GB598198A - Improvements in and relating to micro-wave wattmeters - Google Patents

Abstract

598,198. Impedance-matching. SPERRY GYROSCOPE CO., Inc. June 18, 1945, No. 15499. Convention date, June 17, 1944. [Class 40 (iii)] [Also in Group XXXVI] A micro wave wattmeter comprises a liquid dielectric into which the micro waves whose power is to be measured are directed so as to be dissipated in the form of heat and means for measuring the rate of heating of the dielectric. In one application, the wattmeter which provides an enclosed concentric termination of an air-filled coaxial line includes a quarter-wave impedance matching section having a solid low-loss dielectric such as polystyrene, and an end section having a circulating liquid dielectric 4. In a modification, Fig. 3 (not shown), the sections with air solid and liquid dielectrics all have the same characteristic impedance, the portion with the solid dielectric then acts merely as a plug, its length is immaterial and the device is suitable for a wide band of frequencies. If water is used as the power absorbing dielectric in the latter device, the central conductor of this section must be extremely thin and it may be suitably reinforced, e.g. by a coating of polystyrene, Fig. 3a (not shown). In a further modification, Fig. 4 (not shown), the coaxial sections of Fig. 2 are replaced by wave-guide sections.