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In this paper a new bifurcation synthesis procedure is described. Its foundations are built on an extension of the Conversion Matrix concept, applied to the nonlinear sub network of the circuit simulated through Harmonic Balance. The Cross-frequency Stability Curves (CSC) are defined, which are the nonlinear equivalent of the Stability Circles valid for linear networks. The CSC gives us regions of reflection coefficient values for the loads that yield potential eriod doubling in the circuit. The proposed synthesis method can be used within any simulation program based on the Harmonic Balance algorithm, allowing the designer the possibility to check the nonlinear stability of any simulated circuit, or to design intentionally unstable circuits. Results of the CSC method are given for a GaAs FET circuit synthesized to operate as a divider-by-two.

An accurate,non-quasi-static,non-linear equivalent circuit model of a power Si LD-MOSFET valid well into the microwave region has been extracted by means of a reliable and easy procedure.The model is intended for applications to high-efficiency power amplifiers in the low microwave region.The extraction is based on linear S-parameter measurements at many bias points with a hot-cold method for parasitic and intrinsic element determination.The model differs from the standard BSIM3 or MODEL9 models,ensuring accurate high-frequency performances.

The optimum design of active microwave mixers is addressed by means of a full non-linear technique.Optimum matching conditions at the input/output ports and at all other ports are defined;a stable conversion gain is also defined ensuring high gain within safe stability margins in large-signal operating conditions.

A systematic approach to the design of high efficiency microwave power amplifiers is presented. The technique makes use of second and third harmonic terminating idlers to achieve major improvements in output power, gain and power added efficiency. The approach proposed in this contribution is validated by means of a sample design and realisation, illustrating both the effectiveness and the feasibility of the method, as compared to more conventional harmonic tuning strategies.

The effect of second-harmonic loading on power amplifiers operated with a low-voltage supply is investigated. Closed-form expressions and design formulas are derived, making use of a simplified device model. The correctness of the assumptions and the range of validity of the derived expressions is then verified by means of a full non-linear analysis method and model: a sample low-voltage design for a power stage is performed, demonstrating the potentials of the method.

We present a numerical analysis of travelling Gunn domains in GaAs MESFET's based on a quasi-2D hydrodynamical model. The results are shown to be quite accurate in comparison to Monte Carlo simulations, despite the simplicity of the quasi-2D model. A microscopic description of the domain propagation is also given.

A new type of analytic formulae is given for the representation of the bias-voltage dependence of non-linear elements of a MESFET. Accuracy and range of validity make them suitable for non-linear CAD applications.

This paper describes a method for the stability analysis and stabilization criteria in multi-device paralleled power amplifiers (PA) under large-signal operating conditions. The symmetry of the amplifier is exploited for a simple and effective study of odd- and even-order modes. The overall stability analysis is transformed into a sequence of analyses on single-mode single-transistor large-signal equivalent amplifiers, which are carried out by using a conversion matrix approach. Examples of application of the method are provided on a 9-GHz GaAs pHEMT monolithic-microwave integrated-circuit (MMIC) PA and a 590-MHz power silicon bipolar hybrid microwave integrated-circuit (HMIC) PA.