SU1394440A1 - Phase-frequency characteristics controller for communication channels - Google Patents

Abstract

The invention relates to telecommunications. The purpose of the invention is to improve accuracy. The device contains an input | matching unit 1, a rectifier 2, a clock frequency separation unit 3, a frequency detector 4, a low-pass filter (LPF) 5, an indicator 6, r-r 7 pulses, an output matching unit 11 connected to channel 12 communications, switches 14, 24. In order to improve the accuracy, serially connected switch 8, frequency divider 10 and counter 9 are entered on the transmitting side, and connected to the low-pass filter 18, rectifier 20, averaging block 21 and large-scale on the receiving side amplifier 22, frequency multiplier 13, selection unit 15, the block determining the initial phase shift 16, pulse shaper 17, the tilt unit 19 for determining the sign of the phase response, the switch 23, the subtraction unit 25. 5 il. (ABOUT

Description

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The invention relates to telecommunications and can be used to control the phase-frequency characteristics of communication channels.

The purpose of the invention is to increase accuracy.

Fig. 1 is an electrical block diagram of a device for monitoring phase characteristics.

communication channels; in fig. 2 - the same, block selection; in fig. 3 - the same, the unit for determining the initial phase shift; in fig. 4 - the same block

The signal that passes through the communication channel 12, which has reactivity, acquires a constant phase shift at its output. Moreover, for different frequencies this phase shift is different. This means that there is also a phase shift between two different frequencies, which increases with the increase in this frequency difference. In the limit, the phase shift cp, obtained at the measured frequency se relative to the zero frequency, is the phase modulus of the signal with the frequency Id at the output of channel 12 relative to its input

determine the sign of the slope of the phase –– e, provided that the phase shift is

20

25

thirty

Noah characteristics; Fig. 5 shows timing charts explaining the operation of the device.

The device for monitoring the phase-frequency characteristics of the communication channels (FIG. 1) contains an input matching unit 1, a first rectifier 2, a clock frequency separation unit 3, a frequency detector 4, a first low-pass filter 5, an indicator 6, a pulse generator 7, a switch 8, counting 1 9, frequency divider 10, output matching block 11 connected to communication channel 12, frequency multiplier 13, first switch 14, selection block 15, initial phase shift determining block 16, pulse shaper 17, second low-pass filter 18, definition block 19 inclination of the phase-frequency characteristic, the second rectifier 20, the averaging unit 21, the large-scale amplifier 22, the third 23 and the second 24 switches, and the subtraction unit 25.

The selection unit 15 (Fig. 2) contains the first 26, second 27 and third 28 pulse formers, a delay element 29, a differentiation unit 30, a prohibition unit 31 and a low-pass filter 32.

The initial phase shift determination unit 16 (FIG. 3) includes a switch 33, amplifiers 34 and 35, low-pass filters 36-38, functional converters 39-41, an inverter 42, an adder 43, a division unit 44 and a comparison block 50 45.

Block 19 for determining the sign of the slope of the phase-frequency characteristic (FIG. 4) includes a switch 46, diodes 47 and 48, an inverter 49, a low-pass filter 50, and a pulse shaper 51.

The device works as follows.

45

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There is no zero frequency. Accordingly, the phase modulus Icpgl is measured for the frequency (J relative low frequency of the ESS,. The error that arises can be corrected by multiplying the result and rhenium by the corresponding factor

itfoi lt 5m

However, the value does not indicate the sign of the phase, nor of its true value in the case when frequencies close to O have an initial phase shift tf ,,

To find the magnitude of the initial phase shift at a low frequency of the test signal, the ratio

d) „arctg --- - (6

where and, is the voltage of the first harmonic in the pulse test signal of a low frequency at the input of communication channel 12; and c is the voltage of the first harmonic in the pulse test signal of a low frequency at its output.

The method of determining the sign of the initial phase shift cf is a short-term change in the input resistance of the input unit 1 of the co-operation. If the decrease in its input resistance Cf is insignificant but increases or remains so, this indicates the capacitive nature of the initial phase shift if it decreases, then this is an indication of the inductive character of the initial phase shift.

