Radio Altimeter Path Extending Unit for Wide Range Altitude Measurement
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Solution Overview
Problem
Existing FM-CW radio altimeters face challenges in accurately measuring a wide range of altitudes due to a large dynamic measurement range, which limits their application to short-range detection and makes it difficult to maintain a uniform beat frequency over a significant altitude change, such as from 1 m to 10,000 m.
Innovation Solution
A path extending unit is introduced in the transmission or reception path of the radio altimeter, utilizing an electro-optical converter to convert RF signals to optical signals, which are then delayed through an optical cable and re-converted back to RF signals, reducing the dynamic range by 1/10 to 1/1,000, allowing for a wider measurement range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wide dynamic measurement range is used to measure altitudes from 1 m to 10,000 m, then the measurement range is improved, but the beat frequency varies excessively making accurate measurement difficult
Solution Approach 1:
The patent divides the wide dynamic measurement range into multiple segments by introducing a path extending unit that adds a fixed delay path. This segmentation allows the system to handle different altitude ranges separately, with each segment having a manageable beat frequency range, thereby maintaining measurement precision across the entire extended range.
Solution Approach 2:
The path extending unit acts as an intermediary component that introduces a controlled time delay in the signal path. This intermediary element effectively reduces the dynamic range presented to the beat frequency discriminator, allowing accurate measurement without requiring the discriminator to handle the full wide range directly.
2Measurement precision
If the dynamic range is reduced to maintain uniform beat frequency, then measurement precision is improved, but the measurement range is limited to short distances
Solution Approach 1:
The path extending unit is nested within the existing radio altimeter signal path, adding functionality without replacing the core system. The delay path is embedded in series with the existing transmission and reception paths, allowing the system to maintain its original short-range precision while extending to medium and long distances.
Solution Approach 2:
The patent extends the measurement capability by adding a temporal dimension through the path extending unit. By introducing a time delay component, the system effectively transforms the single-dimensional beat frequency measurement into a multi-dimensional measurement that accounts for both direct path and delayed path signals, enabling extended range measurement.
3Measurement precision
If FM-CW scheme is used for short-range detection, then measurement precision is improved, but it cannot maintain uniform beat frequency over significant altitude changes
Solution Approach 1:
The path extending unit performs a preliminary action by pre-delaying the received signal before it reaches the beat frequency discriminator. This preliminary delay compensates for the frequency variations that would otherwise occur during altitude changes, ensuring that the beat frequency remains stable and uniform throughout the measurement process.
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 effectively reduces the frequency band limitations, enabling accurate altitude measurement from short to medium and long distances, improving the generality and precision of the radio altimeter.
Implementation Method 1
utilizing an electro-optical converter to convert RF signals to optical signals
Implementation Method 2
which are then delayed through an optical cable
Implementation Method 3
and re-converted back to RF signals
Data Source
AI summary
A radio altimeter includes a voltage controlled oscillator outputting a radio frequency signal through a forward path in a direction from the voltage controlled oscillator to a radio frequency antenna, a path extending unit positioned in the forward path to receive the radio frequency signal to delay the radio frequency signal to generate a delayed radio frequency signal. The radio frequency antenna transmits the delayed radio frequency signal to ground and receives the delayed radio frequency signal reflected from the ground. The radio altimeter also includes a mixer that receives the reflected delayed radio frequency signal through a signal reception path from the radio frequency antenna and the radio frequency signal from the voltage controlled oscillator and mixes the radio frequency signal and the reflected delayed radio frequency signal to output a beat frequency signal which is used to calculate altitude with respect to the ground.