Millimeter-wave tubes using the coupled cavity circuit

Two applications of the coupled cavity slow wave circuit at the 5-6 millimeter wavelengths are the subject of this paper. When considering the design of cw high-power amplifiers and oscillators for millimeter wavelengths the characteristics of the coupled cavity structure present several distinct advantages. The heat capacity of the circuit is very good and the tubes can be designed for low voltage operation. A high-power amplifier with cw output power of 150 watts and efficiency of 30 percent has been developed. Initial tubes have been operated as single stage low gain amplifiers, 14 db, with an approximate bandwidth of 8 percent. A severed amplifier with two amplifying sections producing higher saturation gain will be described. A millimeter-wave backward-wave oscillator using the coupled cavity circuit has also been developed. The general properties of this tube are 18 percent tuning bandwidth, output power in excess of 1 watt and depressed collector operation. The techniques that were evolved for the development of these tubes and their electrical performance will be described.