To find the sign of the phase, the phase-frequency characteristic (PFC) property is used, in accordance with

There is no zero frequency. In accordance with this, the phase modulus Icpgl is measured for the frequency (J of the relatively low frequency of the ESS,. The error arising in this case can be corrected by multiplying the measurement result by an appropriate factor

itfoi lt 5m

However, the value does not give an idea of the sign of the phase, nor of its true value in the case when at frequencies close to O there is an initial phase shift tf ,,

To find the magnitude of the initial phase shift at a low frequency of the test signal, the ratio

d) „arctg --- - (6

where and, is the voltage of the first harmonic in a pulsed low frequency test signal at the input of communication channel 12; and, c is the voltage of the first harmonic in a pulsed low frequency test signal at its output.

The method of determining the sign of the initial phase shift cf is the short-term change in the input resistance of the input matching unit 1. If the decrease in its input resistance Cf slightly increases or remains the same, then this indicates the capacitive nature of the initial phase shift, if it decreases, then this is evidence of the inductive nature of the initial phase shift.

To find the sign of the phase, the property of the phase-frequency characteristic (phase response) is used, in accordance with

in which the increment of the phase with a positive sign corresponds to the increasing frequency characteristic of the frequency response from low to high, and with a falling frequency response character, the same frequency increment corresponds to the phase increment with a negative sign. The sign of the slope of the phase response can be detected using block 19.

Thus, the phase of the tp signal frequency 1 cD at the output of communication channel 12 relative to its input is through the increment of the iCf phase between the frequency (0 (5 and low frequency se, close to 0. In the absence of an initial phase shift cf at frequency Q , size

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The pulse sequence from the output of the input matching unit 1 is fed to the input of the first rectifier 2, performing one half-half, rectifying a single-pole 5 signal (Fig. 5a) or a two-half-round rectification of the quasi-tertiary signal. The same sequence is also fed to the information input of the initial phase shift determination unit 16. In it, when the low frequency part of the test signal is applied, the initial phase shift is determined by the ratio of the first harmonics of this low frequency signal at the input and output of channel 12. The control unit 16 is switched on only with a low frequency test signal by applying a control signal to its control input 25

In the presence of an initial phase shift at c at the frequency to, the value Cf t | CfJ q «.

For this, pulses from the output of the generator 7 (Fig. 5q) are fed to the information input of the switch 8 and to the input of the counter 9. The latter counts a predetermined number of pulses from

generator 7 and it outputs at its output

,, „1п from the output of the selection block 15, a voltage jump from O to 1. This is for example and„

Tori selects pulses by frequency.

(Fig. 560 enters the control input of the switch 8, and under its influence the switch 8 connects generator 7 to divider 10, which converts the high-frequency signal of generator 7 into low-frequency pulses. The same voltage jump counter. 9 is reset to its original position and starts A new counting cycle, at the end of which a voltage jump from 1 to 0 occurs. This zero voltage, acting on the control input of switch 8, acts on it so that it connects generator-7 directly to the input of output unit 11 according to In this way, either low-frequency or high-frequency pulses appear at the input of the output matching block 11. The output matching block 11 serves to match the communication channel 12. Resistance matching occurs signal amplitude and type

40

The multiplier 13 is needed to increase the frequency of the low-frequency part of the test signal before it is fed to the block 3 of the clock clock.

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The signal from the frequency multiplier 13 (Fig. 5e) is fed to the input of the first switch 14, to the control input of which pulses are delivered (Fig. ZZH) from block 15. Under the action of these pulses, the first switch 14 passes to its output or the high-frequency part of the test signal the output of the first rectifier 2, or the low-frequency part of this signal from the output of the multiplier 13. I

Block 15 serves to detect high and low frequency parts.

5Q test signal and issue when they receive control signals. The signal of a logical unit acts on the output of block 15 for the entire

a series of high-frequency pulses of the test signal (a single-pole binary signal after the gg signal, and a logical force or a quasi-ferro signal — during the whole series of low-hourly signals). of the current pulses of this signal.

