Computationally Efficient Multitone Analysis of Non-Linear Microwave Circuits

A new approach to the Harmonic-Balance analysis of non-linear microwave circuits driven by multitone excitations is proposed. It is based on the observation that in many practical cases of multitone analyses, signal spectra are characterized by a highly non uniform distribution. In such conditions, a convenient representation of the signal spectra in conjunction with a suitable approximation introduced on the frequency response of the reactive components, allow a relevant decoupling of the Harmonic-Balance circuit equations; consequently, a relevant reduction of computing effort can be easily obtained. By using the approach proposed, the intermodulation analysis of quite complex circuits operating under multitone excitations can be carried out even on small-size computers (e.g., workstations). The validity of the method has been verified in intermodulation analyses of mixers and distributed amplifiers.