Digital signal processing device for calculating real and imaginary parts of an input signal

• US 4,984,188 A
• Filed: 06/06/1989
• Issued: 01/08/1991
• Est. Priority Date: 12/11/1986
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kato, Haruo
• Primary Examiner(s): Shaw, Dale M.
• Application Number:
  US07/363,395
• Time in Patent Office: 581 Days
• Field of Search: 364/725, 364/713.25, 375/61, 375/77, 128/661.07-662.01
• US Class Current: 708/400
• CPC Class Codes: G01F 1/663 by measuring Doppler frequency shift
• CPC Class Codes: G01S 15/582 using transmission of interrupted pulse-modulated waves and based upon the Doppler effect resulting from movement of targets
• CPC Class Codes: G06F 17/14 Fourier, Walsh or analogous domain transformations , e.g. Laplace, Hilbert, Karhunen-Loeve, transforms for correlation function computation G06F17/156; spectrum analysers G01R23/16

Abstract

A digital input signal is input to a real part calculator and an imaginary part calculator. The real part calculator comprises an M-stage shift register formed of an M number of series-connected D-type latch circuits and for delaying the input signal in a stepwise manner where M represents 2 or more positive integers. The imaginary part calculator comprises an N number of series-connected D-type latch circuits for delaying the input signal in a stepwise manner, coefficient registers for storing coefficients corresponding to the respective latch circuits, multipliers for multiplying the output of the latch circuit and the corresponding coefficient thereof, and an adder for adding together all the outputs of the multipliers. Here, N denotes 2 or more positive integers. If N is an odd number, M=(N+1)/2, and, M=N/2 or (N/2)+1 if N is an even number. The coefficient registers store coefficients for enabling the digital filter to perform a Hilbert transformation. The real and imaginary part signals output from the real and imaginary part calculators are input to a phase calculator. The phase calculator comprises a divider for dividing the imaginary part signal by the real part signal, and a calculator for calculating an arctangent of the result of the division. Alternatively, the real and imaginary part signals may be supplied to an envelope calculator, which calculates the root-mean-square of the real and imaginary part signals.

Claims

1. An ultrasonic diagnostic apparatus comprising:

transducer means including an array of ultrasonic transducer elements;

drive means for scanning said ultrasonic transducer elements so as to radiate an ultrasonic pulse to an object of diagnosis;

receiver means for receiving the ultrasonic pulse radiated from said transducer means and reflected by the object of diagnosis and for outputting a digital received signal based on the pulse received;

phase-detecting means for detecting a phase of the digital received signal from said receiver means, said phase-detecting means comprising

imaginary part calculating means for Hilbert-transforming the digital received signal and outputting a Hilbert-transformed signal as an imaginary part signal wherein said imaginary part calculating means is a Hilbert-filter means having a frequency characteristic of a transfer function H(107 ) which is, ##EQU21## if N is an odd number, and ##EQU22## if N is an even number, where h(n) denotes a Hilbert-band-pass filter coefficient and,

if N is an odd number,

a coefficient corresponding to an output of an (N-1)/2-th latch circuit counted from an input end side is h(0), and a coefficient corresponding to an output of an ((N-1)/2)+l-th latch circuit counted from the input end side is ±

(l) and,

if N is an even number,

a coefficient corresponding to an output of an (N/2)±

1-th latch circuit counted from the input end side is ±

h(0), and a coefficient corresponding to an output of an (N/2)±

(1=l)-th latch circuit counted from the input end side is ±

h(∂

), and

real part calculating means for delaying the digital received signal for a given time period which corresponds to a period of time from when the digital received signal is input to said imaginary part calculating means until the Hilbert-transformed signal is output from said imaginary part calculating means, and for outputting a delayed signal as a real part signal;

wherein a transfer function B(ω

) of said real part calculating means is, ##EQU23## if N is an odd number, and ##EQU24## if N is an even number, where b(n) denotes a band-pass filter coefficient and,

if N is an odd number,

a coefficient corresponding to an output of an (-1)/2-th latch circuit counted from the input end side is b(0), and a coefficient of an ((N-1)/2+l)-th latch circuit counted from the input end side is b(l), and

if N is an odd number,

a coefficient corresponding to an output of an (N/2)+1-th latch circuit counted from the input end side is b(0), and a coefficient corresponding to an output of an (N/2)+(1l)-th latch circuit is b(l); and

phase calculating means for calculating an arctangent of a division which is obtained by dividing the imaginary part signal by the real part signal, and for outputting the arctangent as a phase of the digital received signal which indicates a speed and a direction of flow of the object; and

display means for displaying the speed and the direction of the flow of the object on the basis of the phase detected by said phase-detecting means.