The signal from the output of the output unit 11 A pulse signal from the output of the first matching after it passes through the switch 14 is fed to the input 0

through kalal 12 connection (fig. 5d) arrives at the input of the output matching unit 1, performs coordination with communication channel 12. Matching is done on the input impedance and amplitude of the signal, and the input impedance of this block can be briefly changed.

The pulse sequence from the output of the input matching unit 1 is fed to the input of the first rectifier 2, performing one half-half, rectifying a single-pole 5 signal (Fig. 5a) or a two-half-round rectification of the quasi-tertiary signal. The same sequence is also fed to the information input of the initial phase shift determination unit 16. In it, when the low frequency part of the test signal is applied, the initial phase shift is determined by the ratio of the first harmonics of this low frequency signal at the input and output of channel 12. The control unit 16 is switched on only with a low frequency test signal by supplying the control signal to its control input

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The multiplier 13 is needed to increase the frequency of the low-frequency part of the test signal before it is fed to the block 3 in the clock time

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The signal from the frequency multiplier 13 (Fig. 5e) is fed to the input of the first switch 14, to the control input of which pulses are delivered (Fig. ZZH) from block 15. Under the action of these pulses, the first switch 14 passes to its output or the high-frequency part of the test signal the output of the first rectifier 2, or the low-frequency part of this signal from the output of the multiplier 13. I

Block 15 serves to detect high and low frequency parts.

test signal and issuing control signals when they appear. The signal of a logical unit acts on the output of block 15 for the entire

17, which serves to reduce the pulse duration and, thereby, increase the amplitudes of the high-frequency harmonics in them, which is necessary for stable operation of the block 3.

The clock selection unit 3, connected by its input with the output of the driver 17, serves to obtain a regular clock oscillation of one frequency from the incoming test signal of two different, but multiple, frequencies. In the simplest case, block 3 is a narrowband filter tuned to the high-frequency part of the test signal or to its closest harmonic, and a square pulse shaper. When a high-frequency part of the test signal arrives at block 3, which, after passing through communication channel 12, has a definite phase shift, the narrowband filter included in block 3 begins to adjust to the phase of these excitation pulses, i.e. the phases of the signal at the output of block 3, for example, increase. However, as the phase of the signal at the output of block 3 approaches the phase of the exciting high-frequency pulses at its input, the increment of the oscillation phase at the output of block 3 decreases and with exact coincidence of the phases at the input and output, this increment becomes equal to zero. With the arrival of the low-frequency part of the test signal, which has a completely different phase shift, the filter of block 3 is rebuilt for this phase, etc. Thus, in a regular-time oscillation, the output of block 3 (Fig. 5 |, and) constantly changes phase increments. This signal is phase modulated. In the phase-modulated signal, together with the phase fluctuations, the frequency fluctuation also occurs.

To isolate the envelope of these phase fluctuations, a frequency detector serves and, together with the first low-pass filter 5, the voltage from the output of the first filter 5 as cosine-shaped pulses of positive and negative polarity (Fig. 5k), the amplitude of which is determined by the phase difference between the low-frequency and the high-frequency portions of the test signal, goes on to the second low-pass filter 18 and to the block 19 for determining the sign of the phase tilt

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Noah characteristics. With a positive sign of the slope of the phase-frequency characteristic of the communication channel 12, a logical unit signal appears at the output of block 19; with a negative sign of the slope of the frequency response, a logical zero. These signals remain at the output of block 19 for the entire measurement session.

The signal from the output of the first filter 5 is also fed to the second low-pass filter 18, which serves to filter out the remnants of the high-frequency clock wave, as well. also suppressing the phase fluctuations caused by the imposition of noise on the test signal as it passes through the communication channel 12. A second rectifier 20 is connected to its output, which is a full-wave circuit and serves to rectify the envelope voltage of the phase fluctuations.

To eliminate the ripple voltage rectified (Fig. 3a), it is fed from the output of the second rectifier 20 to the averaging unit 21.

The constant voltage from the output of the averaging unit 21 is then fed to the input of the large-scale amplifier 22, which serves to correct for

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multiplier -, measuring and and „| .

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The magnitude of this multiplier determines the choice of the gain factor of the scale amplifier 22, which is a DC amplifier. When measuring phase shifts & (f between any frequencies, the gain of the scale amplifier is taken equal to 1.

