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A multitime circuit formulation for closely spaced frequencies
Author(s) -
Roychowdhury Jaijeet
Publication year - 2005
Publication title -
international journal of rf and microwave computer‐aided engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.335
H-Index - 39
eISSN - 1099-047X
pISSN - 1096-4290
DOI - 10.1002/mmce.20094
Subject(s) - baseband , harmonic balance , electronic circuit , electronic engineering , computer science , decoupling (probability) , computation , frequency domain , radio frequency , cmos , time domain , microwave , mathematics , algorithm , electrical engineering , engineering , telecommunications , physics , nonlinear system , quantum mechanics , control engineering , computer vision
Abstract Verifying circuits with two or more closely‐spaced driving frequencies is important in RF and wireless communications, for example, in the design of down‐conversion mixers. Existing steady‐state calculation methods, like harmonic balance, rely on Fourier series expansions to find the difference‐frequency components typically of interest. Time‐domain methods are, however, better suited for circuits with strong nonlinearities such as switching. Towards this end, we present a purely time‐domain method for direct computation of difference tones in closely‐spaced multitone problems. Our approach is based on multiple artificial time scales for decoupling the tones driving the circuit. Our method relies on a novel multitime reformulation that expresses circuit equations directly in terms of time‐scales corresponding to difference tones. We apply the new technique to an RF‐CMOS mixer to predict baseband bit‐streams and down‐conversion gain and distortion, in two orders of magnitude less CPU time than traditional time‐stepping simulation. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.