Asymmetric multilevel outphasing architecture for multi-standard transmitters

Abstract

We describe a new outphasing transmitter architecture in which the supply voltage for each PA can switch among multiple levels. It is based on a new asymmetric multilevel outphasing (AMO) modulation technique which increases overall efficiency over a much wider output power range than the standard LINC system while maintaining high linearity. For demonstration, the overall transmitter is simulated in a 65nm CMOS process with HSUPA and WLAN signals. The simulation results show an efficiency improvement from 17.7% to 40.7% for HSUPA at 25.3dBm output power and from 11.3% to 35.5% for WLAN 802.11g at 22.8dBm while still meeting system linearity requirements.

Outphasing transmitters, enabling digital-like amplifier operation with high efficiency and spectral purity

“…The extended bandwidth of the branch signals is considered to be about 10-15¥ the original signal's bandwidth [5]. [2,3], and outphasing with only phase modulation (PM-PA) [1,2,4] or using a combination of amplitude and phase modulation (i.e., mixed-mode outphasing) (MM-PA) [5]; and pure switch-mode outphasing with class-E branch amplifiers (E-SMPA) [6]. …”

A Q-band SiGe power amplifier with 17.5 dBm saturated output power and 26% peak PAE

“…One of the potential applications of this PA is in an asymmetric multi-level outphasing (AMO) transmitter system [1]. Specifically, multiple unit PAs operated in a constant envelope, peak efficiency condition, are outphase-combined to generate an overall linear PA gain with maximum efficiency.…”

A LINC-based polar transmitter with reduced envelope bandwidth for wideband communications

“…The asymmetric LINC [17,18], shown in Fig. 2, changes the supply voltages for each of the two PAs independently, which results in smaller outphasing angles compared to the multi-level LINC, so that higher efficiency can be achieved even in relatively high-PAPR standards, such as OFDM.…”

“…But both gain-adjusting and envelope-adjusting do not optimize the PA pair for high power efficiency since only the power supply or the input power is controllable. Asymmetric LINC has been reported in [17,18] to improve the efficiency further by using different power supplies for each PA. The drawback of this structure is that two independent multi-level power supplies are required, which not only increases the complexity also introduces the matching issue.…”