JPH04109940A - Ultrasonic wave diagnostic device - Google Patents

Abstract

PURPOSE:To reduce radiation waves or noise by taking higher harmonic wave components from basic clocks of Doppler reference waves, shaping their waveform, dividing them, and connecting an obtained high speed basic clock generation circuit with a switched capacitor filter. CONSTITUTION:Cos, and sin. are Doppler reference waves and have a similar frequency to a transmission frequency, and LPF 18 is composed of a switched capacitor filter. When square waves of 2.5MHz are transmitted for the Doppler reference waves from a basic clock generator of an ultrasonic device, a zone filter 20 to 7.5MHz is inserted to the square waves of 2.5MHz, so clocks of 7.5MHz as the higher harmonic wave components of 2.5MHz are taken. By dividing them by a dividing circuit 24, clocks fi can be given to the capacitor filter 18. As a result, noise of a Doppler spectrum can be reduced, and need of running high speed clocks to a signal line such as a mother board can be eliminated, thereby noise such as radiation waves can be reduced.

Description

[Detailed description of the invention] (b) Industrial application field INDUSTRIAL APPLICATION This invention is utilized in the field of an ultrasonic diagnostic device.

The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus equipped with a Doppler signal detection circuit for analyzing blood flow velocity, and particularly relates to improvements in the detection circuit.

(b) In an ultrasonic diagnostic apparatus or an ultrasonic Doppler apparatus equipped with a conventional Doppler signal detection circuit, as illustrated in FIG. A filter (HPF) 16 and a low-pass filter (LPF) 18 having a cutoff frequency of 1/2 of the sampling period Fs are required, and these require steep characteristics.

However, when an active filter is used, the number of stages increases, the circuit becomes complicated, and the cutoff frequency of the filter is generally variable, so recently, swissotide capacitors have been increasingly used. .

(c) Problems to be Solved by the Invention However, this type of filter requires a clock, and the cutoff frequency of the filter is changed by inputting a clock that is 50 to 100 times the cutoff frequency.

When a clock generator is added to control this filter, if it is asynchronous with the Doppler pulse rate, the newly added clock generator becomes a noise source.

On the other hand, when dividing the frequency of the Doppler reference wave itself to use as a clock for a capacitor filter, the clock may not be divided by an integer, and in such a case, a higher frequency than the Doppler reference wave is required.

An object of the present invention is to generate high-speed locking necessary for the filter using a basic clock of a Doppler reference wave in an ultrasonic diagnostic apparatus that uses a switched capacitor filter as a low-pass filter constituting a Doppler signal detection circuit. An object of the present invention is to provide an ultrasonic diagnostic apparatus in which radiated radio waves or noise on a circuit are reduced.

(d) Means for solving the problem The above purpose is to solve the basics of Doppler reference waves that are mixed with echo signals in ultrasonic diagnostic equipment equipped with a Doppler signal detection circuit using a switched capacitor filter as a low-pass filter. This is achieved by extracting harmonic components from the clock through a bandpass filter, shaping the waveform, and connecting a circuit for generating a faster basic clock obtained by frequency division to a switched capacitor filter.

(E) Effect Obtain a higher frequency clock than a lower frequency clock. By obtaining a clock higher than the Doppler reference wave and further dividing it, clocks with various frequencies can be created.

(f) Embodiment A preferred embodiment of the present invention will be explained based on FIG.

Note that FIG. 2 shows a Doppler signal detection circuit using the above-mentioned general quadrature phase method. In this Figure 2,
Cos and sin are Doppler reference waves, which have a frequency equal to the oscillation frequency, and are turned into mutually orthogonal phase signals by the phase shifter 12. 10 is a mixer, 14 is a sample gate, 16 is a bypass filter (HPF)
, 1B is a low-pass filter (LPH), and the Doppler signal has a real part and an imaginary part.
ry) and are output separately.

Here, the LPF 18 is configured with a switched capacitor filter. The Doppler reference wave is 2.5 MHz, and the cutoff frequency fc of the capacitor filter 18 is 60Xfc=fi with the clock fi that operates the capacitor filter. is 8KHz, 12.5KHz, 25KH
If you need z and 3 types, it will be as follows: fc fi 8.33KHz 500KHz12.50KH
z 750KHz 25.0KHz 1
500 KHz In this way, a frequency that cannot be divided by this reference wave (2.5 MHz) is required for the cutoff frequency fc.

An appropriate cut-off frequency fc is required depending on the blood flow speed, and a high-speed clock fi is required due to the above relationship, but the frequency at which fc is 8.33 KHz cannot be obtained by frequency division on the upper side, making it difficult to use. limited.

Therefore, the embodiment shown in FIG. 1 is applied.

It is assumed that the same Doppler reference wave is a 2.5 MHz square wave and is sent from a basic clock generator of an ultrasound device (not shown).

For this 2.5MHz square wave, if you insert a bandpass filter (BPF) 20 of 7.5M) (2.5MHz), it becomes 2.5MHz.
A clock of 7.5 MHz, which is a harmonic component of z, can be extracted.

Furthermore, if the frequency is divided by the frequency dividing circuit 24, the clock fi
can be applied to the capacitor filter 18.

In the example shown in Fig. 2, when a 2.5 MHz square wave is used as the Doppler reference wave, 7.5 MHz with BPF 20 is used.
After creating the z signal, the comparator 22 shapes the waveform to make it a TTL level signal, and the digital frequency divider circuit
4, the clock for the capacitor filter 18 is created.

(g) Effects According to the present invention, Doppler spectrum noise is reduced, and since there is no need to run a high-speed clock on a signal line of a motherboard or the like, noise such as radiated radio waves is reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a general Doppler signal detection circuit diagram. 10 is a mixer, 18 is a lonipass filter (LPF), 2
0 is a bandpass filter (BPF), 22 is a waveform shaper,
24 is a frequency dividing circuit. Patent applicant Shimadzu Corporation Representative Patent attorney Ike 1) Sadao

Claims (1)

[Claims] 1. In an ultrasound diagnostic equipment equipped with a Doppler signal detection circuit using a switched capacitor filter as a low-pass filter, harmonic components are extracted from the basic clock of the Doppler reference wave that is mixed with the echo signal via a bandpass filter. , an ultrasonic diagnostic apparatus characterized in that a circuit for generating a faster basic clock obtained by waveform shaping and frequency division is connected to a switched capacitor filter.