Harmonic generation in TR tubes

Spurious harmonic power generated in TR tubes was investigated to determine if intersystem interference problems exist and to provide design criteria for controlling spurious signal generation. Harmonic power radiated from typical TR tubes was measured as a function of incident power, pressure, and geometry for discharges in chlorine, water vapor, hydrogen, nitrogen, and argon. Harmonic power decreased by about 20 dB for each decade increase in total pressure in the 0.2 to 20 torr range. Conversion loss varied from 28 to 70 dB. Harmonic power was radiated in a series of resonant peaks which varied with incident power and pressure. TR tubes meet the desired requirements for spurious radiation of -40 dBm/kHz for incident pulse widths less than 1.0 µs when filled to total pressures in the usual 10 to 15 torr range. At pulse widths greater than about 10 µs it becomes necessary to suppress spurious radiation by either filtering or harmonic trapping to reduce intersystem interference.