Effects of source and load impedance on the intermodulation products of GaAs FETs

Linearity of the GaAs field effect transistor (FET) power amplifier is greatly influenced by source and load impedances for the FETs. The third order intermodulation products (IMD/sub 3/) of the GaAs FET are investigated in relation to source and load impedances. From heuristic as well as analytic point of view, the Volterra-series technique is employed to show that the least IMD/sub 3/ are found at the minimum source resistance (R/sub S/) and maximum load resistance (R/sub L/). The simulated results are compared with the load and source pull data with good agreements. The simulation also shows that source impedance has a greater effect on the IMD/sub 3/ than the load impedance.