Abstract: A miniaturized wideband balun circuit is disclosed which includes a first dielectric substrate having substantially planar opposing surfaces; first and second conducting strips disposed on a first one of the opposing surfaces of the first dielectric substrate and each having a first terminal and a second terminal; a second dielectric substrate having substantially planar opposing surfaces, with a first one of the opposing surfaces of the second dielectric substrate being disposed over the first and second conducting strips; third and fourth conducting strips disposed on a second one of the opposing surfaces of the second dielectric layer and each having a first terminal and a second terminal The first and second conducting strips overlie the third and fourth conducting strips, respectively. The first and second terminals of the first conducting strip, the first terminal of the second conducting strip and the second terminal of the fourth conducting strip are electrically grounded.

Abstract: A high efficiency dual-band RF power amplifier has an output and/or input of a high frequency transistor well terminated at the second harmonic frequency for dual-band operation. Diode switches or voltage controlled varactors implement dual-band resonators such that they can offer low impedance at the second harmonic of each frequency band, while, in some cases, presenting high impedance at the fundamental frequency as an RF choke circuit.