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Modern radar and sonar systems rely on active sensing to accomplish a variety of tasks, including detection and classification of targets, accurate localization and tracking, autonomous navigation and collision avoidance. Bats have relied on active sensing for over 50 million years and their echolocation system provides remarkable perceptual and navigational performance that are of envy to synthetic systems. The aim of this study is to investigate the mechanisms bats use to process echo acoustic signals and investigate if there are lessons that can be learned and ultimately applied to radar systems. The basic principles of the bat auditory system processing are studied and applied to radio frequencies. A baseband derivative of the Spectrogram Correlation and Transformation (SCAT) model of the bat auditory system, called Baseband SCAT (BSCT), has been developed. The BSCT receiver is designed for processing radio-frequency signals and to allow an analytical treatment of the expected performance. Simulations and experiments have been carried out to confirm that the outputs of interest of both models are “equivalent”. The response of the BSCT to two closely spaced targets is studied and it is shown that the problem of measuring the relative distance between two targets is converted to a problem of measuring the range to a single target. Nearly double improvement in the resolution between two close scatterers is achieved with respect to the matched filter. The robustness of the algorithm has been demonstrated through laboratory measurements using ultrasound and radio frequencies (RF). Pairs of spheres, flat plates and vertical rods were used as targets to represent two main reflectors.

In this thesis, the design procedures, implementation methods and performance characteristics for various fan beam planar lens antennas mainly synthesized using Luneburg lens principles are developed with regard to acceptable radiation performance and ease of low cost fabrication. The lenses presented are characterised at 24 GHz for industrial, scientific, and medical (ISM) band (24 - 24.25 GHz) or for wide-band automotive short-range radar systems (21.65 - 26.65 GHz), and at 27 GHz for potential millimetre wave applications. The derivation of the original Luneburg lens equations are illustrated using ray tracing theory. Then the problems associated with conventional discrete 3D spherical LL fabrication are presented and summarised. The realization of the gradient refractive index of a cylindrical Luneburg lens achieved by three novel techniques is reported. These are: (1) use of a combination method of improved artificial refractive index grading in the lens central region together with the application of the transverse resonance method (TRM) in the lens outer region; (2) use photo lithographically etched holes of different sizes into one side of a standard low loss PCB ground plane in order to introduce a local inductive variation which partially neutralizes the intrinsic permittivity of the material in prespecified localized regions of the lens; (3) use a shape contoured fixed dielectric constant disc with no metal plates. Further the design and performance of two planar extended hemi-elliptical polystyrene lens operated at 28.5 GHz are given. This type of lens, though Supplied by The British Library - 'The world's knowledge' homogeneous, has similar characteristics to that of the planar inhomogeneous Luneburg lens. Finally the general theoretical properties of two types of reconfigurable spherically symmetrical lenses are analyzed and their potential summarized for future electronic scanning applications.

The research work presented in this thesis sets out to investigate improvements to the power amplifier design cycle through the use of recently developed radio-frequency waveform measurement and characterisation systems. One key objective of this work is to improve the overall efficiency of the modern wireless communication system by focusing on the radio-frequency power amplifier stage. More specifically, the direct utilisation of waveform-engineering techniques in the development of methodologies for the design and realisation of efficiency enhanced radio-frequency power amplifiers was targeted. In developing these power amplifier design methodologies, work has also led to significant advancements into the possibilities of 'first-pass-design' success. Through the direct import of captured waveform data into a computer-aided design environment, along with efficiency-optimised multi-harmonic and intermediate-frequency impedance information, a stable and highly efficient power amplifier has been realised. This direct implementation of waveform measurements completely by-passes any involvement with potentially unreliable nonlinear device models. Hence this has eliminated the need for multiple iterations of matching networks, resulting in a dramatically more time-efficient design process. Waveform-engineering-based designs completed in this research have been demonstrated with both very high-efficiency (70-80%), narrowband modes of operation, as well as a high-efficiency (60-70%) broadband mode covering almost an octave bandwidth. All designs throughout have been realised as prototype power amplifiers.

