JPH0337938B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultrasonic pulse Doppler apparatus that transmits and receives ultrasonic pulses to non-invasively observe, for example, the blood flow of a subject using the Doppler effect.

[Technical background of the invention]

A tomographic image of a subject and a specific region on the tomographic plane (hereinafter referred to as
It is also called a blood flow observation point. ) is displayed as shown in FIG. 1, for example. That is, in FIG. 1, on one surface of the cathode ray tube, the tomographic image of the subject detected by the sector-scanning ultrasound probe is displayed with scanning lines spreading out in a fan shape (such a display is hereinafter referred to as B mode). ) At the same time, a blood flow observation point 2 and a Doppler beam mark (hereinafter referred to as M mark) 3 indicating that the scanning line includes the blood flow observation point 2 are displayed. Simultaneously with the display on the cathode ray tube 1, on the cathode ray tube 4, a pattern image 5 (hereinafter also referred to as an M mode image) indicating the temporal change of the subject tissue at the M mark 3 and a blood flow velocity at the blood flow observation point 2 are displayed. A pattern image 6 (hereinafter sometimes referred to as a Doppler pattern image) and a temporal change in average blood flow velocity (not shown) are shown. The state in which the B mode image, M mode image, and Doppler pattern image are displayed simultaneously in this manner is called B/D mode.

Here, the blood flow velocity pattern image 6 is a blood flow in which the frequency of the transmitted ultrasound emitted from the sector-scanning ultrasound probe and the frequency of the received ultrasound (hereinafter sometimes referred to as an echo signal) are the same. It can be obtained by detecting the frequency of the received ultrasound based on the fact that Equation (1) is satisfied due to the Doppler effect caused by.

d=2νccosθ/c...(1) [where c is the frequency of the transmitted ultrasound, ν is the flow velocity of the blood flow, c is the speed of sound in the medium, θ is the angle between the ultrasound beam and the blood flow, and d is the shift frequency caused by the Doppler effect contained in the received ultrasound (hereinafter sometimes referred to as Doppler shift frequency).
shows. ] This detection method, for example, multiplies the received signal by a reference signal of approximately the same frequency as the ultrasonic transmission frequency, removes the frequency band of the transmission frequency with a high-cut filter, and detects the signal containing the Doppler shift signal. Extract. Then, in order to extract and frequency analyze only the Doppler shift signal near the observation point, the extracted signal is sampled at the observation point. Note that in the case of blood flow observation, a bandpass filter may be used to remove Doppler shift signals caused by movements other than blood flow, such as blood vessels.

More specifically, the ultrasonic waves emitted from the ultrasonic probe have a frequency spectrum as shown in FIG. 2a, for example. That is, when the center frequency of the transmission frequency is c and the repetition frequency of the transmission pulse is rate, a line spectrum of frequency c±nrate exists according to the envelope W().
Note that the envelope W( ) is determined by the frequency characteristics of the ultrasonic probe used. When this ultrasonic pulse propagates in a medium, if the attenuation in the medium is small, the received ultrasonic echo signal will also have a similar frequency spectrum W().
When subjected to a Doppler shift, the frequency spectrum becomes, for example, as shown in FIG. 2b. In other words, it contains an ultrasound echo signal whose rate fluctuates by α・rate due to the Doppler effect, and as a result, the frequency (c±
A frequency spectrum of n·rate)/(1-α) is generated. Calculation of each Doppler shift frequency is as follows.

d={c±n・rate)/(1−α)} −(c±n・rate)=α/1−α(c±n・ra
te) In other words, α/of the frequency of each line spectrum
A frequency spectrum shifted by (1-α) times is generated as the frequency spectrum of the Doppler shift signal. As can be seen, the higher the frequency of the line spectrum, the higher the shift frequency of the associated Doppler shift signal.

When phase detection is performed by multiplying the received ultrasonic echo signal (hereinafter also referred to as an echo signal) including the Doppler shift signal as shown in Fig. 2b by a reference signal r (r = c), the result is as shown in Fig. 2c. A frequency spectrum as shown in is obtained, and when this is sampled and held, the second frequency spectrum is obtained.
A Doppler shift signal as shown in Figure d is detected.
The frequency spectrum of this Doppler shift signal is
This is similar to the frequency spectrum of the received ultrasonic echo signal shown in FIG. b, where the frequency axis is compressed.

