Device and method for measuring physical parameters using saw sensors
AssigneeEnvironetix Technologies Corp.
InventorsTHOMAS POLLARD, DONALD McCANN
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Abstract
A SAW mode sensor for sensing parameters such as temperature, pressure, and strain. The sensor is made of a piezoelectric crystal cut at selected angles, with an attached electrode layer with a signal receiver and signal transmitter. The signal receiver initiates a wave in the substrate which propagates in the substrate and the speed of the wave and amplitude of the wave is interpreted as the parameter being sensed.
Claims17
A wireless sensor for variable temperature environments, comprising:
- a piezoelectric crystal substrate of the LGX family of crystals with a SAW propagation path defined by selected Euler angles between an uncut LGX material and a cut surface of LGX material;
- a SAW sensor;
- a power source for powering a SAW input transducer, wherein said input transducer is configured for receiving an RF interrogating signal;
- and
- an antenna attached to said input transducer for receiving an RF interrogating signal from a signal processing system, with said sensor powered by said RF signal;
- with said RF signal being converted to a SAW electromechanical signal via the input transducer for propagating within the crystal substrate
- with said propagating signal being encoded to include information regarding states of sensor measurands
- with said encoded signal being redetected by input transducer creating an encoded RF signal
- with said encoded RF signal being retransmitted by said antenna to said signal processing system;
- with said crystal being cut to selected Euler angles φ, θ, and ψ defining a selected crystal orientation and propagating direction.
The sensor of claim one wherein said SAW sensor further comprises:
- a periodic interdigital transducer of several wavelength periodicities in width, said interdigital transducer, affixed to said piezoelectric crystal as a thin layer.
The sensor of claim one wherein said SAW sensor further comprises:
- an input transducer;
- a reflector located on both sides of said input transducer oriented to reflect SAW along the propagation direction.
A surface acoustic wave device comprising:
- Piezoelectric crystal langasite and having a cut angle and SAW propagation direction represented by Euler angle expression (φ, θ, ψ) having values selected from one of the following groups:
- Group 1:
- where φ is from 30 to 55°, where θ is from 15 to 60° and ψ is from 10 to 65°,
- Group 2:
- where φ is from 30 to 45°, where θ is from 15 to 60° and ψ is from 150 to 200°,
- Group 3:
- where φ is from 35 to 55°, where θ is from 140 to 180° and ψ is from 45 to 105°.
A surface acoustic wave device comprising:
- Piezoelectric crystal langatate and having a cut angle and SAW propagation direction represented by Euler angle expression (φ, θ, ψ) having an φ value within the range of 35 to 55° with θ and ψ values selected from one of the following groups:
- Group 1:
- where θ is from 20 to 45° and ψ is from 30 to 80°,
- Group 2:
- where θ is from 140 to 165° and ψ is from 45 to 100°,
- Group 3:
- where θ is from 20 to 45° and ψ is from 0 to 180°,
- Group 4:
- where θ is from 140 to 165° and ψ is from 0 to 180°.
Dependencies are inferred from the claim text.