Nonlinear analysis has become a popular field of study in recent years because of the rapid adoption of digital modulation formats in modern wireless communications. But harmonic-balance approaches have been used for nonlinear analysis in computer-aided-engineering (CAE) software tools for more than 25 years, as detailed in a new, six-page white paper from AWR, "The Advantages of Multirate Harmonic Balance (MRHB)Advanced, Multitone Harmonic Balance Technology Pioneered by AWR."
The white paper provides a brief history of harmonic-balance analysis and how it has been applied to nonlinear circuit problems. One of the stumbling blocks for implementing software tools based on harmonic balance, prior to the availability of low-cost memory and high-speed microprocessors, has been the problem of limiting the number of frequencies handled by a harmonic-balance analysis. In any multitone system, a circuit element must be solved not only for the harmonics of each tone, but for the various combinations of linear intermodulation effects of different tunes. The number of solutions can grow rapidly.
The MRHB approach helps to bring efficiency to nonlinear analysis. In contrast to traditional harmonic-balance techniques, which assume that the frequency content through the function blocks in a high-frequency system (such as mixers, filters, and amplifiers) will be the same at every part of the circuit, the MRHB approach allows different parts of the circuit to have different dominating frequencies.
The MRHB analysis method adds the contribution of each element or block in a circuit only at the desired frequencies, to dramatically reduce the number of equations. By intelligently addressing the fact that dominating frequencies differ in the various parts of a circuit, harmonic-balance analysis can be performed more efficiently and accurately in less time than when performing traditional harmonic-balance methods. The white paper uses a Global Positioning System (GPS) double-downconversion receiver block diagram to illustrate the use of the MRHB analysis on a standard personal computer.
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