A VHF Implementation of a LINC Amplifier

LINC is a technique that uses signal processing to produce Linear amplification of bandpass signals with grossly Nonlinear circuit Components. The important signal processing functions in LINC are forming two constant envelope phase modulated signal components from the bandpass input signal and recombining the amplified components to produce an amplified replica of the input signal. Two- and three-tone laboratory tests of a complete LINC amplifier show that, at full output, spurious levels 40 dB below tone level are achievable for tone spacings of 100 kHz. Because the laboratory model is operated at relatively low frequencies (hundreds of MHz), scaling up in frequency should result in a LINC with < 40 dB spurious over a considerably wider band. Lower spurious levels or bandwidths of several tens of MHz will require a phase modulator that is less sensitive to delay in a feedback loop and a wider-bandwidth lower-distortion input limiter.