Harmonic extraction from high-efficiency avalanche diodes

A novel harmonic-extraction method for operation of high-efficiency avalanche diodes has been demonstrated. It has been shown that high-efficiency power output can be obtained not only at the trapped-plasma frequency, but also at harmonic frequencies with respect to the trapped-plasma frequency. Second-harmonic powers of 110 W at 2.67 GHz with 22-percent efficiency from L-band diodes, and 64 W at 4.85 GHz with 15-percent efficiency from S-band diodes have been obtained. Third-harmonic extraction has extended the power output into the lower X-band frequency. Microstrip circuits for harmonic-extraction have been developed and analyzed. The circuit impedance requirements at the diode terminals have been computed. The circuit has been discussed in terms of a multiple-reflection triggering process. Useful information for circuit design has been deduced from a series of harmonic-extraction experiments. The voltage waveforms have been measured and have shown evidence of harmonic extraction and its association with the trapped plasma mode.