Single-Crystal Radar Level Gauge for Stable Tx/Rx Frequency Control
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Solution Overview
Problem
Current pulsed radar level gauge systems face challenges in frequency generation stability due to temperature variations and aging, particularly when using two oscillators, and when relying on a single oscillator, they require components susceptible to drift.
Innovation Solution
A pulsed radar level gauge system utilizing a single oscillating crystal with frequency modifying circuitry, including a PLL and integer frequency divider, to generate Tx and Rx frequencies, ensuring precise control of the delta frequency, thereby improving accuracy and reducing drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two matched oscillators are used to generate Tx and Rx frequencies, then frequency stability can be maintained, but the start-up time becomes excessively long due to stabilization requirements
Solution Approach 1:
The patent merges the function of two separate oscillators into a single oscillating crystal that generates both Tx and Rx frequencies. This consolidation eliminates the need for two separate stabilization processes, thereby reducing start-up time while maintaining frequency stability through the single crystal's inherent consistency
Solution Approach 2:
The single oscillating crystal is designed to perform multiple functions: generating both the transmit frequency (Tx) and receive frequency (Rx) simultaneously. This multi-functional approach replaces the dedicated two-oscillator system, reducing component count and stabilization time while maintaining the required frequency relationships
2Loss of time
If a single oscillator is used to generate both Tx and Rx frequencies, then start-up time is reduced, but components become susceptible to drift due to temperature variation and aging
Solution Approach 1:
The patent implements a feedback mechanism using a phase-locked loop (PLL) that continuously monitors and adjusts the phase and frequency of the oscillating crystal's outputs. This closed-loop control compensates for drift caused by temperature variation and aging, maintaining accurate frequency relationships between Tx and Rx signals over time
Solution Approach 2:
The system dynamically adjusts frequency parameters through the PLL circuitry, which modifies the oscillation characteristics in real-time to compensate for environmental changes. By changing the control voltage to the VCO based on phase detection errors, the system maintains stable frequency relationships despite temperature and aging effects
3Measurement precision
If frequency modifying circuitry with PLL is used to generate precise frequencies from a single oscillator, then frequency accuracy is improved, but device complexity increases
Solution Approach 1:
The frequency modifying circuitry is segmented into functional blocks: a phase comparator, voltage-controlled oscillator (VCO), and frequency dividers. This modular segmentation of the PLL circuit allows for easier implementation and debugging while achieving precise frequency generation from the single oscillating crystal
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 provides improved frequency generation stability and accuracy, enabling precise determination of the filling level in tanks with reduced susceptibility to temperature variations and aging, using a single oscillator to generate frequencies with a delta frequency in the order of Hz.
Implementation Method 1
The frequency generator includes one single oscillating crystal for providing an oscillator frequency fosc
Implementation Method 2
at least one of the first and second paths including a PLL configured to receive said oscillator frequency fosc as input frequency and deliver a regulated output frequency being equal to the oscillator frequency fosc multiplied M/N
Implementation Method 3
a frequency divider connected to receive the regulated output frequency and deliver an output frequency equal to the regulated output frequency divided by an integer factor P
Implementation Method 4
a transceiver for providing a transmit signal in the form of a pulse train and receiving a reflected signal resulting from a reflection of the transmit signal at a surface of the product
Implementation Method 5
the reflected signal resulting from a reflection of the transmit signal at a surface of the product
Implementation Method 6
sampling circuitry connected to the transceiver and to the frequency generator, and configured to sample the reflected signal with a sampling frequency equal to the Rx frequency in order to provide a time expanded tank signal
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A pulsed radar level gauge for determining the filling level of a product contained in a tank, comprising a frequency generator for generating a Tx frequency signal and a Rx frequency signal. The frequency generator includes one single oscillating crystal for providing an oscillator frequency fosc and frequency modifying circuitry. The frequency modifying circuitry comprises a path including a PLL configured to receive said oscillator frequency fosc as input frequency and deliver a regulated output frequency being equal to the oscillator frequency fosc multiplied M/N, and a frequency divider connected to receive the regulated output frequency and deliver an output frequency equal to the regulated output frequency divided by an integer factor P. A PLL combined with an integer frequency divider is used to generate at least one of the Tx and Rx frequencies based on an oscillator frequency provided by one single oscillator.