[Problems with background technology]

The higher the frequency of ultrasound, the greater the attenuation, so
The deeper the position of the observation point is, the weaker the energy of high-frequency components in the frequency spectrum of the echo signal is, as shown in FIG. 2e.

However, in conventional ultrasonic pulse Doppler equipment, for example, the value of the reference frequency of the phase detector is set to be the same as the center frequency of the transmitted ultrasonic wave, and the received ultrasonic echo signal, in which the energy of the high frequency component is attenuated, is directly converted into Doppler. Detecting a deviation signal. Therefore, as mentioned above, the frequency spectrum of the Doppler shift signal is similar to the frequency spectrum of the received ultrasonic echo signal compressed on the frequency axis. When a signal is detected, its frequency spectrum becomes one in which high-frequency energy is weakened, as shown in FIG. 2f, and the peak frequency of the Doppler shift signal is lower than in the case without attenuation. Further, even if the average frequency is calculated from the frequency spectrum shown in FIG. 2(f), the obtained average frequency is lower than in the case without attenuation. As described above, at deep observation points, the amount of information in the Doppler shift signal is biased toward low frequency components, and there is a problem that accurate observation data cannot be obtained.

For example, as shown in Figure 3a, the center frequency
The frequency spectrum of an ultrasound echo signal with a Doppler shift signal of 5 MHz, -3 dB bandwidth, and 4 MHz becomes an envelope as shown by A in the figure when there is no attenuation, but as the observation point becomes deeper, As a result of being attenuated by the biological attenuation coefficient of 0.7 dB/cm・Hz,
B ₁ , B ₂ ... B ₅ in the figure deform as shown. When looking at the peak frequency C and average frequency D of the Doppler shift signal detected from the deformed frequency spectrum, as shown in FIG. 3b,
It can be seen that there is a large deviation compared to the case without attenuation.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and provides a Doppler shift signal having an accurate frequency spectrum and an accurate average frequency by correcting errors caused by attenuation of high frequency components in a received ultrasound echo signal. The object of the present invention is to provide an ultrasonic pulse Doppler device that can output.

[Summary of the invention]

The outline of this invention for achieving the above object is as follows:
In an ultrasonic pulse Doppler device capable of detecting a Doppler signal by phase-detecting a received ultrasonic echo signal with a reference signal, a first correction means for correcting frequency distortion of the Doppler signal caused by a change in the frequency band of the ultrasonic echo signal. and a second correction means for correcting the shift in peak frequency caused by the first correction means, and is characterized in that it obtains a frequency spectrum of an ultrasound echo signal that is symmetrical about the corrected peak frequency. .

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. This embodiment is shown in the block diagram of FIG.

The basic signal generating section 7 includes a main oscillator 7a that generates clock pulses at a frequency necessary for the operation of the apparatus, and a clock pulse output from the main oscillator 7a at a frequency (pulse rate frequency) necessary for observing the tissue and blood flow of the subject. A first frequency dividing circuit 7b that divides the frequency to, for example, 4KHz, a second frequency dividing circuit 7c that determines the scanning ratio for alternately obtaining a B mode image, an M mode image, and a Doppler pattern image, and an M mark 3
and a third frequency dividing circuit 7d that supplies a clock pulse of several Hz to the M mark position setting circuit 11a and the observation point position setting circuit 11b so that the movement of the observation point 2 can be observed reliably, and a first frequency dividing circuit. A first gate circuit 7e converts the rate pulse outputted from the second frequency dividing circuit 7b into a rate pulse for obtaining an M-mode Doppler pattern according to the output signal from the second frequency dividing circuit 7c, and outputs the rate pulse. It is composed of a second gate circuit 7f that converts the rate pulse output from the frequency dividing circuit 7b into a rate pulse for obtaining B mode according to the output signal from the second frequency dividing circuit 7c, and outputs the rate pulse. . For example, the B mode and M mode Doppler patterns are 1:1.
When attempting to scan alternately, the second frequency dividing circuit 7
Configure c to become a 1/2 frequency divider circuit.