2. An ultrasonic diagnostic apparatus comprising:

transducer means including an array of ultrasonic transducer elements;

drive means for scanning said ultrasonic transducer elements so as to radiate an ultrasonic pulse to an object of diagnosis;

receiver means for receiving the ultrasonic pulse radiated from said transducer means and reflected by the object of diagnosis and for outputting a digital receiving signal based on the pulse received;

phase-detecting means for detecting a phase of the digital received signal from said receiver means, said phase-detecting means comprising

digital filter means for outputting, as a real part signal, a predetermined frequency component of the digital received signal;

digital Hilbert-filter means for outputting, as an imaginary part signal, a predetermined frequency component of the digital received signal which is Hilbert-transformed wherein said Hilbert-filter means is a digital Hilbert-filter means having a frequency characteristics of a transfer function (Hω

) of said digital Hilbert-filter means is, ##EQU25## if N is an odd number, and ##EQU26## if N is an even number, where h(n) denotes a Hilbert-band-pass filter coefficient and,

if N is an odd number,

a coefficient corresponding to an output of an (N-1)/2-th latch circuit counted from an input end side is h(0), and a coefficient corresponding to an output of an (N-1)/2)±

l-th latch circuit counted from the input end side is ±

(l) and,

if N is an even number,

a coefficient corresponding to an output of an (N/2)±

1-th latch circuit counted from the input end side is ±

h(0), and a coefficient corresponding to an output of an (N/2)±

(1=l)-th latch circuit counted from the input end side is ±

h(l), and wherein

a transfer function B(ω

) of said digital filter means is, ##EQU27## if N is an odd number, and ##EQU28## if N is an even number, where b(n) denotes a band-pass filter coefficient and,

if N is an odd number,

a coefficient corresponding to an output of an (N-1)/2-th latch circuit counted from the input end side is b(0), and a coefficient of an ((N-1)/2±

l)-th latch circuit counted from the input end side is b(l), and

if N is an odd number,

a coefficient corresponding to an output of an (N/2)±

1-th latch circuit counted from the input end side is b(0), and a coefficient corresponding to an output of an (N/2)±

(1+l)-th latch circuit is b(l); and

phase calculating means for calculating an arctangent of a division which is obtained by dividing the imaginary part signal by the real part signal, and for outputting the arctangent as a phase of the digital received signal which indicates a speed and a direction of flow of the object; and

display means for displaying the speed and the direction of the flow of the object on the basis of the phase detected by said phase-detecting means.

3. An apparatus as in claim 2 wherein said digital Hilbert-filter means comprises:

a shift register formed of an N number (N;

2 or more positive integer) of series-connected latch circuits;

a coefficient register for storing Hilbert-band-pass filter coefficients corresponding to respective outputs of the latch circuit; and

a calculator for multiplying the outputs of the latch circuits by corresponding coefficients and for adding together the results of all multiplications; and

said digital filter means comprises;

a shift register formed of an N number of series-connected latch circuit;

a coefficient register for storing band-pass coefficients corresponding to respective outputs of the latch circuit; and

a calculator for multiplying the outputs of the latch circuits by corresponding coefficients and for adding together the results of all multiplications.

4. An ultrasonic diagnostic apparatus comprising:

transducer means including an array of ultrasonic transducer elements;

drive means for scanning said ultrasonic transducer elements so as to radiate an ultrasonic pulse to an object of diagnosis;

receiver means for receiving the ultrasonic pulse radiated from said transducer means and reflected by the object of diagnosis and for outputting a digital received signal based on the pulse received;

envelope-detecting means for detecting an envelope of the digital received signal from said receiver means, said envelope-detecting means comprising

imaginary part calculating means for Hilbert-transforming the digital received signal and outputting a Hilbert-transformed signal as an imaginary part signal

real part calculating means for delaying the digital received signal for a given time period which corresponds to a period of time from when the digital received signal is input to said imaginary part calculating means until the Hilbert-transformed signal is output from said imaginary part calculating means, and for outputting a delayed signal as a real part signal wherein said Hilbert transform is by way of a digital Hilbert-filter means having a frequency characteristic of a transfer function H(l) of said digital Hilbert-filter means is, ##EQU29## if N is an odd number, and ##EQU30## means h(n) denotes a Hilbert-band-pass filter coefficient and, if N is an odd number,

a coefficient corresponding to an output of an (N-1)/2-th latch circuit counted from an input end side is h(0), and a coefficient corresponding to an output of an ((N-1/2)+l-th latch circuit counted from the input end side is +(l) and,

if N is an even number,

a coefficient corresponding to an output of an (N/2)+1-th latch circuit counted from the input end side is +h(0), and a coefficient corresponding to an output of an (N/2)+(1=∂

