Harmonic and IMD frequency components affecting nonlinear distortion with feed back in MOSFET amplifiers

In some low power wireless systems, such as ZigBee, a single amplifier can be designed to perform the functions of both the front endpsilas low noise amplifier and power amplifier. Such an amplifier, usually a very low power one, would lack highly effective, usually high power consuming, linearization techniques but also suffer from linearity issues associated with high power operation. One of these issues is the generation of extra intermodulation components through feeding back several frequency components produced from different orders of nonlinearity. These effects worsen as the operating power increases. This phenomenon is extensively investigated in this work by analyzing the effect of feeding back frequency components generated from all orders of nonlinearity up to 7^th-order on the generation of 3^rd, 5^th and 7^th-order intermodulation products. The analysis, based on polynomial substations, reveals previously unknown components which can significantly affect nonlinear performance at higher-than-usual input powers. The investigation assumes a CMOS amplifier. All polynomial substitutions were performed in the mathematics software, Mathematica.