Passive tire pressure sensor and method
First Claim
1. A pressure sensor comprising:
- (a) a surface acoustical wave conductive body having an input transducer disposed to transmit a directional acoustical wave across at least a surface portion of the body;
(b) at least one reflection transducer disposed to receive and reflect the acoustical wave back as a reflected signal;
(c) a pressure transducer disposed adjacent to the surface acoustical wave conducting body, the pressure transducer comprising a flexible conductive membrane;
(d) a cavity sealed by the membrane at a preset reference pressure; and
(e) the membrane deflecting responsive to a predetermined external pressure level to contact the reflection transducer and modulate the signal reflected by the reflection transducer.
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Accused Products
Abstract
A surface acoustic wave device includes a micro-machined pressure transducer for monitoring tire pressure. The device is configured having a micro-machined cavity that is sealed with a flexible conductive membrane. When an external tire pressure equivalent to the cavity pressure is detected, the membrane makes contact with ridges on the backside of the surface acoustic wave device. The ridges are electrically connected to conductive fingers of the device. When the detected pressure is correct, selected fingers on the device will be grounded producing patterned acoustic reflections to an impulse RF signal. When the external tire pressure is less than the cavity reference pressure, a reduced reflected signal to the receiver results. The sensor may further be constructed so as to identify itself by a unique reflected identification pulse series.
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Citations
20 Claims
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1. A pressure sensor comprising:
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(a) a surface acoustical wave conductive body having an input transducer disposed to transmit a directional acoustical wave across at least a surface portion of the body; (b) at least one reflection transducer disposed to receive and reflect the acoustical wave back as a reflected signal; (c) a pressure transducer disposed adjacent to the surface acoustical wave conducting body, the pressure transducer comprising a flexible conductive membrane; (d) a cavity sealed by the membrane at a preset reference pressure; and (e) the membrane deflecting responsive to a predetermined external pressure level to contact the reflection transducer and modulate the signal reflected by the reflection transducer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A pressure sensor comprising:
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(a) a surface acoustical wave conductive body having an input transducer disposed to transmit a directional acoustical wave across at least a surface portion of the body; (b) at least one reflection transducer disposed to receive and reflect the acoustical wave back as a reflected signal, the reflection transducer comprising at least one conductive finger switching between an electrically floating state and an electrically grounded state; (c) a pressure transducer disposed adjacent to the surface acoustical wave conducting body, the pressure transducer comprising a flexible conductive membrane;
a cavity sealed by the membrane at a preset internal reference pressure; and(d) the membrane deflecting responsive to a predetermined external pressure to electrically engage and ground the one conductive finger to modulate the signal reflected by the one conductive finger. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A method for sensing pressure comprising the steps:
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(a) transmitting an acoustical wave across at least a surface portion of a sensor body; (b) positioning a reflection transducer to intercept the acoustical wave and reflect a signal back; (c) positioning a pressure transducer adjacent to the sensor body, the pressure transducer comprising a flexible conductive membrane, a cavity sealed by the membrane at a preset internal reference pressure; (d) deflecting the membrane into electrically contacting engagement with the reflection transducer responsive to the presence of a predetermined external pressure level; and (e) modulating the signal reflected by the reflection transducer by electrical engagement between the reflection transducer and the deflected membrane. - View Dependent Claims (17, 18, 19, 20)
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Specification