DE1441201A1 - Method for measuring the absolute transit time of a quadrupole, in particular a transmission line - Google Patents

Description

^L i I

d Munich · 2, the 13th May 19β Η

St / Bla

P 14 41 201. 2 PA 62/2998

Procedure for measuring the absolute running time of a Vierpolo, in particular a transmission line

In communications engineering, it is often of interest to know not only the propagation time distortions but also the absolute propagation time of a quadrupole, e.g. a transmission line. In transmission lines FehlerruCicmeldung to ¹ J a statement gives examples öpielsweise from the magnitude of the absolute running time, which is subjected to the signal to be transmitted, about emitted v / hich portion of the signal in the case einer..Übertragungsstörung again MUI.

1u Known procedure for measuring the absolute running time of a Quadrupoles use a frequency-tunable sine wave generator, its output voltage, if necessary after a modulation onto a carrier oscillation, to the four-pole input is placed, while the possibly demodulated four-pole output voltage together with the generator output voltage is subjected to a phase comparison. From the frequency change that is necessary for both voltages to move 3bo against each other in the phase can be then infer the absolute running time of the quadrupole. at

However, this method has the disadvantage that an accurate

Measurement of the frequency change is necessary and that to Durchc ^ conduct of the phase comparison own display devices

ο are to be provided, e.g. a separate Katli- ^ c'.enstrahloszillo- ^ graph, whose horizontal deflector one and ° 25 whose vertical deflection device closes the other of the two

cn is supplied to comparative voltages. Q

I TO I

The present invention relates to a method for the heating of the absolute running time of a quadrupole, in particular a transmission line, using a quadrupole traversing, modulated carrier oscillation, with the one on the quadrupole output side the modulation voltage back through demodulation is obtained and its phase shift compared to the ur.r jr borrowed modulation voltage with the help of phase comparison devices as a measure for the group delay determined \. 'ird and in which the disadvantages of the known methods are avoided.

The erfindungsgeiiiäiSe method is characterized in cU \ i two group delay measurements for a fixed V / ert the 'i'r; -:.. .- gerfrequenz f f, but <frequencies for two different modulation f _m2 are made, wherein on a display or viewing device calibrated for the one modulation frequency f, the difference Δτ of the two measurement results; ·. ^ e read and according to the relationship

t = Δτ.
^ax m2 ¹ InI

is used to determine the absolute running time t ^.

The method according to the invention is illustrated below with reference to a measuring arrangement shown schematically in the drawing explained in more detail.

A generator 1 generates a low-frequency output voltage, the frequency of which is set to two frequency values f. and ί ',., _; is adjustable. The output voltage of the frequency f supplied by a generator 2 is now fed to a modulation device 3 as a carrier oscillation and in this the output voltage of the generator 1 is modulated so that the setting of 1 becomes the Frequencies f, f + f. ₁ , xi _v -. or

. ~ 111 I 111 I.

^{a frequency changing} the frequencies f, f + f ₂ » ^ ~ ^ _r -2 ^en 'fcil

mis cli ani '"output of the Modulati ons device 3 will appear. The Auegangbspannung 3 is amplified in an amplifier 4 and guided over the to be measured quadrupole X. The Vierpolaus transfer voltage is stärkerß after passing through a further encryption D 5 demodulated in a demodulator 6 At the output of the demodulator, the phase of the voltage, which is influenced by the runtime properties of the quadrupole, appears

ireouenz f _Λ or f _n , which is in a subsequent ml m2

Phase measuring device 7 with the output voltage of the Genera-1u tors 1 is compared. The phase comparison is carried out in a manner known per se so that one of the phase difference Output voltage proportional to both voltages is formed, which is fed to a display instrument 8 -will. 'The display instrument 8 can be used for one of the two I> ■ Llödulationfrequenzen, e.g. f., 'are calibrated in such a way that • the associated group delay (or modulation phase delay) for the respective transmitted carrier frequency f, which is yes by the phase shift of the demodulated oscillation of the frequency f ^ compared to the oscillation specified by the generator 1 is intended, can be read directly. The method steps described above with reference to the drawing are in application to a particular modulation frequency and a for. this calibrated viewing instrument is known.

In order to measure the absolute transit time of the quadrupole X, the following procedure is now used according to the invention: The carrier frequency f of generator 2 is set to a fixed value, which is preferably in a frequency range of low propagation time distortions, and a propagation time measurement in.

Y specified / else f for Modulationsxrequenz, made. The measured value obtained on the display instrument 8 is denoted by Tj. Then the modulation frequency f _? is set and the measurement is repeated while maintaining the fixed carrier frequency, the result for the modula-

tion frequency f., calibrated display instrument another measured value τ rs. The difference amount Δτ = τ ^ - ^ is now according to the relationship

f '
t = Δτ. ^m1

^af m2 ~ ^f m1

for this purpose "is used to determine the absolute transit time t _{ri of} the quadrupole X.

, The modulation frequencies f ^ and chosen so that the factor

^f m1

^f m2 ~ ^f m1

gives a simple numerical value; if, for example, f ₂ is chosen to be 10 / o larger than f ^, the value 1ü results for the mentioned factor. In this Pail it is also possible to use the scale graduation of the display instrument 8 to determine the absolute running time, taking into account the factor 10.

mere difference formation of the two measurement results without any further to determine numerical conversion.

The method according to the invention can also be used with advantage in measuring stations for group delay measurement, such as contain a display device instead of a display instrument. In the case of such measuring stations, the carrier frequency is periodic and run continuously within a certain frequency range (wobbled), while a writing device of the display device * E.g. the electron beam of a cathode ray tube, in the horizontal direction with a linear dependence on the carrier frequency f and deflected in the vertical direction by the value formed during the phase comparison, a measure of the group delay output voltage representing is deflected. The on The group run time characteristic described with the display device is average. 'Scale graduation' attached to the screen only for

a specific modulation frequency assigned to this scale division, for example f., can be evaluated in terms of size. If a different modulation frequency f _{2 is} set, a second group delay characteristic results. ¹ : which is shifted by a certain amount compared to the first. This degree of displacement can then be evaluated in the same way as the difference Δτ determined on the basis of the measuring arrangement according to the drawing.

Since the phase measuring device 7, on the one hand _{, has to be supplied directly with the voltage of frequency f ^ or f 2} ^wa ^ ⁱ derived via the quadrupole, on the other hand, the output voltage generated by the generator 1 without any significant phase shift, it is in the case of extended test objects X, e.g. longer transmission lines , a loop measurement in which the transmitting and receiving devices are set up at the same measurement location.

2 patent claims

Claims (1)

- b Patent a ns Method for measuring the absolute transit time of a quadrupole, in particular a transmission line, using a modulated carrier oscillation passing through the quadrupole, in which the modulation voltage is recovered by demodulation on the quadrupole output side and its phase shift compared to the original modulation voltage with the help of phase comparison devices as MnLi for the group delay is determined, characterized in that two group delay measurements are made for a fixed V / ert of the carrier frequency (f), but for two different modulation frequencies (f ι, fp), one being used for the one modulation frequency (f'- i) calibrated display or viewing device (8) read the difference άτ of the two measurement results and according to the relationship ^a m2 m1
is used to determine the absolute running time t _n . Method according to Claim 1, characterized in that the modulation frequencies (f., F _m2 ) ^are chosen so that the factor ^f m1 f -f m2 m1
takes on the value of a power of ten. r ι ι .. ι _