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.

Title
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
Assignee
Siemens
IPC
G01R 27/28
H04B 03/48
G01R 27/00
H04B 03/48
G01R 27/28
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