| 摘要 |
A touch-sensitive device includes a touch panel, drive unit, and measurement unit. A touch applied to a given node of the panel changes a mutual capacitive coupling between a given drive and sense electrode of the touch panel, or changes a self-capacitive coupling the between a given electrode and ground. The drive unit delivers to the drive electrodes of the touch panel or to the self-capacitance measurement amplifiers of all electrodes, subcarriers of a composites carrier modulated OFDM signal by using SSB or DSB modulation based up-conversion, and these subcarriers are complementary code sequence-based phase encoded for PAPR reduction of the OFDM signal. The measurement unit receives signals from the receive electrodes, or directly from local receiver amplifiers at each electrode, and analyzes the signal using FFT or maximum likelihood estimation to determine the mutual coupling capacitance between each of the drive and receive electrodes or the self-capacitance of each electrode. Time-windowing is applied inside the FFT window, and a tone skipping or nulling technique is adopted, when it is required to reject interferences at frequencies that are too close to that of the drive signal frequencies. |
| 主权项 |
1. A touch-sensitive apparatus, comprising:
a panel comprising a touch surface, a plurality of drive electrodes, and a plurality of receive electrodes; an electronic subsystem comprising a plurality of drive amplifiers, a plurality of sense amplifiers, and an analog and digital signal processing unit; wherein each drive amplifier is configured to deliver to a corresponding said drive electrode an up-converted drive signal comprising a set of one or more drive frequency tones that are subcarriers around a common carrier frequency; and wherein each set of said drive frequencies is configured to be disjoint to every other set of drive frequencies of all other said drive electrodes; and wherein all said drive frequencies in all said sets are configured to be orthogonal to each other such that their separations are selected to be an integer multiple of a common frequency spacing Δf that defines the subcarrier spacing of an associated composite carrier modulated orthogonal frequency division multiplexed (OFDM) signal comprising of all said subcarrier frequencies of all the said drive unit signals at said common carrier frequency received at a said receive electrode output; and wherein the phase of each drive frequency tone is given a predetermined value based on a complementary code sequence that is chosen to reduce the peak to average power of the composite sum of all said drive signals that appear at said receive electrode output as said composite carrier modulated OFDM signal; and wherein each sense amplifier input is connected to a corresponding said receive electrode to receive said composite carrier modulated OFDM response signal at said common transmitter carrier frequency from its said receive electrode; and wherein each said sense amplifier output is delivered to said analog and digital signal processing unit which is configured to down-convert said composite carrier modulated OFDM signal with further means to analyze said down-converted response signal to determine therefrom a coupling capacitance between every drive electrode and its corresponding receive electrode using fast Fourier transform (FFT) or maximum likelihood estimation; and wherein said analog and digital signal processing unit is configured for up-conversion of said drive signals, wherein said up-conversion is selected from a group comprising of (a) an equivalent multiplication between real baseband signal and a real transmitter carrier signal that corresponds to creating a double side-band (DSB) modulated signal, and (b) an equivalent complex multiplication between a complex baseband signal and a complex transmitter carrier signal with the real output of the complex product taken that corresponds to creating a single side-band (SSB) modulated signal, and wherein each said complex baseband signal, said complex carrier signal and said complex product comprises of in-phase and quadrature-phase components, and (c) other known methods of up-conversion of signals including up-conversion of a SSB or DSB modulated intermediate frequency signal to a carrier frequency; and wherein said analog and digital signal processing unit is configured for down-conversion of said sense electrode signal wherein said down-conversion is selected from a group comprising (a) an equivalent multiplication between said signal at said transmitter carrier frequency and a real single-phase local un-modulated carrier signal at the same carrier frequency, followed by filtering and sampling, (b) an equivalent multiplication between said signal at said transmitter carrier frequency and a complex in-phase and quadrature-phase local un-modulated carrier signal at the same carrier frequency, followed by filtering and sampling, and (c) oversampling of said signal and separating the time samples into an in-phase and a quadrature-phase path, followed by suitable low pass filtering for removal of unwanted frequency components. |
