A new linear amplifier using low-frequency second-order intermodulation component feedforwarding

A new linearization method by feedforwarding low-frequency second intermodulation component (f(2) - f(1)) is proposed. Drain voltage modulation by the forwarding second intermodulation voltage improves linearity significantly. This new technique, which adopts a simple circuit configuration, has advantages in the stability and bandwidth due to the feedforwarding nature and shows a very good performance in comparison with other harmonic tuning circuits. Analytical derivation of low-frequency feeding voltage gain (beta) to obtain perfect cancellation of IMD3 is presented. For verification of the proposed circuit topology, a two-tone test and a CDMA signal test at carrier frequency 2.15 GHz are performed and show about 18- and 10-dB improvement of IMD3 and adjacent channel power ratio (ACPR), respectively.