Multi-Way Lossless Outphasing System Based on an All-Transmission-Line Combiner

Abstract

Abstract-A lossless power combining network comprising cascaded transmission line segments in a tree structure is introduced for a multi-way outphasing architecture. This architecture addresses the suboptimal loading conditions in Chireix outphasing transmitters while offering a compact and microwavefriendly implementation compared to previous techniques. In the proposed system, four saturated power amplifiers interact through an all-transmission-line power combining network to produce nearly ideal resistive load modulation of the branch power amplifiers over a 10:1 range of output powers. This work focuses on the operation of the combining network, deriving analytical expressions for input-port admittance characteristics and an outphasing control strategy to modulate output power while minimizing reactive loading of the saturated branch amplifiers. A methodology for combiner design is given, along with a combiner design example for compact layout. An experimental four-way outphasing amplifier system operating at 2.14 GHz demonstrates the technique with greater than 60% drain efficiency for an output power range of 6.2 dB. The system demonstrates a W-CDMA modulated signal with a 9.15-dB peak to average power ratio (PAPR) with 54.5% average modulated efficiency at 41.1 dBm average output power.Index Terms-base stations, outphasing, power amplifier (PA), wideband code division multiple access (W-CDMA), Chireix, LINC, load modulation.

High Efficiency Power Amplifiers for Modern Mobile Communications: The Load-Modulation Approach

“…Moreover, similarly to the Doherty PA case, the HEPR can be further enhanced by adopting multi-way/multi-stage architectures [103], while even better results are obtained by combining the outphasing architecture with other back-off efficiency enhancement techniques, such as the supply-modulated outphasing PA [104] or the Doherty-Outphasing PA [97,105,106].…”

Load Modulation of Harmonically Tuned Amplifiers and Application to Outphasing Systems

“…Amplitude modulation of the original signal is reconstructed by vectorial summation of the output of each branch in the combiner. Because of this advantage, outphasing has received renewed interest in recent years [20], [21], [29], [36]- [39]. Nevertheless, the reactive loading which each PA branch is presented with, during non-isolating outphasing operation is a significant obstacle to its implementation [13].…”

“…In outphasing systems employing Chireix reactive compensating techniques, the branch amplifiers are typically designed as class E [20]- [26], F [27], F −1 [28], [29] power amplifiers or as saturated class B amplifiers [30], [31]. Recently in [21], continuous class E theory was utilised in the design of a wideband outphasing system showing promising results.…”

Measurement and nonlinear behavioral modeling of the dynamic bias current in an LTE‐A Chireix PA

“…Power amplifiers developed for modern LTE-A base stations are thus mostly operating around the average power level with infrequent operation around peak power levels. Special PA architectures such as the Doherty, 1,2 Chireix, 3 and envelope tracking 4 are then used to provide a high power-efficiency at both peak and backoff power while maintaining a reasonably good linearity. In this study, a 17 Watts dual-input Chireix PA operating in class F and realized with two GaN high-electron-mobility transistors (HEMTs) is considered.…”

“…More recently, using miniaturized substrate-integrated waveguide (SIW), Kang and Lim 2 designed a dual-band antenna with frequencyreconfigurability at a single band while the resonance frequency at the other band is fixed. As an improvement, Ge et al 3 proposed a stacked-patch antenna with independent control of both operating bands. Those aforementioned antennas exhibit broadside radiation patterns at both frequency bands.…”