Delay-line stabilized microwave oscillator with frequency control

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The technique whereby the frequency of an oscillator is stabilized using an external feedback network incorporating a delay-line is extended in this thesis to provide digital control of the frequency of the oscillator. Novel circuit techniques have been developed and analysed to permit the implementation of the proposed frequency control technique in a compact format, suitable for implementation in either hybrid or monolithic microwave integrated circuits. Two new microstrip circuits have been introduced, namely the three-port ring discriminator and the single PIN diode phase shifter. Frequency control of an oscillator is achieved by digitally controlling the time delay through phase shifters in the feedback path of the oscillator's stabilization circuit. A new microstrip phase shifting circuit has been developed which has the advantage of requiring only one active switching element to achieve each digital bit of phase change. The circuit has been analysed in detail and results obtained at X-band to support the theoretical predictions. As part of the analysis of this new component, and in order to permit a greater degree of precision in the design of the phase changes, some new microstrip design techniques have been introduced. These have led to a more exact design for coupled line phase shifters and to an equivalent circuit to represent the excess phase in microstrip DC breaks. Delay-line stabilization of an oscillator requires the use of a phase sensitive network, or frequency discriminator. Whilst this could be realised on microstrip using conventional circuitry, by interconnecting two hybrid rings, a new circuit component, namely the three-port ring discriminator, was developed to provide a simpler, more compact solution. A rigorous analysis of the new circuit is presented, and the behaviour verified through measurements over the frequency range 8-12GHz. The new single PIN diode phase shifter has been incorporated in the delay path of a three-port ring discriminator, and used to control the frequency of an oscillator. Results are presented for circuits at X-band which show the degree of frequency stabilization that has been obtained, together with the reduction in oscillator phase noise. In addition, the original concept of delayline switching to control the frequency of an oscillator has been extended to yield a further new circuit, based on a three-port ring with a switchedfeed mechanism; results are presented which verify the operation of this new circuit both theoretically and through practical measurement. New techniques for controlling the frequency of microstrip oscillators have thus been established, both theoretically and through practical measurement, which combine simple methods of frequency selection with inherent low-noise performance

Design of a Torque Current Generator for Strapdown Gyroscopes

The design, analysis, and experimental evaluation of an optimum performance torque current generator for use with strapdown gyroscopes, is presented. Among the criteria used to evaluate the design were the following: (1) steady-state accuracy; (2) margins of stability against self-oscillation; (3) temperature variations; (4) aging; (5) static errors drift errors, and transient errors, (6) classical frequency and time domain characteristics; and (7) the equivalent noise at the input of the comparater operational amplifier. The DC feedback loop of the torque current generator was approximated as a second-order system. Stability calculations for gain margins are discussed. Circuit diagrams are shown and block diagrams showing the implementation of the torque current generator are discussed

Direct optical control of a microwave phase shifter using GaAs fieldeffect transistors

The design and analysis of a novel optical-to-microwave transducer based upon direct optical control of microwave gallium arsenide (GaAs) field-effect transistor (FET) switches is the subject of this thesis. The switch is activated by illuminating the gate depletion region of the FET device with laser light having a photon energy and wavelength appropriate to the generation of free carriers (electron-hole pairs) within GaAs. The effects of light on the DC and microwave properties of the GaAs FET are explored and analyzed to permit the characterization of the switching performance and transient response of a reflective microwave switch. The switch is novel in that it utilizes direct optical control, whereby the optically controlled GaAs FET is directly in the path of the microwave signal and therefore relies on optically-induced variations in the microwave characteristics of the switch. This contrasts with previous forms of optically controlled switches which rely on indirect methods with the optical stimulus inducing variations in the DC characteristics of the GaAs FET, such that there is no direct interaction between the optically illuminated GaAs FET and the microwave signal. Measured and simulated results relating to the switching performance and transient response of the direct optically controlled microwave switch have been obtained and published as a result of this work. For the first time, good agreement is achieved between the measured and simulated results for the rise and fall times associated with the transient response of the gate photovoltaic effect in optically controlled GaAs FET switches. This confirms that the GaAs FET, when used as an optically controlled microwave switch, has a transient response of the order of several micro-seconds. An enhanced model of the GaAs FET switch has been developed, which represents a more versatile approach and leads to improved accuracy in predicting switching performance. This approach has been shown to be valid for both optical and electrical control of the GaAs FET. This approach can be used to model GaAs FET switches in discrete or packaged forms and predicts accurately the occurrence of resonances which may degrade the switch performance in both switching states. A novel method for tuning these resonances out of the switch operating band has been developed and published. This allows the switch to be configured to operate over the frequency range 1 to 20 GRz. The agreement between the models and measured data has been shown to hold for two very different GaAs FET structures. The results of the direct optically controlled microwave GaAs FET switch have been used as the basis for the design of a novel direct optically controlled microwave phase shifter circuit; Measured and simulated results are in good agreement and verify that the performance of the optically controlled phase shifter is comparable with previously published results for electrically controlled versions of the phase shifter. The 10 GRz phase shifter was optically controlled over a 1 GRz frequency range and exhibited a mid-band insertion loss of 0.15 dB. The outcome of the work provides the basis for directly controlling the phase of a microwave signal using the output of an optical sensor, with the GaAs FET acting as an optical-to-microwave transducer through a monolithic interface

