Theoretical Facet and Experimental Results of Harmonic Tuned PAs Paolo Colantonio, 1 Franco Giannini, 1 Giorgio Leuzzi, 2 Ernesto Limiti 1 1 Department of Electronic Engineering, University of Roma “Tor Vergata,” Via di Tor Vergata 110, 00133 Roma, Italy 2 Department of Electrical Engineering, University of L’Aquila, Poggio di Roio, 67040 L’Aquila, Italy Received 15 November 2002; accepted 10 June 2003 ABSTRACT: High-efﬁciency power ampliﬁer design criteria imply a synthesis of input and output networks with particular emphasis on their harmonic behavior. In this article, a simpliﬁed approach to clarify the relevance of such terminations is presented. Starting from the implications of power balance for stage performance, design criteria to improve the efﬁciency of high-frequency applications are presented. In order to validate the approach, comparisons among the performances of single-stage ampliﬁers, all operated at 5 GHz under a sinusoidal driving signal and synthesized by utilizing different design methodologies, are presented. Drain efﬁciencies at 1-dB compression of 44.5%, 53.3%, and 61.56% have been measured respectively for the tuned load and harmonically manipulated (2 nd and 2 nd &3 rd ) realized ampliﬁers, compared with a simulated drain efﬁciency of 55% using the Class E approach. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 459 – 472, 2003. Keywords: power ampliﬁers; high efﬁciency; multi harmonic manipulation I. INTRODUCTION The power ampliﬁer (PA) is a crucial element of transmitter units whose main design requirements are high-power efﬁciency coupled with suitable gain and output power levels. High-power efﬁciency increases battery lifetime, thus reducing operating cost and eas- ing thermal management. High gain reduces the num- ber of ampliﬁer stages required, thus reducing the ampliﬁer’s size, weight, and manufacturing cost. The output power must be sufﬁcient to meet the equipment speciﬁcations, which are sometimes dictated by in- dustry standards. Such requirements are often contrasting ones, and therefore they demand a design compromise for achievable performances. A suggested solution to im- prove both efﬁciency and output power resides in the use of harmonic tuning strategies, that is, an opti- mized selection of fundamental and harmonic termi- nations at both the input and output ports of the active device [1, 2]. Several approaches have been suggested and the- oretically investigated since 1958 [3–5] and deeply presented and discussed in relevant books [6, 7]; nevertheless, they are not completely clariﬁed in their practical use for high frequency applications, that is, when the number of the harmonic terminations that can be effectively controlled is limited. This can be due to both circuit complexity issues, compared with poorer achievable improvements [8], and practical considerations [9]. In this article, starting from the power balance considerations approach for switching mode operation [10, 11], extended to encompass the general problem Correspondence to: Paolo Colantonio; e-mail: paolo. colantonio@uniroma2.it. Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mmce.10106 © 2003 Wiley Periodicals, Inc. 459