Radar Frequency Adjustment for Ground Clutter Rejection
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Solution Overview
Problem
Conventional aircraft radar systems face difficulties in detecting wind shear at lower altitudes due to the interference of ground clutter and RF artifacts, leading to false alerts and inefficiencies in signal processing, especially with smaller antennas and aging hardware.
Innovation Solution
A radar system that adjusts the frequency of radar signals based on the aircraft's ground speed to effectively filter out ground clutter and mitigate spurious signals by using a processor to determine Doppler velocity data and adjust the transmitter frequency, allowing for improved rejection of ground clutter and reduction of false alerts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high pass filters are used to remove ground clutter returns, then ground clutter rejection is improved, but spurious signals are generated and moved to other frequencies causing false alerts
Solution Approach 1:
The patent applies preliminary action by adjusting the transmitter frequency before radar signal transmission to account for anticipated Doppler shifts. This prevents ground clutter from being translated to DC where it would generate spurious signals, thereby eliminating the harmful effect before it occurs in the signal processing chain
Solution Approach 2:
The patent changes the frequency parameter of the transmitted radar signal based on calculated Doppler velocity data. By dynamically adjusting the transmitter frequency, the system maintains ground clutter at non-DC frequencies while avoiding the generation of spurious signals that would otherwise occur with conventional fixed-frequency transmission
2Object-affected harmful factors
If post-reception frequency translation is used to move ground clutter to 0 Hz, then ground clutter filtering is improved, but RF artifacts are moved to other frequencies causing false wind shear targets
Solution Approach 1:
The patent performs preliminary frequency adjustment of the transmitted signal based on predicted Doppler shifts, eliminating the need for post-reception frequency translation. This prevents RF artifacts from being moved to frequencies where they would be misinterpreted as wind shear targets, thereby maintaining measurement precision
Solution Approach 2:
Instead of translating frequencies after reception as in conventional systems, the patent inverts the approach by pre-adjusting the transmission frequency to account for expected Doppler effects. This reversal eliminates the harmful side effect of moving spurious signals into the wind shear detection frequency range
3Measurement precision
If stronger signals are used to improve wind shear detection, then detection capability is improved, but ground clutter and spurious signals increase causing more false alerts
Solution Approach 1:
The patent changes the transmission frequency parameter dynamically based on Doppler velocity data, allowing the system to maintain optimal signal strength for wind shear detection while keeping ground clutter and spurious signals at frequencies where they do not cause false alerts
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 enhances the accuracy of wind shear detection by reducing ground clutter and spurious signals, leading to fewer false alerts and improved radar system performance without increasing spurious frequency signals.
Implementation Method 1
a processor for providing a ground speed estimate based upon Doppler velocity data
Implementation Method 2
The frequency of radar signals from the transmitter is adjusted according to a velocity of the aircraft determined using the ground speed estimate
Data Source
AI summary
A radar system includes an antenna. The radar system comprises a processor for providing an error in ground speed estimate based upon Doppler velocity data, and a transmitter. The frequency of radar signals from the transmitter is adjusted according to a velocity of the aircraft calculated using the error in ground speed estimate or using the error in ground speed estimate. The adjusted frequency can allow ground clutter to be removed by high pass filtering in one embodiment.