Exploring the impedance coverage limitation at current generate plane of transistors up to millimeter‐wave band based on comprehensive large signal model

Abstract

The harmonic power amplifiers (PAs) have potential to be used in the millimeter-wave band, but the sophisticate parasitic network effects on the projection of reflection coefficient coverage from transistor package (TP) plane to current generator (CG) plane is an important challenge. In this work, every typical parasitic element with unique effect is derived theoretically. Thus, in the millimeter-wave band, the reduced and rotated projection of parasitic network between the two planes becomes clear. The fundamental frequency (20 GHz), second harmonics (40 GHz), and third harmonics (60 GHz) loadpull simulations using the commercial standard nonlinear transistor modeling are simulated. The simulation and derivation are consistent and show that output power and efficiency become less sensitive to harmonic tuning due to the lossy parasitic network. This work will be helpful for harmonic tuned transistor and PA design in the millimeter-wave band, in the future. KEYWORDS fundamental and harmonic impedance, impedance coverage, power amplifier 1 | INTRODUCTIONThe rapid development of millimeter-wave systems makes the high-efficiency power amplifier (PA) very important RF components. 1 Its high output power and efficiency have significant influence on the performance of systems. Harmonic tuned PAs provide effective methods to improve the efficiency, and different types have been intensively investigated: Class-F, 2,3 Class-F -1,3 continuous Class-F, 4,5 in-band mode transferring between continuous Class-F, and continuous Class-F -1,6 Class-J. 7 In comparably higher frequency or even the millimeter-wave band, however, harmonic tuned PAs are more challenging, and the parasitic network effect is an important reason.In order to reduce the parasitic network effect, intrinsic fundamental and harmonic impedance 8 at the current generator (CG) plane, waveform engineering, 9 and low frequency (LF) I/V 10,11 methods have been introduced. Intrinsic plane means that virtual ports in the transistor modeling are located right at the CG plane in the active device, without the effects of package parasitic. The observation of intrinsic current and voltage is important to verify the PA's class and to optimize the fundamental and harmonic impedance. 8 Roblin et al introduced an intrinsic method from the CG plane and embedded the nonlinear and linear parasitic components, to predict the harmonic load at the transistor package (TP) plane, based on nonlinear models. 12 Similarly, waveform engineering conception was also summarized by Tasker as "the ability to modify the time-varying voltage and current present in quantified manner. 9 " The waveform design method and RF I/V waveform

Guest Editorial for the special issue on devices and circuits for millimeter‐wave and THz applications

“…Chen et al proposed a multisection coupling cavity for high‐frequency extended interaction klystrons. All of these efforts toward active device modeling can provide a deeper understanding of the relationship between models and circuits as demonstrated in the paper by Chen and Xu, which theoretically explores the impedance of transistor for circuit design based on a large‐signal model.…”