Agilent Calibration of Precision Step Attenuators - White Paper 5991-1226EN c20140515 [14] free download

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Keysight Technologies Calibration of Precision Step Attenuators White Paper Abstract This paper describes an automated parallel IF substitution system for precision attenuator calibration which has been in use for over 15 years and presents results of tests made on some very accurate attenuators. The calibration system was originally developed to meet the calibration needs of a step attenuator in a new synthesizer. Years of data have shown this attenuator to have phenomenal accuracy. The system has been continually refined and is now used for high-accuracy calibration of several other types of step attenuators. The data presented establishes confidence in the accuracy of the system and the attenuators. Presenter and Author Bill Bruce Hewlett-Packard Company 1998 NCSL Workshop & Symposium Introduction During 1978, there was a need to verify the accuracy of an excellent attenuator in a new synthesizer product. The author attempted to calibrate one attenuator using the existing manual method and found it to be an exasperating process. The natural consequence was to develop an automated calibration system. The system has been in use since that time, and with some refinements over the years, it has been used to calibrate a large number of very accurate step attenuators. This paper describes the system and some of the considerations necessary for achieving high accuracy. One particular data set has become more or less standardized and many attenuators have been measured using this data set. Graphs and histograms of some of the data from approximately 90 attenuators are presented. The data demonstrates the capability of the system and also indicates that a well-designed attenuator can exhibit very small errors. Description and Basic Operation of the System The method chosen for the automatic calibration system is parallel IF substitution[1]. This method has the capability to achieve excellent accuracy and fairly wide dynamic range. A programmable ratio transformer is used as the system standard. The system capability covers frequencies between approxi- mately 0.3 MHz and 80 MHz, and attenuation between 0 dB and 100 dB. With some re-connection to a non-mixer configuration, 1 kHz is also a usable freq