The paper presents a novel, unified technique to evaluate, through physics-based modeling, the frequency conversion and noise behavior of semiconductor devices operating in large-signal periodic regime. Starting from the harmonic balance (HB) solution of the spatially discretized physics-based model under (quasi) periodic forced operation, frequency conversion at the device ports in the presence of additional input tones is simulated by application of the small-signal large-signal network approach to the model. Noise analysis under large-signal operation readily follows as a direct extension of classical approaches by application of the frequency conversion principle to the modulated microscopic noise sources and to the propagation of these to the external device terminals through a Green's function technique. An efficient numerical implementation is discussed within the framework of a drift-diffusion model and some examples are finally provided on the conversion and noise behavior of rf Si diodes.

SUMMARYA general numerical technique is proposed for the assessment of the stability of periodic solutions and the determination of bifurcations for limit cycles in autonomous nonlinear systems represented by ordinary differential equations in the differential-algebraic form. The method is based on the harmonic balance (HB) technique, and exploits the same Jacobian matrix of the nonlinear system used in the Newton iterative numerical solution of the HB equations for the determination of the periodic steady state. To demonstrate the approach, it is applied to the determination of the bifurcation curves in the parameters' space of Chua's circuit with cubic nonlinearity, and to the study of the dynamics of the limit cycle of a Colpitts oscillator.

The paper presents a review on physics-based noise simulation techniques for RF semiconductor devices, starting with the small-signal case but with greater stress on noise in largesignal (quasi)-periodic operation. The nonautonomous (forced) operation case will be considered, which is relevant to all RF applications apart from oscillators. Besides their importance in device design, physics-based noise models can also suggest viable and correct strategies to implement circuit-oriented models, e.g., compact models. From this standpoint, the connection between physicsbased and circuit-oriented modeling will be discussed both in the small-signal and in the large-signal case, with particular stress on the treatment of colored noise in the large-signal periodic regime.Index Terms-Circuit modeling, circuit noise, semiconductor device modeling, semiconductor device noise.

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In this paper, a Doherty power amplifier for K-band point-to-point microwave radio, developed in TriQuint GaAs 0.15-m PWR pHEMT monolithic technology, is presented. Highly efficient driver stages on both the main and auxiliary branches have been designed and optimized to boost gain with minimal impact on power-added efficiency. The selected architecture enables a modular combination to reach higher power levels. Matching network structures have been designed, according to simple equivalent circuit approaches, to obtain the desired 10% fractional bandwidth. The fabricated power amplifier (PA) exhibits, at 24 GHz in continuous-wave conditions, an output power of 30.9 dBm, with a power-added efficiency of 38% at saturation and 20% at 6 dB of output power back-off, together with a gain of 12.5 dB. System-level characterization at 24 GHz, in very demanding conditions, with a 28-MHz channel 7.5-dB peak-to-average ratio modulated signal, showed full compliance with the standard emission mask, adopting a simple predistorter, with average output power of 23.5 dBm, and average efficiency above 14%. The measured performance favorably compare with other academic and commercial K-band PAs for similar applications.Index Terms-Doherty power amplifiers (DPAs), gallium arsenide (GaAs), monolithic microwave integrated circuits (MMICs), point-to-point radio.