Frequency Doubler Based Outphasing System for Millimeter Wave Vector Signal Generation

In this paper we propose a compensation technique for millimeter wave (mm-wave) frequency doubler based outphasing system adopted to generate wideband vector modulated signals. The compensation technique utilizes multi-tone test signals to detect the system's distortions. These include the frequency doubler's unavoidable non-linearity due to the band limitation of the phase modulated outphasing signals and the gain and phase mismatch between the two outphasing signal paths. For that, an interleaved multi-tone modulated signal is used to characterize these non-idealities and synthesize a memoryless predistorter and a linear outphasing mismatch compensation filter to mitigate their effects. These blocks are subsequently applied for generating digitally modulated signals at 25 GHz with modulation bandwidths of 80 and 160 MHz with improved quality of signal.