Phase delay compensation in HF Cartesian-loop transmitters

Radio transmitters intended for use with amplitude modulation, including single side-band, require a linear power amplifier to raise the power of the modulated signal to that necessary for transmission. In this amplification process lies a problem: that of obtaining good spectral purity of the output signal whilst maintaining a reasonable power conversion efficiency. This paper describes briefly an HF Cartesian-loop transmitter, and then gives details of the phase delay compensation scheme developed to maintain stable operation of the feedback loops over the entire HF band.<>