The signal from the output of the scale amplifier 22 is fed to the input of the second switch 24. At its control input, as well as to the control input of the third switch 23, a signal is received from the tilt-sign symbol determining unit 19 of the phase characteristic.

If the sign of the slope of the phase characteristic is positive, the control inputs of the second 24 and third 23 switches receive a logic unit signal from the output of block 19. Under the action of this voltage, the signal input of the second switch 24 is connected to its first output, which in turn , is connected to the first (direct) input of subtraction unit 25. Simultaneously under the action

The same control voltage of the information input of the third switch 23 is connected to its first output, which, in turn, is connected to the second (inverse) input of block 25. As a result of subtracting two DC voltages, a voltage proportional to the phase of the signal the output of communication channel 12 relative to its input. This voltage, the sign of which, determined by the difference in voltage at the input of block 25, is applied to indicator 6,

If the sign of the slope of the phase response is negative, the control inputs of the second 24 and third 23 switches receive a logical zero signal. Under the action of this signal, the information input of the second switch 24 is connected to its second output, which, in turn, is connected to the second input of the block 25. Simultaneously under the action of this control voltage

the information input of the third switch-25 signal is fed to the input of the block 44 of 40

torus 23 is connected to its second output, which, in turn, is connected to the first input of block 25, the voltage from its output, the sign of which is determined by the difference in voltage at its input, is fed to indicator 6, during phase shift measurements &; (f between any frequencies supplied to communication channel 12, the signal to the information input of the third switch 23 is not supplied, 35 f

Block 3 works on the principle of pulse selection for the duration. The initial phase shift in block 16 is determined by comparing the first harmonic voltages at the input and output of channel 12. Since the first harmonic voltage of the low-frequency part of the test signal at channel 12 is a priori known, it is represented as a known constant voltage quantities. The dp of determining the voltage of the first harmonic after passing through the channel 12 is used in the construction of block 16 (Fig. 3). The pulse signal is fed 50 to the input of the key 33, which passes only the low-frequency part of the test signal upon a command from the selection unit 15. Further, these pulses go to amplifier 34, which 55 brings their peak value to a value that is wound to the peak value of these same pulses at the input of link 12, to another input of which a signal comes from the output of filter 38. At the output of the dividing circuit, the voltage proportional c, This voltage is applied to the input of the functional converter 41, which performs the operation y arctgx. The signal from its output If arctg- Uj -U. / U, e is then fed to the input of the third switch 23

formula of invention

45

A device for monitoring the phase-frequency characteristics of the channels; on the transmitting side contains a pulse generator and an output matching unit, the output of which is the input of the communication channel, and on the receiving side an input matching unit whose input is the output of the communication channel, a serially connected clock extraction unit, a frequency detector and The first low-pass filter, the first rectifier, the first and second switches and the indicator, characterized in that, in order to improve the accuracy, a series-connected switch is introduced on the transmitting side; which is connected to the output of the pulse generator; a frequency divider, the output of which is combined with another output of the switch and connected to the input of the output unit;

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0

. Therefore, if the flat part of the pulses is not distorted, the voltage of the first harmonic in them is the same as at the input of channel 12, if distorted, then less, the voltage of the first harmonic is separated from the pulses using a low-pass filter 36. Further, this voltage is measured, filtered and supplied to functional converter 39, which performs the operation of squaring (U). The voltage from its output after inverting in inverter 42 is fed to the input of adder 43, to another input of which is supplied constant This voltage is proportional to UJ. The output of the adder 43 is a voltage proportional to U, -UJg, which is then fed to the input of the function converter 40, which performs the square root extraction operation. Its voltage is proportional to Vu | -UJ., More

f

This device receives a signal from the output of the filter 38. The output of the dividing circuit is a voltage proportional to, This voltage is applied to the input of the function converter 41, which performs the operation y arctgx. The signal from its output If arctg- Uj -U. / U, e is then fed to the input of the third switch 23