The scan control unit 8 controls scanning in various display modes, and for example, scans the scanning line of the M mark 3 set by the M mark position setting circuit 11a in the observation point position setting unit 11 using the switch SWA. an M mark scanning control circuit 8a that encodes the position (for example, converts it into a 7-bit binary code) and outputs this encoded signal in synchronization with the output pulse from the first gate circuit 7e; and the second gate circuit 7f. B uses the output pulse from B as a clock.
A B-mode scan control circuit 8b that sequentially outputs coded signals corresponding to the scanning lines or transducer elements constituting the transducer 14, and an M-mark scan control circuit 8a and B
The first adding circuit 8c adds the output coded signals from the mode scanning control circuit 8b and outputs the result to the transducer control section 9 and the B-mode display circuit 10a of the display mode control section 10.

The transducer control section 9 drives the transducer elements constituting the transducer 14 in accordance with the coded signal output from the first addition circuit 8c. The transducer 14 emits ultrasonic pulses and receives echo signals reflected from within the subject. For example, a transducer scanning circuit 9a controls the delay time and sector scanning to focus the ultrasonic beam, and a pulse is generated to drive the ultrasonic transducer according to the output from the transducer scanning circuit 9a. The transmitter/receiver circuit 9b applies this to the transducer 14 and amplifies the echo signal received by the ultrasonic transducer.

The display mode control section 10 controls the display sections 12a and 12.
B mode image, M mode image/Doppler mode image, and average frequency pattern image of the Doppler signal can be displayed on the main oscillator 7a. Input the basic signal and set the blood flow observation point on the M mark using the switch SWB.
A position setting unit 1 that causes the set blood flow observation point to appear as a pulse at an arbitrary point in the period of scanning the M mark.
A second adding circuit 10b adds the pulse signal output from the observation point position setting circuit 11b in the observation point position setting circuit 11b and the echo signal output from the wave transmitting/receiving circuit 9b. It is configured to output the coded signal outputted from the first addition circuit 8c as a modulation signal and as a scanning signal from the B mode display circuit 10a to the display unit 12a, and also to output the coded signal outputted from the first addition circuit 8c as a scanning signal from the B mode display circuit 10a to the display section 12a. As a circuit that performs display, the Doppler detection unit 13 combines the blood flow signal detected from the echo signal output from the wave transmitting/receiving circuit 9b and the M mode display circuit 1.
0c and the M mode signal formed by the third adder circuit 1.
It is configured to add at 0d and output display signals of M mode and Doppler mode to the display section 12b.

The Doppler detection unit 13 receives the echo signal output from the wave transmitting/receiving circuit 9b, and inputs the clock pulse from the main oscillator 7a and a phase detection circuit 13a that detects a Doppler shift signal by multiplying it with a reference signal. Reference signal circuit 13b that produces a reference signal
and a high-cut filter 13c that removes unnecessary frequency components higher than the band of the Doppler shift signal detected by the phase detection circuit 13a and shapes the frequency spectrum of the received echo signal almost symmetrically around its peak. Then, from the echo signal obtained by one ultrasonic pulse, an echo signal with a Doppler shift is detected at the position (depth) set by the observation point position setting unit 11, and the next A sample hold circuit 13d that holds until an echo caused by an ultrasound pulse appears; a band pass filter 13e that removes unnecessary signals (for example, a Doppler shift signal due to movement of a blood vessel wall) contained in the output of the sample hold circuit 13d; A real-time frequency analyzer 13f (hereinafter referred to as a frequency analyzer) that analyzes the frequency of the output Doppler signal in real time and outputs the frequency spectrum of the Doppler signal, and calculates an average from the size and frequency of the output frequency spectrum. Average frequency circuit 13g that calculates frequency
is output from the reference signal circuit 13b, and the switch
Based on the reference signal frequency variable information set by SWE, the characteristics of the high cut filter 13c are set, and the Doppler polarization detected by following the movement of the peak frequency of the echo signal caused by attenuation of the high frequency component of the echo signal is set. A correction circuit 13 that causes the real-time frequency analyzer 13f to perform correction to shift the peak center of the frequency spectrum of the shifted signal by the Doppler shift frequency corresponding to the change in the reference frequency.
h, a switch SWC that selects the spectrum of the Doppler shift signal and its average frequency, and
It is comprised of a fourth addition circuit 13i that adds the spectra of the SWD and Doppler shift signals and their average frequencies, and outputs the result to a third addition circuit 10d.

