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A Novel Design Methodology for the Design of Low Phase Noise Oscillators Based on the ISF

Mostajeran, Ali | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44471 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Sharif Bakhtiar, Mehrdad
  7. Abstract:
  8. We present a novel and simple method to calculate each Fourier series coefficient of ISFs in LC oscillators, analytically. This new approach explains the relationship between Fourier series coefficient of ISF and oscillator topology and parameters. This technique helps designers to obtain the great insight of how to decrease the output noise in oscillators. This method also can be used to derive the waveform of ISFs in time domain.Based on the features of our new technique and by presenting a general method to change the stationary noises to Cyclo-stationary ones, we suggest a step by step design guide which elucidates new ideas for designers to manipulate the oscillator parameters and structure in order to improve the phase noise. We apply our design guide to cross coupled and Colpitts oscillators and presente new structures that improve the phase noise significantly with no more power consumption.For the Colpitts oscillator it is shown that the noise contribution of the tail transistor as well as the main transistor can be reduced by modifying their respective effective ISF. Two circuit modification methods to improve the effective ISF of the tail and the main transistors are then discussed. A closed-form formula for the phase noise, based on the ISF has been derived and the amount of the phase noise improvement is theoretically evaluated. Simulations resulats prove that improvements of more than 5.6dB can be achieved with simple modifications in a RF Colpitts oscillator without increasing the power consumption
  9. Keywords:
  10. Phase Noise ; Noise ; Oscillators ; Impulse Sensitivity Function (ISF) ; Voltage Controlled Oscillator ; Oscillator Phase Noise

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