JPH01101015A - Delaying circuit for ultrasonic wave diagnosing device - Google Patents

Abstract

PURPOSE:To successively obtain a necessary delaying time with a high accuracy by providing an amplifier having two inputs of an inversion and a non-inversion, three resistors and a capacity variable capacitor, and controlling the capacity variable capacitor with a control voltage which a delay control means outputs. CONSTITUTION:In a ROM 3a, optimum delaying time data decided by a distance, at which an echo signal is reflected, and the central frequency information of an ultrasonic wave and stored. Stored delay data are made into the data in which the voltage-to-capacity of the variable capacity diode and the capacity- to-delaying-time which a circuit has are calibrated. They are converted to a voltage Vc by a D/A converter 3b, a quantization noise is removed by a low- pass filter 3c, they are converted to +Vc and -Vc, thereafter, a capacity variable diode Cd is controlled, an inputted echo signal Ve is delayed, and a Ved is outputted. Thus, since a constitution is made into the basic constitution to use one amplifier (operational amplifier), a successive variable delaying circuit can be inexpensively formed in which the constitution is simple, accuracy is good, and a dynamic range is wide.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ultrasonic diagnostic apparatus that transmits and receives ultrasonic waves into a living body using a plurality of electroacoustic transducers to obtain biological information. The present invention relates to a delay circuit for an ultrasonic diagnostic apparatus for focusing and deflecting signals.

A conventional ultrasonic diagnostic apparatus transmits an ultrasonic beam into a living body, receives echo signals from a reflector on the beam, and obtains a tomographic image while scanning.

In order to improve the image quality of this tomographic image, it is common to perform focus processing on both transmission and reception. In play-type transducers with multiple elements, the necessary delay time is given to each element so that the ultrasonic pulses transmitted from each element reach the target point at the same time.
Similarly, for reception, a delay time is given to the echo signals obtained by each element so that they arrive at the addition point C2 at the same time. - In addition to using an LC delay line, there is also a digital delay method in which the echo signal is digitized as means for performing the delay. In addition, in order to obtain better image quality, dynamic focusing is required, which changes the focus distance according to the distance at which the echo signal is obtained.
The above two methods have problems such as generation of delay time switching noise and difficulty in control. Therefore, a method has been proposed that uses resistors and varicap diodes to continuously vary the focus distance using voltage control.

FIG. 3 shows a conventional voltage-controlled continuously variable delay line. In the figure, 101 is an inverting circuit that outputs the input echo signal Ve in opposite phase, and 102 is a non-inverting circuit that outputs the input echo signal in the same phase. The gains are the same.

Further, R is a resistance, Cd is a varicap diode whose capacitance is variable depending on the control voltage applied to the control terminal 1, and CC is a coupling capacitor (Cc)Cd, and the value of CC is negligible compared to Cd. The above delay circuit forms a generally called phase shift circuit, and the inverting circuit 101
When the gains of the non-inverting circuit 102 and the non-inverting circuit 102 are both 1, the transfer characteristic is expressed by the following equation.

Ved/Ve = −(R-j/ωQI)/(R
+j /ωcd)・・・・・・・・・ (1) The size of equation (1) is l Ved /Ve l = 1 −
(2) Phase angle ψ is tp=-Ztan-' (ωcd-R) ---
(3) From the above equations (2) and (3), the delay circuit shown in FIG. 3 has a constant gain regardless of the frequency, and can only change the phase.

The conventional configuration as described above is disclosed in Japanese Patent Application Laid-Open No. 62-137043.
It is stated in the No.

Problems to be Solved by the Invention However, in the above configuration, the above equations (1) and (
In order to satisfy the conditions 2) and (3), the inverting circuit 101 and the non-inverting circuit 102 need to have extremely low output impedance, and have small delay time differences and gain differences between them. This is difficult to achieve. If you want to obtain a large delay time, capacitor C
If the capacitance of d is increased, the inverting circuit 101 and
Since the load impedance of the non-inverting circuit 102 decreases, when the signal amplitude is large, the small output impedance of both causes distortion of the output waveform, amplitude difference, delay time difference, etc., and accurate delay cannot be obtained.

The present invention solves the above conventional problems, and includes an inverting circuit,
Without using a non-inverting circuit, a simple configuration consisting of one operational amplifier, two fixed resistors, a fixed resistor for delay, and a variable capacitance diode achieves high delay accuracy regardless of the capacitance value of the variable capacitance diode. A stable amplitude can be obtained,
It is an object of the present invention to provide a delay circuit for an ultrasonic diagnostic apparatus that can reduce costs.

Means for solving the problems The technical means of the present invention for solving the above problems are as follows:
an amplifier having two inputs, inverting and non-inverting; a first resistor provided between the output of the amplifier and the inverting input; and a second resistor provided between the inverting input and the echo signal input terminal; , a third resistor divided into two parts C between the echo signal input terminal and the non-inverting input terminal, and a variable capacitance capacitor with one end grounded between the non-inverting input and the third resistor. The capacitor includes a delay control means for electrically controlling the capacitance value of the variable capacitance capacitor and setting a delay time.

For production The present invention has the following effects due to the above configuration.

That is, by controlling the variable capacitance capacitor with the control voltage output by the delay control means, the necessary delay time can be obtained continuously and accurately.