This thesis extends the use of Radio Frequency Identification (RFID) data for accounting of warehouse costs and services. Time Driven Activity Based Costing (TDABC) methodology is enhanced with the real-time collected RFID data about duration of warehouse activities. This allows warehouse managers to have an accurate and instant calculations of costs. The RFID enhanced TDABC (RFID-TDABC) is proposed as a novel application of the RFID technology. Application of RFID-TDABC in a warehouse is implemented on warehouse processes of a case study company. Implementation covers receiving, put-away, order picking, and despatching. RFID technology is commonly used for the identification and tracking items. The use of the RFID generated information with the TDABC can be successfully extended to the area of costing. This RFID-TDABC costing model will benefit warehouse managers with accurate and instant calculations of costs. Although the study is limited in the scope to applying presented RFIDTDABC model only to warehouse operations of a SME company, RFIDTDABC concept will be of value to both academics and practitioners by showing how warehouse costs can be accurately measured by using this approach. Providing better understanding of incurred costs may result in a further optimisation of warehousing operations, lowering costs of activities, and thus provide competitive pricing to customers.

Creating and controlling well-defined single-photon states is important for many quantum enhanced technologies. Information can be encoded in any degree of freedom associated with a single-photon field excitation, for example in the polarization or transverse spatial mode structure. The ability to encode multiple qubits in these states is desirable for high data transmission rates and increased information processing capacity. The spectral-temporal domain offers a large Hilbert space for encoding information, well suited to integrated optical architectures owing to the low cross-talk between channels. Indeed, time-frequency encoding is an integral component of existing information technologies infrastructure. Thus, complete, coherent control of the spectral-temporal mode structure of light is essential to advancing optical quantum technologies. Arbitrary control of single-photon states has been demonstrated in the polarization and spatial-momentum degrees of freedom however, is yet to be established in the spectral-temporal domain. Recently it was shown that spectral-temporal pulse shaping is experimentally feasible using nonlinear optical methods. However, such techniques can introduce noise photons, are challenging to implement deterministically and require specially prepared auxiliary pump pulses. Furthermore, they are typically only possible at relatively low repetition rates to avoid damage of nonlinear optical materials. Here, we demonstrate deterministic pulse shaping of single-photon wave packets by introducing a time-varying phase. Applying linear or quadratic phase to the wave packet introduces a spectral shift or spectral broadening, respectively. Achieving significant spectral manipulation requires temporal-phase modulation on the order of p. The phase must also vary on the same time scale as the optical pulses, approximately 1 ps in duration here. This relatively rapid phase variation is achieved using a fast electro-optic phase modulator. The modulator is driven by a time-varying voltage that is synchronized with a pulse train of single-photon wave packets for accurate temporal phase control. In this thesis, we experimentally demonstrate control of the spectral-temporal state of single-photon wave packets using this method. Heralded single-photon wave packets are generated by spontaneous parametric down conversion pumped by a frequency-doubled Titanium-Sapphire laser oscillator with 80 MHz repetition rate. To achieve significant modulation of single-photon pulses a 10 V peak-to-peak radio-frequency signal of 40 GHz drives the phase modulator, which requires approximately 3.6 V to achieve a p phase shift. The signal is synchronized with the oscillator pulse train using custom designed electronics. Details of these electronics are presented, resulting in a robust phase and amplitude controllable 40 GHz voltage source, phase locked to the single-photon pulse train. To demonstrate the utility of this pulse-shaping method we experimentally show spectral shearing of almost 1 nm for single-photon wave packets with 830 nm central wavelength and 1 nm bandwidth. Measurement of the second-order intensity correlation before and after the wave-packet manipulation remains constant within uncertainty of the measurement, showing that the quantum nature of the single-photon source is not deteriorated by the modulator. Preservation of the wave-packet coherence is verified by two-photon interference between spectrally sheared and non-modulated single-photons.

No description available.

