JPH0315997B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a reception processing device that pulse-coherently detects echo signals using ultrasonic pulse signals;
That is, the present invention relates to a device that precisely detects the phase of an ultrasonic echo signal based on its relationship with a transmitted pulse signal. The present invention relates to an ultrasonic diagnostic apparatus, a sonar apparatus, or other apparatus for measuring echo signals of ultrasonic pulses as a function of time.

[Prior art] In devices such as radar and sonar that irradiate a target object in a medium with a transmitted pulse signal and receive the echo signal, thereby measuring the position and velocity of the target object, the echo signal is pulse-coherent. It is necessary to detect the wave. That is, in order to measure not only the return time of the echo signal but also the phase shift due to the Doppler effect, it is necessary to measure the phase of the echo signal with respect to the transmitted pulse signal. For this purpose, it is necessary to maintain a constant mutual relationship between the phase of the transmission pulse signal and the phase of the local oscillation signal. This is because if there is a variation between the two phases, the detection results will vary, phase noise will occur, and accurate measurement will not be possible.

Therefore, conventionally, it has been necessary to control either the phase (periodicity) of the transmitted pulse signal or the phase of the local oscillation signal. If it is difficult to precisely control the phase of the transmitted pulse signal due to instability of the thermal characteristics of the elements that make up the pulse generator, the phase of the local oscillation signal may be adjusted to the phase of the transmitted pulse signal. Generally, it was controlled to follow the target.

A device for controlling the phase of a local oscillation signal is generally configured to forcibly start local oscillation using a transmitted pulse signal, and such a local oscillator for preserving the phase is called a coherent oscillator. There is.

In devices that use ultrasound, especially medical ultrasound diagnostic devices, transmission and reception are performed in a high frequency band over a wide band, and the transmitted pulse signal is also an impulse or step-like "time signal". It is somewhat difficult to determine the oscillation phase. This is because an oscillator using a resonator with a high Q value has a poor response to a trigger input for forced synchronization, and requires a high-level impulse. On the other hand, a resonator with a low Q value can respond well to a synchronization input, but has the drawback of causing problems in frequency and phase stability, which are the objectives of a coherent oscillator. Further, when the trigger level is high, the operation of the oscillator becomes unstable when the trigger signal is input, and this effect lingers, resulting in fluctuations in phase and frequency.

An object of the present invention is to provide a device that pulse-coherently measures echo signals without using a coherent oscillator, and to easily add a pulse Doppler function to a device that is not equipped with a pulse-coherent oscillator.

[Means for solving problems]

The ultrasonic echo signal reception processing device of the present invention includes:
The device is configured to detect a phase difference between the transmitted ultrasonic pulse signal and the carrier wave for detection by extracting a ringing signal containing phase information of the transmitted ultrasonic pulse signal and detecting it with a carrier wave signal of a local oscillator. It is characterized by

That is, the first invention includes a pulse generator that generates a transmission pulse, and a pulse generator that converts the transmission pulse from the pulse generator into an ultrasonic pulse signal and repeatedly transmits it into a medium to generate echoes due to the ultrasonic pulse signal. A probe that receives a signal, converts it into an electrical signal, and outputs it, and the intensity of the echo signal converted into an electrical signal by this probe as a function of the elapsed time after transmitting the ultrasonic pulse signal. a local oscillator that generates a carrier signal with a frequency accuracy sufficiently higher than the repetition frequency accuracy of the ultrasonic pulse signal; and a carrier wave generated by the local oscillator. A phase shifter converts a signal into two carrier waves with phases substantially orthogonal to each other, and the detection output of the probe is used as a modulated input, and the output signal of the phase shifter with a phase that is orthogonal to each other is used as a carrier wave input. a first two balanced modulators, a phase detection means for detecting the phase of a ringing signal synchronized with the ultrasonic pulse signal with respect to a carrier signal of the local oscillator, and an output of the phase detection means to detect the first balance. phase correction means for correcting the phase of the output signal of the modulator; the phase detection means includes means for extracting a ringing signal synchronized with the transmitted pulse from the output of the pulse generator; a second two balanced modulators that perform balanced modulation using mutually orthogonal phase output signals of the phase shifter as carrier waves as modulation inputs; and the carrier wave of the signal balanced modulated by the second balanced modulator. and detection means for detecting the phase relative to the phase.