Moreover, the configuration can be simplified.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows the most basic circuit configuration of the delay circuit of the present invention. In the figure, 1 is an amplifier having an inverting input and a non-inverting input, and is generally called an operational amplifier. R1 and R2 are resistors Rr == R2
``C''.R is a resistor determined together with the delay time Cd, and Cd is a variable capacitor whose capacitance can be changed electrically.In the circuit configured above, the transfer characteristic is as described in (1) above.
, (2), and 13). In addition, the conventional configuration shown in FIG. 3 has an inverting circuit 101 and a non-inverting circuit 1.
2Ve for the amplitude of the input signal Ve between the outputs of 02
Since an output signal of 1 is generated, a large load current flows through R and Cd, which serve as loads. In comparison, in the embodiment shown in FIG. 1, the current flowing through the capacitor and Cd is due to Ve and is half of that of the conventional configuration, so that the burden on the output of the circuit at the previous stage can be reduced. Further, even if a signal with a larger amplitude is input and the output waveform of the previous stage is distorted, the delay time is not affected.

FIG. 2 is a circuit configuration diagram of an embodiment in which delay time control is performed by applying the basic configuration of the delay circuit shown in FIG. 1.

In the figure, 1 is an amplifier with an inverting input and a non-inverting input, R1 and R2 are resistors, R is a resistor determined together with the delay time Cd, and Cd is a variable capacitance capacitor consisting of a varicap diode in a bridge configuration. , Cc are coupling capacitors, and Cd < CC.
2 is an equilibrium amplifier, which has two control voltages +Vc with different polarities.
.

-Vc is output. 3 is a delay control circuit, which includes a ROM that outputs appropriate data based on depth information, the center frequency of the received signal, etc., a D/A converter 3b that converts the data output from the ROM 3a into a control voltage, and a D/A converter 3b that converts the data output from the ROM 3a into a control voltage. /A
It is composed of a low-pass filter 3C that removes quantization noise contained in the control signal output from the converter 3b. In the same figure, optimal delay time data determined by the distance at which the echo signal is reflected and information about the center frequency of the ultrasonic wave is stored in ROMaa. In addition, the stored delay data has been calibrated for the voltage vs. capacitance of the variable capacitance diode and the capacitance vs. delay time of the circuit, which is converted into voltage Vc by the D/A converter 3b, and then passed through the low-pass filter. After removing quantization noise with 3C and converting it into +Vc and -Vc with a balance amplifier 2, the variable capacitance diode Cd is controlled to delay the input echo signal Ve and output Ved.

Here, Cd is a bridge circuit constituted by four varicap diodes, and the capacitance is controlled by applying a reverse voltage to the varicap diodes using the control voltages +Vc and -Vc output from the balance amplifier 2. This is to prevent the control voltage from entering the delay circuit. Vc is changed according to the receiving distance, and the delay time becomes shorter as the distance increases, so Vc changes as time elapses from the transmission time.
It is necessary to make the disc thicker and gradually reduce the capacity of the CD.

It should be noted that although the amplifier 1 must have a very high band, it has recently been supplied as an IC at a low price, and this does not pose a problem in implementing the present invention.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention has a basic configuration using one amplifier (op-amp), so that a continuously variable delay circuit with a simple configuration, high precision, and a wide dynamic range can be provided at low cost. I think it's possible.

[Brief explanation of the drawing]

FIG. 1 is the most basic circuit configuration diagram of a delay circuit for an ultrasonic diagnostic apparatus according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an applied example of the delay circuit shown in FIG. 1. , 3rd
The figure is a circuit configuration diagram of a conventional delay circuit. DESCRIPTION OF SYMBOLS 1... Amplifier, 2... Balance amplifier, 3... Delay control circuit, 3a... Storage means, 3b... D/A converter, 3C... Low pass filter, 101... Inverting circuit , 1o2...non-inverting circuit. Name of agent: Patent attorney Toshio Nakao (1st person, 2nd person)
figure

Claims (4)

[Claims] (1) an amplifier having an inverting input and a non-inverting input; a first resistor provided between the output of the amplifier and the inverting input;
a second resistor provided between the inverting input and the echo signal input terminal; a third resistor provided between the input terminal and the non-inverting input of the amplifier; and a connection between the non-inverting input and ground. It has a basic element consisting of at least a variable capacitance capacitor provided between the basic elements, the basic elements are connected in cascade in one or more stages, and the capacitor of the basic element is electrically controlled to set a delay time. 1. A delay circuit for an ultrasonic diagnostic apparatus, comprising a delay control means for controlling the delay. (2) The delay circuit for an ultrasonic diagnostic apparatus according to claim 1, wherein the amplifier is an operational amplifier using an IC. (3) The delay circuit for an ultrasonic diagnostic apparatus according to claim 1, wherein the capacitor is constructed of a bridge circuit including four varicap diodes. (4) The delay control means includes a storage means that stores a control value for controlling the delay circuit based on at least one of the echo signal reflection distance, ultrasonic frequency, and scanning line information; D converts the control value to be output into an analog value
A delay circuit for an ultrasonic diagnostic apparatus according to claim 1, characterized in that the delay circuit is comprised of a /A converter and a low-pass filter that removes quantization noise contained in analog control values from the D/A converter. .