Analysis on Memory Effects of Frequency Multipliers for the Frequency Translation of Complex Modulated Signals

Memory effects on frequency multipliers have been analyzed in this paper for the application of digital predistortion techniques. Although the memory effects are generally thought to exist in PAs since they handle high power signals and have bias networks, previous predistortion results showed that some amount of memory effects exist in frequency multipliers. The behavioral model of parallel cascade method was compared with the memoryless polynomial model. A frequency tripler with back-to-back Schottky diodes was implemented, and a QPSK test vector was generated at 820 MHz to capture higher-than- third order nonlinearities at 2.46 GHz. As a result, the parallel cascade model shows that the modeling accuracy can be improved by more than 4 dB in error function defined hereafter. In addition, the error function represents that the frequency tripler has memory effects concentrated up to 18 ~ 30 kHz.