Extraction of frequency response of receiver input filter from characteristic of receiver susceptibility to third-order intermodulation

摘要

Techniques for experimental evaluation of the amplitude-frequency characteristic of a radio receiver input filter on basis of the measured frequency characteristic of the receiver susceptibility to two-signal (or three-signal) third-order intermodulation are developed: the known technique based on the fitting of parameters of the filter's theoretical model is generalized to deal with a switchable input filter having a high shape factor of the amplitude-frequency characteristic; two new techniques which do not require solving the optimization problem are proposed. The developed techniques are validated experimentally by examination of two radio-receiving paths with different types of the preselection filter: with narrow-band tunable filter and with wide-band switchable filter. The techniques are useful for synthesis of a receiver's behavioral model (describing the intermodulation and other nonlinear effects) on basis of experimental data.