Ultra-wideband impedance sensor
First Claim
1. An ultra-wideband impedance (UWBZ) sensor, comprising:
- a pulse generator for producing ultra-wideband gating pulses;
an ultra-wideband sampler connected to the pulse generator which samples during the gating pulses;
a transmission line whose impedance is a function of the near proximity of objects, connected to the sampler to produce changes in sampler output caused by changes in impedance of the transmission line caused by the near proximity of objects to the transmission line;
an output device connected to the sampler output to provide an output signal;
wherein the sensing range is determined by half the pulsewidth of the gating pulses.
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Accused Products
Abstract
The ultra-wideband impedance sensor (UWBZ sensor, or Z-sensor) is implemented in differential and single-ended configurations. The differential UWBZ sensor employs a sub-nanosecond impulse to determine the balance of an impedance bridge. The bridge is configured as a differential sample-and-hold circuit that has a reference impedance side and an unknown impedance side. The unknown impedance side includes a short transmission line whose impedance is a function of the near proximity of objects. The single-ended UWBZ sensor eliminates the reference side of the bridge and is formed of a sample and hold circuit having a transmission line whose impedance is a function of the near proximity of objects. The sensing range of the transmission line is bounded by the two-way travel time of the impulse, thereby eliminating spurious Doppler modes from large distant objects that would occur in a microwave CW impedance bridge. Thus, the UWBZ sensor is a range-gated proximity sensor. The Z-sensor senses the near proximity of various materials such as metal, plastic, wood, petroleum products, and living tissue. It is much like a capacitance sensor, yet it is impervious to moisture. One broad application area is the general replacement of magnetic sensors, particularly where nonferrous materials need to be sensed. Another broad application area is sensing full/empty levels in tanks, vats and silos, e.g., a full/empty switch in water or petroleum tanks.
90 Citations
20 Claims
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1. An ultra-wideband impedance (UWBZ) sensor, comprising:
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a pulse generator for producing ultra-wideband gating pulses; an ultra-wideband sampler connected to the pulse generator which samples during the gating pulses; a transmission line whose impedance is a function of the near proximity of objects, connected to the sampler to produce changes in sampler output caused by changes in impedance of the transmission line caused by the near proximity of objects to the transmission line; an output device connected to the sampler output to provide an output signal; wherein the sensing range is determined by half the pulsewidth of the gating pulses. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A differential ultra-wideband impedance (UWBZ) sensor, comprising:
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a pulse repetition frequency (PRF) generator for producing a sequence of PRF pulses; a gating pulse generator connected to the PRF generator for producing ultra-wideband gating pulses; a differential sampling impedance bridge comprising first, second, third and fourth nodes, the first node being connected to the gating pulse generator, a first Schottky diode having its cathode connected to the first node and its anode to the second node, a first charge holding capacitor and a reference impedance connected in series between the second node and the third node, the third node being connected to ground, a second Schottky diode having its cathode connected to the first node and its anode to the fourth node, a second charge holding capacitor and a sensor impedance connected in series between the fourth node and third node; a transmission line whose impedance is a function of the near proximity of objects, connected in parallel across the sensor impedance; a differential amplifier having a first input connected to the second node and a second input connected to the fourth node to detect sampling bridge imbalance caused by the near proximity of objects to the transmission line; wherein the sensing range is determined by half the pulsewidth of the gating pulses. - View Dependent Claims (13, 14, 15, 16)
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17. A single-ended ultra-wideband impedance (UWBZ) sensor, comprising:
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a pulse repetition frequency (PRF) generator for producing a sequence of PRF pulses; a pulse forming network (PFN) connected to the PRF generator for producing ultra-wideband gating pulses; a single ended sampler comprising a Schottky diode having its cathode connected to the PFN, and a charge holding capacitor connected to the anode of the Schottky diode; a transmission line whose impedance is a function of the near proximity of objects, connected to the charge holding capacitor; an amplifier having an input connected to the anode of the Schottky diode to detect changes in sampler output caused by the near proximity of objects to the transmission line; wherein the sensing range is determined by half the pulsewidth of the gating pulses. - View Dependent Claims (18, 19, 20)
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Specification