Proximity detecting apparatus
First Claim
1. A radio frequency receiver for use in a proximity detecting system, the radio frequency receiver comprising at least one antenna coil operable to receive radio frequency signals;
- tunable receiver circuitry arranged in operative association with the antenna coil and being arranged to modify the frequency at which radio signals are received by the radio frequency receiver;
a signal processor arranged to amplify and filter signals received by the radio frequency receiver; and
a processing system is arranged to receive radio signals amplified and filtered by the signal processor so as to evaluate a signal strength associated with each said antenna coil, the processing system being arranged to evaluate a distance between a radio frequency transmitter and the radio frequency receiver on the basis of evaluated signal strengths associated with radio signals received by at least one antenna coil;
wherein the radio frequency receiver is operable to receive and process radio signals of frequencies between 100 kHz and 10 MHz.
1 Assignment
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Accused Products
Abstract
Arrangements according to the invention embody a radio frequency receiver for use in a proximity detecting system, the radio frequency receiver comprising at least one antenna coil operable to receive radio frequency signals; tunable receiver circuitry arranged in operative association with the antenna coil and being arranged to modify the frequency at which radio signals are received by the radio frequency receiver; and a signal processor arranged to amplify and filter signals received by the radio frequency receiver, wherein the radio frequency receiver is operable to receive and process radio signals of frequencies between 100 kHz and 10 MHz. By operating in the low frequency range, multi-path problems associated with high frequency equipment (such as reflections from objects located between the path of the transmitter and receiver) are significantly reduced, whilst distance between transmitter and receiver can be identified extremely accurately.
47 Citations
35 Claims
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1. A radio frequency receiver for use in a proximity detecting system, the radio frequency receiver comprising
at least one antenna coil operable to receive radio frequency signals; -
tunable receiver circuitry arranged in operative association with the antenna coil and being arranged to modify the frequency at which radio signals are received by the radio frequency receiver;
a signal processor arranged to amplify and filter signals received by the radio frequency receiver; and
a processing system is arranged to receive radio signals amplified and filtered by the signal processor so as to evaluate a signal strength associated with each said antenna coil, the processing system being arranged to evaluate a distance between a radio frequency transmitter and the radio frequency receiver on the basis of evaluated signal strengths associated with radio signals received by at least one antenna coil;
wherein the radio frequency receiver is operable to receive and process radio signals of frequencies between 100 kHz and 10 MHz. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A low frequency radio receiver for use in a proximity detecting system, the radio frequency receiver comprising three antenna coils each being operable to receive radio frequency signals at frequencies less than 10 MHz;
- tunable receiver circuitry arranged in operative association with each coil and being arranged to modify the frequency at which signals are received by the radio frequency receiver;
signal processing means arranged to amplify and filter signals received by the radio frequency receiver; and
frequency sequence identifying means arranged to identify, within a time period, a sequence of frequencies in the amplified and filtered signals. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
- tunable receiver circuitry arranged in operative association with each coil and being arranged to modify the frequency at which signals are received by the radio frequency receiver;
- 24. A frequency radio transmitter for use in proximity detection apparatus, the radio frequency transmitter being operable to selectively transmit signals at a plurality of different frequencies, and comprising an antenna circuit having a variable impedance and a frequency bandwidth associated therewith, the frequency bandwidth defining a frequency band within which the radio frequency transmitter is operable to transmit signals, wherein the antenna circuit is operable to modify the impedance so as to modify the magnitude of said frequency bandwidth, and to transmit a radio frequency signal having a frequency within said modified frequency bandwidth.
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34. A radio frequency transmitter comprising an antenna circuit, wherein the antenna circuit comprises a capacitance (C), and a coil comprising a plurality of windings having an inductance (L), the antenna circuit having a frequency bandwidth (δ
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) associated therewith and including tapping means for connection to the coil so as to create a first set of windings and a second set of windings, each set of windings having a number of turns, wherein the number of turns of the first set is related to the number of turns of the second set by a turns ratio (n), and the frequency bandwidth of the antenna circuit is at least- View Dependent Claims (35)
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Specification