Limit-Cycle Free Complex Biquad Recursive Digital Filters

A new form of complex biquad recursive digital structure is proposed which is based on the concept of generalized immittance converter. Orthogonal filters which are widely used in TDM-FDM transmultiplexers can be obtained as a special class of these complex biquads. It is shown that the proposed structure is completely free from zero-input limit cycles under linear conditions and further the stability under finite arithmetic conditions can be achieved using the technique of magnitude truncation. It is also shown that for this new structure, the stability of the forced response can be ensured for certain types of overflow nonlinearities. © 1989 IEEE