I/Q Receiver Module for Quadrature Proximity Sensing
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Solution Overview
Problem
Existing touch sensors, particularly those using proximity sensor devices, face challenges in accurately demodulating signals from active pens due to unknown phase synchronization with local oscillators, leading to suboptimal performance in detecting touch inputs.
Innovation Solution
The implementation of an in-phase and quadrature (I/Q) receiver module that alternates integration and demodulation processes across four consecutive quarter cycles, allowing for both in-phase and quadrature demodulation components to be produced from signals received from receiver electrodes, effectively addressing phase offset issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional single-phase demodulation is used in touch sensors, then the device complexity is reduced, but the measurement precision of signal phase and magnitude deteriorates due to unknown phase synchronization with active pens
Solution Approach 1:
The patent segments the demodulation process into two independent components: in-phase (I) demodulation and quadrature (Q) demodulation. By dividing the single demodulation task into two parallel channels with different phase references (0° and 90°), the system can accurately extract both magnitude and phase information of the received signal regardless of the active pen's phase offset, thus resolving the measurement precision issue without requiring complex adaptive synchronization mechanisms
Solution Approach 2:
The patent transitions from single-phase demodulation (one-dimensional measurement) to I/Q demodulation (two-dimensional measurement in the complex plane). By adding the quadrature dimension with a 90° phase-shifted local oscillator, the system creates a two-dimensional measurement space that captures both in-phase and quadrature components of the signal, enabling accurate determination of signal magnitude and phase angle through vector reconstruction
2Reliability
If I/Q demodulation with multiple demodulator modules is implemented, then the reliability of touch sensing is improved, but the device complexity increases due to additional charge integrators and demodulator modules
Solution Approach 1:
The patent merges the functionality of multiple demodulator modules into a unified I/Q demodulation architecture. By combining the in-phase demodulator and quadrature demodulator into a single integrated receiver module that processes the same input signal through two parallel but synchronized channels, the system achieves reliable touch sensing with active pens while minimizing the total number of independent demodulator modules required
Solution Approach 2:
The patent employs periodic switching between in-phase and quadrature demodulation modes using charge integrators that alternate their operation in a periodic fashion. This periodic action allows the system to implement full I/Q demodulation functionality while reusing the same hardware resources (integrators and demodulators) in time-division manner, thereby reducing the total component count while maintaining reliability
Data Source
AI summary
A processing system for an input device includes an in-phase and quadrature (I/Q) receiver module including a first and second charge integrators, and first and second demodulator modules. The I/Q receiver module alternates integration of a resulting signal, received from a receiver electrode of the input device, between the first and the second charge integrators in four consecutive quarter cycles, to obtain four consecutive integration results. The four consecutive quarter cycles coincide with one cycle of a local oscillator signal for the first and second demodulator modules. The I/Q receiver module further alternates demodulation of the four consecutive integration results between the first and second demodulator modules. The first demodulator module performs an in-phase demodulation to produce an in-phase component of a sensing signal associated with the first resulting signal, and the second demodulator module performs a quadrature demodulation to produce a quadrature component of the sensing signal.