Time-of-Flight Measurement Using Phase-Locked Variable Frequency Oscillators
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Solution Overview
Problem
Existing time-of-flight measurement technologies face challenges in achieving high resolution at low cost and low power, requiring expensive precisely tuned transducers and intensive computation, especially in devices using acoustic or electromagnetic signals.
Innovation Solution
The use of variable frequency oscillators to generate transmitter signals, phase locking them to received signals, and determining time-of-flight based on frequency differences, along with noise filtering and automatic gain control, eliminates the need for expensive transducers and sub-nanosecond timing circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic transit-time flow meters use powerful precisely tuned transducers with response time between 50-100 pico-seconds to get good signal to noise ratio, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent changes the operating parameters by using lower frequency transducers (20-100 kHz) instead of high frequency precisely tuned transducers. The system compensates for the reduced signal-to-noise ratio through software-based correlation processing and digital signal averaging, achieving comparable measurement precision without requiring expensive precisely tuned transducers with 50-100 pico-second response times.
Solution Approach 2:
The patent replaces the mechanical/physical requirement for precisely tuned transducers with a computational approach. Instead of relying on hardware-level signal processing with specialized transducers, the system uses digital correlation processing, Fourier transforms, and software-based filtering to achieve the same measurement precision, thereby eliminating the need for expensive precisely tuned components.
2Measurement precision
If prior art transit-time devices based on the speed of light use sub-nanosecond timing circuitry to measure distances with good resolution, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent replaces expensive sub-nanosecond timing circuitry with a phase-based measurement approach using standard frequency counters and phase detectors. By measuring the phase difference of continuous wave signals at known frequencies, the system achieves sub-nanosecond equivalent resolution using much lower cost standard electronic components, avoiding the need for specialized high-speed timing circuitry.
Solution Approach 2:
The patent changes from time-domain measurement (requiring sub-nanosecond timing) to frequency-domain measurement using phase comparison. By operating at lower frequencies (e.g., 10-100 MHz) and measuring phase differences, the system achieves equivalent or better resolution using standard frequency counters rather than expensive sub-nanosecond timing circuits.
3Measurement precision
If phase based methods use digital to analog converter to digitize voltage for phase determination, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent replaces the power-intensive analog-to-digital conversion and Fourier transform processing with a more efficient phase detection method. By using analog phase detectors or simple digital phase comparison of the received signal with a reference signal, the system achieves comparable phase measurement accuracy with significantly reduced power consumption, avoiding the need for continuous ADC operation and intensive computational processing.
4Ease of manufacture
If low resolution analog to digital converters are used to digitize signal for phase determination, then device cost decreases, but measurement precision deteriorates requiring long averaging time
Solution Approach 1:
The patent replaces the ADC-based digitization approach with direct analog phase detection or simple digital sampling at the signal frequency. By using phase detectors that directly compare the phase of received and reference signals, the system achieves high measurement precision without requiring high-resolution ADCs or long averaging times, thereby maintaining low device cost while improving measurement speed and accuracy.
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 enables high-resolution time-of-flight measurements with improved signal-to-noise ratio and reduced power consumption, achieving accurate distance calculations with minimal errors.
Implementation Method 1
One or more oscillators are controlled to phase lock the transmitter signals to the corresponding received signals at different frequencies that differs by a predetermined number of cycles within the time-of-flight
Implementation Method 2
noise filtering circuitry, and noise detection circuitry for automatic receiver gain control; providing a high signal to noise ratio with minimum power
Implementation Method 3
noise detection circuitry for automatic receiver gain control; providing a high signal to noise ratio with minimum power
Data Source
AI summary
This invention relates to apparatus and methods for measuring the time-of-flight of a signal. The signal may be acoustic energy or electromagnetic energy such as x-ray, radio frequency, microwave, millimeter-wave, radar, and laser. Unlike unambiguous ranging devices that measures the phases of two or more signals to determine the time-of-flight and requires long averaging to achieve some degree of accuracy, this invention phase lock one or more transmitter signals to the corresponding received signals in predetermined phase relationships and measures the frequencies of one or more variable frequency oscillators having frequencies several times higher than the frequency of the transmitter signal to determined the time-of-flight with much higher accuracy.