This thesis presents the design and implementation of a millimeter-wave Gunn diode oscillator operating at 35 GHz (Ka (R) 26.5-40 GHz Band). The aim of the study is to produce a high frequency, high power signal from a negative resistance device situated in a waveguide cavity by applying a direct current bias. First the physics of Gunn diodes is studied and the requirements that Gunn diode operates within the negative differential resistance region is obtained. Then the best design configuration is selected. The design of the oscillator includes the design of the waveguide housing, diode mounting and the bias insertion network. Some simulation tools are used to predict, approximately, the behaviour of the oscillator and the bias coupling circuit. For tuning purposes, a sliding backshort and a triplescrew- tuner system is used. For different bias values and different positions of the tuning elements oscillations are observed. A much more stable and higher magnitude oscillations were obtained with the inclusion of &ldquo / resonant disc&rdquo / placed on top of the diode. 15 dBm power was measured at a frequency of 28 GHz. Laboratory measurements have been carried out to determine the oscillator frequency, power output and stability for different bias conditions.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / Thesis presented in partial fulfilment of the requirements for the degree Master of Science in Engineering at the University of Stellenbosch / ENGLISH ABSTRACT: In 1966, D.B. Leeson presented his model on phase noise in a letter entitled A Simple Model of Feedback Oscillator Noise Spectrum. This model usually requires an additional e ffective noise figure in order to conform with measured results. (This e ffective noise fi gure has to be determined by means of curve-fi tting Leeson's model with the measured results.) The model is, however, relatively simple to use, compared with other more accurate phase noise models that have since been developed and which can only be solved numerically with the aid of computers. It also gives great insight regarding component choices during the design process. Therefore several experiments were conducted in order to determine conditions under which Leeson's model may be considered valid and accurate. These experiments, as well as the conclusions drawn from their results, are discussed in this document. / AFRIKAANSE OPSOMMING: In 1966 stel D.B. Leeson sy faseruis model bekend in 'n brief getiteld A Simple Model of Feedback Oscillator Noise Spectrum. Hierdie model vereis gewoonlik die gebruik van 'n bykomende e ektiewe ruissyfer, sodat die model ooreenstem met die gemete resultate. (Hierdie e ektiewe ruissyfer kan slegs bepaal word deur middel van krommepassings tussen Leeson se model en die gemete resultate.) Die model is egter relatief eenvoudig om te gebruik in teenstelling met ander, meer akkurate, faseruis modelle wat sedertdien ontwikkel is en slegs met behulp van rekenaars opgelos kan word. Dit bied ook onoortre ike insig ten opsigte van komponent keuses tydens die ontwerpsproses. Om hierdie rede is verskeie eksperimente uitgevoer met die doel om toestande te identi seer waaronder Leeson se model as geldig en akkuraat geag kan word. Hierdie eksperimente, asook die gevolgtrekkings wat van hul resultate gemaak is, word in hierdie dokument behandel.

The temperature sensor design discussed in this thesis, is meant mainly to monitor temperature at power outlets. Current variations in power cords have a direct impact on the surrounding temperature. Sensing these variations ,enables us to take necessary measures to prevent any hazards due to temperature rise. Thus, for this application we require a sensor with a moderate temperature error (_10C) over a sensing range of -200C to 1500C. Low power consumption and simple digitizing scheme alleviate measurement errors due to self heating effects of the sensor. A current starved inverter based ring oscillator was chosen for the sensor design in 130nm technology. The inverter delay variation with temperature is used for sensing. Linearity and process invariancy of these characteristics are fundamental to the sensor design. We observed through simulations, and confirmed by mathematical analysis, that the sensing characteristics are governed by bias current dependence on temperature. Control voltage for the bias circuitry of the oscillator determines current through the inverter stages. Hence, for linear sensing characteristics, a control voltage(Vc) just above the maximum threshold voltage of bias transistor is used. This enables generation of PTAT saturation current for current starved inverters, due to dominance of threshold voltage decrease with temperature over mobility decrease. I.Another limitation, process dependency of the sensing characteristics, was overcome through the proposed calibration based compensation technique. A changing Vc proportional to threshold voltage variation with process, process independent bias current and current temperature characteristics were obtained. This compensated for the process variation effects on frequency. Thus, a variable Vc was generated using a reference with low temperature sensitivity of 17.6_V=0C, and resistive divider combinations for various processes. Incorporating this compensation technique we achieved good linearity in sensor characteristics and a maximum temperature error of± 1.60C over the sensing range. The sensor consumes a low power of 0.29mW and also occupies minimal area.