A Novel Digital-Intensive Hybrid Polar-I/Q RF Transmitter Architecture

Abstract

A novel digital-intensive hybrid transmitter (TX) architecture is presented, combining conventional inphase and quadrature (I/Q) with constrained phase modulation. The proposed architecture utilizes an RF-DAC with phase modulated RF clock and adjusted I/Q components. By incorporating phase modulation the quadrature component is kept small while the inphase component approaches the complex signal envelope. Compared to a digital-quadrature TX architecture this results in a significantly reduced average and peak RF-DAC cell utilization. Therefore, the RF-DAC can be operated in less backoff at higher average output power and drain efficiency. The phase modulation is constrained in order to relax the phase modulators system requirements. Compared to a digital polar TX architecture utilizing an RF digital phase-locked loop with two-point phase modulation, this results in reduced frequency modulation and digital-controlled oscillator tuning range requirements. In addition, the design effort is further shifted from analog to digital domain in order to better exploit the benefits of CMOS technology scaling. Index Terms-Wireless communication, digital polar transmitter, digital quadrature transmitter, hybrid polar-I/Q transmitter, phase modulation, quadrature modulation, RF digital-to-analog converter (RF-DAC), RF digital power amplifier (RF-DPA), RF digital phase-locked loop (RF-DPLL). I. INTRODUCTION W IRELESS transceivers for multi-band, multi-standard mobile handset applications operating in the sub-6 GHz range are usually implemented in ultra-deep

A Circuit-Inspired Digital Predistortion of Supply Network Effects for Capacitive RF-DACs

“…1. Capacitive RF-DACs can be implemented as polar, quadrature, multiphase, or even as hybrid IQ transmitters [17]- [22], [30]- [32].…”

Multilevel outphasing power amplifier system with a transmission-line power combiner

“…It enables efficient and digital-intensive implementation, but faces the problem of needing to reproduce very narrow pulses in the PA output. In addition, some more experimental architectures have been proposed, including hybrids between Cartesian and polar transmitters [96], or between polar and outphasing transmitters [97], both of which ease the bandwidth requirements of polar modulation by combining it with other methods. Mixed-mode outphasing, which is distinct from outphasing as previously described due to the use of amplitude modulation in the two signal paths, has been explored primarily in analog PAs implemented with discrete components and passive elements [98,99].…”

A Systematic Solution for the Problem of Spectral Degradation in Multiphase TX Architectures

“…A VOIDING analog signal processing in transmitters for wireless communications results in benefits such as decreased power consumption and good technology scaling. Therefore, polar [1]- [5] and IQ [6]- [9] digital-intensive wireless transmitter (TX) architectures, as well as novel hybrid approaches such as multiphase [10]- [13], outphasing [14], triphasing [15], or hybrid IQ-polar [16] are becoming a popular choice for today's and future wireless TX architectures. The major challenge of TX architectures is the up-conversion of the baseband (BB) signal to a specific radio-frequency (RF) band, in ideal case without any unwanted spectral components, with high power efficiency supporting wideband single carrier and carrier-aggregated signals.…”