Single-Stage Frequency Quadrupler With SBD and Four-Octave LPF at 335 GHz

This paper presents designs of a single-stage quadrupler at 340 GHz based on Schottky varactors with 7 mW maximum output power. The Schottky diode model is invented to improve the accuracy of design, which considers the behaviors of current-voltage (I/V), capacitance-voltage (C/V ), plasma resonance, self-heating effect, and skin effect of Schottky diodes under deep driven situation into consideration. Compact suspended microstrip resonators (CSMRs) are adopted as harmonic rejection structure with minimized length/width ratio and shorted idlers at both the second and third harmonics. The measurement results indicate that the CSMR low-pass filter has stopband bandwidth of more than four-octave, whose S12 <;-10 dB within 140-385 GHz and S11 <;-10 dB below 95 GHz. The measured quadrupler output power is above 1 mW at 322-345 GHz, and the measured peak efficiency achieves above 4.2% at 339.2 GHz with 100 mW driven power.