formula of invention

0

0 5

five

A device for monitoring the phase-frequency characteristics of the channels; on the transmitting side contains a pulse generator and an output matching unit, the output of which is the input of the communication channel, and on the receiving side an input matching unit whose input is the output of the communication channel, a serially connected clock extraction unit, a frequency detector and The first low-pass filter, the first rectifier, the first and second switches and the indicator, characterized in that, in order to improve the accuracy, a series-connected switch is introduced on the transmitting side; Secondly, it is connected to the output of the pulse generator, a frequency divider, the output of which is combined with another output of the switch and connected to the input of the output matching unit, and a counter, the input of which is connected to the output of the pulse generator, and the output to the control inputs of the switch, frequency divider and output unit matching, and on the receiving side - a second low-pass filter connected in series, the input of which is connected to the output of the first low-pass filter, the second rectifier, the averaging unit and the large-scale amplifier, od which is connected to the signal input of the second switch, a frequency multiplier, whose input is combined with the first signal input of the first switch and coupled to an output of the first vshr DC converter, and an output coupled to a second signal input of the first switch, formi139444010

a low-frequency block, the selection block whose input is connected to the output of the first rectifier, and the output is connected to the control input of the first switch and to the second input of the block for determining the sign of the slope of the phase-frequency characteristic, the initial phase shift determining block, the first and second inputs of which are connected respectively to the outputs an input matching unit and a selection unit, a subtraction unit, the output of which is connected to the indicator input, and a third switch, the signal input of which is connected to the output of the initial phase detection unit Whig, a control input is combined with the control input of the second switch and is connected to the output of opredele10

15

pulse generator, the input of which is connected to the tilt sign of the phase frequency is connected to the output of the first switch, and the output is connected to the input of the clock selection unit, the phase response characteristic sign determining unit, the first input of which is connected to the output of the first filter

and

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The characteristics, and the first and second outputs are combined respectively with the first and second outputs of the second switch and connected respectively to the first Bbw and the second inputs of the subtraction unit.

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Claims (1)

Claim A device for monitoring the phase-frequency characteristics of communication channels, comprising, on the transmitting side, a pulse generator AND an output matching unit, the output of which is the input of the communication channel, and on the receiving side, an input matching unit, the input of which is the output of the communication channel, a frequency the detector and the first low-pass filter, the first rectifier, the first and second switches and the indicator, characterized in that, in order to improve accuracy, introduced on the transmitting side not connected in series to the switch, the signal input of which is connected to the output of the pulse generator, a frequency divider, the output of which is combined with another output of the switch and connected to the input of the output matching unit, and a counter whose input is connected to the output of the pulse generator, and the output to the control inputs switch, frequency divider and output matching unit, and on the receiving side, a second low-pass filter connected in series, the input of which is connected to the output of the first low-pass filter, A swarm rectifier, jg chopper, averaging unit and a large-scale amplifier, the output of which is connected to the signal input of the second switch, a frequency multiplier whose input is combined with the first signal input of the first switch and connected to the output of the first rectifier, and the output is connected to the second signal input of the first switch, a pulse shaper, the input of which is 20 connected to the output of the first switch, and the output is connected to the input of the clock frequency allocation unit, a unit for determining the sign of the slope of the phase-frequency characteristic, whose first input is 2 5 is connected to the output of the first low-pass filter, a selection block, the input of which is connected to the output of the first rectifier, and the output is connected to the control input of the first switch and to the second input of the slope determination unit of the phase-frequency characteristic, the initial phase shift determination unit, the first and second inputs of which connected respectively to the outputs of the input matching unit and the selection unit, a subtraction unit whose output is connected to the indicator input, and a third switch, the signal input of which is connected to the output of the unit to determine the initial phase shift, the control input is combined with the control input of the second switch and connected to the output of the slope determination unit of the phase-frequency characteristic, and the first and second outputs are combined with the first and second outputs of the second switch, respectively, and connected to the first and second inputs of the subtraction unit. Fig 2 ^p fig.z FIG. 4 Π S P Π Π Π Π Π Π Π Π Π Π Π Π G. t 't I__IT ^ -I__LLLLLLLL /, t <_ □ Π Π Π ______. ’Π Π Π ΠΠΠΠΠΠΠΠΠ • hnnnnnnnnnnnnnnr ' FIG. 5 t - * t