Intermodulation cancellation in HEMTs

This paper examines intermodulation (IM) minima generated by the nonlinear drain-source current characteristics of HEMTs. This investigation is based on a more accurate intermodulation distortion model recently proposed by Qu and Parker (see The Proc. of 14th Australian Microelectronics Conference, p. 70-5, Oct. 1997). The IM cancellation conditions in terms of the Taylor series coefficients are established and verified with measurement and simulation. Second and third-order intermodulation cancellation can be assessed by simple examination of the transconductance characteristics of the device. This permits routine selection of optional bias after characterising the devices.