Ultrasonic probe, ultrasonic diagnostic apparatus, and ultrasonic transmission/reception switching method
A switch circuit connected to a transducer, a reception circuit connected to the switch circuit, a first switch element connected to a reception terminal provided between the switch circuit and the reception circuit, a first resistance element connected to a control terminal of the switch circuit, a second resistance element provided inside the reception circuit, and a second switch element provided inside the reception circuit are provided.
1. An ultrasonic probe comprising:
a transducer;
a switch circuit connected to the transducer; a reception circuit connected to the switch circuit;
a first switch element connected to a reception terminal provided between the switch circuit and the reception circuit;
a first resistance element disposed outside of the switch circuit and connected to a control terminal of the switch circuit;
a second resistance element provided inside the reception circuit;
a second switch element provided inside the reception circuit;
a third switch element provided inside the reception circuit; and
a capacitor provided inside the reception circuit; wherein
the switch circuit is composed of a pair of MOS transistors;
the control terminal constitutes a gate of each of the pair of MOS transistors;
at least two or more elements of a first impedance of the control terminal, a second impedance of the reception terminal, a time constant of the reception circuit, and a gain of the reception circuit sequentially switch, in a certain period of time after a transmission period ends, from a different state to a steady reception state, the different state being different from the steady reception state which occurs after the certain period of time elapses;
the first impedance of the control terminal is determined by the first resistance element connected to the control terminal;
the second impedance of the reception terminal is determined by the first switch element connected to the reception terminal;
in the certain period of time, the time constant of the reception circuit is a first time constant which is determined by the capacitor and a resistance of the third switch element;
in a steady reception period after the certain period of time, the time constant of the reception circuit is a second time constant which is determined by the capacitor and the second resistance element provided inside the reception circuit, the first time constant is smaller than the second time constant; and
the gain of the reception circuit is determined by the second switch element provided inside the reception circuit.
2. The ultrasonic probe according to claim 1 , wherein a saturation signal is not output in the different state maintained for the certain period of time.
3. The ultrasonic probe according to claim 1 , wherein the first impedance of the control terminal is controlled by switching a resistance value of the first resistance element.
4. The ultrasonic probe according to claim 1 , wherein the gain of the reception circuit is controlled by switching the second switch element provided between differential outputs of the reception circuit.
5. The ultrasonic probe according to claim 1 , wherein the gain of the reception circuit is controlled by short-circuiting a single-ended output of the reception circuit by the second switch element connected to a DC output common voltage.
6. The ultrasonic probe according to claim 1 , wherein
the first switch element is composed of a transistor connected between the reception terminal of the switch circuit and a ground terminal, and
the second impedance of the reception terminal is controlled by the transistor.
7. The ultrasonic probe according to claim 6 , wherein
the transistor is composed of an FET formed on an SOI substrate, and
the FET is electrically isolated by being surrounded by DTI.
8. The ultrasonic probe according to claim 2 , wherein among the pair of MOS transistors constituting the switch circuit, a first channel width of the first MOS transistor positioned on the transducer side is configured to be smaller than a second channel width of the second MOS transistor positioned on the reception terminal side.
9. The ultrasonic probe according to claim 1 , wherein the first resistance element is directly connected to the control terminal of the switch circuit without any circuit elements therebetween.
10. An ultrasonic diagnostic apparatus comprising:
an ultrasonic probe including
a plurality of transducers,
a transmission/reception circuit that is provided corresponding to each of the plurality of transducers and switches an ultrasonic wave from transmission to reception,
an adder circuit that adds outputs of a plurality of the transmission/reception circuits, and
a control circuit that controls the transmission to the reception switching; and
a main unit that receives an output of the adder circuit and transmits a predetermined control signal to the control circuit,
the ultrasonic probe having
a switch circuit connected to the plurality of transducers,
a reception circuit connected to the switch circuit,
a first switch element connected to a reception terminal provided between the switch circuit and the reception circuit,
a first resistance element disposed outside of the switch circuit and connected to a control terminal of the switch circuit,
a second resistance element provided inside the reception circuit,
a second switch element provided inside the reception circuit,
a third switch element provided inside the reception circuit, and
a capacitor provided inside the reception circuit, wherein
the switch circuit is composed of a pair of MOS transistors;
the control terminal constitutes a gate of each of the pair of MOS transistors;
at least two or more elements of a first impedance of the control terminal, a second impedance of the reception terminal, a time constant of the reception circuit, and a gain of the reception circuit sequentially switch, in a certain period of time after a transmission period ends, from a different state to a steady reception state, the different state being different from the steady reception state which occurs after the certain period of time elapses;
the first impedance of the control terminal is determined by the first resistance element connected to the control terminal;
the second impedance of the reception terminal is determined by the first switch element connected to the reception terminal;
in the certain period of time, the time constant of the reception circuit is a first time constant which is determined by the capacitor and a resistance of the third switch element;
in a steady reception period after the certain period of time, the time constant of the reception circuit is a second time constant which is determined by the capacitor and the second resistance element provided inside the reception circuit, the first time constant is smaller than the second time constant; and
the gain of the reception circuit is determined by the second switch element provided inside the reception circuit.
11. The ultrasonic diagnostic apparatus according to claim 10 , wherein the control circuit controls so that a saturation signal is not output in the different state maintained for the certain period of time.
12. The ultrasonic diagnostic apparatus according to claim 10 , wherein the first resistance element is directly connected to the control terminal of the switch circuit without any circuit elements therebetween.