Patent attributes
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.