Modeling and Analysis of Power Processing Systems (MAPPS). Volume 1: Technical report

Computer aided design and analysis techniques were applied to power processing equipment. Topics covered include: (1) discrete time domain analysis of switching regulators for performance analysis; (2) design optimization of power converters using augmented Lagrangian penalty function technique; (3) investigation of current-injected multiloop controlled switching regulators; and (4) application of optimization for Navy VSTOL energy power system. The generation of the mathematical models and the development and application of computer aided design techniques to solve the different mathematical models are discussed. Recommendations are made for future work that would enhance the application of the computer aided design techniques for power processing systems

A Modular Programmable CMOS Analog Fuzzy Controller Chip

We present a highly modular fuzzy inference analog CMOS chip architecture with on-chip digital programmability. This chip consists of the interconnection of parameterized instances of two different kind of blocks, namely label blocks and rule blocks. The architecture realizes a lattice partition of the universe of discourse, which at the hardware level means that the fuzzy labels associated to every input (realized by the label blocks) are shared among the rule blocks. This reduces the area and power consumption and is the key point for chip modularity. The proposed architecture is demonstrated through a 16-rule two input CMOS 1-μm prototype which features an operation speed of 2.5 Mflips (2.5×10^6 fuzzy inferences per second) with 8.6 mW power consumption. Core area occupation of this prototype is of only 1.6 mm 2 including the digital control and memory circuitry used for programmability. Because of the architecture modularity the number of inputs and rules can be increased with any hardly design effort.This work was supported in part by the Spanish C.I.C.Y.T under Contract TIC96-1392-C02- 02 (SIVA)

Theory of phaselock techniques as applied to aerospace transponders

Phaselock techniques as applied to aerospace transponder

COMPUTER ANALYSIS OF CURRENT SOURCE INVERTER INDUCTION MOTOR DRIVE SYSTEMS

The known concept of supplying an induction motor from a static current source converter results in ac drive performance with several important advantages over the more familiar voltage fed inverter. All ac drive using such a current source inverter is shown in Fig. 1. Basically, it consists o

Requirements for a transformerless power conditioning system

Requirements for development of a Transformerless Power Conditioning Subsystem (TPCS) that will meet utility, manufacturer, and customer needs are detailed. Issues analyzed include current utility guidelines, safety and grounding issues that appear as local codes, various kinds of TPCS connections that can be developed, dc injection, and a brief survey of TPCS circuit topologies that will meet requirements. The major result is that a finite time exists for control operation before dc injection into the distribution transformer causes customer outage (on the order of seconds). This time permits the control system to sense a dc injection condition and remove the TPCS from the utility system. Requirements for such a control system are specified. A three wire connection will ensure balanced operation for customer loads and two wire connections caused average value dc to be injected into single phase loads. This type of connection also allows for the lowest array voltage. The conclusion is that requirements for a TPCS can be determined and that there are not showstopping issues preventing implementation. The actual design and topology of the TPCS was left for further study