JPS63209632A - Ultrasonic wave receiver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an ultrasonic receiving device that mixes a plurality of received high frequency signals with a local oscillation frequency signal, converts the frequency into an intermediate frequency signal, and adds the phased signal. .

(Prior Art) B-mode devices that obtain tomographic images are often used as ultrasonic diagnostic Ili devices. There are various scanning methods for this device, but the internal mold sector scanning is an electronic scanning method that does not involve mechanical scanning, can increase the scanning speed, and is free from mechanical wear. It has the advantage of not making mechanical noise, and has been widely used in recent years. An example of this electronic sector scanning method is shown in FIG. Figure (a) shows the state when transmitting waves, and figure (b) shows the state when receiving waves. In the figure, reference numeral 1 denotes a camera element, which controls the phase of each transducer element 1 using a delay line 2 to emit an electrosonic beam in the direction of the arrow. The received signals obtained from each transducer element 1 are delayed through a delay line 2 and synthesized so that they are in phase in the same direction as the emitted ultrasonic beam shown in FIG. Note that the length of the delay wA2 in the figure is proportional to the delay time.

(Problem to be Solved by the Invention) Incidentally, it is essential in the pulsed ultrasound method to perform phasing and addition of multiple delivered signals using a delay line, but the delay line is essentially a low-pass filter ( (LPF), if a long delay line is used, the loss of the received radio frequency signal (RF) will increase, and there is a limit to the length of the delay line that can be used. Therefore, the received wave ^
If a frequency signal is frequency-converted into an intermediate frequency signal (IF) and a delay line is used, the loss is considerably improved and a long delay line can be used. Furthermore, when the delay time step is the same as in the high frequency case, more accurate phasing and addition can be performed than in the high frequency case. However, when multiplying multiple received high-frequency signals q by the local excavation frequency to obtain each intermediate frequency signal, the phase of each received high-frequency signal with respect to the local oscillation frequency signal (shiF) is determined by its arrival delay time. Because of this, correct phasing and addition cannot be performed even if the obtained intermediate frequency signal is passed through a delay line. In order to perform correct phasing and addition of intermediate frequency signals, it is necessary to adjust the phase of the local oscillation frequency signal to rA for each delivered high-frequency signal, but the phase of each delivered high-frequency signal changes depending on the azimuth of the ultrasound beam. Therefore, it is troublesome to adjust the phase of the intermediate frequency signal accordingly.

The present invention has been made in view of the above points, and an object of the present invention is to convert a plurality of received high-frequency signals into intermediate frequency signals and perform phasing and summation of the received high-frequency signals using a delay line. The object of the present invention is to realize an ultrasonic receiving device in which the phase can be easily adjusted.

(Means for Solving the Problem) The present invention which solves the above problem mixes a plurality of received high frequency signals with a local oscillation frequency signal, converts the signal into an intermediate frequency signal, and performs phasing and addition using a delay line. In an ultrasonic receiver, means for inputting a local oscillation frequency signal to the starting end of a delay line, and extracting each local oscillation frequency signal from a delay point on the delay line corresponding to the arrival delay time of each of the plurality of received 1% frequency signals. means for frequency converting the corresponding received high frequency signals into intermediate frequency signals using these local oscillation frequency signals; and means for inputting each converted intermediate frequency signal to each local oscillation frequency signal extraction point on the delay line. and means for outputting an intermediate frequency phasing and addition signal from the terminal end of the delay line.

(Function) The delay line for phasing and adding intermediate frequency signals is also used as a delay line for adjusting the phase of the local oscillation frequency signal, so the phase of the local oscillation frequency signal always matches the phase of the received high frequency signal. Match.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

In the figure, RF1, RF2. RF3 is a received high frequency signal from each transducer element that received the ultrasound reflected from inside the subject. The number of receiving high-frequency signal inputs is actually large, but for convenience, the receiving high-frequency signal inputs are the three mentioned above.
This will be explained assuming that there are 1. Reference numeral 3 denotes a delay line having a total delay time of T for giving a predetermined delay to the received signal from each transducer element according to the distance from each direction within the subject.

The delay line 3 has taps c and d between a and e at both ends, and the delay time between each tap is set as follows.

a-b; r1' b-e: rta-c:
r2/c −e; τ2a −d; r3'
d −e ; r3 where τ1'+ τ2', τ3'
is the received high frequency signal RF1. RF2. With a delay time equal to the arrival delay time of EF3, τ1. τ2. τ3 is a delay time necessary for the intermediate frequency signal based on the received high frequency signal to be phased and added at the terminal end e of the delay line 3.

