SU1100504A1 - Device for measuring frequency of first harmonic of quasi-periodic signals - Google Patents

Abstract

) A DEVICE FOR MEASURING THE FREQUENCY OF THE FIRST HARMONIC OF QUASI-PERIODIC SIGNALS, containing N + 1 detectors, a logic unit and a control unit, the first input of which is connected to the input (N + 1) -ro of the detector, the second - to the device input, the third input to the logical block, the first output is the output of the device, and the outputs of the detectors are connected to the corresponding inputs of the logic block, characterized in that, in order to improve accuracy and speed, an interpolating filter and N series-connected filters are inserted into it, sync The drop inputs are connected to the second output of the control unit, and the signal inputs are connected to the inputs of the respective detectors, the signal input of the first filter is connected to the output of the interpolating filter and the output of the Nth filter to the first input of the control unit, the signal input of the interpolating filter is connected to the input of the device, and its synchronization input is connected to the first input (L of the control unit.

Description

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4 ;: The invention relates to automation and measurement technology. Devices are known for distinguishing the fundamental tone (the first harmonic of quasi-periodic, in particular, speech signals), containing switched trace filters. A disadvantage of the known device is the great complexity due to the significant number of tunable (adaptive) filters. The closest to the technical essence of the invention is a device for separating the first harmonic of a qua-ziperiodic, in particular speech, signals, containing successively connected N adaptive filters and a control unit containing a smart amplifier, a low-pass filter, and N +1 detector and logic unit, the detector inputs are connected to the inputs of the corresponding adaptive filters, their outputs are connected to the second input of the control unit through the logic unit, and the output of the control unit is connected to and the inputs of the adaptive filters, and the corresponding output of the last hell tive filter connected to the control unit third input, a fourth input coupled to the input (N1 + 1) th detector. However, the known device is characterized by low accuracy and low speed, due to the limited hardware implementation capabilities of adaptive filters on digital delay lines, performed in the form of shift registers, when in order to improve accuracy it is necessary to increase the size of the shift registers to values that drastically reduce the speed affinity. The purpose of the invention is to increase accuracy and speed. The goal is achieved by means of a device for measuring the frequency of the first harmonic of quasi-periodic signals, containing N +1 detectors, a logic unit and a control unit, the first input of which is connected to the input (N + 1) -ro detector, the second with the input of the device, the third with the output of the logic unit, the first output is the output of the device, and the outputs of the detectors are connected to the corresponding inputs of the logic unit, an interpolating filter and N serially connected fillers are inserted There are synchronous inputs of which are connected to the second output of the control unit, and signal inputs are connected to the inputs of the respective detectors, the signal input of the first filter is connected to the output of the interpolating filter, and the output of the Nth filter is connected to the first input of the control unit, the signal input of the interpolating filter is connected the device input, and its sync input is connected to the first input of the control unit. Figure 1 shows the block diagram of the device; Fig. 2 illustrates the operation of the interpolating filter; Fig. 3 illustrates the operation of the device as a whole. The device (Fig. 1) contains an input busbar 1, N + 1 of detectors 2.1-2.N + 1, each of which has an input and an output, a logical block. 3, having N + 1 inputs and output, control unit 4, having three inputs and two outputs, synchronization unit 5, having an input and an output, interpolating filter 6, having a signal input, a synchronizing input and output, N filters 7.1-7.N having a signal input, a sync input and a vpsod. The signal input of the interpolating filter 6 is connected to the device input, the synchronizing input of the interpolator filter is connected to the output of the synchronization unit 5. Filters 7.1-7.N are connected in series, the signal input of the filter 7.1 is connected to the output of the interpolating filter 6, the output of the filter 7.N is connected to the first input control unit 4. The synchronization inputs of all filters 7.1-7.N are connected to the output of the synchronization unit 5. The inputs of the detectors 2.1-2N are connected to the inputs of the corresponding filters 7.1-7.N, the input of the detector 2.N + 1 - to the output of the filter 7.N . The outputs of all N + 1 detectors are connected to the corresponding inputs of logic unit 3. The output of logic unit 3 is connected to the third input of control unit 4. The second input of control unit 4 is connected to device input, the first output of control unit 4 is connected to input of synchronization unit, second output control unit 4 - with the output of the device. The device works as follows. Filters 7.1-7.N perform the digital convolution of the input signal 311 with impulse filter responses. Filters 7.1-7. are non-adaptive, suppressing the frequencies in a certain area around the tuning frequency corresponding to the minimum of the gain modulus. Filters can be implemented,. for example, on the basis of a digital delay line, which is a shift register, and a weighted sum block, which is a register and a multiplier. The interpolation filter changes the sampling rate of the signal under investigation x (t). Changing the sampling rate is done by interpolating (restoring) the samples of the signal under study. Let us consider the work of the interpolating filter. The sampled signal x (t) under investigation, which is obtained from the analog signal x, (), which