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Design of an N-Path Tunable Bandpass Filter for RF Range

Mohammadpour Darzinaghibi, Amin | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43409 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Atarodi, Mojtaba; Sadughi, Sirous
  7. Abstract:
  8. A high-Q tunable bandpass filtered amplifier structure is proposed which is based on N-path Q enhancement. Using Fourier series analysis, frequency response of an N-path filter and aliasing effect of this filter is achieved. This effect is caused by frequency translation to bandpass frequency as harmonic fold back (HFB). It is shown that using an additional N-path filter with the same clock frequency but different clock phase HFB is reduced. The conditions for fold back elimination are derived from Fourier series expansions for switched signals. In order to realize HFB reduction and increasing stop-band rejection and Q factor, an LNA associated with N-path filter is added to each of the N-path filters. The LNA in the proposed structure is designed for high linearity and low NF, using the noise and distortion cancellation methods. The method is based on the addition of pulse generator circuits with the same clock frequency, but different phases. The resulting circuit acts as a 2N-path filter with reduced fold back effect without increasing the clock frequency. In the front end of a receiver an LNA follows the filter; therefore, a second N-path filter is combined with the LNA in order to achieve HFB reduction. The LNA is designed for low noise and low distortion characteristics in order to compensate for excess nonlinearities due to high impedance of the secondary of balun placed between input of filter and LNA.

  9. Keywords:
  10. Low Noise Amplifier (LNA) ; Complementary Metal Oxide Semiconductor Technology (CMOS) ; Fourier Series ; Receivers ; Bandpass Filters ; N-Path Filter ; Tunable Filter

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