Vehicle Distance Measurement Using Phase Difference Detection
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Solution Overview
Problem
Existing hands-free access and boot systems for vehicles face challenges in accurately measuring the distance between the vehicle and the identifier due to interference from surrounding signals, which affects the security and reliability of locking and starting operations.
Innovation Solution
The method employs a synchronized vehicle and identifier emission device system using high-frequency radio signals (at least 1GHz) to select frequencies distant from conventional disturbing frequencies, measuring phase differences to calculate the distance, and filters slopes to minimize errors from signal reflections and refractions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If low frequency signal power measurement is used to calculate distance, then energy consumption is reduced and refraction effects are limited, but measurement precision deteriorates due to interference from surrounding signals
Solution Approach 1:
The patent changes the measurement parameter from low frequency signal power (RSSI) to phase difference measurement. By using phase difference of high frequency signals, the system achieves higher measurement precision while avoiding interference from surrounding low frequency signals, thus resolving the contradiction between measurement precision and environmental interference.
Solution Approach 2:
The patent replaces the traditional power-based distance measurement mechanism with a phase difference-based mechanism. This substitution allows the system to achieve more accurate distance measurements by measuring the phase shift of reflected signals, which is less susceptible to interference from surrounding equipment.
2Measurement precision
If high frequency radio signals are used for distance measurement, then measurement precision is improved, but device complexity increases due to synchronized emission and phase measurement requirements
Solution Approach 1:
The patent merges the emission and reception functions into a single transceiver unit at both the vehicle and identifier. This integration simplifies the synchronized emission system by combining multiple functions into unified components, reducing overall device complexity while maintaining high measurement precision through phase difference measurement.
Solution Approach 2:
The system uses the identifier's own transmitted signal as the reference for phase difference measurement. The identifier transmits a signal, the vehicle receives and reflects it, and then the vehicle measures the phase difference between the received and reflected signals. This self-service approach eliminates the need for complex external synchronization systems.
3Ease of operation
If low frequency polling signals are used for hands-free access, then ease of operation is maintained, but reliability deteriorates due to signal interference from surrounding equipment
Solution Approach 1:
The patent changes the signal frequency parameter from low frequency (20-150kHz) to high frequency (at least 1GHz) for the measurement signals. This parameter change allows the system to maintain hands-free operation ease while significantly improving reliability by operating in a frequency range less susceptible to interference from surrounding equipment.
Solution Approach 2:
The patent introduces phase difference measurement as an intermediary mechanism between the identifier transmission and distance determination. Instead of directly using signal power or presence detection, the system uses phase difference of reflected signals as an intermediary parameter that provides more reliable distance measurement while maintaining the hands-free operation interface.
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 provides a more accurate and secure distance measurement, reducing interference from surrounding signals and enhancing the reliability of hands-free access and start operations by minimizing errors in distance calculation.
Implementation Method 1
The method employs a synchronized vehicle and identifier emission device system using high-frequency radio signals (at least 1GHz)
Data Source
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AI summary
The invention relates to a method (METH) for measuring a distance R between a vehicle (V) and an identifier (I) for accessing and starting the vehicle (V), the vehicle (V) and the identifier (I) being synthronised. The method (METH) comprises the following steps: - selecting (Sel_fp) N frequencies fp, pϵ[1;N], N being a natural number at least higher than 3; - implementing N sequences Sqp, each sequence Sqp comprising the following steps: • transmitting (Em_Svp) a first signal (Svp) of frequency fp from an emitter (TXv) of the vehicle (V) to a receiver (Rxi) of the identifier (I); • measuring (Mes_ϕvip) with a calculator (Xi) of the identifier (I) a phase ϕvip, modulo 2π, of the first signal (Svp) received, relative to a second signal (Sip) of phase ϕip(t) = ϕ0ip + 2πfpt; • transmitting (Em_Sip) the second signal (Sip) from an emitter (TXi) of the identifier (I) to a receiver (RXv) of the vehicle (V); • calculating (Mes_ϕivp) with a calculator (Xv) of the vehicle (V) a phase ϕivp, modulo 2π, of the second signal (Sip) received, relative to the first signal (Svp); • calculating (Cal_ϕp) the average ϕp of the phase ϕvip and of the phase ϕivp; - for each p between 1 and N-1, calculating (Cal_Pp) a ramp Pp using the formula Pp=(ϕp+1-ϕp)/(fp+1-fp); and - calculating (Cal_R) distance R from the ramps Pp, pϵ[1;N].