Coherent Noise Filtering via Phase Shifted Radar Signals
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Solution Overview
Problem
Current detection systems are vulnerable to false alarms caused by coherent noise sources, such as those from aviation radar, ship navigation, and cell phones, which can lead to control system malfunctions and safety risks in collision avoidance systems.
Innovation Solution
The system applies varying phase shifts or pulse width modulations to radar signals before transmission, and upon reception, applies complementary phase shifts or aligns pulse midpoints to transform coherent noise into non-coherent noise, allowing a matched filter to distinguish and filter out the coherent noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current signal processing techniques are used to filter noise, then random noise can be reduced to some extent, but coherent noise sources cause false alarms and system vulnerability increases
Solution Approach 1:
The system applies a preliminary phase shift to the transmitted signal before it encounters the coherent noise source. This pre-applied phase shift creates a phase difference between the desired signal and the coherent noise, allowing the noise to be distinguished and filtered out during reception. The phase shift acts as a preemptive measure to prevent coherent noise from causing false alarms.
Solution Approach 2:
The system changes the phase parameter of the transmitted signal by applying a controlled phase shift. This parameter modification allows the receiver to differentiate between the phase-shifted desired signal and the coherent noise that did not undergo the same phase transformation, enabling effective filtering of the noise while preserving the signal.
2Measurement precision
If phase shifts are applied to outgoing signals to differentiate sources, then coherent noise can be transformed into non-coherent noise, but system complexity increases
Solution Approach 1:
The phase shift sequence is predetermined and applied to the signal before transmission. This preliminary action simplifies the reception process because the receiver only needs to apply the known inverse phase shift to recover the original signal, rather than performing complex real-time analysis to determine the appropriate phase correction.
Solution Approach 2:
The phase shift acts as an intermediary transformation that temporarily modifies the signal in a known, reversible way. This intermediary step facilitates the separation of the desired signal from coherent noise by creating a distinguishable difference, while the reversibility of the phase shift keeps the overall system complexity manageable.
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 effectively reduces false alarms by ensuring accurate signal processing and maintaining system reliability in high-coherent noise environments, enhancing safety and preventing potential damage or injury.
Implementation Method 1
A pulsed electronic signal receives varying phase shifts for each of its pulses prior to transmission. When coherent noise interferes with the transmitted signal, received signal receives a phase shift opposite of that applied prior to transmission such that the electronic signal is restored and the coherent noise becomes non-coherent.
Data Source
AI summary
Systems and methods are provided for the filtering of coherent noise signals. In an illustrative embodiment, a pulsed electronic signal receives varying phase shifts for each of its pulses prior to transmission. When coherent noise interferes with the transmitted signal, received signal receives a phase shift opposite of that applied prior to transmission such that the electronic signal is restored and the coherent noise becomes non-coherent. In another embodiment, width of each transmitted pulses can be varied prior to transmission, but a constant midpoint-to-midpoint time is maintained. After receiving a signal with coherent noise interference, the midpoints of the pulses are aligned causing the coherent noise to become non-coherent.