A Temperature-Controlled Ultrasonic Solid Acoustic Delay Line (Abstract)

A temperature-controlled ultrasonic solid acoustic delay line designed for radar calibration purposes is described. It has a delay of 24.73 microseconds. ±0.1 microseconds over an ambient temperature range from -25° C to +60°C. It is designed for use at 60 megacycles and has a bandwidth of at least 8 megacycles and a loss not exceeding 60 db. when used with a 150 ohm termination, It gives at least five reflections with no greater than 74 db. loss. A compact form is accomplished by using a thermostatically controlled oven in the form of a plastic encasement around a hermetically sealed metal enclosed delay line. The delay element, of vitreous silica, is held at 50°C with a deviation of less than ±5°C therefrom over the ambient temperature range up to 55°C. Heater power consumption at 115 volts ac is approximately 20 watts during the heating cycle which constitutes about 25% of the time for a 25°C ambient. Life tests on oven units over approximately two years in the ambient range of 23°C to 28°C show variations in temperature at the delay element well within ±2°C. Details of the construction are discussed and performance data on the oven and delay line are shown.