Orthogonal frequency scan scheme in touch system
System and processes for transmitting orthogonal frequencies on a touch sensor are provided. In one example process, the rows of the sensor panel can have signals transmitted thereon having orthogonal frequencies. The orthogonal frequencies can be separated by a frequency spacing (Δf) that is at least the reciprocal of a measurement period τ (e.g., an integration time) of the touch sensor. Touch events cause and correspond to signals on the columns, which can be received by a receive system including appropriate amplifiers. The orthogonal frequencies can be detected by the receiver with a Fourier Transform or filter bank. Separate digitization and signal processing can be implemented for every column. The receiver can measure the quantity of each of the orthogonal transmitted signals present on each column, identifying the rows in touch with each column and may also provide additional (e.g., qualitative) information concerning the touch.
1. A system comprising:
signal generator operable to generate a plurality of signals having a plurality of orthogonal frequencies, each orthogonal frequency of the plurality of orthogonal frequencies being a different frequency, the plurality of signals simultaneously driving a plurality of rows of a touch sensor, wherein frequencies of the plurality of orthogonal frequencies are spaced by a frequency that is at least a reciprocal of a predetermined measurement period of the touch sensor, and a highest orthogonal frequency of the plurality of orthogonal frequencies is less than twice a lowest orthogonal frequency of the plurality of frequencies.
2. The system of claim 1 , wherein the system further comprises:
the touch sensor, the touch sensor comprising:
the plurality of rows, wherein each of the plurality of rows is coupled to receive a different signal of the plurality of signals from the signal generator; and
a plurality of columns capacitively coupled to the plurality of rows; and
receiver coupled to receive a plurality of signals from the plurality of columns and operable to detect a touch event associated with the touch sensor based on the received plurality of signals.
3. The system of claim 2 , wherein the signal processor for each of the plurality of columns are the same signal processor.
4. The system of claim 1 , wherein the signal generator comprises, for each of the plurality of signals:
a digital generator;
a digital to analog converter coupled to receive an output of he digital generator; and
a transmitter coupled to receive an output of the digital to analog converter and coupled to output a signal of the plurality of signals to a row of the plurality of rows.
5. A system comprising:
a touch sensor comprising:
a first row; and
a second row; and
signal generator coupled to the first and second rows and operable to:
generate on the first row a first signal having a first frequency; and
generate on the second row a second signal having a second frequency,
the second frequency different from the first frequency, wherein:
a difference between the first frequency and the second frequency is at least a reciprocal of a predetermined measurement period of the touch sensor, and either the first frequency is less than twice the second frequency or the second frequency is less than twice the first frequency, and
the signal generator simultaneously generating signals on the first row with the first signal and the second row with the second signal.
6. The system of claim 5 , wherein the touch sensor further comprises a plurality of columns capacitively coupled to the first and second rows, and wherein the system further comprises receiver coupled to receive a plurality of signals from the plurality of columns and operable to detect a touch event associated with the touch sensor based on the received plurality of signals.
7. The system of claim 5 , wherein the system is included within a computer display, flat panel display, LCD display, plasma display or OLED display.
8. A system comprising:
a touch sensor comprising:
a plurality of rows; and
a column capacitively coupled to the plurality of rows; and
signal generator coupled to the plurality of rows and operable to simultaneously generate on the plurality of rows a plurality of row signals, each row signal of the plurality of row signals having a different frequency, wherein:
the plurality of row signals are spaced by a frequency that is a reciprocal of a predetermined measurement period of the touch sensor, and a highest row signal frequency of the plurality of row signals is set to be less than twice a lowest row signal frequency of the plurality of row signals,
the column is operable to generate a column signal in response to the plurality of rows being driven by the row signals, and
the column signal comprises an interference component having a frequency corresponding to a difference in frequency between the frequencies of the row signals.
9. The system of claim 8 , wherein the system further comprises receiver coupled to receive the column signal from the column and operable to detect a touch event associated with the touch sensor based on the received column signal.
10. The system of claim 8 , wherein the frequencies of the row signals are orthogonal.
11. A system comprising:
signal generator operable to generate a plurality of signals having a plurality of orthogonal frequencies, each orthogonal frequency of the plurality of orthogonal frequencies being a different frequency, the plurality of signals simultaneously driving a plurality of rows of a touch sensor, wherein frequencies of the plurality of orthogonal frequencies are spaced by a frequency that is a reciprocal of a predetermined measurement period of the touch sensor, and a highest orthogonal frequency of the plurality of orthogonal frequencies is less than twice a lowest orthogonal frequency of the plurality of frequencies.
12. The system of claim 11 , wherein the system further comprises:
the touch sensor, the touch sensor comprising:
the plurality of rows, wherein each of the plurality of rows is coupled to receive a different signal of the plurality of signals from the signal generator; and
a plurality of columns capacitively coupled to the plurality of rows; and
receiver coupled to receive a plurality of signals from the plurality of columns and operable to detect a touch event associated with the touch sensor based on the received plurality of signals.
13. The system of claim 12 , wherein the signal processor for each of the plurality of columns are the same signal processor.
14. The system of claim 11 , wherein the signal generator comprises, for each of the plurality of signals:
a digital generator;
a digital to analog converter coupled to receive an output of the digital generator; and
a transmitter coupled to receive an output of the digital to analog converter and coupled to output a signal of the plurality of signals to a row of the plurality of rows.