SU760461A1 - Device for measuring phase-frequency characteristics of communication channels - Google Patents

Description

The invention relates to telecommunications and can be used for measurements on the track in the channels of the tone frequency (PM) with non-synchronous carrier systems of multi-channel communication with frequencies of ^ 5 channels, channels.

A device is known for measuring the frequency-frequency characteristics of communication channels, which contains a measuring frequency generator on a transmission, the first U and the second outputs of which are connected respectively to the first and second inputs of the adder, the output of which is connected to the input of the communication channel, and tel frequencies, the first and second filters combined in input and in series (connected phase discriminator and indicator [1]. 20

However, the known device has insufficient accuracy and a large measurement time.

The purpose of the invention is to increase the accuracy of (and reduce the measurement time. 25

To do this, the device for measuring the frequency and frequency characteristics of the communication channels / containing in transmission is the generator of measuring frequencies, the first.

and whose second outputs are connected. ' ЗЦ

; 2

respectively, to the first and second inputs of the adder, the output of which is connected to the input of the communication channel> and at the reception - a generator of reference measurement frequencies, the first and second filters combined in series and connected in series to the phase discriminator and indicator, a preamplifier, a mixer and four divider frequency, while the output of the communication channel through a serially connected first filter, first frequency divider, frequency converter, second (the input of which is connected via the second frequency divider to the output the second one (filter and mixer, the second input of which is connected to the first output of the reference measurement generator through the third frequency divider, is connected to the first input of the phase discriminator, the second input of which is connected via the fourth frequency divider O to the second output of the reference measurement generator.

Na'chertezhe shows a block electric (diagram of the apparatus. "The apparatus for measuring the phase-frequency characteristics of the communication channels on the transmission comprises a generator 1 iz ¹

760461

measuring frequencies, adder 2, at the reception - generator 3 of reference measuring frequencies, first and second filters 4 and 5, four dividers 6,7,8 and 9. frequencies, frequency converter 10, mixer 11, phase discriminator. 12, indicator 13 and communication channel 14. ⁵

The device works as follows. '

All dividers 6,7,8 and 9 have the same ... division ratio ^- ! ·) 'And realize the frequency division of the signals with simultaneous division of their phase. Generator 1. provides synthesis, and adder 2 is one-time sending 14 signals of two frequencies to the communication channel - reference, £ _op and 15 next of the measuring £ ^. During the passage through communication channel 14, they are incremented by frequency (Δ £) and phase shift due to the value of the phase-frequency characteristic 20 (phase response) of the communication channel 14 at a given frequency. At the output of the communication channel 14, the signals £ _op + d £ and £ _n - + l £ are separated by filters 4 and 5, are divided by dividers b and 7 so that the phase shift between them does not exceed 180 °, and the converter goes to ^ 5 10. Here signals are converted and differential frequency signals are highlighted: ~ ζ

· £ · ϊ * ^ ί _. £ -) ~ £ op,

η ъ * and 30

B. The conversion process frequency divergence is eliminated (first stage conversion).

Difference frequency signals having a phase corresponding to the relative frequency response of the communication channel 14 are fed to mixer 11, where they subtract with the corresponding signals from generator 3, similar signals of measuring frequencies generated in the generator dd 1 (second conversion stage). Signals from the generator 3 before entering the mixer 11 pass through the divider 8. as a result of subtraction —Hy '. ^ Rp. On the output of the mixer η n

For 11, a signal of a fixed frequency -η-® ⁰ · is obtained, in the phase of which information on the frequency response of the communication channel 14 is enclosed. This signal arrives at the phase discriminator 12, where it is compared in phase with the reference phase signal received from the second generator output through a divider 9. The phase difference of these signals will represent the relative phase response of the communication channel 14 as measured at fixed points * (at ⁵⁵ iemeri--negative frequencies) making it to the measured characteristic starts at zero, it follows a phase shifter that can be placed between Delhi elem phase discriminator 9 and 12, at 60

measuring the first point of the phase shift, bring in such a phase shift so that the phase meter is

called 0 °. Subsequent measurements will be <

they are showing a phase shift increment relative to this conditional zero point-65

45

ki The measurement results are fixed by the indicator 13.

Consequently, the proposed device allows to measure (relative phase response relative to the phase of the signal ^ of communication channel 14 along the route, eliminating the error from frequency discrepancies and from transmitting information on the reverse channel.

The advantages of the proposed device are the reduction of the measurement time of each point and the reduction of the requirements for the phase meter accuracy class. Reduction of time is achieved by the fact that there is no time expenditure on the passage of information through the return channel. The frequencies of the generators 1 and 3 do not have time to change significantly. In addition, the measured value does not charge an additional component that allows you to determine it with greater accuracy. For example, with a large length of the communication channel 14 (10-12 re-use plots) the value of the forward phase response of the forward channel, i.e. full phase shift at a frequency of 300 Hz can have a value of 6 · 10 = 60 1 ?. With the passage of information on, the frequency of 1800 Hz on the return channel is added 3601 ?. If the shift at the next measured point is 60.61? then the difference between them is 0.61 G, i.e. the increase in the phase response will be 1%. Does the phase meter measure 420.61? i.e. in this case, the order of change of the measured value (its increase) will be 0.14%. To maintain the same accuracy, it is necessary to use more sensitive phase meters (higher accuracy class) in the device prototype /

The proposed device allows to increase the measurement accuracy at the same temperature or reduce hardware costs with the same accuracy.

Claims (1)

Claim A device for measuring the phase-frequency characteristics of the communication channels, containing a measuring frequency generator on the transmission, the first and second outputs of which are connected respectively to the first and second inputs of the adder, the output of which is connected to the input of the communication channel, and at the reception a reference measurement generator, combined by the first and second inputs the second filters and the phase discriminator and the indicator connected in series with it, and with the fact that, in order to increase the accuracy and reduce the measurement time, azovatel frequency mixer and four frequency divider, the output of the communication channel through a first filter connected in series, a first frequency divider, a frequency converter, a second input ko760461 The second frequency divider is connected to the output of the second filter, and the mixer, the second input of which is connected to the first output of the reference measurement generator through the third frequency divider, is connected to the first input of the phase discriminator, the second input of which is connected through the fourth frequency divider the second generator output reference measuring frequencies.