4 are the received high frequency signals RFl, RF2 . A local frequency oscillator (LO) that generates a local oscillation frequency signal for converting RF3 into an intermediate frequency signal in mixers 6A, 6B, and 6C.The output local oscillation frequency signal is 3co
This is a signal represented by aωLt. A resistor 5 has a resistance value equal to the characteristic impedance ZO of the delay line, and is connected to one end a of the delay line 3. 7A, 7B, and 7G are buffer amplifiers that amplify the local oscillation frequency signal output from the local frequency loss oscillator 4, and the output signal is passed through a bandpass filter (BPF).
It passes through 8A, 8B, and 8C and is input to mixers 6A, 6B, and 6C. 9A, 9B, and 9C pass only intermediate frequency signals obtained by down-converting input high frequency signals by mixers 6A, 6B, and 6G.

This is a low frequency wave generator that blocks high frequency signals and local oscillation frequency signals, and its output signal is sent to amplifiers 10A and 10B.

10C and tap b of delay line 3.

They are input to C and d, respectively. Reference numeral 11 denotes a terminating resistor connected to the output end of the delay line 3 and having a resistance value equal to the characteristic impedance Zo of the delay line 3. From the I terminal e of the delay line 3, a signal obtained by phasing and adding all the intermediate frequency signals is amplified by the amplifier 12 and output.

Next, the operation of the embodiment configured as described above will be explained.

The received high frequency signal RFl is input to the mixer 6Δ. On the other hand, the local oscillation frequency signal output from the local frequency oscillator 4 is input to the delay line 3 through a resistor 5, and is output from tap b after being delayed by τl'. Let this output signal be LFl. This output signal LF1 is amplified by a buffer amplifier 7A, and is input to a mixer 6A via a bandpass filter 8A. The mixer 6A multiplies RFl and LFl to convert the received high frequency signal into an intermediate frequency signal. The mixer 6△
The output signal has the upper sideband signal removed by the low frequency waveform generator 9A to become an intermediate frequency signal IF1 of only the lower sideband, which is inputted again to the tap b of the delay line 3 via the amplifier 10A. Bandpass filter 8A prevents this intermediate frequency signal from flowing back to mixer 6A. The intermediate frequency signal IF1 input to the delay line 3 is delayed by τ1 and reaches the terminal e.

Received signal RF2. RF3 is tap C with a delay of $113.

The local excavation frequency signal output from tap d is F2.1
The frequency is converted by F3, and the intermediate frequency signal IF2. IF
The operation in which signal 3 is output from the terminal e of the delay line 3 is the same as in the case of RFI, so a description thereof will be omitted. The intermediate frequency signals subjected to the three respective delays are phased and summed at the terminal e of the delay a3 and amplified in the amplifier 12.

Next, the state of phasing and addition in the operation of the above circuit will be explained by calculation.

The high frequency signals of frequency ω0 from each vibrator element are expressed as follows.

RFl:A+CO3ωo (t+τt T)RF2
:A2cosωo (j+τ2−T)RF3:AtC
O3ω3 (j+τ3−■)...(1) Tap b of the delay line 3 of the output signal of the 8-part frequency oscillator 4,
Signals LF1.c, d. LF2. LF3 has a delay m
3, each receives a delay of 1', τ/, and τ3', resulting in the following equation.

LFl: acosωc, (j−τ1′)LF2;
BcosωL (−τ2′)LF3:3cosω
L (t-τ3')...(2) As is clear from the configuration of the delay line 3 in FIG. 1, the relationship between the delay times is as shown in the following equation.

τ1+τ1′ Wealth τ2+τ2′ Expansion τ3+τ3′−T
...(3) Mixer 6A,
68.6C multiplies the received high frequency signal and the local oscillation frequency signal, and the low frequency wave generator 9A.

If only the lower sideband is taken out at 9B and 9C, IFl of the following formula
, IF2. TF3 is 1'? It will be done.

In the mixer 6A, (1), (2), (3) formula% formula% ))] IF2 − (A2 B/2 ) cos (ω rF (t
+τ2-lower)) IF3 = (A3 B/2) CO8((t) IF
(3-T at t+)) ... (4) (4) Formula (7) rFl, [F2. HF3 is further l wire extension 3
1. τ2. Since they are added after receiving a delay of τ3, the output ΣIF is ΣIF=(A+8
/2) cos (cc+ HF(t −T) )+
(A2 B/2) COS (ωIF (t
-T) )+ (A3 B/2)cos (ωIF
(t −T) )−(A!+△2 +A!) (
B/2)cos(ωI+-(t-T)). In this way, by using one delay line for both the delay of the local oscillation frequency signal and the delay of the intermediate frequency signal obtained by converting the received high frequency signal, it is possible to obtain an intermediate frequency signal that is correctly phased and summed. .

A timing chart of this signal is shown in FIG.