Furthermore, the reference signal circuit 13b includes, for example, a PLL.
When a frequency synthesizer is used, as shown in the block diagram of FIG. 5, a frequency dividing circuit _13b1 divides the clock pulse from the main oscillator 7a to the minimum step frequency when varying the reference frequency r;
When no control voltage is applied, the voltage controlled oscillator 13b ₂ oscillates at the same frequency as the transmitted ultrasound frequency, and when a control voltage is applied, the oscillation frequency changes.
, a programmable frequency divider circuit 13b ₃ that divides the output of the voltage controlled oscillator to Δ on the premise that the voltage controlled oscillator is oscillating a desired reference frequency, and a switch.
Reference frequency setting circuit 1 that operates a counter by pressing SWE and outputs a program code to obtain the desired frequency division number to the programmable frequency division circuit 13b ₃
3b4, and a phase comparator _13b5 that compares the outputs of the frequency divider circuit _13b1 and the programmable frequency divider circuit _13b3 and outputs _a control voltage that cancels out the difference to the voltage controlled oscillator _13b2 . Ru.

The high-cut filter 13c is a filter with a variable cutoff frequency _B , as shown in FIG. 6, for example, and when the high frequency component of the echo signal is attenuated due to a deep observation point, as shown in FIG. As a result of the multiplication of the echo signal and the reference signal in the phase detection circuit 13a, the frequency spectrum folded by direct current as shown in FIG. 7e is converted into a frequency spectrum as shown in FIG. By switching the cutoff frequency _B , the waveform is shaped to produce the same effect as when the frequency spectrum of the echo signal is shaped to be almost symmetrical about the peak frequency r', as shown in Figure 7g. configured to provide a signal.

When the reference frequency r is changed by the switch SWE of the reference signal circuit 13b, the correction circuit 13h outputs information regarding the change in the cut-off frequency _B corresponding to the change to the high-cut filter 13c, and also outputs the Doppler shift signal. outputting correction information to the real-time frequency analyzer 13f for shifting the center of the frequency spectrum by the Doppler shift frequency corresponding to the change in the reference frequency r;
The real-time frequency analyzer 13f is configured to automatically perform corrections associated with variations in the reference frequency r. An example of a method for switching the cutoff frequency _B in the high-cut filter 13c based on the information from the correction circuit 13h is to electronically switch the elements constituting the high-cut filter 13c. Further, as a method of moving the spectral center of the Doppler signal obtained by the Doppler shift frequency corresponding to the change in the reference frequency by the real-time frequency analyzer 13f based on the correction information by the correction circuit 13h, for example,
When adopting the FFT method for the frequency analyzer 13f,
One method is to correct the spectrum that is the result of FFT calculation by the variation in the center of the frequency spectrum of the Doppler shift signal by setting the initial value of the address of the output RAM where the FFT calculation result is stored and the readout clock frequency. It will be done.

The configuration of the blood flow observation apparatus which is an embodiment of the present invention has been described above in detail.Next, the operation of the main part of the present invention will be explained in detail using the embodiment.

First, a power supply (not shown) is input to operate the basic signal generating section 7, and output necessary pulse signals to the scanning control section 8, display mode control section 10, and observation point position setting section 11. The ultrasound probe 14 is driven via the transducer controller 9 by the coded signal from the scan controller 8 to emit ultrasound pulses, and the reflected echo signal is amplified by the transducer controller 9. Thereafter, this is outputted to the display mode control section 10 as a data signal. The display mode control section 10 inputs the coded signal and data signal from the scan control section 8, and causes the display section 12a to scan scanning lines in a fan shape, thereby displaying a tomographic image.

Next, when simultaneously displaying an M mode image and a Doppler mode image of a specific region in the tomographic image appearing on the display section 12a on the display section 12b, the display section 12
M mark 3 and observation point 2 at a are moved as follows.

That is, by operating the switch SWA of the M mark position setting circuit 11a, the M mark scanning control circuit 8a
The M mark 3 is moved by changing the M mark position signal output to the M mark position signal. Next, observation point position setting circuit 11
When the switch SWB in b is operated, the number of clock pulses from the main oscillator 7a of the observation point position setting circuit 11b is changed, and the clock pulses from the main oscillator 7a are counted appropriately from the starting point of the M mark 3. Move the position of observation point 2.

