Fence Disturbance Sensor With End-to-End Correlation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing cable sensors for perimeter security suffer from decreased performance and sensitivity due to RF attenuation, leading to increased False Alarm Rate (FAR) and Nuisance Alarm Rate (NAR) with increasing cable length, as signal strength and Signal to Noise Ratio (SNR) decrease with distance from the processor.
Innovation Solution
The implementation of a Coupled Line Reflectometer (CLR) sensor system with end-to-end correlation (E2EC) using two processors at opposite ends of the cable, where a movable sensor element is detected and located by both processors to ensure uniform detection sensitivity along the cable length, utilizing time domain reflectometry and matched filters to correlate disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If cable length is increased to cover larger perimeter areas, then monitoring coverage is improved, but signal strength and SNR decrease due to RF attenuation
Solution Approach 1:
The patent divides the monitoring system into multiple segments, each with its own processor located at different positions along the cable. This segmentation allows each processor to handle a specific section of the cable independently, maintaining high SNR for each segment while collectively covering a large perimeter area. The cable is effectively divided into multiple monitoring zones, each optimized for reliable detection.
Solution Approach 2:
The patent transitions from a single-end monitoring approach to multi-end monitoring by placing processors at both ends of the cable. This dimensional change from one-dimensional (single point) to two-dimensional (multiple points) monitoring enables simultaneous detection from multiple locations, maintaining signal strength across the entire cable length while expanding coverage area.
2Area of stationary object
If cable length is increased to extend monitoring range, then perimeter coverage is improved, but False Alarm Rate and Nuisance Alarm Rate increase
Solution Approach 1:
By segmenting the monitoring into multiple processor zones along the cable, each processor independently analyzes signals from its local section. This reduces the accumulation of noise and false alarm sources that would occur in a single long-chain processing system, thereby maintaining low FAR and NAR rates across extended perimeter coverage.
Solution Approach 2:
The system implements feedback mechanisms where processors at multiple ends continuously monitor and analyze signals, comparing detected events against established thresholds. This feedback loop enables real-time adjustment and validation of alarm conditions, reducing false alarms while maintaining comprehensive perimeter surveillance.
3Device complexity
If single processor is used at one end of the cable, then device complexity is reduced, but detection sensitivity becomes non-uniform along the cable length
Solution Approach 1:
The patent employs asymmetric placement of processors at both ends of the cable, creating a balanced monitoring architecture. This asymmetric configuration from a single-end setup enables uniform detection sensitivity along the entire cable length, as each end processor compensates for signal attenuation in its respective direction.
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 provides uniform detection sensitivity and improved SNR, reducing FAR and NAR, allowing precise localization of intrusions and enabling fail-safe operation even if the cable is cut, with processors on both ends simultaneously detecting and locating disturbances.
Implementation Method 1
cable sensors using Time Domain Reflectometry (TDR) in one form or another... a pulse of RF energy is transmitted down the coaxial line and the coupled response is measured on the sense wire line
Implementation Method 2
Coupled Line Reflectometer (CLR) sensor line... the coupled response is measured on the sense wire line. As in TDR, the time delay between the onset of the pulse and the receipt of the change in the coupled response
Implementation Method 3
RF attenuation in the cables. This attenuation is largely due to resistive losses in the conductors
Implementation Method 4
dielectric losses in the cable dielectric
Data Source
AI summary
In at least one embodiment, a fence disturbance sensor is disclosed wherein a sensor cable having a signal processor on each end of the cable correlates the response data as seen from both ends of the cable to detect and locate intruders attempting to breach the fence. The processors at each end of the cable time multiplex the transmission of a phase coherent coded pulse sequence along the coaxial line creating both co-directional and contra-directional signals to propagate along the shielded moving-wire transmission line. When the cable is disturbed, the impedance of the shielded moving-wire transmission line, causing a change in the coupled signals which are used to detect and locate the disturbance. Hence when the cable is disturbed time multiplexed contra-directionally coupled responses are detected in complementary range bins where the amplitude and phase of the two responses are correlated by taking the complex product of the complementary range bin responses, thereby detecting the audio signal creating a magnitude and phase response in the array of complementary range bins. Hence to create an Event, a disturbance must be detected at the same time at the same location and with the same audio. When a prescribed number of Events occur at the same location within a prescribed time window an Alarm is declared.