has a frequency range, is fed to the input of the interpolating filter by pre-sampling at a frequency. : j.2fg). From the theory of digital signal processing, it is known that the spectrum of F., the sampled signal x (t) is periodic with a sampling frequency of d. Spectrum P; (and signal Xc, {fc) is shown in Figure 2a, spectrum F) (signal x () is shown in Figure 26). The interpolating filter is a low-pass filter and has an impulse response of Ni (tl sampled with a frequency f, a multiple of frequency d (the ratio D - an integer must be chosen, depending on the range of possible values of the first harmonic frequency of the signal x (i), the specified error of the device, and the width of the filter tuning frequency region 7), impulse response h (i} has rhcj, samples. Amplitude-frequency characteristic F, interpol The duster filter (Fig. 2b) has a flat top in the frequency band occupied by the signal x (t), whereby the signal x (t) passes through the interpolation filter without distorting the spectrum. Interpolating the signal x (t | reduces to performing the operation of convolving the signal x (t) and impulse response bc (-t) of the interpolating filter. The convolution is performed for sampling the signal x ({) and b ((- t) at the times, according to pt, where p.0,1, 2, ... -, t is the sampling period of the output signal x (t), which is the result of the interpolation of the signal x (t). The sampling frequency f (fj 1 / T) of the signal x () must be a multiple of the frequency .., i.e. the relationship should be. where 1 is an integer (1 f t). The spectrum of the fi signal x (i) is periodic with a frequency df in the frequency range f (-fg coincides with the spectrum of the analog signal xg (t) (figg), i.e. signal x (fc) is actually a sampling at the frequency f of the signal x (t). Consequently, the interpolating filter is able to reconstruct the sample under test at a sampling frequency f different from the original sampling frequency f. Setting and changing the frequency f for the operation of the interpolating filter is done by feeding the corresponding signals to its sync input. A matching filter can be built on the basis of a digital delay line and m blocks of weighted summation implemented using a register and a multiplier. -Analog quasi-periodic signal X (i) (FIG. 3A) having a frequency range. Pre-sampled by an analog-to-digital converter with sampling frequency A (D fg) is fed to the input of the device (Fig. 36), i.e., to the input of the interpolirting filter 6. The interpolating filter 6 interpolates (according to the synchronization signals received at its sync input from the synchronization unit 5) x (t) signal sstanavlivaet) counts with a frequency of d (fig.Zv). The spectra Fj of the signal x (-t) and Fj of the signal x (t) coincide in the frequency band f -. the investigated signal (fig.Zg). The X (-t) signal is filtered by series-connected 7.1-7N fencing filters, whose impulse responses are calculated for. the sampling frequencies, and the tuning frequencies are chosen in such a way that F. fulfills the relation where, 2, ..., N. The total amplitude-frequency characteristic of a chain of series-connected 7.1-7.N filters for the sampling frequency f is shown in FIG. The required sampling frequency d of the impulse responses of the filters was set by the synchronization unit 5 controlled by the control unit. The filtering is performed to perform the operation of convolving the input signal x () and the impulse response of the filters at times corresponding to nT, where n 0, 1, 2, ..., a. The control unit 4 takes the signal x (t) to the signal received at the output of the filter 7.N, and the output signal of the logic unit 3 arriving at its inputs using the synchronization unit 5 controls the change of the sampling rate fj of the interpolating filter and filters 7.1- 7.N, i.e. changing the frequency scale of the frequency response of filters. For some value of d i-a (i -1,2, ..., N) the harmonic of the signal x () falls into the frequency range of the 1st filter 7.IN. In this case, the frequency of the first harmonic f, the signal XU) (and, therefore, the frequency of the perCoR harmonic of the signal x (O) is equal to the frequency of the first filter. The fact of the i-th (, 2, ..., N) harmonics of the signal x (+ ) in the frequency range of tuning the 1st filter. is determined by logic block 3, based on the levels of detected signals x (t) and signals from filter outputs 7.1-7.N, which in this case should have a minimum, since the harmonics of the signal carrying its main energy is suppressed by the corresponding filters, (Fig. 3g and Ze). The found value of the frequency the first harmonic f of the signal x (i) in the form of a digital code is output to the second output of the control unit 4. Thus, the proposed device is faster than the known one by eliminating adaptive filters and more accurate operation. due to the use of non-adaptive filters with variable sampling frequency, the barrier bandwidth of which varies in proportion to the change in the frequency of tuning the filters.

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Claims (1)

(57-) DEVICE FOR MEASURING THE FREQUENCY OF THE FIRST HARMONIC OF QUASI-PERIODIC SIGNALS, containing N + 1 Detectors, a logic unit and a control unit, the first input of which is connected to the input (N + 1) -ro of the detector, the second to the input of the device, the third - with the output of the logical unit, the first output is the output of the device, and the outputs of the detectors are connected to the corresponding inputs of the logical unit, characterized in that, in order to improve accuracy and speed, an interpolating filter and N series-connected filters are inserted into it, synchronously whose inputs are connected to the second output of the control unit, and the signal inputs are connected to the inputs of the respective detectors, the signal input of the first filter is connected to the output of the interpolating filter ^ and the output of the Nth filter is connected to the first input of the control unit, the signal input of the interpolating filter is connected to the input of the device , and its synchronizing input is connected to the first input of the control unit.