DocumentCode :
1191918
Title :
A Varactor Null Detector for Aduio Frequency Capacitance Bridges
Author :
Cutkosky, Robert D.
Volume :
17
Issue :
4
fYear :
1968
Firstpage :
232
Lastpage :
238
Abstract :
A two-varactor, double-sideband up-converter pumped at 30 MHz has been constructed. Operated at room temperature with a signal frequency of 104 rad/s, the device has an optimum source resistance of 105 ohms and a minimum noise figure of 0.01 dB. Immersed in liquid N2, minimum noise figures below 0.001 dB referred to a room temperature source have been measured. The device is particularly useful as a null detector for audio frequency capacitance bridges. At 104 rad/s, a signal current of 10-14 amperes through a capacitance of 1000 pF can be detected in less than one second with this instrument. Techniques for suppressing microphonics and other extraneous sources of noise are described.
Keywords :
Bridge circuits; Capacitance; Detectors; Electrical resistance measurement; Frequency; Instruments; Noise figure; Noise measurement; Temperature; Varactors;
fLanguage :
English
Journal_Title :
Instrumentation and Measurement, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9456
Type :
jour
DOI :
10.1109/TIM.1968.4313712
Filename :
4313712
Link To Document :
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