Apparatus and method for interrogation of passive sensors
First Claim
1. A sensor system comprising a passive sensing apparatus comprising:
- a passive sensor; and
an antenna associated with said passive sensor, wherein, in use, the sensor is powered and interrogated by a radio frequency signal (Fs) received via the antenna, the system being characterized by switching means for controlling the connection between the passive sensor and the antenna such that, in a first state of said switching means, said antenna is prevented from transmitting a signal generated by the passive sensor, and, in a second state of said switching means, said antenna is permitted to transmit a signal generated by the passive sensor; and
remotely operable control means for controlling the state of the switching means.
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Accused Products
Abstract
A monitoring system, particularly suitable for monitoring conditions (e.g. pressure or temperature) of a vehicle tire comprises a passive sensor (102, 104), an antenna (106) associated with said passive sensor, and switching means (108) for controlling the connection between the passive sensor and the antenna such that, in a first state of said switching means, said antenna is prevented from transmitting a signal generated by the passive sensor, and, in a second state of said switching means, said antenna is permitted to transmit a signal generated by the passive sensor. The switching means is operated remotely by means of a control signal. The control signal may be derived from the sum or difference of RF signals (F1 and F2) applied to a filter (112) In alternative embodiments the control signal is the modulating frequency of an AM or FM modulated radio signal or a radio signal carrying a digital code.
27 Citations
11 Claims
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1. A sensor system comprising a passive sensing apparatus comprising:
- a passive sensor; and
an antenna associated with said passive sensor, wherein, in use, the sensor is powered and interrogated by a radio frequency signal (Fs) received via the antenna, the system being characterized by switching means for controlling the connection between the passive sensor and the antenna such that, in a first state of said switching means, said antenna is prevented from transmitting a signal generated by the passive sensor, and, in a second state of said switching means, said antenna is permitted to transmit a signal generated by the passive sensor; and
remotely operable control means for controlling the state of the switching means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
- a passive sensor; and
Specification