1429858-A is referenced by 10 patents.

1429858 Measuring the variation of attenuation with frequency SIEMENS AG 12 March 1973 [22 March 1972] 11724/73 Heading G1U In a system for determining the attenuationfrequency characteristic of a circuit under test 3, a reference signal UM having a continuously or step-wise swept frequency f M , is transmitted to a mixer 5 via two parallel paths, the first including the circuit under test 3 and a modulator 4, and the second including an identical modulator 6, the modulation products are passed from the mixer 5, first via a further modulator 9 having a carrier frequency f U swept synchronously with the input reference frequency f M , and then via a variable gain amplifier 18 to two filters 20 and 21 one of which, 20, is arranged to select from the complex signal resulting from the modulator 9 a component that has passed through the circuit under test 3, and the other of which, 21,; is arranged to select a component that has not passed through the circuit under test, so that by controlling the gain of amplifier 18 in such a way that the component selected by filter 21 has a constant amplitude, this being effected by a loop including a rectifier 28, a reference level source 38 and a differential amplifier 29, the component selected by filter 20 from the circuit under test 3 scaled by such a factor by the amplifier 18 that when measured against an absolute scale of voltage, in an analyzer device 24, it provides a meaningful measure of attenuation, even though the amplitude of the reference signal UM and/or the transmission properties of elements feeding amplifier 18 may vary with frequency.; An optional additional feature, which produces a system similar to that described in Specification 1428776 is to bring the frequency of the component selected by filter 21 to that of that selected by filter 20, by a further modulator 32, so that the analyzer can also evaluate other circuit parameters such as phase shift.

Frequency-selective test apparatus for measruing attenuation and other parameters
Application Number
GB19730011724 19730312
Publication Number
1429858 (A)
Application Date
March 12, 1973
Publication Date
March 31, 1976
G01R 27/28
H04B 03/48
G01R 27/00
H04B 03/48
G01R 27/28
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