The Power amplifier linearizer based on the feedforward method was designed and fabricated. The design procedure determing circuit parameters was presented. The effects of amplitude imbalance, phase imbalance and delay mismatch were studied
When the linearizer was incorporated into the average 1 W amplifier with IMD 30dBc, The two tone test showed more than 30 dB intermodulation distortion suppression. The center frequency of the linearized amplifier is 1.855 GHz with 30 MHz bandwidth.
The linearizer is composed of the error amplifier, the phaseshifter, the variable attenuator, the directional coupler and the power divider. Every component was designed and fabricated. the design procedure was fully presented. The phaseshifter and the variable attenuator were designed to control the phase and the attenuation independently. The directional coupler which have the high directivity was designed using the interdigital capacitor. This directional coupler showed more than 40dBc directivity.