Nonlinear distortion analysis of RF power amplifiers for wireless signals

One of the critical and costly components in digital cellular communication systems is the RF power amplifier. Theoretically, one of the main concerns in an RF power amplifier design is the nonlinear effect of the amplifier. Quantitatively, no explicit relationship or expression currently exists between the out-of-band emission level and the nonlinearity description related to the third-order intercept point (IP₃). Further, in experiments and analysis, it was discovered that, in some situations, using IP₃ only is not accurate enough to describe the spectrum regrowth, especially when the fifth-order intercept point (IP₅) is relatively high compared to the third-order intermodulation. We analyze the nonlinear effect of an RF power amplifier in CDMA (IS-95 Standard), TDMA (IS-54 Standard) and MIRS M-16-QAM (Motorola integrated radio system standard) systems, give expressions for the estimation of the out-of-band emission levels for each system expressed by power spectrum, in terms of the IP₃ and the IP₅, as well as the power level of the signal. This result may be useful in the design of RF power amplifiers for these wireless communication systems.