JP3822832B2 - Transmission circuit of ultrasonic diagnostic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmission circuit of an ultrasonic diagnostic apparatus, and more particularly to generation of a transmission drive signal.
[0002]
[Prior art]
In a conventional ultrasonic diagnostic apparatus, a transmitter is provided for each vibration element (channel). A transmission circuit is constituted by the plurality of transmitters. FIG. 3 shows the configuration of a conventional transmitter. Each transmitter includes a digital waveform generator 12, a D / A converter 14, and a linear amplifier 16. The transmission drive signal output from the linear amplifier is output to the vibration element 18. Thereby, an ultrasonic wave is transmitted from the vibration element 18. The signal 100 is a transmission timing signal, and the signal 102 is an amplitude control signal.
[0003]
Conventionally, for example, in order to perform amplitude weighting for each vibration element 18, the amplitude in the digital signal is adjusted at the stage of digital waveform generation, that is, inside the digital waveform generator 12.
[0004]
[Problems to be solved by the invention]
However, according to the above-described conventional configuration, the amplitude is reduced on the input side of the D / A converter 14. Therefore, on the output side of the D / A converter 14, the quantum per bit in comparison with the entire signal waveform The ratio of the conversion error increases relatively. That is, in the case of a large amplitude, the quantization error that can be virtually ignored becomes significant when the amplitude is small. In the case of harmonic imaging, chirp wave transmission, etc., it is necessary to supply the specified waveform (Gaussian waveform, frequency modulation wave, etc.) as faithfully as possible to the vibrating element, but the relative increase in the quantization error described above Will have the opposite result. That is, problems such as image quality degradation and SNR degradation occur.
[0005]
The present invention has been made in view of the above conventional problems, and an object thereof is to reduce a quantization error even in the case of a small amplitude.
[0006]
Another object of the present invention is to make it possible to reproduce an original waveform as faithfully as possible and supply it to a vibration element even in amplitude control.
[0007]
[Means for Solving the Problems]
(1) To achieve the above object, the present invention provides a waveform generator that outputs a digital transmission waveform signal, and a D / A that converts the digital transmission waveform signal output from the waveform generator into an analog transmission waveform signal. A converter, an attenuation circuit for suppressing the amplitude of the analog transmission waveform signal output from the D / A converter, and an analog transmission waveform signal after the amplitude suppression output from the attenuation circuit is amplified and transmitted. It is seen containing an amplifier for outputting a signal to the ultrasonic transducer, wherein the attenuation circuit includes a plurality of attenuating transistor amplitude suppression effect was different emitter grounded each other, on the emitter side of each of the plurality of attenuating transistor A plurality of selection transistors connected to each other in parallel, by selectively turning on the plurality of selection transistors. It continued to said plurality of attenuating transistor selectively operated, thereby, amplitude suppression effect is variably controlled, characterized in that.
[0008]
According to the above configuration, the digital signal waveform signal representing the original waveform is converted into an analog transmission signal waveform, and the analog transmission signal waveform is subjected to suppression processing or attenuation processing by the analog circuit. Compared to the case where the amplitude is directly controlled, the quantization error can be made relatively small with respect to the amplitude of the entire signal. Here, amplitude suppression may be performed in an analog manner using only the attenuation circuit, or may be combined with digital amplitude suppression. Even in the latter case, the above relative quantization error can be improved.
[0009]
The amplifier is desirably a linear amplifier, and the gain thereof may be constant or variable. In the latter case, since the circuit scale increases, the former is more advantageous in terms of circuit configuration. However, in the latter case, for example, the gain common to all channels can be collectively adjusted by each linear amplifier, and the weighting of the amplitude between the channels can be individually adjusted by an attenuation circuit.
[0010]
Preferably, the attenuation circuit has a continuous or stepwise amplitude suppression action, and control means for variably controlling the amplitude suppression action of the attenuation circuit is provided. Preferably, control means for turning off the amplitude suppressing action of the attenuation circuit is provided. Here, when turning off the amplitude suppression action, control for bypassing the attenuation circuit may be performed.
[0011]
Preferably, the attenuation circuit includes a plurality of attenuation circuits that suppress the amplitude of the analog transmission waveform signal and have different amplitude suppression actions, and a switching circuit that selectively operates the plurality of attenuation circuits.
