Two Pass Detection for Non-Echo Pulsed Ranging

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Solution Overview

Problem

Pulsed ranging systems in indoor environments face inaccuracies due to non-line-of-sight issues and weak signal penetration through obstacles, leading to incorrect location determination of mobile devices, especially when relying on reflected signals rather than direct ones, and are limited by processing power and battery constraints in mobile devices.

Innovation Solution

A non-echo pulsed ranging system using ultrasonic transponders and existing audio circuitry in mobile devices, with a digital signal processor analyzing signal pulses in the 19-22 kHz range to distinguish direct and reflected signals through initial low-selectivity detection followed by re-analysis for accurate timing measurements, allowing for trilateration-based positioning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If advanced detection techniques are applied to distinguish direct and reflected signals, then measurement precision is improved, but processing power and battery consumption increase

Engineering Contradiction:

Improvesignal detection accuracyVSAvoidbattery consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The signal processing is divided into two distinct passes: a first pass using low-selectivity detection for initial signal identification, and a second pass using high-selectivity detection only for signals detected in the first pass. This segmentation allows the system to achieve high measurement precision when needed while conserving battery energy during normal operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system applies full-selectivity detection (excessive action) only partially - specifically, only to signals that were initially detected by the low-selectivity detector. This partial application of advanced detection techniques ensures measurement precision for valid signals while avoiding the energy cost of applying the same techniques to all incoming signals.

Inventive Principle:

Principle #16Partial or excessive action

2Reliability

If high-power emitters are used to penetrate obstacles, then signal strength is improved, but energy consumption increases

Engineering Contradiction:

Improvesignal penetration capabilityVSAvoidemitter power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

The system changes the selectivity parameter of the detection circuitry between two passes. The first pass uses low-selectivity settings to detect all potential signals with minimal energy, while the second pass uses high-selectivity settings only for signals that passed the first filter, achieving reliable signal differentiation without sustained high energy consumption.

Inventive Principle:

Principle #35Parameter changes

3Area of stationary object

If reflected signals are used for ranging, then device coverage is improved, but measurement precision deteriorates

Engineering Contradiction:

Improveranging coverage areaVSAvoidlocation accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The first pass of low-selectivity detection serves as a preliminary action that identifies all potential signal sources including both direct and reflected signals. This preliminary detection enables the system to then apply selective filtering in the second pass to distinguish between direct and reflected signals, maintaining broad coverage while ensuring accurate ranging measurements.

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

This approach enhances the accuracy of mobile device location determination by effectively differentiating direct and reflected signals, optimizing signal processing performance while conserving processor utilization and battery life, and is applicable to both ultrasonic and RF systems.

Implementation Method 1

an ultrasonic receiver including an ultrasonic transducer

Methodology Applied

Scientific EffectUltrasonic transduction: Piezoelectric Effect

Data Source

PatentUS10802108B2Two pass detection technique for non-echo pulsed ranging

Publication Date: 2020.10.13 SYMBOL TECHNOLOGIES LLC

AI summary

A technique for non-echo pulsed ranging of a mobile device within an environment includes a plurality of emitters within the environment transmitting signal pulses of a predefined frequency to a mobile device that can receive a signal pulse, convert the signal pulse into a digital waveform, store the digital waveform into a buffer having a predetermined length of time, and analyze the digital waveform to detect a signal pulse at the predefined frequency. If a signal pulse is detected, the mobile device can re-analyze the digital waveform that was stored in the buffer to see if another signal pulse can be detected within the waveform, indicating the existence of a reflected signal. If another signal pulse is detected, the mobile device can select the signal pulse that was received first in time, i.e. the direct signal, for use in ranging of the mobile device.