FET Frequency doubler with out-of-phase switchable output and application in balanced frequency doubler.

A field effect transistor (FET) frequency doubler, with 180° out-of-phase alternate output by switching the bias status of FET at pinch-off ( V ≈ Vt) or saturation ( V ≈ 0) is proposed.With such bias conditions, the former conducts in the positive half-cycle of the input signal, while the latter conducts in the negative half-cycle. Based on this concept, a new frequency doubler architecture is proposed. Without an input balun, it is more compact than conventional balanced frequency doubler. In addition, it provides an alternate doubler with differential output. To demonstrate this concept, a single-ended 5-10 GHz doubler tested at the two bias conditions is designed and demonstrated experimentally to provide opposite-phase outputs for the two cases. The output phase difference error is less than 4° and over 42-dB fundamental frequency rejection is achieved. The conversion gain measured at 10 GHz is 2.5 dB for an input power of 5 dBm. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26172 [ABSTRACT FROM AUTHOR]