Analog RF predistorter simulation using well-known behavioral models

This paper describes an envelope predistortion linearizer scheme that uses integrated analog components for the low cost implementation of intermodulation distortion product (IMDs) reduction in RF power amplifiers (RFPAs). Integrated logarithmic amplifiers & phase detectors are used to sample the input and output signals before and after the RFPA to measure the complex gain & phase information, which is used to control an integrated pre-distorter integrated circuit (IC) that contains adjustable gain & phase components within a single IC package. Comparisons of a range of well-known and updated RFPA behavioral models are evaluated to determine the most suitable behavioral model for this linearization scheme. The simulation model also allows for the addition of RFPA memory effects and driver & RFPA noise figures to be included and compared. All component models are based on parameters extracted from device data sheets for the driver & RFPA, thus minimizing the need for special measurements.Paul O. Fisher and Said F. Al-Saraw