An anti-alias harmonic-reject phase modulation for digital outphasing transmitter

Abstract

This paper proposes a sufficient anti-alias and harmonic-reject phase modulation (PM) technique for digital outphasing transmitter. Instead of using complicated spectrum shaping modulation or power-hungry digital-to-analog (DAC) and high-order filters, the proposed less-complex modulation employs cross point estimation (CPE) algorithm to improve the adjacent channel leakage ratio (ACLR) performance and adopts harmonic rejection algorithm to achieve out-of-band (OOB) noise attenuation. When evaluated with a 10 dB peak-to-average power ratio (PAPR) 16 QAM orthogonal-frequency-division-multiplexing (OFDM) signal with a 30 MHz intermediate frequency (IF) carrier, the proposed modulation achieves an ACLR of −65 dBc, providing 17 dB improvement compared with −48 dBc for conventional modulation. Moreover, 56 dB and 57 dB extra attenuations for the 2rd and 3rd images are achieved, respectively.