Stylus sensing circuit and stylus

Patent metadata

Field	Value
Publication number	US-12585356-B2
Application number	US-202418586529-A
Country	US
Kind code	B2
Filing date	Feb 25, 2024
Priority date	Feb 25, 2024
Publication date	Mar 24, 2026
Grant date	Mar 24, 2026

Abstract

A stylus sensing circuit includes a receiving circuit, a demodulation circuit and a detection circuit. The receiving circuit receives a downlink signal from a stylus, wherein the downlink signal includes a plurality of frequency signals. The demodulation circuit, coupled to the receiving circuit, demodulates the downlink signal to extract each of the plurality of frequency signals. The detection circuit, coupled to the demodulation circuit, chooses one of the plurality of frequency signals to perform a signal processing.

First claim

What is claimed is:

1 . A stylus sensing circuit comprising:
a receiving circuit to receive a downlink signal from a stylus, the downlink signal comprising a plurality of frequency signals; a demodulation circuit, coupled to the receiving circuit, to demodulate the downlink signal to extract each of the plurality of frequency signals; and a detection circuit, coupled to the demodulation circuit, to receive the plurality of frequency signals from the demodulation circuit and choose one of the plurality of frequency signals to perform a signal processing, and ignore another one of the plurality of frequency signals which is determined to be interfered with by a noise.

2 . The stylus sensing circuit of claim 1 , wherein each of the plurality of frequency signals is a single tone signal.

3 . The stylus sensing circuit of claim 1 , wherein the receiving circuit comprises:
an analog front-end (AFE) circuit to sample the downlink signal; and an analog-to-digital converter (ADC), coupled to the AFE circuit, to convert the downlink signal into a digital form and output the downlink signal to the demodulation circuit.

4 . The stylus sensing circuit of claim 1 , wherein the detection circuit performs the signal processing to obtain a coordinate of the stylus on a touch panel.

5 . The stylus sensing circuit of claim 1 , wherein the detection circuit chooses only one of the plurality of frequency signals to perform the signal processing.

6 . The stylus sensing circuit of claim 1 , wherein a first frequency signal and a second frequency signal among the plurality of frequency signals carry a same information.

7 . The stylus sensing circuit of claim 1 , wherein a first frequency signal and a second frequency signal among the plurality of frequency signals carry different information.

8 . The stylus sensing circuit of claim 1 , wherein the detection circuit detects the noise corresponding to each of the plurality of frequency signals, to choose the one of the plurality of frequency signals to perform the signal processing according to a detection result of the noise.

9 . The stylus sensing circuit of claim 8 , wherein the detection circuit chooses the one of the plurality of frequency signals not interfered with by the noise to perform the signal processing.

10 . The stylus sensing circuit of claim 1 , wherein the detection circuit further detects a signal variation of each of the plurality of frequency signals, to choose the one of the plurality of frequency signals to perform the signal processing according to the signal variation.

11 . The stylus sensing circuit of claim 10 , wherein the detection circuit chooses one of the plurality of frequency signals having the minimum signal variation to perform the signal processing.

12 . The stylus sensing circuit of claim 1 , wherein the stylus sensing circuit is in a hand mode, and determines to be switched to a stylus mode when the detection circuit detects that a signal strength on a frequency of each of the plurality of frequency signals is greater than a threshold value.

13 . The stylus sensing circuit of claim 12 , wherein the stylus sensing circuit stays in the hand mode when the detection circuit detects that the signal strength on the frequency of at least one of the plurality of frequency signals is smaller than the threshold value.

14 . The stylus sensing circuit of claim 12 , wherein the plurality of frequency signals comprise a first frequency signal and a second frequency signal, and the detection circuit determines that there is a first noise on a first frequency of the first frequency signal when detecting that the signal strength on the first frequency of the first frequency signal is greater than the threshold value and the signal strength on a second frequency of the second frequency signal is smaller than the threshold value.

15 . The stylus sensing circuit of claim 14 , wherein the detection circuit chooses the second frequency signal to perform the signal processing.

16 . The stylus sensing circuit of claim 1 , wherein the stylus sensing circuit is in a stylus mode, and determines to be switched to a hand mode when the detection circuit detects that a signal strength on a frequency of each of the plurality of frequency signals is smaller than a threshold value.

17 . The stylus sensing circuit of claim 16 , wherein the stylus sensing circuit stays in the stylus mode when the detection circuit detects that the signal strength on the frequency of at least one of the plurality of frequency signals is greater than the threshold value.

18 . The stylus sensing circuit of claim 16 , wherein the plurality of frequency signals comprise a first frequency signal and a second frequency signal, and the detection circuit determines that there is a first noise on a first frequency of the first frequency signal when detecting that the signal strength on the first frequency of the first frequency signal is smaller than the threshold value and the signal strength on a second frequency of the second frequency signal is greater than the threshold value.

19 . The stylus sensing circuit of claim 18 , wherein the detection circuit chooses the second frequency signal to perform the signal processing.

20 . A stylus comprising:
a plurality of signal generators to generate a plurality of frequency signals having different frequencies; and a mixer, coupled to the plurality of signal generators, to combine the plurality of frequency signals to generate a downlink signal; wherein a first frequency signal and a second frequency signal among the plurality of frequency signals carry a same information; wherein the downlink signal is received by a stylus sensing circuit, and the stylus sensing circuit comprises a demodulation circuit for demodulating the downlink signal to extract each of the plurality of frequency signals; wherein the stylus sensing circuit comprises a detection circuit for receiving the plurality of frequency signals from the demodulation circuit and choosing one of the plurality of frequency signals to perform the signal processing and ignoring another one of the plurality of frequency signals determined to be interfered with by the noise.

21 . The stylus of claim 20 , wherein each of the plurality of frequency signals is a single tone signal.

22 . The stylus of claim 20 , further comprising:
a digital-to-analog converter (DAC), coupled to the mixer, to convert the downlink signal into an analog form and output the downlink signal.

23 . The stylus of claim 20 , wherein each of the plurality of frequency signals carry the same information.

24 . The stylus of claim 20 , wherein the second frequency signal and a third frequency signal among the plurality of frequency signals carry different information.

Assignees

• Novatek Microelectronics Corp

Inventors

• Chan Ting-Yu
• Yeh Yun-Hsiang
• Lin Chi-Te

Classifications

• G06F2203/04106

  Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection · CPC title

• G06F3/0383

  Signal control means within the pointing device · CPC title

• G06F3/03545 Primary

  Pens or stylus · CPC title

• G06F2203/04114

  Touch screens adapted for alternating or simultaneous interaction with active pens and passive pointing devices like fingers or passive pens · CPC title

• G06F3/04182

  Filtering of noise external to the device and not generated by digitiser components · CPC title