Antenna Proximity Detection Circuit for Filtering Switching Capacitance

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Solution Overview

Problem

Capacitive proximity sensors in mobile terminals often incorrectly detect objects due to internal circuit capacitance changes, leading to reduced detection accuracy.

Innovation Solution

A detection circuit comprising a first antenna module with a multiplexer and a first inductor connected in parallel, which filters out capacitance generated by the internal circuit, allowing the capacitive proximity sensor to accurately detect external object capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a capacitive proximity sensor is used to detect objects, then the detection function is provided, but internal circuit capacitance changes cause false detection and reduce detection accuracy

Engineering Contradiction:

Improvedetection accuracyVSAvoidfalse detection

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent segments the capacitance detection into two parts: total capacitance (including internal circuit capacitance) and external object capacitance. By measuring the total capacitance of the antenna module and subtracting the known internal circuit capacitance value, the system isolates and detects only the external object capacitance, thereby eliminating false detections caused by internal circuit variations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary measurement approach by using the antenna module as a common element for both wireless communication and capacitance sensing. The antenna module serves as an intermediary structure that naturally presents the total capacitance (internal + external), which is then processed to extract the external object information while filtering out internal circuit interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If internal circuit capacitance is present, then the circuit can function, but it interferes with the capacitive proximity sensor's ability to accurately detect external objects

Engineering Contradiction:

Improvecircuit functionalityVSAvoidcapacitance detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent extracts the internal circuit capacitance component from the total capacitance measurement. By determining the capacitance value of the antenna module (which includes both internal and external capacitance) and subtracting the known internal circuit capacitance, the system isolates the external object capacitance signal, thereby eliminating the interference of internal circuit capacitance on detection accuracy.

Inventive Principle:

Principle #2Taking out (Extraction)

3Adaptability or versatility

If the multiplexer switches between different operating frequency bands, then the antenna can operate in multiple bands, but capacitance is generated during switching that triggers false detection

Engineering Contradiction:

Improveoperating frequency bandsVSAvoidswitching capacitance

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by measuring and recording the total capacitance value of the antenna module before actual object detection begins. This pre-measurement captures the baseline capacitance including internal circuit capacitance and any switching capacitance from the multiplexer. During subsequent detection, this baseline is subtracted from new measurements, thereby eliminating the effect of switching capacitance and enabling accurate multi-band operation without false detections.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution significantly improves the detection accuracy of capacitive proximity sensors by distinguishing between internal and external capacitance changes, reducing false object detection triggers.

Implementation Method 1

the multiplexer is connected in parallel with the first inductor, so that the first inductor is configured to filter out capacitance generated during switching of the multiplexer

Methodology Applied

Scientific EffectCapacitance filtering: Filter (electronic)

Implementation Method 2

the capacitive proximity sensor is connected to the first antenna and configured for detecting a capacitance value of the first antenna module

Methodology Applied

Scientific EffectCapacitance detection: Capacitance

Implementation Method 3

the capacitive proximity sensor is connected to a feeding point of the first antenna, so that in the case where an object approaches the first antenna module, an induced capacitance is formed between the first antenna and the object

Methodology Applied

Scientific EffectElectrostatic induction: Electrostatic Induction

Data Source

PatentUS20250070778A1Detection circuit, detection method, and mobile terminal

Publication Date: 2025.02.27 REALME MOBILE TELECOMM SHENZHEN CO LTD

AI summary

A detection circuit includes a first antenna module and a capacitive proximity sensor, the first antenna module includes a multiplexer, a first antenna and a first inductor. One terminal of the multiplexer is connected to the first antenna, and the multiplexer is configured for controlling the first antenna to operate in different operating frequency bands. The other terminal of the multiplexer is connected to a ground terminal. The first inductor is connected in parallel with the multi-path switch. The capacitive proximity sensor is connected to the first antenna and configured for detecting a capacitance value of the first antenna module. A detection method and a mobile terminal are further provided.