| 摘要 |
1,071,980. Measuring phase distortion. SIEMENS A. G. May 16, 1966 [May 17, 1965], No. 21602/66. Heading G1U. In an arrangement for determining phase distortion in e.g. a signal transmission system X, a first voltage representing the group transit time distortion in the system is derived from a frequency wobbulation measurement of the group transit time, and the first voltage is multiplied by a second produced by differentiation of a voltage proportional to the wobbulated measuring frequency. The product voltage is integrated to provide a voltage representing the phase distortion. The measurement of the group transit time of the system may be carried out by a known method wherein a wobbulated signal U m is derived by frequency modulating the signal from a variable frequency greater 1 by a wobbulator 3 and mixing the resultant signal in a modulator 4 by a carrier oscillation U 2 of frequency f 2 amplitude modulated by a voltage U 3 of frequency f3. The signal from the modulator 4 is passed via a low pass filter 8 and amplifier 9 to the system under test X. The output from the system passes via an amplifier 10 to a demodulator 12, which receives the modulating voltage U 3 . This is compared with a similar voltage U 3 ' of the same frequency derived from a reference generator 14 in a phase discriminator 13, which produces an output U # of amplitude representing the phase difference between U 3 and U 3 ', thus indicating the group transit time distortion of the system X. The output voltage from the amplifier 10 is also fed to a frequency discriminator 11 which produces a voltage whose amplitude depends upon the instantaneous value of the carrier frequency of the signal U m . This voltage is differentiated at 18 and then passed to one input of a Hall plate multiplier 19 while the other multiplier input is supplied by the voltage U # . The multiplier output is integrated at 20 and amplified at 21. The measuring system output, representing the phase distortion produced by the system X, may be indicated at 23 or displayed relative to frequency on an oscilloscope 22. |