[0012]
(2) In order to achieve the above object, the present invention provides an array transducer including a plurality of transducer elements, a plurality of waveform generators provided for each of the transducer elements and outputting digital transmission waveform signals, A plurality of D / A converters that convert a plurality of digital transmission waveform signals output from a plurality of waveform generators into a plurality of analog transmission waveform signals, and a plurality of analog transmissions output from the plurality of D / A converters A plurality of attenuation circuits that suppress the amplitude of the waveform signal, and a plurality of analog transmission waveform signals after amplitude suppression output from the plurality of attenuation circuits are amplified, and a plurality of transmission drive signals are sent to the plurality of vibration elements. look including a plurality of linear amplifiers that outputs, each attenuation circuit, amplitude suppression effect is different emitter grounded plurality of damping transistors and the plurality of attenuation to each other A plurality of selection transistors connected to the emitter side of each of the transistors, and the plurality of selection transistors are selectively turned on to selectively select the plurality of attenuation transistors connected in parallel. Thus, the amplitude suppression action is variably controlled . Preferably, a gain common to all channels is collectively adjusted by the plurality of linear amplifiers, and weighting of amplitude between channels is individually adjusted by the plurality of attenuation circuits.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
FIG. 1 shows a preferred embodiment of a transmission circuit according to the present invention, and FIG. 1 is a block diagram showing the main configuration of the transmission circuit. The transmission circuit is composed of a plurality of transmitters provided for each channel, and FIG. 1 shows the configuration of the transmitter.
[0015]
The digital waveform generator 20 is configured as a digital circuit including, for example, a ROM that stores a signal waveform as a digital signal. When the timing signal 100 is input from a control unit (not shown), the digital waveform generator 20 outputs a digital waveform signal (digital transmission waveform signal). In this embodiment, the amplitude of the signal is adjusted by an attenuator (attenuator circuit) 22 described later, and the digital waveform generator 20 basically has the maximum amplitude without adjusting the waveform of the signal. Is output. Of course, the signal 102 for adjusting the waveform may be input to the digital waveform generator 20 and the amplitude may be adjusted based on the control signal.
[0016]
The D / A converter 14 converts the input digital waveform signal into an analog waveform signal. The analog waveform signal is output to the attenuator 22.
[0017]
The attenuator 22 is configured as an analog circuit that performs amplitude adjustment, specifically, suppression or attenuation processing on the analog waveform signal. The amplitude suppression degree or attenuation degree is adjusted based on the input signal 104. Of course, when the amplitude is not suppressed, the attenuator 22 can be bypassed and the input signal can be output to the amplifier 16. The amplifier 16 is configured as an amplifier that amplifies an input analog waveform signal. In the present embodiment, a linear amplifier is used as the amplifier 16. The analog waveform signal amplified by the amplifier 16 is output to the corresponding vibration element 18 as a transmission drive signal. Thereby, ultrasonic waves are generated by the vibration element 18.
[0018]
In this embodiment, the amplification factor, that is, the gain of the amplifier 16 is fixed to a predetermined value. However, the signal 106 may be input to the amplifier 16 and the amplification factor of the amplifier 16 may be variably controlled based on the signal 106. Is possible. However, when the amplifier 16 is composed of a linear amplifier, the circuit scale is remarkably increased if a configuration capable of changing the amplification factor is employed. Therefore, it is desirable to adjust the amplitude of the signal with the attenuator 22 as the center.
[0019]
According to the configuration shown in FIG. 1, a digital waveform signal having the maximum amplitude is output as the output of the digital waveform generator 20, and the amplitude is adjusted by the attenuator 22 after the signal is converted into an analog waveform signal. There is an advantage that the ratio of the quantization error to the entire amplitude can be reduced. That is, the original waveform represented by the digital waveform signal can be reproduced as faithfully as possible and output to the vibration element 18.
[0020]
As a result, for example, in the case of harmonic imaging that constructs an ultrasonic image using harmonic components, or in the case of transmitting a chirp wave as a frequency-modulated waveform, the transmission waveform can be brought close to an ideal one, As a result, the image quality of the ultrasonic image can be improved.
[0021]
Although not shown in FIG. 1, the above-described signals 100, 102, 104, and 106 are supplied from a host controller or the like as a control unit. In FIG. 1, the configuration of the receiving circuit is not shown.
