The widespread use of embedded mixed-signal cores in system-on-chip (SoC) or System-on-Package (SoP) design has been increasingly important in cost-effective manufacturing test for mixed-signal devices. A typical SoP encapsulates many of its internal functions, and its production test is performed by application of test signals to the SoP under control of external Automatic Test Equipment (ATE). However it is a problem that the external ATE does not have direct access to all the internal embedded functions of the SoP. Thus a classical test approach to SoP suffers from limited controllability and observability of its subsystems. Built-in Self-Test (BIST) and Built-off Self-test (BOST) schemes have been suggested and developed to overcome the limitations of conventional test, such as limited test Input/Output (I/O) accessibility as well as high test cost. However most BIST/BOST approaches have limited test accuracy. The focus of the dissertation is to develop a cost-effective performance-based test methodology based on BIST/BOST, while maintaining the same accuracy as conventional test. This dissertation proposes one BIST approach and two BOST schemes. Our BIST methodology presents a methodology for efficient prediction of circuit specifications with optimized signatures. The proposed Optimized Signature-Based Alternate Test (OSBAT) methodology accurately predicts the specifications of a Device Under Test (DUT) using a strong correlation mapping function. The approach overcomes the limitation that analytical expressions cannot precisely describe the nonlinear relationships between signatures and specifications. Our first BOST approach presents a practical methodology for effective prediction of individual dynamic performance parameters of differential devices with a cascaded Radio-Frequency (RF) transformer in loopback mode. The RF transformer produces differently weighted loopback responses, which are used to characterize the DUT dynamic performance. The approach overcomes the imbalance problem of Design for Test (DfT) circuitry on differential signaling, thereby accurately measuring the dynamic performance of differential mixed-signal circuits. The second BOST scheme is an efficient methodology for accurate prediction of aperture jitter using cost-effective loopback methodology. Aperture jitter is precisely separated from input and clock jitter as well as additive noise present in the DUT, by using an efficient loopback scheme. Hardware measurements were performed for all our approaches, and good results were obtained. This fact verifies that all approaches can be practically used for production test in industry.

This work describes a thirty-two channel programmable transmitter unit for driving an ultrasonic transmitting array using transducers with thickness resonances of up to 2 MHz. It has been developed to allow the performance of time delay focussed transmitting arrays to be thoroughly investigated before their eventual use in an imaging system. The unit will produce a pulse or continuous wave output which is programmable using either a microprocessor or a computer, in both amplitude and delay or phase. The unit's operation is discussed in some detail and the experimental underwater 1 MHz transducer array used for the functional tests is described. Results are presented showing the performance of the transmitting unit when used with this array and demonstrate that the system provides an effective tool by which a proper assessment of time delay focussing may be made. A computer prediction technique·has been introduced. The computer prediction of the field in the region in front of a focussed ultrasonic array has been obtained by the summation of the fields due to the individual array elements. The shape of the short duration acoustic pulses due to the individual elements is determined.by the electrical drive and transducer characteristics. The prediction technique is valid for any pulse shape which can be represented mathematically, however the results presented here have been limited to the pulse shape used in the experimental work. The algorithm used is suitable for a wide range of array formations and the close agreement of the practical and the simulation work shows the validity of the prediction technique. The experimental array has been used as the basis of a detailed investigation into the resolving power of focussed arrays and a number of results have been derived from this investigation. These are used to support extensive simulation studies and computer prediction techniques. The validity of the simulation techniques is assessed and the effect of considering each transducer in the array as a single small but finite sized centrally placed element is compared with that where each transducer is represented by a number of synchronously driven Huygens radiators. The significance of these results with respect to imaging is discussed. The effect on performance of system error is investigated and an assessment of the tolerance of the time delay technique to these errors is made.

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Strain-sensing elements, fabricated in standard communications-grade single mode optical fibre, are increasingly being considered for application in structural health monitoring. The reason for this is the numerous advantages demonstrated by these devices compared with traditional indicators. This thesis describes work carried out on optical sensors at the University of Plymouth. The aim of this work was to achieve an optical fibre strain sensing system capable of measuring absolute strain with good resolution and having wide dynamic range, without bulky optical equipment and not susceptible to misalignment due to handling. Earlier work was devoted to study on an intrinsic Fabry-Perot interferometric sensor and an optical phase-shift detection technique. The sensing element investigated relied on the end face of an optical fibre as one mirror and the second mirror being a layer of Titanium Dioxide (TO2). Although some results are included, it was soon realised that this sensor had a number of problems, particularly with fabrication. As no simple solution presented itself, consideration was given to a sensor that made use of the change in reflectance of an intra-core fibre Bragg grating when the grating was subjected to strain. The bulk of work described in this thesis is concerned with this type of sensing element. The grating structure is inherently flexible and a number of structural formats were studied and investigated. The first and simplest grating considered was two linearly chirped Bragg gratings used in a Fabry-Perot configuration (a grating resonator). The sensor was tested using the sensing detection system and although the fabrication problems were overcome absolute strain measurement was unattainable. To achieve this end, a theoretical study of a number of grating structures was carried out using the T-matrix Formalism. Confidence in using this approach was gained by comparing the spectral behaviour of a proposed grating with results, which were given by another theoretical model for the same proposed grating. The outcome of this study was that two structures in particular showed promise with regard to absolutism (the measure of true strain) and linearity. Discussions held with the department of Applied Physics at Aston University about fabrication resulted in one of the proposed designs being abandoned due to difficulties of fabrication. The second structure showed more promise and fabrication attempts were put in hand. This grating is linearly-chirped with a Top-hat function and a sinusoidal perturbation as a taper function of the refractive index modulation. Experiments were performed, data were acquired and system performance for this sensor is presented. The thesis concludes that using such a fibre Bragg grating as the sensing element of a strain sensing system enables it to measure absolute strain without using bulky optical equipment. At present, the resolution of strain is limited by the quality of the grating being fabricated (anomalies on profile), this should improve once the fabrication technique is refined.

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