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US 12,754,633 B1Granted
Reduction of radiated emission from touchscreen
AssigneeMicrochip Touch Solutions Limited
InventorsLionel Portmann, Richard P. Collins, John Dubery
Life of this patent
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Abstract
Radiation emission of a capacitive sensing system may be reduced. The amplitude of the residual emission per chip may be reduced by reassigning CDMA codes to TX electrodes. The skirt of the emitted spectrum of the residual emission may be reduced by ordering the chips by their absolute amplitude and scheduling their appearance so that chips at the beginning and end of the scan have the lowest amplitude, while those in the middle have the highest amplitude. The residual emission may be reduced by modifying chip polarity by inverting the polarity of all transmit signals applied to the X electrodes during a chip.
Claims20
A method comprising:
- providing a capacitive sensing system comprising first, second, third, and fourth transmit electrodes and a receive electrode positioned to have mutual capacitances between the first, second, third, and fourth transmit electrodes and the receive electrode at mutual capacitance nodes, wherein the mutual capacitance at respective ones of the mutual capacitance nodes changes when an interfering object is proximate;
- applying a first drive signal to the first transmit electrode;
- measuring a first radiated emission from the capacitive sensing system when the first drive signal is applied;
- applying a second drive signal to the second transmit electrode;
- measuring a second radiated emission from the capacitive sensing system when the second drive signal is applied;
- applying a third drive signal to the third transmit electrode;
- measuring a third radiated emission from the capacitive sensing system when the third drive signal is applied;
- applying a fourth drive signal to the fourth transmit electrode;
- measuring a fourth radiated emission from the capacitive sensing system when the fourth drive signal is applied;
- and
- controlling application of a drive signal to a transmit electrode based on the first, second, third, and fourth radiated emissions to reduce a radiated emission from the capacitive sensing system.
8 more elements
A system comprising:
- a capacitive sensing system comprising first, second, third, and fourth transmit electrodes and a receive electrode positioned to have mutual capacitances between the first, second, third, and fourth transmit electrodes and the receive electrode at mutual capacitance nodes, wherein the mutual capacitance at respective ones of the mutual capacitance nodes changes when an interfering object is proximate;
- a controller circuit to apply a drive signal to a transmit electrode to reduce a radiated emission from the capacitive sensing system based on:
- a measured radiation emission for the capacitive sensing system when a first drive signal is applied to the first transmit electrode, a measured radiation emission for the capacitive sensing system when a second drive signal is applied to the second transmit electrode, a measured radiation emission for the capacitive sensing system when a third drive signal is applied to the third transmit electrode, and a measured radiation emission for the capacitive sensing system when a fourth drive signal is applied to the fourth transmit electrode.
A system comprising:
- a capacitive sensing system comprising first, second, third, and fourth transmit electrodes and a receive electrode positioned to have mutual capacitances between the first, second, third, and fourth transmit electrodes and the receive electrode at mutual capacitance nodes, wherein the mutual capacitance at respective ones of the mutual capacitance nodes changes when an interfering object is proximate;
- a controller circuit to:
- apply first, second, third, and fourth orthogonal drive signals to the first transmit electrode during first, second, third, and fourth chips, respectively;
- apply fifth, sixth, seventh, and eighth orthogonal drive signals to the second transmit electrode during the first, second, third, and fourth, chips, respectively;
- apply ninth, tenth, eleventh, and twelfth orthogonal drive signals to the third transmit electrode during the first, second, third, and fourth chips, respectively;
- apply thirteenth, fourteenth, fifteenth, and sixteenth orthogonal drive signals to the fourth transmit electrode during the first, second, third, and fourth chips, respectively;
- wherein the drive signals are based on:
- a measured radiation emission for the capacitive sensing system when a drive signal is applied to the first transmit electrode, a measured radiation emission for the capacitive sensing system when a drive signal is applied to the second transmit electrode, a measured radiation emission for the capacitive sensing system when a drive signal is applied to the third transmit electrode and a measured radiation emission for the capacitive sensing system when a drive signal is applied to the fourth transmit electrode.
5 more elements
Dependencies are inferred from the claim text.