JPS6083643A - Ultrasonic flow meter doppler sound generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] +al Technical Field of the Invention The present invention relates to an ultrasonic current meter Doppler sound generator, which converts the frequency of a Doppler signal and outputs it. A sonic Doppler blood flow meter measures the state of blood flow by irradiating the blood flow inside the subject with ultrasonic waves as measurement waves and detecting the frequency difference between the reflected waves from blood cells and the above measurement waves. It is something. By converting the signal representing the frequency difference between the detected reflected wave and the measurement wave into an acoustic output, the measurement person can detect the blood flow of the subject by hearing without looking at the display, and can operate the ultrasonic Doppler blood flow meter. becomes easier.

However, in recent years, there has been a demand for detection of blood flow conditions not only in the heart and aorta and veins, but also in small blood vessels. It is necessary to increase the frequency of

Specifically, a frequency of 5 to 40 M11z is used.

However, by increasing the frequency of the measurement wave, the frequency displacement (Doppler signal frequency) between the measurement wave and the reflected wave also increases, and the Doppler signal frequency may exceed the audible frequency.

Therefore, it is necessary for the acoustic output signal to be in an audible range that can be heard by the measurer, not to be harsh on the ears, and to be able to hear changes in the output sound.

tel Prior Art and Problems Conventionally, a frequency conversion means shown in FIG. 1 has been used as a method of converting a Doppler signal into an acoustic signal. In FIG. 1, 1. Oa and 10b are delay circuits having a function similar to a FIFO buffer that sequentially outputs input data after temporarily storing it; 11 is an analog data selector; 12a
, 12b is a digital data selector.

13a, 13b, and 13c are digital signals (clocks) whose frequencies are fl, f2, and f3, respectively.
It is an oscillator that generates

For details of this frequency conversion means, please refer to the Japanese Patent Application No. 56-13
5190, so a detailed explanation will be omitted, but the contents disclosed here can be summarized as follows.

That is, the frequency of the oscillator (clock) is fl>f2
(For example, f2-!4fl) T:Ara 7 and f3 are clocks for switching between writing and reading for the delay circuits 10a and 1Obl, and control the analog data selector 11 to control the delay circuit 10a.
, 10b are alternately switched to send the output of the delay circuit to the next analog amplifier (not shown).

In this frequency conversion means, the Doppler signal is sampled at the clock timing of fl, and the output is sent to the two delay circuits 10a and 10b, fl and 10b, respectively.
At the clock timing of f2, the delay circuit 10a accumulates for a half cycle of the clock timing of f3, and when the delay circuit 10a accumulated at the clock timing of fl becomes full, the contents of the delay circuit 10a are transferred to the clock of f2 in the next half cycle. Control the analog data selector 11 according to the timing,
Output. Specifically, sampling data A stored in the delay circuit 10a is output.

Then, while the output signal of the delay circuit 10a is being outputted, the delay circuit 1i 1810b is controlled to switch its operation so as to sample and accumulate the Doppler signal at the clock timing of fl. Ru.

Thereafter, the same operation is repeated to control the Doppler signal taken in at the clock timing fl to be output through the analog data selector 11 at the clock timing r2.

Therefore, by setting fl and f2 in advance, desired frequency conversion can be performed. Then, by making the output signal read by f2 an audible frequency, Doppler signal 4 is always in the audible frequency range! Sound can be output using the gate signal.

At this time, the clock f3 for switching the outputs of the delay circuits 10a and 10b is designed such that the switching noise generated by the switching operation is not jarring, and the response time for reading and outputting the Doppler signal is not too slow. Range 7, low frequency i (eg 3011z) is selected.

: But 4, d1. ．． ) Ukirakata e-oi 7. As is clear from the figure, the crystal path is complex: in addition to the switching noise mentioned above, there is also a phase shift at the time of switching (always the same phase T:
(This noise does not necessarily change from time to time)
Since this is not so-called harmonic noise, there is a problem in that frequency dispersion occurs as a result.

(d+ Purpose of the Invention In view of the above-mentioned drawbacks of the prior art, the present invention provides a method for producing clear Doppler sound using a simple circuit and without the noise (i.e., three-frequency dispersion) caused by the phase shift during switching that occurs in the conventional method. The purpose of this invention is to provide a frequency conversion circuit that can perform the following steps.

(According to the present invention, a measurement wave which is an ultrasonic wave of a constant frequency is irradiated onto a medium, a reflected wave from the medium is received, and the measurement wave and the reflected wave are combined. frequency scaling detection means for detecting a frequency displacement of and outputting a frequency displacement signal corresponding to the detected frequency displacement; and acoustic signal output means for converting the frequency displacement signal into an acoustic signal and corresponding to the movement of the medium. In the Doppler sound generation section of the ultrasonic anemometer, the ultrasonic anemometer is equipped with a frequency conversion means for converting the frequency displacement signal into a signal within an audible frequency range,
This is achieved by providing a circuit that separates the frequency component and amplitude component of the Doppler sound, reduces the separated frequency, and then resynthesizes the two, making it possible for humans to hear the Doppler signal that has been subjected to Doppler analysis. There is an advantage that Doppler sound with almost no time delay and single frequency dispersion can be heard in the audible frequency band.

