Simulation by Harmonic Balance Techniques of Non-Linear Circuits Driven by Random Modulated Signals

A new method is proposed to perform, by Harmonic Balance (HB) techniques, the simulation of non-linear circuits driven by carrier Random-Modulated (RM) signals. The microwave driving random modulated generator is first transformed in an almost periodic generator with two fundamental frequencies: the carrier frequency (f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">car</inf>) and, on the other hand, the modulating frequency (f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">modframe</inf>) given by the user-defined length (T<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">modframe</inf>) of the modulating random bit sequence. This random bit sequence is mapped into a random symbol sequence with a symbol period (T<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">symb</inf>). The random modulated generator becomes then a Pseudo-Random Modulated (PRM) microwave signal generator. An almost-periodic harmonic balance simulation can be then performed with this driving microwave PRM generator. This paper presents the implementation of the PRM microwave generator in a commercially available circuit simulation software. A software-defined demodulation of the output signal of the DUT, with optimal matched filters to respect the Nyquist criteria, is implemented to extract all the linearity and power metrics performances at design circuit level, in the time and frequency-domains. To check the validity of the PRM-HB simulation, a linear circuit driven by a 16 QAM modulated microwave signal is simulated and the EVM is calculated.