False Lock Filter Circuit for Pulsed Radar Altimeters
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Solution Overview
Problem
Altimeter systems face inefficiencies due to false target detections caused by jamming signals and mutual interference, leading to incorrect switching from search mode to track mode.
Innovation Solution
A false lock filter circuit employing both low and high bandwidth low pass filters, along with a false lock controller that performs statistical analysis on the high bandwidth filter's output to differentiate valid targets from noise, preventing premature switching to track mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low bandwidth low pass filter (LBW LPF) is used to reduce noise fluctuations and improve sensitivity, then the threshold can be set close to the average noise level for better detection, but random high energy noise spikes from jamming signals or mutual interference can cause false target detections leading to incorrect mode switching
Solution Approach 1:
The patent divides the detection system into two parallel filtering paths: one with a low bandwidth low pass filter (LBW LPF) for sensitivity and another with a high bandwidth low pass filter (HBW LPF) for spike detection. Each path processes the detector output independently, allowing the system to simultaneously achieve both high sensitivity and high reliability by comparing results from both paths before making mode switching decisions.
2Measurement precision
If the threshold is set close to the average noise level to maximize sensitivity, then weak valid targets can be detected, but the system becomes vulnerable to false targets caused by noise spikes averaging with background noise
Solution Approach 1:
The patent introduces a false lock controller as an intermediary component that receives outputs from both the LBW LPF and HBW LPF. This controller performs statistical analysis on samples from both filters and acts as a gatekeeper, determining whether to permit mode switching based on whether the detection is validated by both filtering paths, thereby protecting against false targets while maintaining sensitivity to weak valid targets.
3Productivity
If the system switches to track mode upon detecting a target, then focused tracking can be achieved, but false detections from noise spikes cause premature and incorrect switching from search mode to track mode
Solution Approach 1:
The patent implements a feedback mechanism where the false lock controller continuously monitors outputs from both the LBW LPF and HBW LPF, performs statistical analysis on the samples, and provides feedback control over the mode switching decision. The controller only permits transition from search to track mode when both filtering paths confirm a valid target, ensuring reliable mode switching while maintaining tracking efficiency.
Data Source
AI summary
A false lock filter circuit for a pulsed altimeter is provided. The circuit includes a low pass filter having a relatively low bandwidth (LBW LPF), a low pass filter having a relatively high bandwidth (HBW LPF) and a false lock controller. The LBW LPF has an input that is coupled to receive a detector output. The HBW LPF has an input that is coupled to receive the detector output. The false lock controller is coupled to receive outputs from the LBW LPF and HBW LPF. Moreover, the false lock controller is configured to sample an output of the HBW LPF and apply a statistical analysis on the samples to determine if a valid target has been detected.