)-th latch circuit counted from the input end side is +h(l), and wherein

a transfer function B(ω

) of said real part calculating means is, ##EQU31## if N is an odd number, and ##EQU32## if N is an even number, where b(n) denotes a band-pass filter coefficient and,

if N is an odd number,

a coefficient corresponding to an output of an (N-1)/2-th latch circuit counted from the input end side is b(0), and a coefficient of an ((N-1)/2=l)-th latch circuit counted from the input end side is b(l), and

if N is an odd number,

a coefficient corresponding to an output of an (N/2)+1-th latch circuit counted from the input end side is b(0), and a coefficient corresponding to an output of an (N/2)+(1+l)-th latch circuit is b(l); and

envelope calculating means for calculating a root-mean-square of the imaginary part signal and the real part signal, and for outputting the root-mean-square as an envelope of the digital received signal which indicates a luminance of the object; and

display means for displaying a tomographic image represented by the luminance of the object detected by said envelope-detecting means.

5. An ultrasonic diagnostic apparatus comprising:

transducer means including an array of ultrasonic transducer elements;

drive means for scanning said ultrasonic transducer elements so as to radiate an ultrasonic pulse to an object of diagnosis;

receiver means for receiving the ultrasonic pulse radiated from said transducer means and reflected by the object of diagnosis and for outputting a digital received signal based on the pulse received;

envelope-detecting means for detecting an envelope of the digital received signal from said receiver means, said envelope-detecting means comprising

digital filter means for outputting, as a real part signal, a predetermined frequency component of the digital received signal;

digital Hilbert-filter means for outputting, as an imaginary part signal, a predetermined frequency component of the digital received signal which is Hilbert-transformed wherein said Hilbert-filter means is a digital Hilbert-filter means having a frequency characteristics of a transfer function H(ω

) of said digital Hilbert-filter means is, ##EQU33## if N is an odd number, and ##EQU34## if N is an even number, where h(n) denotes a Hilbert-band-pass filter coefficient and,

if N is an odd number,

a coefficient corresponding to an output of an (N-1)/2-th latch circuit counted from an input end side is h(0), and a coefficient corresponding to an output of an (N-1)/2)+l-th latch circuit counted from the input end side is ±

(∂

) and,

if N is an even number,

a coefficient corresponding to an output of an (N/2)±

1-th latch circuit counted from the input end side is ±

h(0), and a coefficient corresponding to an output of an (N/2)±

(1=l)-th latch circuit counted from the input end side is ±

(l), and wherein

a transfer function B(ω

) of said digital filter means is, ##EQU35## if N is an odd number, and ##EQU36## if N is an even number, where b(n) denotes a band-pass filter coefficient and,

if N is an odd number,

a coefficient corresponding to an output of an (N-1)/2-th latch circuit counted from the input end side is b(0), and a coefficient of an (N-1)/2±

l)-th latch circuit counted from the input end side is b(l), and

if N is an odd number,

a coefficient corresponding to an output of an (N/2)±

1-th latch circuit counted from the input end side is b(0), and a coefficient corresponding to an output of an (N/2)±

(1+l)-th latch circuit is b(l); and

envelope calculating means for calculating a root-mean-square of the imaginary part signal and the real part signal, and for outputting the root-mean-square as an envelope of the digital received signal which indicates a luminance of the object; and

display means for displaying a tomographic image represented by the luminance of the object detected by said envelope-detected means.

6. The apparatus according to claim 5, in which said digital Hilbert-filter means comprises:

a shift register formed of an N number (N≧

2 positive integers) of series-connected latch circuits;

a coefficient register for storing Hilbert-band-pass filter coefficients corresponding to respective outputs of the latch circuit; and

a calculator for multiplying the outputs of the latch circuits by corresponding coefficients and for adding together the results of all multiplications; and

said digital filter means comprises;

a shift register formed of an N number of series-connected latch circuit;

a coefficient register for storing band-pass coefficients corresponding to respective outputs of the latch circuit; and

a calculator for multiplying the outputs of the latch circuits by corresponding coefficients and for adding together the results of all multiplications.