Ultrasonic transducer for ranging measurement with high directionality using parametric transmitting array in air and a method for manufacturing same
View Patent ↗A multiple resonances type ultrasonic transducer for a ranging measurement with high directionality using a parametric transmitting array in air, includes an ultrasonic actuator unit formed with a regularly mixing array of first unit actuators having a resonance frequency of f 1 and second unit actuators having a resonance frequency of f 2. The ultrasonic actuator unit generates a difference frequency wave (f d =f 1 −f 2 ) with high directionality by forming a parametric transmitting array in air through generating two ultrasonic waves with high pressure in air. Further, the transducer includes an ultrasonic sensor unit formed with one or more unit sensors having a resonance frequency of the difference frequency (f d =f 1 −f 2 ), for sensing a reflected ultrasonic pulse signal from a target.
1. A multiple resonances type ultrasonic transducer for a ranging measurement using a parametric transmitting array in air, comprising:
an ultrasonic actuator unit formed with a regularly mixing array of first unit actuators having a resonance frequency of f 1 and second unit actuators having a resonance frequency of f 2 , for generating a difference frequency wave (f d =f 1 −f 2 ) with high directionality by forming a parametric transmitting array in air through generating two ultrasonic waves with high pressure in air; and
an ultrasonic sensor unit formed with one or more unit sensors having a resonance frequency of the difference frequency (f d =f 1 −f 2 ) , for sensing a reflected ultrasonic wave signal from a target,
wherein the difference frequency (f d ) is selected within a range of about 20kHz ˜60kHz.
2. The transducer of claim 1 , wherein the ultrasonic actuator unit and the ultrasonic sensor unit are manufactured to be integrated on a same substrate in a thin plate form by using MEMS.
3. The transducer of claim 1 , wherein the unit actuators and the unit sensors are formed with a same laminated structure, the laminated structure including:
a substrate part, wherein an outer portion thereof is formed as a thick fixed supporting portion and the central portion thereof is formed as a thin membrane portion so that the membrane portion is vibrated vertically;
a lower electrode formed on top surface of the substrate part;
a piezoelectric body formed on the lower electrode, for deriving a vibration from the membrane portion by vibrating itself vertically according to an applied voltage thereto; and
an upper electrode formed on the piezoelectric body, for applying a predetermined voltage to the piezoelectric body in cooperation with the lower electrode.
4. The transducer of claim 3 , further comprising an insulating layer formed between the substrate part and the lower electrode, for insulating the substrate part.
5. The transducer of claim 1 , further comprising:
a first lining pattern for electrically connecting the unit actuators of the ultrasonic actuator unit with each other and a pair of first connecting terminals for electrically connecting the first lining pattern with a voltage source; and
at least one second lining pattern, each being separately provided to an unit sensor of the ultrasonic sensor unit for an electrical connection thereof, and at least one pair of second connecting terminals, each for electrically connecting the second lining pattern with a voltage source.
6. The transducer of claim 1 , wherein the regularly mixing array of the first unit actuators and the second unit actuators is one of (a) a square type mixing array, (b) a hexagonal type mixing array, and (c) a ring type mixing array.
7. The transducer of claim 3 , wherein the structure of the membrane portion is one of (a) a general membrane type, (b) a cantilever type, and (c) a piston type.
8. The transducer of claim 3 , wherein, in case the thickness of the membrane portion of the ultrasonic actuator unit and that of the ultrasonic sensor unit are identical, in order to relatively decrease the resonance frequency of the ultrasonic sensor unit, the membrane portion of the respective unit sensors has a size larger than that of the respective unit actuators, or the structure of the membrane portion of the respective unit sensors has a spring coefficient lower than that of the respective unit actuators.
9. The transducer of claim 1 , wherein the length of one square side is determined to be about 30mm˜50mm when assuming the ultrasonic transducer to be in a shape of a square, whereas the diameter thereof is set at about 30mm˜60mm when assuming it to be in a circular shape.
10. The transducer of claim 1 , wherein one unit sensor is provided at the central or any other portion of the ultrasonic transducer.
11. The transducer of claim 1 , wherein two or more unit sensors are provided at the outer portion of the ultrasonic transducer.
12. The transducer of claim 3 , wherein the electrodes of the unit actuators are connected with each other in series by connecting the upper electrode of one unit actuator with a lower electrode of its following unit actuator next thereto.
13. The transducer of claim 3 , wherein the electrodes of the unit actuators are connected with each other in parallel by connecting the upper electrodes together and the lower electrodes together.
14. The transducer of claim 13 , wherein the electrodes of the first and the second unit actuators are together connected with each other in parallel.
15. The transducer of claim 13 , wherein the electrodes of the first unit actuators are connected with each other in parallel whereas the electrodes of the second unit actuators are connected with each other in parallel.
16. The transducer of claim 1 , further comprising an upper housing and a lower housing respectively combined with the upper side and the lower side of the ultrasonic transducer, for protecting the ultrasonic transducer.
17. The transducer of claim 16 , wherein the upper housing is of a grill type and the lower housing is manufactured with a sound-absorbing material.
18. A method for manufacturing multiple resonances type ultrasonic transducer for a ranging measurement with high directionality using a parametric transmitting array in air, comprising the steps of:
preparing an SOT (Silicon on Insulator) wafer with an intermediate oxidation layer;
insulating the SOT wafer by forming thin oxidation layers on the top and the bottom surfaces of the wafer;
forming a lower electrode, a piezoelectric body, and an upper electrode to be laminated in sequence on the top surface of the SOI wafer; patterning the upper electrode, the piezoelectric body, and the lower electrode;
forming an insulating layer for insulating the upper electrode and the lower electrode;
forming a lining pattern by patterning the insulating layer; and
forming the membrane portion by removing the lower side of the central portion of the wafer and the intermediate oxidation layer after removing the oxidation layer on the bottom surface of the wafer.
19. The method of claim 18 , further comprising the step of annealing for improving a performance of the piezoelectric body after forming the piezoelectric body.