Further, a second aspect of the present invention is characterized in that the phase detection means includes means for detecting a ringing signal with an attenuated amplitude that occurs immediately after the transmitted ultrasonic pulse signal, and the phase difference is corrected by this ringing signal. shall be.

Here, the ringing signal refers to a signal that is generated in a phase continuous with the trigger signal and whose amplitude attenuates after a certain period of time. Generally, the decay is exponential. [Examples] Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an ultrasonic echo signal reception processing apparatus according to a first embodiment of the present invention. This device is an example implemented in an ultrasonic diagnostic device.

A pulse generator 1 is connected to a probe 2. The probe 2 is connected to an amplifier 3. Amplifier 3 is connected to two balanced modulators 9-1 and 9-2. The ringing generator 4 has an input connected to the pulse generator 1 via a duplexer, and an output connected to the limiter 5. Limiter 5 is connected to bandpass filter 6. The bandpass filter 6 consists of two balanced modulators 9-3.
and a balanced modulator 9-4. Local oscillator 7 is connected to phase shifter 8 . The 0° phase shifted output of the phase shifter 8 is connected to the balanced modulator 9-1 and the balanced modulator 9-3, and the 90° phase shifted output of the phase shifter 8 is connected to the balanced modulator 9.
-2 and the balanced modulator 9-4. The balanced modulator 9-3 and the balanced modulator 9-4 are the phase detector 1.
Connected to 0. Balanced modulator 9-1, balance modulator 9-2, and phase detection means 10 are connected to phase corrector 11.

The pulse generator 1 generates a transmission pulse 102 using a trigger signal 101 that is repeatedly input as a trigger. Most of the energy of this transmitted pulse 102 is given to the probe 2, but the remaining part is also input to the ringing generator 4.

The probe 2 transmits an ultrasonic transmission pulse signal into the medium using a transmission pulse 102, and further detects an ultrasonic echo signal due to this transmission pulse signal and converts it into an electrical signal. Here, the center frequency of the probe 2 is assumed to be f ₀ .

The amplifier 3 amplifies the echo signal detected by the probe 2 and converted into an electrical signal. Here, amplifier 3
may include filters, equalizers, pulse compressors, and other circuitry as required.

The ringing generator 4 is triggered by the transmission pulse 102 inputted through the loose-coupled duplexer, and starts damped oscillation at a frequency f ₀ to generate a ringing signal 104 . The ringing generator 4 may be a simple single-tuned circuit or a bandpass filter. Further, the Q value is set to an appropriate moderate value.

The limiter 5 and the bandpass filter 6 output a constant amplitude burst signal 105 only while the ringing signal 104 continues.

Local oscillator 7 outputs a carrier wave of frequency f ₀ .
This local oscillator 7 must output a highly stable frequency.

The phase shifter 8 changes the phase of the carrier wave output from the local oscillator 7, and outputs orthogonal carrier waves with a phase shift angle of 0° and a phase shift angle of 90°.

The balanced modulator 9-1 detects the echo signal 103 using a carrier wave with a phase shift angle of 0° and outputs a signal i. The balanced modulator 9-2 detects the echo signal 103 using a carrier wave with a phase shift angle of 90 degrees and outputs a signal q. Balanced modulator 9-3 detects burst signal 105 using a carrier wave with a phase shift angle of 0° and outputs signal i'. Balance modulator 9
-4 detects the burst signal 105 using a carrier wave with a phase shift angle of 90 degrees and outputs a signal q'.

The phase detector 10 detects the phase of the transmitted pulse 102 with respect to the carrier wave from the signal i' and the signal q'.

The phase corrector 11 corrects the phases of the signal i and the signal q based on the output of the phase detector 10.

The echo signal reception processing device configured in this way performs synchronous detection of the burst signal generated by the transmitted pulse using a stable carrier wave from a local oscillator, detects the relative phase of the echo signal with respect to the carrier wave, and thereby , is characterized by performing phase correction of bipolar video signals.

FIG. 2 is a time chart showing the operation of the apparatus of this embodiment.

