A NOVEL HIGH-POWER AMPLIFIER USING A GENERALIZED COUPLED-LINE TRANSFORMER WITH INHERENT DC-BLOCK FUNCTION

The purpose of this paper is to propose a novel generalized single-band transformer for two arbitrary complex load and source impedances and a novel high-power amplifier using this new transformer. By adding two reactive parts at across terminals, the coupled line with flexible electrical length has practical even- and odd-mode characteristic impedances. Thus, the total circuit layout can be realized on common printed circuit board without any restriction. The synthesis theory of this proposed transformer is complete and analytical. Furthermore, unlike conventional quarter-wavelength transformers, this structure exhibits four main features such as effective matching for extremely low-resistive load impedance, effective matching for extremely high-resistive load impedance, tunable characteristic for equivalent electrical length and inherent DC-block function. For theoretical verification, several impedance transformers, which include some fixed operating-frequency cases and a tunable case, for smaller than 7 Ohm or larger than 1500 Ohm, are presented. As a typical experimental example, this analyzed transformer with inherent DC-block function has been applied in a 4-Watt power amplifier as output matching structure.