Active stylus with multiple sensors for receiving signals from a touch sensor
In one embodiment, a stylus includes a first sensor disposed proximate a first end of the stylus. The first sensor is adapted to receive a first receive signal via a first capacitive coupling with a touch sensor of a device. The first end of the stylus is at a tip-end of the stylus. The stylus also includes a second sensor disposed proximate the first end of the stylus. The second sensor is adapted to receive a second receive signal via a second capacitive coupling with the touch sensor of the device. A proximity of the first sensor to the first end of the stylus is greater than a proximity of the second sensor to the first end of the stylus. A widest portion of the first sensor has a greater width than at least a portion of the second sensor.
1. A stylus comprising:
a first sensor disposed proximate a first end of the stylus and adapted to receive a first receive signal via a first capacitive coupling between the first sensor and a first signal of a touch sensor of a device, the first end of the stylus being at a tip-end of the stylus; and
a second sensor disposed proximate the first end of the stylus and adapted to receive a second receive signal via a second capacitive coupling between the second sensor and the first signal of the touch sensor of the device;
wherein a proximity of the first sensor to the first end of the stylus is greater than a proximity of the second sensor to the first end of the stylus;
wherein a widest portion of the first sensor has a greater width than at least a portion of the second sensor; and
wherein the first and second sensors are provided such that a capacitance of the first capacitive coupling is larger than a capacitance of the second capacitive coupling, and such that a first sum of the capacitance of the first capacitive coupling and a capacitance of a third capacitive coupling between the first sensor and a first ground reference from the touch sensor of the device is approximately equal to a second sum of the capacitance of the second capacitive coupling and a capacitance of a fourth capacitive coupling between the second sensor and a second ground reference from the touch sensor of the device.
2. The stylus of claim 1 , further comprising an amplifier coupled to the first and second sensors, the amplifier adapted to produce a third signal by amplifying a difference between the first receive signal and the second receive signal.
3. The stylus of claim 2 , further comprising a controller configured to decode information encoded in the first receive signal and the second receive signal by processing the third signal.
4. The stylus of claim 1 , wherein the first sensor has a generally conical shape with a width that generally decreases along a length of the stylus in a direction toward the first end of the stylus.
5. The stylus of claim 4 , wherein the shape of the first sensor is a truncated cone.
6. The stylus of claim 5 , wherein:
a shape of the second sensor is a truncated cone with a width that generally decreases along a length of the stylus in a direction toward the first end of the stylus; and
a largest radius of the first sensor is larger than a smallest radius of the second sensor.
7. The stylus of claim 1 , wherein the second sensor has a generally conical shape with a width that generally decreases along a length of the stylus in a direction toward the first end of the stylus.
8. The stylus of claim 1 , wherein the widest portion of the first sensor has a greater width than a narrowest portion of the second sensor.
9. The stylus of claim 8 , wherein:
the widest portion of the first sensor is at an end of the first sensor closest to the second sensor, and
the narrowest portion of the second sensor is at an end of the second sensor closest to the first sensor.
10. The stylus of claim 1 , wherein the first and second sensors are provided such that the first sum is approximately equal to the second sum at a first angle of approximately 90 degrees between the stylus and a surface of the touch sensor of the device and at a second angle of approximately 45 degrees between the stylus and the surface of the touch sensor of the device.
11. The stylus of claim 1 , wherein the first and second sensors are provided such that the first sum is approximately equal to the second sum over a range of angles between the stylus and the surface of the touch sensor of the device, the range extending from approximately 90 degrees to approximately 60 degrees.
12. The stylus of claim 1 , wherein the first and second sensors are provided such that the first sum is approximately equal to the second sum over a range of angles between the stylus and the surface of the touch sensor of the device, the range extending from approximately 90 degrees to approximately 45 degrees.
13. The stylus of claim 1 , wherein a capacitive of a fifth capacitive coupling between the first sensor and a first ground reference of the stylus is approximately equal to a capacitance of a sixth capacitive coupling between the second sensor and a second ground reference of the stylus.
14. A method comprising:
receiving, via a first capacitive coupling between a first sensor of a stylus and a first signal of a touch sensor of a device, a first receive signal, wherein the first sensor is disposed proximate a first end of the stylus, the first end of the stylus being at a tip-end of the stylus;
receiving, via a second capacitive coupling between a second sensor of a stylus and the first signal of the touch sensor of the device, a second receive signal, wherein the second sensor is disposed proximate a first end of the stylus;
producing a third signal by amplifying the difference between the first receive signal and the second receive signal; and
decoding information encoded in the first receive signal and the second receive signal by processing the third signal;
wherein a proximity of the first sensor to the first end of the stylus is greater than a proximity of the second sensor to the first end of the stylus;
wherein a widest portion of the first sensor has a greater width than at least a portion of the second sensor; and
wherein the first and second sensors are provided such that a capacitance of the first capacitive coupling is larger than a capacitance of the second capacitive coupling, and such that a first sum of the capacitance of the first capacitive coupling and a capacitance of a third capacitive coupling between the first sensor and a first ground reference from the touch sensor of the device is approximately equal to a second sum of the capacitance of the second capacitive coupling and a capacitance of a fourth capacitive coupling between the second sensor and a second ground reference from the touch sensor of the device.
15. The method of claim 14 , wherein the first sensor has a generally conical shape with a width that generally decreases along a length of the stylus in direction toward the first end of the stylus.
16. The method of claim 15 , wherein the shape of the first sensor is a truncated cone.
17. The method of claim 16 , wherein:
a shape of the second sensor is a truncated cone with a width that generally decreases along a length of the stylus in a direction toward the first end of the stylus; and
a largest radius of the first sensor is larger than a smallest radius of the second sensor.
18. The method of claim 14 , wherein:
the widest portion of the first sensor has a greater width than a narrowest portion of the second sensor;
the widest portion of the first sensor is at an end of the first sensor closest to the second sensor; and
the narrowest portion of the second sensor is at an end of the second sensor closest to the first sensor.