Transmission pulse 1 generated by pulse generator 1
02, a transmission pulse signal (ultrasonic pulse signal) is sent from the probe 2, and this transmission pulse signal is reflected within the subject and becomes an ultrasound echo signal.
It is converted into an electrical signal and becomes an echo signal 103.
On the other hand, the transmitted pulse 102 split by the loose couple splitter is input to the ringing generator 4, which generates a ringing signal 104. The ringing signal 104 is transmitted through the limiter 5 and the bandpass filter 6.
As a result, the ringing signal 104 is converted into a burst signal 105 whose amplitude is constant only while the ringing signal 104 continues. This burst signal 105 is detected by a pair of orthogonal carrier waves generated by the local oscillator 7 and separated by the phase shifter 8. That is, it is detected by a carrier wave with a phase angle of 0° and becomes a signal i', and detected by a carrier wave with a phase angle of 90° and becomes a signal q'.

The signal i' and the signal q' have meaning only during the burst signal 105, and include phase information for the carrier wave of the transmission pulse 102 (that is, phase information for the carrier wave of the ultrasonic transmission pulse signal). Therefore, it is possible to know the phase angle from the value of the signal i' and the value of the signal q'. Furthermore, the signal i
By subtracting the phase angle of signal i' and signal q' from and signal q, a pulse coherent bipolar video signal is obtained.

This "subtracting the phase angle" is a vector rotation, which can be performed by multiplication or division in the complex plane. The phase angle θ between the signal i′ and the signal q′ can be obtained as θ=tan ⁻¹ q′/i′ (1). Therefore, the signal i
The relationship between the signal q, the signal i ₀ after phase correction, and the signal q ₀ is expressed as i q = cos θ sin θ − sin θ cos θ·i ₀ q ₀ (2). Therefore, pulse coherent signal i ₀ and signal q ₀ are obtained by i ₀ q ₀ = cos θ − sin θ sin θ cos θ·i q (3).

These calculations can be performed simultaneously with the detection of signal i and signal q. Further, the phase detector 10 and the phase corrector 11 are configured to include an analog-to-digital conversion circuit, a memory circuit, a microprocessor, etc., and the time functions of the signal i and the signal q,
It is desirable that the time functions of the signal i' and the signal q' be converted into analog-to-digital data and stored in a storage circuit, and this data be digitally processed.
Furthermore, if the dynamic range of the device is sufficiently large, it may not be necessary to use the limiter 5 or the bandpass filter 6.

FIG. 3 is a block diagram of an ultrasonic echo signal reception processing apparatus according to a second embodiment of the present invention.

A pulse generator 1 is connected to a probe 2. The probe 2 is connected to an amplifier 3. Amplifier 3 is connected to two balanced modulators 9-1 and 9-2. Local oscillator 7 is connected to phase shifter 8 . The 0° phase shifted output of the phase shifter 8 is connected to a balanced modulator 9-1, and the 90° phase shifted output of the phase shifter 8 is connected to a balanced modulator 9-2. The balanced modulator 9-1 and the balanced modulator 9-2 are connected to separate low-pass filters 12, respectively. The low pass filter 12 is connected to an analog-to-digital conversion circuit 13. Analog-to-digital conversion circuit 13 is connected to storage circuit 14 . The memory circuit 14 is connected to the arithmetic unit 15 .

The low-pass filter 12 removes high-frequency components of the detection signal in order to perform analog-to-digital conversion. The analog-to-digital conversion circuit 13 receives the signal i
and signal q are converted from analog to digital. The storage circuit 14 stores the digitized waveform signal. The arithmetic unit 15 includes a microprocessor, corrects the phase angle, and digitally outputs the signal i ₀ and the signal q ₀ .

FIG. 4 is a time chart showing the operation of the apparatus of this embodiment.

Transmission pulse 10 generated by pulse generator 1
2, a transmission pulse signal (ultrasonic pulse signal) is sent from the probe 2, this transmission pulse signal is reflected within the subject, becomes an ultrasound echo signal, and is converted into an electrical signal to become an echo signal 103. Echo signal 103 dominated by transmitted pulses and their attenuation
The section of region A has a phase relationship with the transmitted pulse with good reproducibility. Therefore, the echo signal 10
As a result of orthogonal detection regarding the section of region A of No. 3, that is, region A of signal i and signal q also has a reproducible phase relationship with the transmitted pulse.

Therefore, by using region A of the echo signal 103 as a ringing signal, the same phase correction as in the first embodiment device is possible.

〔Effect of the invention〕

As explained above, the ultrasonic echo signal reception and processing device of the present invention can realize a device that pulse-coherently measures echo signals without using a coherent oscillator, and can also provide a pulse Doppler function for devices not equipped with a pulse-coherent oscillator. This has the effect of making it possible to easily add .

