New microwave applications for thick-film thermistors

Two new microwave applications for temperature-sensitive thick-film materia ls are described. The first is a po power-screening termination, which is b ased on a linear negative temperature coefficient (NTC) thick-film thermist or used in combination with a linear positive temperature coefficient (PTC) material to convert RF power to DC voltage. The device can be used with a coupler to moniter power and compensate for temperature re variations. The passive device! described here is linear and represents an inexpensive repl acement for currently used active devices. Processing and properties of the screen-printed , specially for formulated linear NTC and PTC thermistor ma terials are presented. The second application involves the use of thick-fil m thermistor materials to fabricate a temperature attenuator: In this desig n, highly nonlinear NTC materials are combined with PTC materials in T and pi configurations to maintain signal levels at constant impedance in microw ave circuits. Device needs and how they may be met with thick film material s and processing are discussed.