Design And Development Of A 3.6 GHz Dielectric Resonator Oscillator With Wide Tuning Sensivity

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Date
2011-09
Authors
Muhammad Afifi, Amir Effendy
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Publisher
Universiti Sains Malaysia
Abstract
An oscillator is required as a second stage LO in a superheterodyne SA. The oscillator operating frequency is a fixed 3.6 GHz, which is at the lower end of the microwave frequency range. There are several options of active devices and resonators that can be considered for the oscillator. A bipolar junction transistor (BJT) is chosen for the amplifier block due to its low flicker noise corner frequency and a dielectric resonator (DR) is chosen for its high Q factor. This combination yields a low phase noise oscillator. Apart from its high Q factor, a DR is a high dielectric constant ceramic thus enabling a miniaturized microwave oscillator design compared to a cavity resonator. A varactor-tuned technique is adopted because it results in a simple planar circuit design compared to optically and magnetically tune DR. This dielectric resonator oscillator (DRO) must have very high frequency accuracy. The SA is specified to operate from 0C to 55C, thus among the design requirement for the DRO is to be operable in a wide temperature range and, to last for many, many years. Hence the DRO is controlled by a phase-locked loop (PLL). As the DRO signal drifts with temperature as well as due to aging, a wide tuning range is necessary to guarantee a reliable and repeatable performance over its operating life. An existing DRO with a tuning range of 0.14% at of 3.6 GHz was used as a benchmark. The development of the new DRO began with investigation on several proposed varactor-tuned DR resonant structures. The resonant structures were observed for the resonant frequency tuning range, the linearity of resonant frequencies versus tuning voltages and the tuning sensitivity. The promising DR resonant structures – with wide tuning range, linear response and high tuning sensitivity, were further analyzed to understand the resonant structures coupling mechanism as well as the potential effect on the DRO performance like phase noise.
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Design and development of a 3.6 GHz , dielectric resonator oscillator
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