Radar Level Meter Reference Pulse Generation
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Solution Overview
Problem
Existing level measuring devices face inaccuracies due to unstable reference pulses caused by mixed reflections from antenna coupling, plug connections, and leakage signals, leading to shifts in the zero point and increased power consumption from high attenuation in delay lines.
Innovation Solution
A microwave module with separate echo and reference pulse generation units, using independent sampling mixers and oscillators to process these signals separately, eliminating the need for delay lines and reducing interference from leakage signals and large echoes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an internally generated reflection is used as a reference pulse in conventional level gauges, then the device complexity is reduced, but the measurement precision deteriorates due to instability of the reference pulse caused by mixed reflections from antenna coupling, connectors, and leakage signals
Solution Approach 1:
The invention separates the reference pulse generation from the echo signal processing by introducing a dedicated reference pulse generation unit that is electrically isolated from the transmit/receive switch. This segmentation allows the reference pulse to be generated independently without contamination from leakage signals, antenna coupling reflections, or connector reflections, thereby improving measurement precision while maintaining reasonable device complexity through modular design
Solution Approach 2:
The invention extracts the reference pulse generation function from the main signal path by taking out a portion of the transmitted signal through a directional coupler before it reaches the transmit/receive switch. This extraction creates a clean reference signal that is free from the harmful reflections and leakage signals present in the main path, resolving the contradiction between simplicity and precision
2Measurement precision
If conductors with length corresponding to resolution are inserted to separate reflections, then the measurement precision improves, but the device complexity increases due to additional components and longer signal paths
Solution Approach 1:
The invention introduces a directional coupler as an intermediary device that taps off a portion of the transmitted signal to create the reference pulse. This intermediary approach separates the reference signal generation from the main signal path without requiring multiple conductors of specific lengths, achieving reflection separation while maintaining device simplicity through a single well-placed coupler component
3Measurement precision
If a cable with length of transmit pulse is inserted between transmit/receive switch and microstrip cable to reduce interference, then the measurement precision improves, but the device complexity and signal path length increase
Solution Approach 1:
The invention performs preliminary separation of the reference pulse from the transmitted signal using a directional coupler positioned before the transmit/receive switch. By creating the reference pulse in advance and isolating it from the main path, the system eliminates the need for subsequent cable insertions or delay lines to separate reflections, achieving precision improvement without increasing device complexity
4Measurement precision
If signal is extracted earlier and fed back via directional coupler with delay line, then the measurement precision improves, but the use of energy increases due to high attenuation requiring amplifier compensation
Solution Approach 1:
The invention extracts the reference pulse signal early in the transmit path using a directional coupler, before the signal encounters high-attenuation delay lines or requires amplifier compensation. This early extraction provides a clean reference signal with sufficient amplitude, eliminating the need for energy-intensive amplifier stages and reducing overall power consumption while maintaining measurement precision
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 solution provides a stable and accurate reference pulse independent of leakage and echo reflections, reducing power consumption and enhancing measurement accuracy by allowing separate processing of echo and reference signals.
Implementation Method 1
a first portion of the transmitted signal is coupled out of the transmitted signal using a directional coupler
Implementation Method 2
a first sampling mixer converts the coupled reference signal into a reference pulse
Implementation Method 3
level measuring device for determining a level in a tank using the pulse transit-time method
Data Source
Figure 1~2
Figure 3~3a
Figure 4~5
AI summary
In radar level meter devices according to the pulse delay time method reflection generated internally in a microwave module is used for the measurement of the propagation time. According to one embodiment example of the present invention, the microwave module for the reference pulse generation has its own sampling mixer, or its own mixer, or its own oscillator. The echo signal and the reference pulse can subsequently be separated or jointly processed further. A delay line is not necessary on the transmission frequency of the radar sensor. Any errors due to leak signals are largely impeded.