AC Field Target Detection Using Ambient Mains Perturbations
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Solution Overview
Problem
Existing target detection systems using ambient static DC electric fields struggle to detect stationary targets and face complexity when dealing with multiple targets, particularly in accurately discriminating between them.
Innovation Solution
Employing an array of sensors attuned to AC perturbations within an external AC excitation field, such as the domestic mains supply, to detect and track both stationary and moving targets by monitoring changes in AC signal amplitude, which allows for the detection of target position and movement without the need for active excitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ambient static DC electric field is used for target detection, then the system can detect moving targets, but stationary targets cannot be detected
Solution Approach 1:
The patent changes the field parameter from static DC electric field to time-varying AC electric field. The AC field's time-varying nature enables detection of both moving and stationary targets, as stationary targets modulate the AC field through their presence, creating detectable signal variations that DC fields cannot provide.
2Adaptability or versatility
If ambient AC signals are used for target detection, then both stationary and moving targets can be detected, but the system complexity increases for multiple targets
Solution Approach 1:
The system employs feedback mechanisms where detected AC signal perturbations are processed and used to update target position estimates. This feedback loop enables the system to handle multiple targets by continuously refining detection accuracy and discriminating between different target signatures through iterative signal processing.
Solution Approach 2:
The patent segments the detection space into multiple sensing zones using an array of sensors. Each sensor independently monitors AC field perturbations in its local zone, and the combined data from multiple segmented zones enables sophisticated multi-target discrimination and tracking while distributing processing complexity across the sensor array.
3Device complexity
If DC field detection is used, then the system is simpler to implement, but it requires target movement to generate a detectable signal
Solution Approach 1:
The patent employs periodic AC excitation signals instead of continuous DC fields. The periodic nature of AC signals creates time-varying electric field conditions that interact with both stationary and moving targets, generating modulated signals that are easier to detect and process reliably without requiring target motion to initiate detection.
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 the detection and tracking of targets within existing extensive AC fields, effectively locating and monitoring stationary and moving objects by utilizing ambient AC signals, overcoming limitations of prior art by using AC signal amplitude variations to generate useful information for target position and movement data.
Implementation Method 1
a number of sensors, usually two per axis, have been employed to infer the location of a single moving object within a detection area defined by the positions of the sensors
Implementation Method 2
an amplifier connected to the electrode for receiving and amplifying the detection signals to produce AC measurement signals as output
Implementation Method 3
at least one feedback circuit from an output of the amplifier to an input thereof for enhancing the input impedance of the amplifier
Implementation Method 4
a filter circuit adapted to filter out frequencies that are outside a pre-defined pass band, wherein the AC source has a frequency or a band of frequencies within the pass band
Implementation Method 5
a level detector responsive to the AC measurement signals for monitoring signal amplitude and generating amplitude information for use in producing target object data
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention provides a target object detection system, comprising a plurality of sensing nodes (10) for positioning at respective detection locations with respect to a detection area (12) that is situated within a field generated by an ambient AC source of excitation. Each sensing node has at least one electric potential sensor (22, 42) designed to detect perturbations in said field caused by a target object (14), said one sensor including an electrode (20, 40) responsive to the AC excitation field for generating detection signals, an amplifier (28) connected to the electrode for receiving and amplifying the detection signals to produce AC measurement signals as output, and at least one feedback circuit (30, 36) from an output of the amplifier to an input thereof for enhancing the input impedance of the amplifier. A signal processing arrangement (24, 26, 44) is associated with each sensing node and comprising a filter circuit (24) adapted to filter out frequencies generated by the ambient AC source of excitation that are outside a pre-defined bandwidth, and a level detector (26) responsive to the AC measurement signals for monitoring signal amplitude and generating amplitude information for use in producing target object data.