Acoustic touch apparatus and method using touch sensitive Lamb waves
Systems and related methods providing for touch sensors using high sensitivity Lamb waves are disclosed herein. A touch controller may comprise circuitry having operating frequency characteristics, including an operating frequency f and a frequency spread Δf; and circuitry configured to minimize effects of dispersion based upon at least one of selected operating frequency characteristics relative to a frequency dependence of a group velocity of propagating waves and a frequency dependent phase error, wherein the touch controller generates an excitation signal.
1. A touch controller comprising:
circuitry having operating frequency characteristics, including an operating frequency f and a frequency spread Δf, wherein the operating frequency characteristics are selected to minimize effects of dispersion of acoustic wave propagation, and wherein selecting operating frequency characteristics comprises selecting an operating frequency f near an inflection point of a group velocity V G Lamb of a substrate through which the acoustic waves are propagating;
circuitry configured to generate an anti-dispersed excitation signal; and
circuitry configured to provide the anti-dispersed excitation signal to a transmitting transducer.
2. The touch controller of claim 1 , further comprising a digital-to-analog converter (DAC) for aiding in generation of the anti-dispersed excitation signal.
3. The touch controller of claim 2 , wherein the digital-to-analog converter (DAC) comprises a conversion rate higher than four times the operating frequency f.
4. The touch controller of claim 1 , wherein the acoustic waves comprise Lamb waves.
5. The touch controller of claim 4 , wherein the Lamb waves comprise one or more of near-longitudinal-resonance Lamb waves or near Lame waves.
6. The touch controller of claim 1 , further configured to select an operating frequency such that the group velocity V G Lamb of a substrate through which acoustic waves are propagated has a low frequency dependence within the frequency spread Δf.
7. The touch controller of claim 6 , wherein the acoustic waves comprise Lamb waves.
8. The touch controller of claim 7 , wherein the Lamb waves comprise one or more of near-longitudinal-resonance Lamb waves or near Lame waves.
9. The touch controller of claim 1 , wherein anti-dispersion of an excitation signal is based in part on dispersive phase errors.
10. A method, comprising:
selecting operating frequency characteristics relative to a frequency dependence of a group velocity of propagating acoustic waves, the operating frequency characteristics selected to minimize effects of dispersion of acoustic wave propagation, wherein selecting operating frequency characteristics comprises selecting an operating frequency f near an inflection point of a group velocity V G Lamb of a substrate through which the acoustic waves are propagating;
performing touch controller operations with the operating frequency characteristics, the operating frequency characteristics including an operating frequency f, and a frequency spread Δf around the operating frequency f;
generating an anti-dispersed excitation signal; and
sending the anti-dispersed excitation signal to a transmitting transducer.
11. The method of claim 10 , further comprising converting from digital to analog a magnitude and a phase of a signal.
12. The method of claim 11 , further comprising utilizing a conversion rate higher than four times the operating frequency f for the converting from digital to analog.
13. The method of claim 10 , wherein the acoustic waves comprise Lamb waves.
14. The method of claim 13 , wherein the Lamb waves comprise one or more of near-longitudinal-resonance Lamb waves or near Lame waves.
15. The method of claim 10 , further comprising selecting an operating frequency f such that the group velocity V G Lamb of a substrate through which acoustic waves are propagating has a low frequency dependence within the frequency spread Δf.
16. The method of claim 15 , wherein the acoustic waves comprise Lamb waves.
17. The method of claim 16 , wherein the Lamb waves comprise one or more of near-longitudinal-resonance Lamb waves or near Lame waves.
18. The method of claim 10 , wherein anti-dispersion of the excitation signal is based in part on a time-delay dependent and frequency dependent phase error.
19. A touch controller comprising:
circuitry having operating frequency characteristics, including an operating frequency f and a frequency spread Δf, wherein the operating frequency characteristics are selected to minimize effects of dispersion of acoustic wave propagation, and wherein selecting operating frequency characteristics comprises selecting an operating frequency f such that the group velocity V G Lamb of a substrate through which the acoustic waves are propagating has a low frequency dependence within the frequency spread Δf,
circuitry configured to generate an anti-dispersed excitation signal; and
circuitry configured to provide the anti-dispersed excitation signal to a transmitting transducer.
20. A method, comprising:
selecting operating frequency characteristics relative to a frequency dependence of a group velocity of propagating acoustic waves, the operating frequency characteristics selected to minimize effects of dispersion of acoustic wave propagation, wherein selecting operating frequency characteristics comprises selecting an operating frequency f such that the group velocity V G Lamb of a substrate through which the acoustic waves are propagating has a low frequency dependence within the frequency spread Δf,
performing touch controller operations with the operating frequency characteristics, the operating frequency characteristics including an operating frequency f, and a frequency spread Δf around the operating frequency f,
generating an anti-dispersed excitation signal; and
sending the anti-dispersed excitation signal to a transmitting transducer.