[0022]
FIG. 2 shows a circuit configuration example of the attenuator 22 shown in FIG. The transistor Q1 is an input stage element with a gain of 1. A transmission signal (analog signal) output from the D / A converter is input to the base of the transistor Q1. The signal output from the emitter side of the transistor Q1 is input to the bases of two transistors Q2 and Q4 that are selectively operated. The gain of the transistor Q2 is determined by the resistance value ratio between the resistors R5 and R4. Similarly, the gain of the transistor Q4 is determined by the resistance value ratio between the resistors R5 and R9. Here, both of the transistors Q2 and Q4 perform an attenuation operation, and their attenuation amounts are different from each other (however, one may be attenuation amount 0 (gain 1)). The alternative operations of the transistors Q2 and Q4 are controlled by the transistors Q3 and Q5. Specifically, the transistors Q3 and Q5 are controlled by varying the voltages of the control signals VCNT1 and VCNT2 input to the bases of the transistors Q3 and Q5. Operation is controlled. When the control signal VCNT1 is high, VCNT2 is low, and in this case, only the transistor Q3 is turned on, and as a result, only the transistor Q2 is attenuated. On the contrary, when the control signal VCNT2 is high, VCNT1 is low, and in this case, only the transistor Q5 is turned on, and as a result, only the transistor Q4 is attenuated. In this way, the attenuation amount can be controlled in an analog manner. A signal output from the collector side of the transistors Q2 and Q4 is input to the base of the transistor Q6, and the signal is output to the next amplifier via the transistor Q6. The transistor Q6 is an output stage transistor with a gain of 1, and performs conversion to low impedance. In FIG. 2, R1, R2, R3, R7, R8, and R10 represent resistors, and C1 and C2 represent capacitors.
[0023]
In the configuration of FIG. 2, by further increasing the number of attenuation transistor circuits, it becomes possible to select a larger amount of attenuation. Of course, the circuit shown in FIG. 2 is an example, and various circuits can be adopted as long as an attenuator can be configured as an analog circuit. For example, the attenuation amount may be variably controlled continuously instead of selectively.
[0024]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the quantization error and improve the image quality of the ultrasonic image.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a preferred embodiment of a transmission circuit according to the present invention.
FIG. 2 is a circuit diagram showing a specific configuration example of the attenuator shown in FIG. 1;
FIG. 3 is a block diagram showing a configuration of a conventional transmission circuit.
[Explanation of symbols]
14 D / A converter, 16 amplifier (linear amplifier), 18 vibration element, 20 digital waveform generator, 22 attenuator.

Claims (4)

A waveform generator for outputting a digital transmission waveform signal;
A D / A converter for converting the digital transmission waveform signal output from the waveform generator into an analog transmission waveform signal;
An attenuation circuit for suppressing the amplitude of the analog transmission waveform signal output from the D / A converter;
An amplifier that amplifies the analog transmission waveform signal after amplitude suppression output from the attenuation circuit, and outputs a transmission drive signal to the ultrasonic transducer;
Only including,
The attenuation circuit includes a plurality of attenuating transistors whose emitters have different amplitude suppression effects, and a plurality of selection transistors connected to the emitter side of each of the attenuating transistors.
By selectively turning on the plurality of selection transistors, the plurality of attenuation transistors connected in parallel selectively operate, whereby the amplitude suppression action is variably controlled.
A transmission circuit for an ultrasonic diagnostic apparatus. The transmission circuit according to claim 1,
The attenuation circuit has a continuous or stepwise amplitude suppression action,
A transmission circuit for an ultrasonic diagnostic apparatus, characterized in that a control means for variably controlling the amplitude suppression action of the attenuation circuit is provided. An array vibrator comprising a plurality of vibration elements;
A plurality of waveform generators provided for each of the vibration elements and outputting digital transmission waveform signals;
A plurality of D / A converters for converting a plurality of digital transmission waveform signals output from the plurality of waveform generators into a plurality of analog transmission waveform signals;
A plurality of attenuation circuits for suppressing amplitudes of a plurality of analog transmission waveform signals output from the plurality of D / A converters;
A plurality of linear amplifiers for amplifying a plurality of analog transmission waveform signals after amplitude suppression output from the plurality of attenuation circuits and outputting a plurality of transmission drive signals to the plurality of vibration elements;
Including
Each of the attenuation circuits has a plurality of attenuating transistors whose emitters are grounded and having different amplitude suppressing actions, and a plurality of selecting transistors connected to the emitter side of each of the attenuating transistors. By selectively turning on the selection transistor, the plurality of attenuating transistors connected in parallel selectively operate, whereby the amplitude suppression action is variably controlled.
A transmission circuit for an ultrasonic diagnostic apparatus. The transmission circuit according to claim 3, wherein
The gain common to all channels is collectively adjusted by the plurality of linear amplifiers, and the weight of the amplitude between the channels is individually adjusted by the plurality of attenuation circuits.
A transmission circuit for an ultrasonic diagnostic apparatus.

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