Furthermore, since no coherent oscillator is used, it is possible to configure an all-digital processing circuit, which is much more constant, reliable, and flexible than traditional analog processing. It has a great effect on achieving this.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an ultrasonic echo signal reception processing device according to a first embodiment of the present invention. FIG. 2 is a time chart showing the operation of the device of the first embodiment. Third
The figure is a block diagram of an ultrasonic echo signal reception processing apparatus according to a second embodiment of the present invention. FIG. 4 is a time chart showing the operation of the device of the second embodiment. DESCRIPTION OF SYMBOLS 1... Pulse generator, 2... Probe, 3... Amplifier, 4... Ringing generator, 5... Limiter, 6... Bandpass filter, 7... Local oscillator, 8...
... Phase shifter, 9 ... Balanced modulator, 10 ... Phase detector, 11 ... Phase corrector, 12 ... Low pass filter, 13 ... Analog-to-digital conversion circuit, 1
4... Memory circuit, 15... Arithmetic device.

Claims (1)

[Claims] 1. A pulse generator that generates a transmitted pulse, and a pulse generator that converts the transmitted pulse from the pulse generator into an ultrasonic pulse signal and repeatedly transmits it into a medium to generate an echo signal by the ultrasonic pulse signal. a probe that receives the ultrasound pulse, converts it into an electrical signal, and outputs it; and measures the intensity of the echo signal converted into an electrical signal by this probe as a function of the elapsed time after transmitting the ultrasonic pulse signal. a local oscillator that generates a carrier wave signal with a frequency accuracy sufficiently higher than the accuracy of the repetition frequency of the ultrasonic pulse signal; and a carrier wave signal generated by the local oscillator. a phase shifter that converts the signal into two carrier waves with phases substantially orthogonal to each other; two balanced modulators; a phase detection means for detecting a phase of a ringing signal synchronized with the ultrasonic pulse signal with respect to a carrier signal of the local oscillator; and an output of the phase detection means to detect the first balanced modulation. and a phase correction means for correcting the phase of the output signal of the pulse generator. A second 2-channel circuit that performs balanced modulation using the mutually orthogonal phase output signals of the phase shifter as carrier waves as inputs.
1. An ultrasonic echo signal receiving and processing device comprising: a second balanced modulator; and detection means for detecting a phase of a signal balanced-modulated by the second balanced modulator with respect to the carrier wave. 2. The phase detection means and the phase correction means include an analog-digital conversion circuit that converts the output signal of the balanced modulator into a digital signal, a storage circuit that inputs the output digital signal of this analog-digital conversion circuit, and this storage circuit. and a microprocessor for processing the above data.
2. The ultrasonic echo signal reception processing device described in 2. 3. A pulse generator that generates a transmitted pulse; converts the transmitted pulse from this pulse generator into an ultrasonic pulse signal, repeatedly transmits it into the medium, receives an echo signal from this ultrasonic pulse signal, and generates an electrical signal. and a means for measuring the intensity of the echo signal converted into an electrical signal by the probe as a function of elapsed time after transmitting the ultrasonic pulse signal. The ultrasonic echo signal reception and processing device includes a local oscillator that generates a carrier wave signal with a frequency accuracy sufficiently higher than the repetition frequency accuracy of the ultrasonic pulse signal, and a local oscillator that generates a carrier wave signal with a phase substantially orthogonal to each other. a phase shifter for converting into two carrier waves; two balanced modulators each having the detection output of the probe as a modulated input, and the output signals of mutually orthogonal phases of the phase shifter as carrier wave inputs; a phase detection means for detecting the phase of a ringing signal synchronized with the ultrasonic pulse signal with respect to a carrier signal of the local oscillator; and a phase correction means for correcting the phase of the output signal of the balanced modulator based on the output of the phase detection means. An apparatus for receiving and processing ultrasonic echo signals, characterized in that the phase detection means includes means for detecting a signal of attenuation amplitude of an ultrasonic echo signal generated immediately after transmission of an ultrasonic pulse signal. 4. The phase detection means and the phase correction means include an analog-digital conversion circuit that converts the output signal of the balanced modulator into a digital signal, a storage circuit that inputs the output digital signal of this analog-digital conversion circuit, and this storage circuit. and a microprocessor for processing the above data.
2. The ultrasonic echo signal reception processing device described in 2.