Next, the echo signal from the wave transmitting/receiving circuit 9b is input to the Doppler detection section 13, and first, the echo signal is multiplied by the reference signal from the reference signal circuit 13b in the phase detection circuit 13a, and a Doppler shift signal is extracted. On this occasion,
When observing a shallow area, the frequency spectrum of the received ultrasonic echo signal has small attenuation in the high frequency part, and it is considered to be symmetrical about the center frequency of the frequency spectrum of the transmitted ultrasonic pulse, for example 2.4MHz. Set frequency r to 2.4MHz. When observing a deep part, the frequency spectrum of the received ultrasonic echo signal has a large attenuation in the high frequency part, and its peak moves to the side lower than the center frequency of the frequency spectrum of the transmitted ultrasonic pulse, for example 2.4MHz. Therefore, as shown in Figure 7d, r
to its peak frequency to increase the detection efficiency of the Doppler shift signal. These operations can be performed by setting the frequency division number of the programmable frequency divider _13b3 to r/rate. The frequency division number is set by operating the switch SWE and outputting an appropriate program code from the reference frequency setting circuit _13b4 to the programmable frequency divider _13b3 .

The Doppler shift signal detected by the phase detection circuit is
The high cut filter 13c removes unnecessary high frequency components, and the correction circuit 13h sets the cutoff frequency _B to an appropriate value following changes in the reference frequency r. The echo signal is corrected by attenuating high frequency components. After that, the sample hold circuit 13d
The Doppler shift signal at the position of the observation point set in is extracted and enters the bandpass filter 13e.

The output of the bandpass filter 13e is input to a frequency analysis circuit 13f, and the frequency spectrum of the Doppler shift signal is outputted every moment. The average frequency circuit calculates the average frequency m by equation (2) m = 〓 ⁱ i・Pi / 〓 ⁱ Pi ...(2) m: Average frequency of the frequency spectrum of the Doppler shift signal i: Frequency spectrum of the Doppler shift signal Frequency Pi: Calculates the magnitude of the frequency spectrum of the Doppler shift signal. These results are selected by SWC and SWD, and are output to the display section 12b together with the M mode image via the fourth addition circuit 13i and the third addition circuit 10d. Furthermore, due to the correction information output from the correction circuit 13h, the peak frequency of the frequency spectrum of the echo signal during deep observation shifts to the lower frequency side, so that the frequency spectrum of the Doppler shift signal follows the displacement of the reference frequency r. will be corrected.

Although one embodiment of the present invention has been described in detail above,
It goes without saying that the present invention is not limited to the embodiments described above, and includes various modifications without departing from the gist of the invention. For example, in the embodiment described above, the reference frequency r was manually changed by the switch SWE of the reference signal circuit 13b, but the reference signal circuit 13b changes the reference frequency r automatically in conjunction with the depth of the observation point. 1
3b, and the characteristics of the high-cut filter 13c are changed according to the reference frequency r of the reference signal output from the reference signal circuit 13b, and the frequency analyzer 13f is made to perform correction based on the correction information. good. Also, the reference frequency r is
The change may be made automatically by providing a peak detection circuit that detects the peak of the frequency spectrum of the received ultrasonic echo signal.

Further, in the embodiment, a high-cut filter 13c that is linked to the reference frequency r is provided at the rear stage of the phase detection circuit 13a, but a high cut filter 13c that changes the center frequency in conjunction with the reference frequency r is provided at the front stage of the phase detection circuit 13a. A first correction means having a circuit configuration as shown in FIG. 8, for example, including a bandpass filter may be employed. In FIG. 8, a gate circuit 15 extracts an echo signal at a desired observation point from the received echo signal output from the wave transmitting/receiving circuit 19b, and an echo signal at the desired observation point output from the gate circuit 15 is input. , a frequency spectrum detection circuit 1 that measures the frequency spectrum of an echo signal while performing averaging within a predetermined volume in order to remove errors due to differences in phase of the echo signal.
6, the measured frequency spectrum and the reference frequency r set by the switch SWE of the reference signal circuit 13b.
A filter characteristic determining circuit 17 calculates the optimum filter characteristics for shaping the frequency spectrum into a symmetrical frequency spectrum with reference frequency r as the center, and calculates the high frequency components and low frequency components of the echo signal based on the filter characteristics. The first correction means includes an echo filter 18 that cuts out the component. With this configuration, the Doppler detection section 1
3, the frequency spectrum of the echo signal whose high frequency components have been attenuated can be shaped accurately and symmetrically about the reference frequency r. In this case, the delay circuit 19 is used to compensate for the time required to calculate the filter characteristics. Further, the high-cut filter 13c is used to cut off high frequencies in the phase-detected echo signal. Furthermore, the frequency spectrum detection circuit 16 may be configured with a frequency analyzer, and the filter characteristic determining circuit 17 may be configured with an arithmetic device such as a microcomputer.

