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Noise Analysis and Performance Improvement of Microwave Diode Mixers, and Improving the Method of Noise Figure Measurement

Rahmati, Mohammad Mehdi | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55677 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Banai, Ali
  7. Abstract:
  8. In spite of developments in microwave mixers, reducing its noise figure is still a designers’ challenge in receiver applications. Due to generating intermodulations and saturating the following stages, the low noise amplifier cannot have a so much gain to decrease the noise of the following stages in a typical receiver. This problem is intensified in special applications because of low dynamic range of low noise amplifiers. Accordingly, the low noise amplifier is replaced sometimes by the mixer. Therefore, the design of a low noise mixer is an important issue in improving the noise performance of a total receiver.To this end, it is required to accurately analyse the nonlinear and noise performance of the mixer. Since the mixer is a nonlinear three-port network with so frequency components, its nonlinear and noise analysis is more complicate than usual two-port networks. In this thesis, because of the desirable features, the conversion matrix and the noise correlation matrix methods are used for the nonlinear and noise analysis, respectively. These two methods are based on Harmonic Balance analysis and so, the mixer can be accurately analyzed. Accordingly, the analytical expressions of the gain and noise figure of the mixer are derived as a function of terminations of the frequency component. After that, the noise and gain optimization of the mixer is investigated. Due to the complexity involved in the obtained expressions, an analytical optimization was not achieved and instead, numerical optimization was applied to introduce an algorithm for optimum design of a non-active mixer. In following, an appropriate structure of a diode mixer is presented to demonstrate the findings in practice. In its noise figure measurement, however, the measurement procedure is different from the common two-port networks; where is investigated here. The methods used for noise figure measurement are then studied in detail, and considering the measurement equipment limitations, two methods based on the Y-factor and cold-source methods are expanded. These two methods measure the noise figure simultaneously fast and accurate using typical equipment that is available in many labarotories. The accuracy obtained by the presented methods is comparable to methods employing a redundant number of source impedances
  9. Keywords:
  10. Noise Analysis ; Conversion Matrix ; Cold Source Method ; Noise Figure Analyzer Calibration ; Noise Figure Measurement ; Y Factor Method ; Diode Mixer ; Noise Parameter Characterization

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