A stability analysis technique of microwave amplifiers, valid for large- or small-signal regimes, is presented. The technique calculates the system poles and zeroes from a closed-loop frequency response of the circuit linearised around its steady state. The method has been applied to an S-band monolithic amplifier, detecting spurious oscillations for certain specific bias conditions and input power levels, in good agreement with measurements.

A new way of sensing displacement for subnanometric applications using RF resonant cavities is presented and experimentally demonstrated on a laboratory prototype. The new sensor physical principle of operation is summarized, and a first working prototype is described and tested. It is shown by experiment that very high and linear sensitivity characteristic curves, in the range of several kilohertz per nanometer, are easily obtainable using this kind of devices, making them serious candidates as alternative and reasonably priced sensors for subnanometric displacement measurement.

Multistage power amplifiers are prone to parametric oscillations of an odd-mode nature. In this article, a technique for detecting and avoiding odd-mode parametric oscillations in microwave power amplifiers under large-signal excitations is extended and improved. For that, two monolithic amplifiers, having different topology and different oscillation mode, are extensively analyzed. A previously analyzed X-band two-stage power amplifier is used as a first example. Then, the technique is applied to a novel L-band one-stage power amplifier exhibiting a different oscillation mode. The success in determining the oscillation nature of these two different examples and the strategies used for their stabilization clearly illustrate the potential of this technique to address the complex problem of parametric oscillations in microwave amplifiers. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE 15, 2005.