Four-terminal network frequency characteristic analyzer

FIELD: measurement technology.

SUBSTANCE: analyzer can be used for measuring level of frequency distortions introduced by audio channel. Analyzer has two spectrum analyzers which are used to determine signal spectra at output and input of tested four-terminal network. Input and output signal spectra are subject to normalization and are introduced into subtraction unit and later to unit for determining normalized signals difference module. Signal from unit for determining module is sent to integrator to find end value, which characterizes area of frequency distortions introduced by four-terminal network. According to another version of analyzer the module is substituted by squarer. Analysis of frequency characteristics can be performed without turning four-terminal network into special measuring mode.

EFFECT: improved truth of information; increased precision of measurement.

2 cl, 3 dwg

 

The invention relates to the field of radio, and is intended for integral evaluation of the frequency distortion of a two-port in the original random signal. In particular, the analyzer can be used in problems of quality control signal in AudioTrack.

At the present time to assess the frequency distortions introduced by two different purposes, use device, allowing you to either determine the amplitude-frequency characteristic (AFC) of a quadrupole, or to provide for a visual analysis of the spectrum of the output signal. In the first case, non-uniformity of the frequency response is judged on alleged misstatements and their size, in the second case about the distortion is judged by how different the shape of the spectrum of the output signal from some reference, for example, the shape of the spectrum of white noise. Device (prototype), which serves to implement the above described techniques of analysis contains the test signal generator and spectrum analyzer, the output of which is an information output device, test the output of which serves as the generator output test signal and the test input is the input of the spectrum analyzer [Rosenberg VIA Radio methods of measurement of parameters of processes and systems. M.: Publishing house of the Committee of standards, measures and measuring instruments, 1970, p.123-124].

Fault the mi of the prototype are low informativity assessment and limited functionality, not allowing you to control the amount of insertion frequency distortions in the process of execution by a quadrupole their job functions without translation in a special measurement mode.

Technical result achieved when using the present invention is to increase the depth of analysis of the frequency properties of the investigated two-port network and to provide opportunities for analysis of frequency characteristics of two-port network without translation of his work in a special measuring (test) mode.

The technical result is achieved by the fact that the analyzer frequency properties of a quadrupole in the first embodiment, containing the first spectrum analyzer, the input of which is the first test input, according to the invention further comprises a second spectrum analyzer, two blocks of rationing, the subtraction unit, the unit selection module and the integrator, the output of which is an information output of the analyzer, the second test input which is the input of the second spectrum analyzer, the output of the first spectrum analyzer connected to the input of the first block of rationing, the output of which is connected to the first input of the subtraction unit, a second input connected to the output of the second block of rationing, the input connected to the output of the second spectrum analyzer, the output of block subtraction is connected to the input of the block you the population module, the output of which is connected to the input of the integrator.

On the second version of the technical result is achieved in that the analyzer frequency characteristics of two-port network containing the first spectrum analyzer, the input of which is the first test input, according to the invention further comprises a second spectrum analyzer, two block rating, block subtraction, Quad splitter and the integrator, the output of which is an information output of the analyzer, the second test input which is the input of the second spectrum analyzer, the output of the first spectrum analyzer connected to the input of the first block of rationing, the output of which is connected to the first input of the subtraction unit, a second input connected to the output of the second block of rationing, the input connected to the output of the second spectrum analyzer, the output of the subtraction unit is connected with the input of the Quad, the output of which is connected to the input of the integrator.

The invention is illustrated graphic material. Figure 1 shows the functional diagram of the analyzer of the frequency properties of the quadrupole (the first option). Figure 2 shows graphs illustrating the principle of the analysis of frequency characteristics. Figure 3 shows a functional block diagram of rationing (the example implementation).

The scheme of figure 1 contains the spectrum analyzers 1, 2, blocks 3, 4 of the regulation, the subtraction unit 5, block selection module, the integrator 7 and the test quadrupole representing the amplifier 8 connected with the load resistance RL. The input of the spectrum analyzer 1 is the first test analyzer input frequency properties, the second test input which is the input of the spectrum analyzer 2 to the first test input connected to the output of the test amplifier 8, whose input is combined with the second test input, the output of the spectrum analyzer 1 is connected to the input unit 3 of the regulation, the output of which is connected to the first input of the subtraction unit 5, to the second input of which is connected the output of block 4 of the regulation, an input connected to the output of the spectrum analyzer 2, the output of the subtraction unit 5 is connected to the input unit 6 selection module, the output of which is connected to the input of the integrator 7, the output of which serves as an informational entrance ρ analizator frequency properties.

Figure 2 contains a graph of Y1(ω) normalized value range of the input signal under test amplifier 8 obtained at the output of block 4; the graph of Y2(ω) normalized value range of the output signal of the tested amplifier 8 from the output unit 3.

Functional diagram in figure 3 contains a potentiometer 9 (adjustable voltage divider), band-pass filter 10 and the probe 11 of the signal level. Upper circuit on the output of the potentiometer 9 is in the Odom block regulation, and the average output of the potentiometer 9 is the output power rating, the bottom of the scheme, the output of the potentiometer 9 is connected with a common bus and to the center pin of the potentiometer 9 is connected to the input of bandpass filter 10, the output of which is connected to the meter level 11.

As a quantitative measure for insertion frequency distortions of the adopted functional ρ(Y1, Y2), which defines the distance between the functions Y1(ω) and Y2(ω)

where [ω1that ω2] - operating frequency quadrupole;

Y1(ω) and Y2(ω) - normalized spectra, respectively, the input and output signals of the quadrupole (signal source and signal distortion).

