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This letter presents a method for improving the efficiency of an outphasing amplifier by pulse modulating the input signals. By pulse modulating the two input signals to the outphasing amplifier, the outphasing angle can be kept small and hence attain higher efficiency. Whereas, compared to a pulse modulated polar transmitter, the need for high resolution pulsewidth modulation is reduced. To validate the proposed technique, a prototype transmitter system is constructed using commercially available components. Using a CDMA2000 1X signal at 836.5 MHz, the proposed technique achieved a 26% improvement in power-added efficiency compared to a conventional outphasing amplifier at 25.2 dBm output power level while passing the adjacent and alternate channel power ratios for the CDMA2000 standard.
Date of Publication: Dec. 2010