Single Antenna Radio Altimeter With Circulator Isolation
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Solution Overview
Problem
Traditional radio altimeter systems require multiple antennas and labor-intensive cable routing and shielding to achieve accurate altitude information, prone to false detections due to signal leakage and requiring precise coaxial cable lengths for correct operation.
Innovation Solution
A single antenna system using a source generator for frequency modulated continuous wave signals, a coupler to split the signal, a circulator for isolation, and a digital signal processor to determine range based on low frequency return signals, achieving isolation of at least 30 dB between transmission and reception signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional closed-loop radio altimeter systems use multiple antennas with coaxial cable routing, then altitude measurement function is achieved, but installation complexity increases and signal leakage occurs requiring greater than 120 dB isolation
Solution Approach 1:
The patent combines the transmit and receive antenna functions into a single antenna element, eliminating the need for separate Tx and Rx antennas and their associated cable routing. This merging approach simplifies installation while the circulator component provides the necessary signal isolation (greater than 120 dB) between transmit and receive paths, resolving the contradiction between ease of manufacture and signal isolation reliability
Solution Approach 2:
The circulator acts as an intermediary component that enables single-antenna operation while maintaining signal isolation. It directs signals in a specific direction, allowing the same antenna to be used for both transmission and reception without harmful interference, thus achieving both simplified installation and reliable signal separation
2Measurement precision
If precise coaxial cable lengths are used for correct AID calibration, then measurement precision is improved, but device complexity and installation time increase
Solution Approach 1:
The patent extracts the AID calibration requirement from the physical cable length constraint and relocates it to the signal processing domain. By using a single antenna with electronic signal processing, the system eliminates the need for precise mechanical cable length measurements while maintaining measurement precision through digital calibration methods
Solution Approach 2:
The patent replaces the mechanical cable length measurement system with an electronic signal processing system. Instead of relying on precise physical cable routing and length measurements, the system uses electronic signals and digital processing to achieve accurate altitude measurements, thereby reducing device complexity and installation time
3Reliability
If multiple antennas are used for transmission and reception, then signal isolation is achieved, but the system form factor increases and skin friction drag increases
Solution Approach 1:
The patent merges multiple antenna functions into a single antenna element, reducing the system form factor and minimizing skin friction drag on aircraft surfaces. The circulator component provides the necessary signal isolation (greater than 120 dB) between transmit and receive paths, ensuring that reliability is maintained despite the reduction in physical antenna count
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
Enables accurate radio altimetry with a small form factor, reducing installation complexity and eliminating the need for precise cable lengths, while maintaining high isolation and minimizing skin friction drag on aircraft surfaces.
Implementation Method 1
The reception signal may be isolated from the transmission signal within the circulator by at least 30 dB
Implementation Method 2
a mixer to mix the reception signal received from the circulator and the coupled signal received from the coupler to generate a low frequency return signal
Implementation Method 3
determine a round trip time delay of the transmission signal based on the low frequency return signal
Implementation Method 4
The reception signal may be a reflection of the transmission signal from a radio frequency selective surface
Data Source
AI summary
A system and related method is disclosed for determining a range between a single antenna array and a surface. The system includes a source generator configured to generate a source signal, a coupler, a circulator, a mixer, and a digital signal processor. The source generator generates a frequency modulated continuous wave source signal. The coupler splits the source signal into a transmission signal and a coupled signal. The circulator receives the transmission signal from the coupler, outputs the transmission signal to an antenna, and receives a reception signal from the antenna, which may be a reflection of the transmission signal from the surface. The mixer mixes the reception signal from the circulator and the coupled signal from the coupler to generate a low frequency return signal. The digital signal processor determines a range between the antenna and the surface based on the low frequency return signal.