This expression defines the structure and algorithm of operation of the analyzer, the scheme of which is shown in figure 1. The output and input signals of the two-port network (in our case, the amplifier 8) are fed to the inputs of spectrum analyzers 1 and 2, respectively. Calculated in each of them the values of the functions S1(ω) and S2(ω), which is the spectra of the input and output signals, respectively, then normalized and fed to the subtraction unit 5. Under the rationing refers to the calculation of the relative values of Y1(ω) and Y2(ω) by the formula

where ω0- some fixed mean frequency in the band of operating frequencies (channels of amplification and audio processing ω0usually corresponds to a frequency of 1 kHz).

After separation in block 6 the absolute value of the difference (Y1(ω)-Y2(ω)) the result is sent to the integrator 7 for final receipt of the required assessment of functional ρ(Y1, Y2), the meaning of which is clearly illustrated by figure 2. The shaded area between the graphs of the functions Y1(ω) and Y1(ω) collectively have a total area that is numerically equal to the value of the functional ρ(Y1, Y2). Thus, we can conclude that the analyzer by comparing the spectra of the output and input signals as shown above, calculates the square of the distortion parameter, designed to give an integrated assessment made by the quadrupole frequency distortions. Of course, the minimum distortion must meet the minimum of the expression (1) is the minimum area, and the condition ρ(Y1, Y2)=0 corresponds to the ideal situation of complete lack of frequency distortion.

Given that the output signal in the real spectrum analyzers is a function of time, carrying information about the analyzed spectrum, it should be stressed that, in practice, instead of expression (1) will Vici shall be his temporary copy

where [t1, t2] is the time interval during which the signals Y1(t), Y2(t);

Y1(t) signal, which is the display time of the normalized spectrum of Y1(ω) and remove from the output of block 4;

Y2(t) signal, which is the display time of the normalized spectrum of Y2(ω) and remove from the output of block 3,

With regard to the signals Y1(t), Y2(t) note also that if during the session of the measurements are repeated and the integrator 7 is not provided synchronous periodic reset, the output voltage of the integrator 7 is continuously grow proportionally to the number of sessions. Therefore, during one session of measurement at the output of spectrum analyzers 1, 2 voltage should appear only once in the form of pulses whose shape reflects the S2(ω) and S1(ω), respectively. Of course, to start a new session of measurements integrator 7 should be zero (in the diagram of figure 1 circuit reset not shown).

As has been shown above, rationing is reduced to the computation of relations of the form (2), which implies that the blocks 3, 4 can be implemented as devices division of functions S1(t) and S2(t) on the previously calculated constant coefficients corresponding to the frequency ω0(S1(t) and S2(t) - signals n is the output spectrum analyzers 2, 3, respectively). However, in some cases, this method of valuation may be unduly difficult, so figure 3 shows an example implementation of block rationing, working on a slightly different principle. The essence of his work is reduced to the manual, the testing division of the output voltage of the spectrum analyzer as long as the voltage corresponding to the frequency ω0not reaches the specified level, for example, units as in figure 2. If the specified operation to perform on the signals S1(t), S2(t) prior to the measurements at constant parameters of two-port network, it will obtain a picture similar to that shown in figure 2. Of course, the accuracy of rating will depend on the identity element parameters used in blocks 3, 4, and resolution of the meter level 11. The Central frequency of the band pass filter 10 is selected equal to ω0and the bandwidth of the possibility of a small (about a half octaves) and based on the given requirements to the accuracy of the analysis.

The second variant of realization of the considered analyzer (figure 1) can be a device containing instead of the unit selection module squarer. In this case, the assessment will be functional

Advantages analyzer in comparison with the known devices, you is alnaimi similar functions, are the possibility of its use for continuous monitoring of spectral changes that occur in tracts passing random signals, and the integral nature of assessing the degree of distortion introduced. The latter is especially true for audio, as the assessment of their quality is determined by the physiological characteristics of the recipient information, and the proposed criterion allows to enhance the evaluation of the distortion of the spectrum from the point of view of subjective sensations, while being simply a technical parameter.

1. The analyzer frequency characteristics of two-port network containing the first spectrum analyzer, the input of which is the first test input, characterized in that it introduced the second spectrum analyzer, two blocks of rationing, the subtraction unit, the unit selection module and the integrator, the output of which is an information output of the analyzer, the second test input which is the input of the second spectrum analyzer, the output of the first spectrum analyzer connected to the input of the first block of rationing, the output of which is connected to the first input of the subtraction unit, a second input connected to the output of the second block of rationing, the input connected to the output of the second spectrum analyzer, the output of the subtraction unit is connected to the input of block allocation module, the output of which is on connected to the input of the integrator.

2. The analyzer frequency characteristics of two-port network containing the first spectrum analyzer, the input of which is the first test input, characterized in that it introduced the second spectrum analyzer, two block rating, block subtraction, Quad splitter and the integrator, the output of which is an information output of the analyzer, the second test input which is the input of the second spectrum analyzer, the output of the first spectrum analyzer connected to the input of the first block of rationing, the output of which is connected to the first input of the subtraction unit, a second input connected to the output of the second block of rationing, the input connected to the output of the second spectrum analyzer, the output of the subtraction unit is connected to the input of the Quad, the output of which connected to the input of the integrator.



 

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FIELD: measurement technology.

SUBSTANCE: analyzer can be used for measuring level of frequency distortions introduced by audio channel. Analyzer has two spectrum analyzers which are used to determine signal spectra at output and input of tested four-terminal network. Input and output signal spectra are subject to normalization and are introduced into subtraction unit and later to unit for determining normalized signals difference module. Signal from unit for determining module is sent to integrator to find end value, which characterizes area of frequency distortions introduced by four-terminal network. According to another version of analyzer the module is substituted by squarer. Analysis of frequency characteristics can be performed without turning four-terminal network into special measuring mode.

EFFECT: improved truth of information; increased precision of measurement.

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