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 digitalto-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.

Optimization of synthesis filters for hybrid filter bank DACs

“…Generally speaking, the most commonly used ADC has a much wider sample-and-hold analog bandwidth than the converter's Nyquist bandwidth [11,12,13,14]. While DAC with zero-order-hold (ZOH) circuit has the same sample-and-hold analog bandwidth with Nyquist bandwidth [15,16], which is much narrow as compared with ADC. To solve this problem, in this work, mixers are adopted in conjunction with hybrid-filter-bank archi-tecture.…”