JPH0648285B2 - Transfer characteristic analysis method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention uses a signal that exists only for a short time, such as an impulse or burst signal, and the frequency characteristic of the signal when propagating through an object to be measured, that is, The present invention relates to a transfer characteristic analysis method and apparatus for analyzing transfer characteristics while arbitrarily selecting a signal propagation mode.

(Prior Art) Conventionally, the frequency characteristic analysis when the signal propagates through an object to be measured by an impulse signal or a burst signal has been performed by the following method. That is, sine waves of different frequencies are sent in bursts to the DUT one after another, and this output signal is temporally selected to measure its level.
One sine wave was used to find one point on the frequency axis.

(Problems to be Solved by the Invention) However, such a conventional measurement method has a drawback that a long measurement time is required because sine waves for all frequency points to be analyzed must be given and measured. It was

The present invention aims to solve the above drawbacks,
The input signal input to the DUT and its output signal are stored in the wave memory respectively, and the input signal and the output signal of the necessary analysis region are read in synchronization with each other.
The purpose of the present invention is to provide a transfer characteristic analysis method and apparatus for performing a digital fast Fourier transform process on the read input / output signal to obtain each spectrum signal in the frequency domain and thereby obtaining the transfer function thereof. There is.

(Means for Solving the Problems) Therefore, the transfer characteristic analyzing method and the apparatus thereof according to the present invention are configured so that an input signal is sent to one end of the DUT and a part of the output signal obtained from the other end of the DUT. (A part of it in terms of time) is arbitrarily selected, and after the selected output signal and the input signal are made to correspond to each other, fast Fourier transform processing is performed,
The transfer relationship of the object to be measured is obtained from the result of the fast Fourier transform processing. Then, a signal generator for sending an input signal to the device under test, a first wave memory for A / D converting the input signal of the signal generator and storing the signal as it is or after delaying for a predetermined time, and in response to the input signal. A second wave memory for A / D converting and storing the output signal output from the device under test, and an A / D conversion of the input signal and its output signal input to the device under test. 1, a waveform writing control circuit to be stored in each of the second wave memories, an analysis waveform designating unit for designating an analysis target waveform of the output signal stored in the second wave memory, and the analysis waveform designating unit. The waveform erasing circuit for removing signal waveforms other than the analysis target waveform and the input signal stored in the first wave memory are read out as they are or after being delayed by an arbitrary time and stored in the second wave memory. And a waveform read control circuit for reading the output signal and an input signal read from the first wave memory and the second read signal output from the second wave memory by the waveform read control circuit. First and second Fourier transformers for Fourier transforming output signals respectively, and an arithmetic circuit for obtaining transfer characteristics from spectrum signals of input signals and output signals Fourier-transformed by the first and second Fourier transformers. And an input signal and an output signal stored in the first and second wave memories and a designation signal for designating an analysis target waveform of the output signal by the analysis waveform designating means, and displaying a transfer characteristic of the arithmetic circuit. A display device for displaying is provided.

An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment) FIG. 1 is a configuration of an embodiment of the present invention, FIG. 2 is a propagation explanatory view explaining a manner of propagation of an acoustic signal in an object to be measured, and FIG.
FIG. 4 is an explanatory diagram of input / output signals, and FIG. 4 is an output waveform diagram of each circuit.

In FIG. 1, 1 is a signal generator, 2 is a waveform write control circuit, 3 is a first A / D converter, 4 is a second A / D converter, 5 is a first wave memory, and 6 is a wave memory. Second wave memory, 7 is a waveform reading control circuit, 8 is a waveform erasing circuit, and 9 is a waveform erasing circuit.
Is a first Fourier transformer, 10 is a second Fourier transformer, 11 is an arithmetic circuit, 12 is a display device, 13 is an analysis waveform designating means, 14 is an input terminal, 15 is an output terminal, 16 is an object to be measured, Reference numeral 17 represents a transmitting transducer, and 18 represents a receiving transducer.