Radio interference from the Middle East is one of the most significant problems plaguing the local radio services in Cyprus today. The issue is particularly noticeable on the highway, where it affects in-car tuners in all coastal areas of the island when the weather is hot and humid. In this work, the problem of interference from the Middle East was explored in the context of field strength variations versus the type of propagation mechanism favouring the radio waves in Band II, allowing them to travel from the Middle East to beyond the horizon in Cyprus. This problem was significant, since no line of sight exists between the two regions. After in-depth analysis adhering to the ITU (International Telecommunications Union) Recommendations, it was demonstrated that interference is caused by “Tropospheric Ducting”, i.e., trapping of the overseas transmitted signals between two layers of the troposphere at different heights. The upper air data were obtained using the Weather Research Forecasting (WRF-ARW version 3.4) model. The results yielded by the present study confirm that this model provides accurate prediction of interference for up to five days in advance. The interference problem is widely recognized, and therefore many attempts have been made to explicate its causes and provide solutions. The aim of the present study was to present a robust solution based on an innovative receiving antenna design. The antenna is a receiver’s component that collects electromagnetic waves from various directions. The rationale behind focusing on a circular array topology is that its tuning ensures that the receiver processes the desired signal only, while rejecting the unwanted interference. This can presently only be achieved by a large directional external antenna that must be steered mechanically in the desired direction. As this arrangement is not practical, an innovative smart antenna was proposed as an alternative. A circular phased array is a very compact antenna that produces a predicted radiation pattern, whereby it receives maximum energy from the desired direction without the need for mechanical control. Circular arrays exhibit high gain as well as immunity to interference, making them ideal for use in high interference environments. This combination allows the antenna to be incorporated into a commercial deck receiver or installed on vehicles.

This thesis describes the development and operation of multiple high power X-band RF test facilities for high gradient acceleration and deflecting structures at CERN, as re-quired for the e+ e- collider research programme CLIC (Compact Linear Collider). Signif-icant improvements to the control system and operation of the first test stand, Xbox-1 are implemented. The development of the second X-band test stand at CERN, Xbox-2 is followed from inception to completion. The LLRF (Low Level Radio Frequency) system, interlock system and control algorithms are designed and validated. The third test stand at CERN, Xbox-3 is introduced and designs for the LLRF and control systems are pre-sented. The first of the modulator/klystron units from Toshiba and Scandinova is tested. CLIC will require crab cavities to align the bunches in order to provide effective head-on collisions. An X-band travelling wave cavity using a quasi-TM11 mode for deflection has been designed, manufactured and tested at the Xbox-2 high power test stand. The cavity reached an input power level in excess of 50 MW, at pulse widths of 150 ns with a measured breakdown rate (BDR) of better than 10-5 breakdowns per pulse (BDs/pulse). At the nominal pulse width of 200 ns, the cavity reached an input power level of 43 MW with a BDR of 10-6 BDs/pulse. These parameters are well above the nominal design pa-rameters of an input power of 13.35 MW with a 200 ns pulse length. This work also de-scribes surface field quantities which are important in assessing the expected BDR when designing high gradient structures.

The research work presented in this thesis sets out to investigate improvements to the power amplifier (PA) design cycle through the use of Waveform Engineering techniques. This is approached using alternative simulation methods with strong links to the data available from time domain based radio frequency waveform measurement and characterisation systems. One key objective of this work is to improve the overall efficiency of the radiofrequency power amplifier stage by focusing on circuit design. More specifically, the direct utilisation of waveform-engineering techniques in the development of multi-stage amplifiers to improve power added efficiency was targeted. In developing these power amplifier design methodologies, the techniques are demonstrated and validated using monolithic microwave integrated circuit (MMIC) implementation. This work has also led to an increase in understanding of the operation of the device terminal waveforms which is used to drive an alternative simulation approach. Through the use of standard computer-aided design (CAD) device models and measured waveform data, a 2-stage MMIC Gallium Nitride power amplifier has been detailed. This amplifier also uses internal node probe points in the interstage matching network, along with a new application of the waveform measurement system, to allow investigation of the terminal waveforms to validate the performance. This direct implementation of these waveform measurements provides valuable information on the design of the interstage networks to reduce the number of design iterations resulting in a more efficient design process. Waveform-engineering-based designs completed in this research have been demonstrated with test circuits and the time domain measurement system to demonstrate new modes of operation, as well as complete designs realised as prototype MMIC power amplifiers.