In the figure, the same parts and signals as in FIG. 1 are given the same reference numerals. In the figure, LFO is the output signal of the local frequency oscillator 4, and the phase when the delay O at the starting end a of the delay line 3 is θ. As shown in the figure, RFI is τs'(-T-τt) and RF2 is τ2'(=T-τz
>, RF3 is input as a signal with a delay of τs' (-T-A3). LFl, IF2, IF3 are LFOs with τ weights′, τ2′, τ3 due to the delay line 3, respectively.
Tap b after a delay of '.

In the signals output from ports c and d, as shown in the figure, the phase points θ are delayed by l, τ2', and τ3', respectively, and are delayed by RFl, RF2. It maintains the same phase position with respect to RF3. Therefore, RFl, RF2. RF3 and L
Fl, IF2. 1, Fl, which are the respective products of lF3,
HF2. HF3 is also input to taps b, c, and d of the delay line 3 as signals having the same delay as the original high-frequency signal.

This IFl, HF2. The signal of IF3 is further transmitted to the terminal fNe of delay line 3 at l, τ2 . After a delay of τ3,
The signals are phased as in-phase signals having the same delay time and added to obtain ΣrF.

Each of these intermediate frequency signals is frequency-converted using a local oscillation frequency signal with a delay equal to that of the received high-frequency signal and inputted again to each position of the delay line 3, so that each local oscillation frequency signal LF1. It is clear from FIG. 2 that phasing and addition can be performed correctly without any special processing on LF2°1F3.

FIG. 4 is a block diagram of another embodiment of the invention. This embodiment is an example in which a short delay line is inserted in each mixer circuit. In the figure, parts equivalent to those in FIG. 1 are given the same reference numerals. In the figure, 13A is a delay line with delay time τA;
B is a delay line with a delay time τB, 13G is a delay line with a delay time τC, and when compared with the delay time of one delay line 3 in FIG. 1, they are as shown in FIG. That is, as shown in the following equation.

T-τA+τB+τC τ1- and ^+τB+τC A2- τB + τC τ! If we assume that there is a delay line with a delay time of 0 between the resistor 5 and the delay line 13A, the circuit in Figure 4 will be as shown in Figure 5. As can be seen from the arrangement of the delay lines, this circuit can be regarded as the same as the circuit shown in FIG. 1, so it is clear that the same result as the circuit shown in FIG. 1 can be obtained.

As explained above, the local oscillation frequency signal is extracted from the delay point of the delay line equal to the arrival delay time of each received high-frequency signal, the received high-frequency signal is frequency-converted, and the obtained intermediate frequency signal is transmitted to each local Since the signals are input to the oscillation frequency signal extraction point, the phases of each signal match perfectly at the end of the delay line, and the signals can be phased and summed without any special measures.

In addition, although the frequency of the intermediate frequency signal in the above embodiment is a single frequency, it is a fairly high frequency (about 10 MH2).
Therefore, the delay line causes attenuation corresponding to the delay W,
If the output of the mixer becomes dependent on the level of the local oscillation frequency signal, an amplitude error will occur due to the apparent amount of delay. It is sufficient to take measures such as inserting a compensation amplifier after converting the frequency into an intermediate frequency signal.

(Effects of the Invention) As described above in detail, according to the present invention, when converting a plurality of received high-frequency signals into intermediate frequency signals and performing phasing and addition on a delay line, each of the plurality of received high-frequency signals and The phase with the local oscillation frequency signal can be easily adjusted, and phasing and addition using the intermediate frequency band can be performed accurately, which has a great practical effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a signal timing chart, FIG. 3 is an explanatory diagram of an electronic sector scanning system, FIG. 4 is a diagram of another embodiment of the present invention, and FIG. FIG. 5 is a diagram comparing the delay lines in the embodiments of FIGS. 1 and 4. 1... Camera element 2.3.13A, 138.13G... Delay line 4...
10 6A, 6B, 6C...Mixer 7A, 78.7G...Buffer amplifier 8Δ, 8B, 8
C...BPF 9A, 9B, 9C...LPF

Claims (1)

[Claims] In an ultrasonic receiving device that mixes a plurality of received high frequency signals with a local oscillation frequency signal, converts the mixture into an intermediate frequency signal, and performs phasing and summation using a delay line, means for inputting a local oscillation frequency signal to a starting end of a delay line; Means for extracting local oscillation frequency signals from delay points on the delay line corresponding to arrival delay times of respective received high frequency signals, and converting corresponding received high frequency signals into intermediate frequency signals using these local oscillation frequency signals. A means for converting the frequency, a means for inputting each converted intermediate frequency signal to each local oscillation frequency signal extraction point on the delay line, and a means for outputting an intermediate frequency phasing and addition signal from the terminal end of the delay line. Features of ultrasonic receiving device.