When a signal transmission signal is sent from the waveform writing control circuit 2 to the signal generator 1, the signal generator 1 outputs an impulse or burst random wave signal. Now, the DUT 1 is interposed between the input terminal 14 and the output terminal 15 via the transmission transducer 17 and the reception transducer 18.
6 is connected, there is a transmission wave a (t which is present only for a short time, such as an impulse or a burst random wave output from the signal generator 1 and whose signal component frequency is in a wide band. ) Is applied to the transmission transducer 17 via the input terminal 14, and is converted into, for example, an acoustic signal by the transmission transducer 17. This acoustic signal propagates from one end of the DUT 16 to the other end, is converted into an electric signal by the reception transducer 18, and the reception wave b
It is output to the output terminal 15 as (t). These two
The signal, that is, the transmission wave a (t) of the input signal input to the input terminal 14 and the reception wave b (t) of the output signal output to the output terminal 15 are provided corresponding to each other. , And is digitized by the second A / D converters 3 and 4, and stored as digital waveforms in the first and second wave memories 5 and 6, respectively.

FIG. 2 is a propagation explanatory diagram for explaining a method of propagating an acoustic signal in the DUT. The transmission wave converted into the acoustic signal by the transmission transducer 17 has a propagation velocity in the DUT 16. The fast longitudinal wave P and the transverse wave S having a slow propagation speed propagate, and these acoustic signals arrive at the receiving transducer 18 at different times. Since the receiving transducer 18 converts these two waves of the longitudinal wave P and the transverse wave S into electric signals and outputs the electric signals, the transmitting wave a (t) from the receiving transducer 18 as shown in FIG. The received wave b (t) having the P and S response waveforms generated based on In the received wave b (t), the waveform N shown at the position corresponding to the transmitted wave is noise.

The input signal and the received wave b of the transmitted wave a (t) shown in FIG.
As described above, the output signal (t) is digitized and stored in the first and second wave memories 5 and 6, respectively.

The input signal and the output signal thus stored in the first and second wave memories 5 and 6 are read by the waveform read control circuit 7 and displayed on the display device 12 as shown in FIG.

The analysis waveform designating unit 13 designates the analysis target waveform of the input / output signal displayed on the display device 12. The analysis waveform designating key group provided in the analysis waveform designating unit 13 causes the analysis waveform designating unit 13 to start the analysis target waveform. The address and the final address are specified. In the designation of the waveform to be analyzed, cursor lines and markers indicating the tip and the end of the waveform to be designated are displayed on the display device 12, so that the waveform to be analyzed is indicated by these cursor lines and markers. Can be specified. FIG. 3 shows an example in which designation of a waveform to be analyzed is displayed by a dotted line.

The start address A _S and the end address A _L of the analysis target waveform of the longitudinal wave P designated by the analysis waveform designation means 13 are sent to the waveform read control circuit 7 and the waveform erasing circuit 8. The waveform erasing circuit 8 passes the waveform data of the longitudinal wave P read from the second wave memory 6 as it is between the start address and the end address sent from the analysis waveform designating means 13, and the start address is passed. All the data of the address before and the data after the last address are set to, for example, "0" to remove the waveform data. Therefore, the analysis waveform designating means 1
Only the waveform to be analyzed of the longitudinal wave P designated by 3 is output from the waveform erasing circuit 8, and the noise N and the transverse wave S are all removed.

On the other hand, the waveform read control circuit 7 sequentially reads the received wave b (t) of the output signal from the second wave memory 6. The second
The read address for accessing the wave memory 6 of
Start address A designated by the analysis waveform designating means 13
When it becomes equal to _S , the reading of the transmission wave a (t) of the input signal stored in the first wave memory 5 is started. That is, the input signal is delayed and read. After that, the transmitted wave b (t) of each input signal and the received wave a (t) of the output signal are sequentially read out in synchronization with both the first and second wave memories 5 and 6, and the first wave provided in each of them is read. The read waveform data is input to the second Fourier transformers 9 and 10.

The first Fourier transformer 9 performs fast Fourier transform processing on the input signal having the waveform shown in FIG.
Complex spectrum as shown in Fig. Is output. Further, in the second Fourier transformer 10, the output signal of the waveform to be analyzed shown in FIG. 4 (e) is subjected to the fast Fourier transform processing to obtain the complex spectrum shown in FIG. 4 (g). Is output.

Then, based on these complex spectra, the arithmetic circuit 11
Is Is calculated for each frequency and the transfer function is calculated as shown in Fig. 4 (H). Is output.