(fl Embodiments of the Invention First, to summarize the gist of the present invention, the present invention separates the output of a Doppler detection circuit (i.e., Doppler signal) into a frequency component and an amplitude component, and divides the frequency component by means such as frequency division. In this method, the desired Doppler sound is obtained by reducing the amount of the Doppler sound by applying a filter, then performing resynthesis, and applying a filter after digital/analog conversion.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 shows digital signal waveforms at various parts in FIG. 2 when the frequency of the sampled Doppler signal is x. This is a diagram.

In the drawing, 21 is an absolute value circuit (ABS), and specifically, an absolute value is obtained by performing an exclusive OR operation between code bin 1- and each data. However, when the sign is negative, 1's complement is taken, and the sampled Doppler signal value becomes a value smaller by 1, but there is no real problem. A frequency converter (f, conv) 22 divides the frequency of the code bit. 23 is a multiplier (m
ul t), specifically the absolute value circuit (ABS) 21
The multiplication result is obtained by taking the exclusive OR of the output of the frequency converter (f, conv) 22 (sign focus). In this case as well, if the sign bit is negative, the sampled Doppler signal value will be smaller by 1, but there is no practical problem. 24 is a low pass filter (L
PF).

Hereinafter, the present invention will be described in detail with reference to FIG. 2 with reference to FIG.

Now, the sampled Doppler signal IN is separated into two parts, the sign bit and the data, one of which is the absolute value circuit (AB
S ) 21, the absolute value is taken and the multiplier (mu
lt) is input to 23. (This is the BS output in FIG. 3.) The other sign bit is converted into an A-period digital signal by a frequency dividing circuit such as a binary counter, and is input to a multiplier (mult) 23. (This is the f, conv output in Figure 3) Multiplier (mult
) 23, the output of the absolute value circuit (AllS) 21 and the output of the frequency converter (f, conv) 22 are subjected to the above-mentioned "multiplication with changing the sign", and as shown in FIG. The mult output shown will be obtained.

Low bass filter (LPF) for fffmult output
By performing waveform shaping through 24, a desired Doppler audio output can be obtained.

Actually, in order to output Doppler sound, it is necessary to perform digital/analog conversion, but this can be placed before the low-pass filter ([, PF) 24.

(gl Effects of the Invention As explained in detail above, the ultrasonic velocity needle Doppler sound generator of the present invention separates the sampled Doppler signal into code bits and data, and the data is transmitted through the absolute value circuit (ABS).
) is converted into absolute value data, and the sign bit is divided into, for example, A by a frequency converter (f, conv), and the respective output signals are combined by a multiplier (multiplying by ±1) and the frequency is divided. After obtaining the Doppler signal, it is configured to perform digital/analog conversion and pass through a low-pass filter (LPF) to obtain Doppler sound in the audible band. mult) is an exclusive OR circuit 1 frequency converter (f, conv)
can be realized with a small amount of hardware such as one or multiple flip-flops, and can eliminate the time delay and three-frequency dispersion that occurs in conventional methods, making the product more economical and highly reliable in medical diagnosis. This has the effect of increasing the

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional Doppler signal frequency conversion method, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is a block diagram showing a Doppler signal frequency conversion method of 2. FIG. 3 is a diagram showing signal waveforms at each part in FIG. 2 in the case of the following. In the drawing, loa, 10b are delay circuits, 11 is an analog data selector, 12a, 12h is a digital data selector, 13a, 13b, 1
3c is an oscillator, 21 is an absolute value circuit (ABS), 2
2 is a frequency converter (f, conv), 23 is a multiplier (+nult), 24 is a low bass filter (LP
F) and IN indicate the sampled Doppler signal, respectively. 1 1st 2

Claims (1)

[Claims] A measurement wave, which is an ultrasonic wave with a constant frequency, is irradiated onto a medium, a reflected wave from the medium is received, a frequency displacement between the measurement wave and the reflected wave is detected, and a frequency corresponding to the detected frequency displacement is determined. An ultrasonic flow velocity needle comprising a frequency displacement detection means for outputting a displacement signal, and an acoustic signal output means for converting the frequency displacement signal into an acoustic signal and corresponding to the movement of the medium, the ultrasonic flow velocity needle having a frequency displacement signal as described in 2. In the Doppler sound generating section of the ultrasonic anemometer, which is equipped with a frequency conversion means for converting the Doppler signal into a signal in the audible frequency range, the frequency component and the amplitude component of the Doppler signal are separated, the separated frequency is reduced, and then both are separated. An ultrasonic flow velocity needle Doppler sound generating device characterized by having a circuit for resynthesizing.