attenuation and frequency meter selet in use especially for measurements with vo bulazione

摘要

A testing and measuring system for determining the attenuation characteristics of a network, wherein a pair of parallel paths are provided to which a variable frequency transmitter is connected and with the network or component to be tested mounted in one of the parallel branches. Modulators are mounted in each of the parallel branches so as to frequency shift the signals in the parallel branches to different frequencies, after which the parallel branches are connected together and pass through a frequency converter to provide an I. F. output at a test receiver. A variable gain control amplifier receives the output I. F. signals and a pair of band pass filters have their inputs connected to the output of the control amplifier and are tuned to respectively pass one of the side band frequencies of the modulator in the branch with the test object converted to the I. F. range, and one of the side band frequencies of the modulator in the parallel branch which did not include the test object converted to the I. F. range. A detector is connected to the output of the band pass filter which passes the signal which does not pass through the test object and supplies an input to a differential amplifier which receives a second input from a reference oscillator and the output of the differential amplifier is connected to the variable gain control of the control amplifier. This signal may also be supplied to the transmitter oscillator to control its amplitude level. The band pass filter which passes the signal that did not pass through the test object has an output which is supplied to a modulator which receives an injection frequency and which converts its frequency to the same as that of the band pass filter which passed the signal from the test object. The output of this modulator is supplied to the evaluation system for additionally determining the phase shift characteristics of the test object or its transmission properties including phase shift.