Single antenna dual frequency transponder
First Claim
1. A single antenna transponder comprising:
- a) signal generating means for generating a first signal of a first desired frequency in response to a trigger signal, and for generating a second control signal having first and second states, said signal generating means changing said second control signal from said first state to said second state after receiving said trigger signal;
b) an antenna coupled to said signal generating means;
c) logic control means coupled to said signal generating means, and including means for receiving said first signal and said second control signal, and having an output, wherein said logic control means includes means for generating a very high impedance at said output when said logic control means receives said first state of said second control signal, and wherein said logic control means includes means for providing a transmitting signal of said first desired frequency when said logic control means receives said first signal and said second state of said second control signal;
d) a first capacitor having a first plate coupled to said output of said logic control means, and a second plate coupled to said antenna and to said signal generating means; and
e) a second capacitor having a first plate coupled to a first fixed voltage, and a second plate coupled to said first plate of said first capacitor, whereinwhen said logic control means receives said first state of said second control signal and said output of said logic control means is at a very high impedance, said first capacitor, said second capacitor, and said antenna comprise a first tuned LC circuit for receiving an incoming signal at a second frequency from which said trigger signal is generated, andwhen said logic control means receives said second state of said second control signal, said output of said logic control means is at a low impendance, and said first capacitance and said antenna comprise a second tuned LC circuit for taking said transmitting signal at said first desired frequency and transmitting the same.
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Accused Products
Abstract
A single antenna, dual frequency transponder is provided. The transponder includes the antenna, first and second capacitors, a microprocessor/coder for generating a first and second control signals, and a logic circuit which uses the two control signals as inputs and depending on the state of the second control signal either provides an open circuit or a frequency signal at its output node. When the second control signal is a dormant (inhibit) signal, an open circuit is provided. As a result, the capacitors and the antenna provide a first tuned LC circuit which will receive an incoming signal at a desired first frequency. The incoming signal thereby resonates the LC circuit which provides a wake-up signal to the microprocessor/coder. In turn, the microprocessor/coder generates the first control signal of a desired second frequency. In turn, the logic circuit provides a related signal of the same second frequency as an output. With such an output, one of the two capacitors is effectively eliminated from the circuit, and the remaining capacitor and the antenna constitute a second tuned LC circuit which is tuned to the second frequency. By providing adjustable capacitance capacitors, the circuit is adjustable to desired incoming and outgoing frequencies.
90 Citations
18 Claims
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1. A single antenna transponder comprising:
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a) signal generating means for generating a first signal of a first desired frequency in response to a trigger signal, and for generating a second control signal having first and second states, said signal generating means changing said second control signal from said first state to said second state after receiving said trigger signal; b) an antenna coupled to said signal generating means; c) logic control means coupled to said signal generating means, and including means for receiving said first signal and said second control signal, and having an output, wherein said logic control means includes means for generating a very high impedance at said output when said logic control means receives said first state of said second control signal, and wherein said logic control means includes means for providing a transmitting signal of said first desired frequency when said logic control means receives said first signal and said second state of said second control signal; d) a first capacitor having a first plate coupled to said output of said logic control means, and a second plate coupled to said antenna and to said signal generating means; and e) a second capacitor having a first plate coupled to a first fixed voltage, and a second plate coupled to said first plate of said first capacitor, wherein when said logic control means receives said first state of said second control signal and said output of said logic control means is at a very high impedance, said first capacitor, said second capacitor, and said antenna comprise a first tuned LC circuit for receiving an incoming signal at a second frequency from which said trigger signal is generated, and when said logic control means receives said second state of said second control signal, said output of said logic control means is at a low impendance, and said first capacitance and said antenna comprise a second tuned LC circuit for taking said transmitting signal at said first desired frequency and transmitting the same. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of receiving and transmitting information over a single antenna contained in a transponder having a signal generating means for generating a first signal and a second control signal, said second control signal having first and second states, where the signal generating means is coupled to said antenna, a logic circuit means including means for receiving said first signal and said second control signal, and providing an output in response thereto, a first capacitor coupled to said antenna and to said logic circuit means, and a second capacitor coupled to said logic circuit means and said first capacitor, said method comprising:
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a) generating with said logic circuit at the output thereof a high impedance when said logic circuit receives said second control signal in said first state from said signal generating means, said high impedance causing said first capacitor, second capacitor, and antenna to constitute a first tuned LC circuit tuned to a first frequency; b) receiving at said antenna a signal at said first frequency, said tuned LC circuit resonating in response thereto to provide a voltage signal; c) applying a signal related to said voltage signal to said signal generating means; d) in response to step c), changing said second control signal from said first state to said second state, and generating with said signal generating means said first signal of a second frequency, whereby said logic circuit provides at the output thereof a transmittal signal of said second frequency, and wherein when said second state of said second control signal is generated by said signal generating means, said output of said logic circuit is at a low impedance and said first capacitor and antenna constitute a second tuned LC circuit tuned to said second frequency; e) transmitting said transmittal signal via said antenna.
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Specification