics of Single Wheat Grain Kernels

This paper describes an instrument, based on microwave techniques and a gas displacement method, to measure the wet mass, moisture content, volume and hence the density of single wheat grain kernels. A low-cost microwave source and detector is designed to drive a microwave cavity to determine the wet mass and moisture content of the grain. The microwave cavity is compactly integrated with the volume meter to combine the measurements into a single assembly with one loading cycle. The loading mechanism is separated from two novel gas compression bellows to improve the accuracy and stability of this measurement. All of the results are processed using a microcontroller. The measured wet mass, moisture content, volume and density of the grain are shown on an LCD display

An Automated Microwave Waveguide Measurement Technique

The tedious and often difficult measurement of dielectric permittivity and permeability as a function of microwave frequency has been simplified using an automated microwave waveguide cell measurement system. The measurement system comprises a microwave VNA under PC control and a data processing section. The overall experimental setup and computer program for the automation of data acquisition are fully discussed. This includes the automatic solution of the transcendental equation to determine the dielectric properties for a frequency band. Experimental data taken using this system is presented to show the feasibility of this automated system for material characterisation. The simplicity, applicability and robustness of this proposed system has applications throughout manufacturing and food processing industries.

Coplanar waveguide scanning microwave profiler

A robust near-field microwave profiler is constructed from a micromachined coplanar waveguide probe coupled to a half wavelength coaxial cavity. This microwave profiler can perform both high resolution scanning microwave measurements and more robust, contactable, in-situ handheld measurements. High resolution measurements are undertaken with the sensor on an X-Y-Z scanning table and results for the investigation of metallic strips on dielectric are compared with measurements using a previously reported tapered conical cavity open-ended coaxial probe. The new micromachined probe is considerably more robust than the fine tipped coaxial probe and yet has been shown to yield higher sensitivity for \S11\ and Q measurements when scanning metallic tracks on a dielectric substrate.

An Overview of Microwave Techniques for the Efficient Measurement of Food Materials

There is critical demand for rapid, low-cost methods to determine food composition to provide a responsive control mechanism and an efficient quality control system in food processes. Four non-destructive microwave techniques used to measure the relative complex permittivity (e*) of food components are reviewed. The open-ended coaxial probe is found to be quick and effective for broadband measurements of liquids and pastes. Narrowband waveguide cells require careful sample preparation but they provide accurate permittivity measurements for solids, particulates and liquids. The resonant cavity method provides a high Q measurement at a single frequency and is suitable for low loss samples that can be inserted into the resonator. For scanning and conveyer belts we describe a horn antenna, free-space transmission line method. Each method is described and real examples are demonstrated for the characterisation of a range of foodstuffs.

Scanning Microwave Profiler

A near-field microwave profiler is constructed from an open ended quarter wavelength coaxial resonator. The open end has tapered inner and outer conductors in order to increase the spatial resolution and sensitivity of the sensor. The sensor is mounted on an X-Y-Z scanning table and used to image a metallic copper track, a woven carbon fibre surface and impact dents on carbon fibre composite specimens

Characterization of the fat content of beef using microwave techniques

The knowledge of fat content in food materials is important for public health and legal requirements such as food labelling. Although accurate chemical analysis methods are available, there is a demand for the rapid in-line and low-cost determination of fat content in food materials to provide a responsive control mechanism and efficient quality control system in food processes. The fat content of beef has been successfully and reliably determined using the microwave measurement methods. A dielectric probe method has proven useful for determining the complex permittivity over a wide frequency range and establishing frequencies at which further detailed analysis using a waveguide cell technique could be undertaken. The waveguide cell technique has been used to show a nearly linear relationship between complex permittivity and fat content of beef and the dependence of complex permittivity on temperature is less pronounced than that of the fat content.

Novel Artificial Transmission Line Approach for Synthesis of MMICs for MMW Communications

A novel error parameter analysis approach for synthesis of an artificial transmission line (ATL) from the ABCD parameters of a uniform transmission line section is presented. An MMIC ATL delay line with 180deg phase shift is synthesized to demonstrate this approach. The MMIC is fabricated using a conventional GaAs process and test results are validated with those of the simulated results.