A miniature balanced-diode frequency doubler using hybrid couplers for fundamental harmonic suppression

This paper presents a miniature balanced-diode frequency doubler. The circuit is based on half-wave diode rectifiers, realised by Schottky diodes, and 3-dB stripline hybrid couplers working as a power splitter and combiner. This frequency doubler technique uses a phase difference when dividing and combining to cancel the leaking fundamental signal. The prototype was designed at 900 MHz on a hydrocarbon ceramic substrate. The Schottky diode and the stripline hybrid coupler used in the circuit are HSMS-282C and XC0900P-03S respectively. The circuit was fabricated on RO4350B with ¿_r = 3.48 and the thickness of 0.762 mm. The total size of the circuit is 17 × 35 mm. It was measured to have over -17.2 dB of conversion gain and less than -34 dB of the fundamental leakage ratio for the whole frequency range.