Further, the first correction means may be configured as shown in FIG. In this case as well, the first correction means is provided before the phase detection circuit 13a, and is based on the attenuation of the echo signal at the observation point at an arbitrary depth, calculated based on the attenuation coefficient of the ultrasonic medium, such as a living body. It has a filter characteristic determination circuit 17 that stores filter characteristics for canceling distortion and reads out the filter characteristics according to the position of an observation point, and the echo filter 18.

〔Effect of the invention〕

According to this invention, the following effects can be achieved. In other words, it compensates for the decrease in reception sensitivity that occurs due to the attenuation of the high frequency part of the received ultrasonic echo signal, which is inevitable when observing deep areas, and also compensates for the decrease in reception sensitivity that occurs due to the attenuation of the high frequency part of the received ultrasonic echo signal. By correcting the deviation toward the low frequency portion, it is possible to obtain an appropriate frequency spectrum when frequency-analyzing and outputting the Doppler signal, and it is also possible to prevent the average frequency from shifting toward the low frequency portion. With the above, the accuracy of the blood flow observation device can be improved.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the B/D mode display, Figures 2 a to f are explanatory diagrams showing the relationship between the frequency spectrum of the echo signal and the frequency spectrum of the Doppler signal, and Figures 3 a to b are the diagrams of the echo signal. FIG. 4 is a block diagram showing an embodiment of the present invention; FIG. 5 is a block diagram showing a reference signal circuit in the embodiment; FIG. 6a
~c is an explanatory diagram showing the characteristics of the high cut filter controlled by the correction circuit of the above embodiment, and FIG. 7a
-g are explanatory diagrams showing correction of the frequency spectrum of an echo signal, and FIGS. 8 and 9 are block diagrams showing a Doppler detection section in other embodiments of the present invention. 7... Basic signal generation circuit, 7a... Main oscillator,
7b...first frequency dividing circuit, 7c...second frequency dividing circuit,
7d...Third frequency dividing circuit, 7e...First gate circuit, 7f...Second gate circuit, 8...Scanning control section, 8a...M mark scanning control circuit, 8b...B
Mode scanning control circuit, 8c...first addition circuit, 9
...transducer control unit, 9a...transducer scanning circuit, 9b...wave transmitting/receiving circuit, 10...
...Display mode control section, 10a... B mode display circuit, 10b... Second addition circuit, 10c... M mode display circuit, 10d... Third addition circuit, 11...
Observation point position setting section, 11a...M mark position setting circuit, 11b...Observation point setting circuit, 12a...Display section, 12b...Display section, 13...Doppler detection section, 13a...Phase detection circuit, 13b ...Reference signal circuit, 13c...High cut filter, 13d
...Sample hold circuit, 13e...Band pass filter, 13f...Real-time frequency analyzer, 1
3g...average frequency circuit, 13h...correction circuit,
13i...Fourth addition circuit, 14...Ultrasonic probe.

Claims (1)

[Claims] 1. In an ultrasonic pulse Doppler device that can detect a Doppler signal by phase-detecting a received ultrasonic echo signal with a reference signal, frequency distortion of the Doppler signal caused by a change in the frequency band of the ultrasonic echo signal is To obtain a frequency spectrum of an ultrasonic echo signal that is symmetrical about the corrected peak frequency, comprising a first correction means for correcting and a second correction means for correcting a shift in peak frequency caused by the first correction means. An ultrasonic pulsed Doppler device featuring: 2. The ultrasonic pulse Doppler apparatus according to claim 1, wherein the first correction means includes a filter whose frequency characteristics are variable depending on the frequency of the reference signal. 3. The ultrasonic pulse Doppler apparatus according to claim 1, wherein the second correction means is a frequency analyzer.