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A set of compact formulas are presented to estimate modern multitone distortion figures of merit from well-established two-tone measurements. In addition, the ability of noise power ratio (NPR) figures to predict in-band distortion of mildly nonlinear systems subject to real continuous spectra is discussed. It is shown that the usual procedure of eliminating one input tone to allow in-band distortion observation leads to an optimistic NPR value 6 dB higher than the real NPR that would be obtained if the correspondent dense spectrum was used.

Normally, when linearity behavior of an amplifier must be evaluated, the two-tone third-order intercept point (IP3) is used as a standard. However, in new telecommunications circuits (such as the ones found in modern digital mobile communications), more complex signals must be analyzed and, thus, the two-tone IP3 standard is no longer a good figure of merit. Therefore, more …