Microwave and Wireless Synthesizers: Theory and Design

APPENDIX B

A GENERAL-PURPOSE NONLINEAR APPROACH TO THE COMPUTATION OF SIDEBAND PHASE NOISE IN FREE-RUNNING MICROWAVE AND RF OSCILLATORS

B-1 INTRODUCTION

We want to look at the contribution of the active devices like FETs and BIPs as well as a novel algorithm for the computation of near-carrier noise in free-running microwave oscillators by the nonlinear harmonic-balance (HB) technique [1].

The application of the HB methodology to nonlinear noise analysis is very effective, because frequency-domain analysis is well suited for describing the mechanism of noise generation in nonlinear circuits. In the last few years, this topic has received the interest of several research teams; however, until now, a rigorous treatment of noise analysis in autonomous circuits has not appeared in the technical literature.

The usual approach relying on a simple noise model of the active device and the frequency-conversion analysis is not sufficient to describe the complex physical behavior of a noisy oscillator. Instead, we apply the following approach:

• A complete bias-dependent noise model for bipolar transistors and FETs is developed.
• The frequency-conversion approach is reviewed and its limitations are pointed out.
• It is shown how the analysis procedure can be extended to include the case of autonomous circuits.
• The capabilities of the proposed algorithm are demonstrated by means of some application examples.

B-2 NOISE GENERATION IN OSCILLATORS

The qualitative picture of noise generation in oscillators ...