In FIG. 4, (a) is the waveform of the transmission wave a (t) of the input signal stored in the first wave memory 5,
FIG. 6B shows the waveform of the transmission wave of the input signal read from the first wave memory 5 after being delayed for a certain period. FIG. 7C shows the waveform of the received wave b (t) of the output signal stored in the second wave memory 6, and the output signal output from the waveform erasing circuit 8 of FIG. The waveforms of the transverse wave S and the noise N other than the longitudinal wave P that is the target waveform are removed, and only the longitudinal wave P of the analysis target waveform is input to the second Fourier transformer 6.

Further, it is apparent that the correspondence between the input signal of FIG. 4D and the output signal of FIG. 5E can be easily made because the head address can be arbitrarily changed by the analysis waveform designating means 13. .

In the above description, the longitudinal wave P of the received wave b (t) has been described, but it is needless to say that if the transverse wave S is designated by the analysis waveform designating means 13, the transfer function of the transverse wave S can be obtained in the same manner. Yes.

Further, when the transmission wave a (t) of the input signal transmitted from the signal generator 1 is stored in the first wave memory 5, it is delayed for a certain period of time to synchronize with the reception wave b (t) of the output signal. With this configuration, when the waveform data is read from the second wave memory 5 as described above, there is no need to delay and read the waveform data.

The transmission wave a (t) of the input signal from the signal generator 14
Has a stable level and frequency distribution, and its distribution Is known, the A / D converter 3, the first wave memory 5, the first Fourier transformer 9 and the like are unnecessary.

(Effects of the Invention) As described above, according to the present invention, it is possible to arbitrarily select the signal propagation mode and measure the transfer function of the DUT in a short time. The transfer characteristic to be obtained includes a complex number component, and the frequency characteristic regarding the phase can also be obtained at the same time.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a propagation explanatory diagram for explaining a method of propagating an acoustic signal in a DUT, and FIG.
FIG. 4 is an explanatory diagram of input / output signals, and FIG. 4 is an output waveform diagram of each circuit. In the figure, 1 is a signal generator, 2 is a waveform writing control circuit, 3
Is a first A / D converter, 4 is a second converter, 5 is a first wave memory, 6 is a second wave memory, 7 is a waveform read control circuit, 8 is a waveform erasing circuit, and 9 is a 1 Fourier transformer, 10 second Fourier transformer, 11 arithmetic circuit, 12 display device, 13 analysis waveform designating means, 14 input terminal, 15 output terminal, 16 object to be measured, 17 A transmitting transducer, 18 is a receiving transducer.

Claims (2)

[Claims] 1. An input signal is sent to one end of a DUT, an output signal obtained from the other end of the DUT is arbitrarily selected, and the selected output signal and the input signal are associated with each other. A transfer characteristic analysis method characterized in that a fast Fourier transform (FET) process is performed on each of the above, and the transfer function of the DUT is obtained from the spectrum signal after this fast Fourier transform process. 2. A signal generator for sending an input signal to a device under test, and a first for A / D converting and storing the input signal of the signal generator.
Wave memory, a second wave memory that responds to the input signal, stores the output signal output from the device under test by A / D conversion, and the input signal input to the device under test and its output Signal
Waveform writing control circuit for A / D conversion and storing in the first and second wave memories, and analysis waveform designation for designating an analysis target waveform of the output signal stored in the second wave memory Means, a waveform erasing circuit for removing a signal waveform other than the analysis target waveform designated by the analysis waveform designating means, and reading the input signal stored in the first wave memory and storing the input signal in the second wave memory. And a waveform read control circuit for reading the output signal, and an input signal read from the first wave memory and the second read signal output from the second wave memory by the waveform read control circuit. First and second Fourier transformers for respectively fast Fourier transforming output signals, and inputs Fourier-transformed by the first and second Fourier transformers Circuit for obtaining the transfer characteristic from the spectrum signal of the signal and the output signal, the input signal and the output signal stored in the first and second wave memories, and the analysis target waveform of the output signal by the analysis waveform designating means. A transfer characteristic analysis device, comprising: a display device that displays a designated code to be designated and that displays the transfer characteristic of the arithmetic circuit.