Combined theoretical and experimental studies of a push–pull Trapatt circuit

New results are presented concerning the anti-parallel or push–pull Trapatt circuit. This circuit consists of two diodes placed at either end of a transmission line, approximately a half-wavelength long. This circuit increases the power impedance product over the single diode circuit and provides a lower spurious harmonic content in the output. The analysis uses the periodic impulse response and ‘pseudo -impedance’ techniques. It explains why the circuit is stable in the anti-parallel configuration but will not work in the parallel configuration. Various self-compensation mechanisms are demonstrated for the circuit and in particular it is shown how mismatched diodes will still oscillate as a pair. The experimental work has been centred around I GHz with efficiencies around 35%. A design has been evolved for a three-slug filter which gives a good match to the diodes and is easy to adjust. The waveforms have been measured with an ultra-broad-band voltage probe and 14 GHz bandwidth sampling oscilloscope and ...