Defu Wang, Nghiem Xuan Anh, Muh-Dey Wei and Renato Negra Chair of High Frequency Electronics, RWTH Aachen University, Germany E-mail: d.wang@umic.rwth-aachen.de Abstract—This paper presents the concept and measurements of a new microwave rectiﬁer based on the time reversal duality of power ampliﬁers. It is shown that the proposed rectiﬁer can simultaneously provide high efﬁciency at large input power range over much more improved bandwidth compared to the conven- tional rectiﬁer from time reversal duality. It is also reported that the proposed rectiﬁer allows reconﬁguration of the efﬁciency at input power range without placing the tunable elements. A 10 W wideband power ampliﬁer with 79 % drain efﬁciency at 1.85 GHz is used to validate the concept. By making the gate bias network short-terminated and replacing the drain termination with the DC load resistor for power ampliﬁer, the circuit can operate as microwave rectiﬁer with taking part of bandwidth from power ampliﬁer. Measurements show the efﬁciency bandwidth with larger than 70 % rectifying efﬁciency at 15 dB input power range over a 1.7-1.95 GHz frequency range. The measurements thereby validate the presented concept and demonstrate the potential of the proposed rectiﬁer for use in future wireless energy harvesting applications. Index Terms—Rectiﬁer, time reversal, input power range, wireless energy harvesting, power ampliﬁer (PA). I. I NTRODUCTION High efﬁciency rectiﬁers have been investigated as key components of rectenna for application in wireless power transfer [1], wireless sensor networks [2] and energy recy- cling [3], [4]. The main limitation of such RF rectiﬁers is that they provide high efﬁciencies over a narrow operating input power range (IPR) which results in long harvesting times. The traditional implementation for rectiﬁer circuits is based on Schottky diodes with suitable matching network to achieve high efﬁciency [5]. However, due to the exit of breakdown voltage of the Schottky diode [6], it is difﬁcult to keep such high efﬁciency with wide IPR. In order to expand the operating IPR, a transistor is suggested to be used and combined with Schottky diode as rectifying device in [7]. Recently, the time reversal duality principle draws more attention while it allowing to design the high efﬁciency rectiﬁer by dual mode of power ampliﬁer (PA) in [8]. A class F -1 power ampliﬁer has been investigated and shown the bidirectional characterisation of power ampliﬁer in [9]. However, it has the high efﬁciency only at a single frequency point for the rectiﬁer operation. It is still a challenge to design a high-performance rectiﬁer in terms of efﬁciency, bandwidth and IPR. The time reversal duality is introduced with the waveforms of a pair of cicuits being reﬂected versions of each other and resulting in opposing directions of energy ﬂow. A high Gate Matching 50 Ω V GG V DD P out,PA Drain Matching Gate Matching V GG Drain Matching R gg 50 Ω P in,Rec Time Reversal Fig. 1. Block diagram of the circuit operated as a power ampliﬁer (left) and as rectiﬁer (right). efﬁciency with certain bandwidth power ampliﬁer in [10] is used to validated the concept in this work. In this paper, the time reversal duality of power ampliﬁer and its rectiﬁer are shown in Fig. 1. In the rectiﬁer design, the input RF power is directly connected to the circuit from the output port of power ampliﬁer. Although the load of rectiﬁer is kept the same value of load in power ampliﬁer, it should have the high power tolerance. Instead of using loadpull mesurement setup connected the gate matching network in [9], this work simply connects the gate matching network to ground and shift the matching problem to the design of power ampliﬁer. II. EFFICIENCY ANALYSIS To predict the rectifying efﬁciency, the mathematical model described in [8] is used to simplify the analysis. The relation of the current and voltage at the drain terminal from the duality of time reversal can be expressed as v Rec (t)= v PA (t) (1) i Rec (t)= -i PA (t) (2) Design of a High Efficiency Rectifier with Wide Bandwidth and Input Power Range Based on the Time Reversal Duality of Power Amplifier 978-2-87487-039-2  2015 EuMA 7 -10 Sept 2015, Paris, France Proceedings of the 45th European Microwave Conference 291