PROXIMITY SENSORS
First Claim
1. A proximity sensor for use with a device that relies on the transmission and/or receipt of a main electromagnetic signal that can be blocked by an object being placed in proximity to the device, the proximity sensor comprising:
- an oscillator;
an antenna for transmitting and receiving electromagnetic signals;
a directional coupler having a first port and a second port connected together by a main line and a third port and a fourth port connected together by a coupled line, the first port being connected to the oscillator, the second port being connected to the antenna, and the third port being connected to a detector and acting as an isolated port of the directional coupler when a transmit signal is supplied from the oscillator to the antenna along the main line and as a coupled port when a receive signal is supplied from the antenna to the oscillator along the main line;
wherein the oscillator is controlled to provide a transmit signal to the antenna along the main line of the directional coupler and wherein the detector provides an alert indicating the presence of a blocking object if the magnitude of the power of the transmit signal that is reflected back to the antenna in the form of a receive signal exceeds a threshold.
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Accused Products
Abstract
A proximity sensor can be used with a device such as a monitoring tag or portable tracking device that relies on GPS signals or other radio-frequency signals. The proximity sensor determines if the signals are being deliberately blocked by an object such as metal foil being placed in proximity to the device. The sensor includes an oscillator, a directional coupler and an antenna. A third port of the directional coupler acts as a coupled port when RF power that has been transmitted by the antenna is reflected back to the antenna by a blocking object. The reflected RF power passes along a main line of the directional coupler and a proportion is coupled to the third port. A detector provides an alert if the magnitude of the power of the transmit signal that is reflected back to the antenna in the form of a receive signal exceeds a threshold.
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Citations
19 Claims
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1. A proximity sensor for use with a device that relies on the transmission and/or receipt of a main electromagnetic signal that can be blocked by an object being placed in proximity to the device, the proximity sensor comprising:
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an oscillator; an antenna for transmitting and receiving electromagnetic signals; a directional coupler having a first port and a second port connected together by a main line and a third port and a fourth port connected together by a coupled line, the first port being connected to the oscillator, the second port being connected to the antenna, and the third port being connected to a detector and acting as an isolated port of the directional coupler when a transmit signal is supplied from the oscillator to the antenna along the main line and as a coupled port when a receive signal is supplied from the antenna to the oscillator along the main line; wherein the oscillator is controlled to provide a transmit signal to the antenna along the main line of the directional coupler and wherein the detector provides an alert indicating the presence of a blocking object if the magnitude of the power of the transmit signal that is reflected back to the antenna in the form of a receive signal exceeds a threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A device that relies on the transmission and/or receipt of a main electromagnetic signal that can be blocked by an objection being placed in proximity to the device, the device incorporating a proximity sensor comprising:
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an oscillator; an antenna for transmitting and receiving electromagnetic signals; a directional coupler having a first port and a second port connected together by a main line and a third port and a fourth port connected together by a coupled line, the first port being connected to the oscillator, the second port being connected to the antenna, and the third port being connected to a detector and acting as an isolated port of the directional coupler when a transmit signal is supplied from the oscillator to the antenna along the main line and as a coupled port when a receive signal is supplied from the antenna to the oscillator along the main line; wherein the oscillator is controlled to provide a transmit signal to the antenna along the main line of the directional coupler and wherein the detector provides an alert indicating the presence of a blocking object if the magnitude of the power of the transmit signal that is reflected back to the antenna in the form of a receive signal exceeds a threshold. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A device that relies on the transmission and/or receipt of a main electromagnetic signal that can be blocked by an objection being placed in proximity to the device, the device incorporating a primary antenna for transmitting and/or receiving the main electromagnetic signal and a proximity sensor comprising:
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an oscillator; an antenna for transmitting and receiving electromagnetic signals located adjacent to the primary antenna; a directional coupler having a first port and a second port connected together by a main line and a third port and a fourth port connected together by a coupled line, the first port being connected to the oscillator, the second port being connected to the antenna, and the third port being connected to a detector and acting as an isolated port of the directional coupler when a transmit signal is supplied from the oscillator to the antenna along the main line and as a coupled port when a receive signal is supplied from the antenna to the oscillator along the main line; wherein the oscillator is controlled to provide a transmit signal to the antenna along the main line of the directional coupler and wherein the detector provides an alert indicating the presence of a blocking object if the magnitude of the power of the transmit signal that is reflected back to the antenna in the form of a receive signal exceeds a threshold.
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19. A proximity sensor for use with a device that relies on the transmission and/or receipt of a main electromagnetic signal that can be blocked by an object being placed in proximity to the device, the proximity sensor comprising:
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an oscillator; an antenna for transmitting and receiving electromagnetic signals; a directional coupler having a first port and a second port connected together by a main line and a third port and a fourth port connected together by a coupled line. the first port being connected to the oscillator, the second port being connected to the antenna, and the third port being connected to a detector and acting as an isolated port of the directional coupler when a transmit signal is supplied from the oscillator to the antenna along the main line and as a coupled port when a receive signal is supplied from the antenna to the oscillator along the main line; wherein the oscillator is controlled to provide a transmit signal to the antenna along the main line of the directional coupler on detection that the main electromagnetic signal is not being transmitted and/or received, and wherein the detector provides an alert indicating the presence of a blocking object if the magnitude of the power of the transmit signal that is reflected back to the antenna in the form of a receive signal exceeds a threshold.
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Specification