Tunable microwave network and application to transmit leakage cancellation circuit in an RFID interrogator
First Claim
1. A RFID interrogator transceiver comprising:
- an antenna;
a directional coupler comprising an input port, a transmitted port, a coupled port, and an isolated port, the transmitted port being operatively coupled to the antenna;
a signal source operatively coupled to the input port to provide an output signal through the antenna;
a signal receiver operatively coupled to the isolated port to receive an input signal from the antenna;
a tunable microwave network operatively coupled to the coupled port, the tunable microwave network comprising;
a phase shifting element operatively coupled to the coupled port;
a first tunable capacitive element operatively coupled to the coupled port through the phase shifting element in a shunt configuration between the phase shifting element and ground; and
a second tunable capacitive element operatively coupled to the coupled port, in a shunt configuration between the phase shifting element and ground,wherein at least one of the first tunable capacitive element and the second tunable capacitive element comprises;
a coarse tunable capacitive element;
a fine tunable capacitive element subranging the coarse tunable capacitive element; and
an impedance transforming network,wherein the fine tunable capacitive element is electrically coupled to said tunable microwave network through the impedance transforming network; and
a control unit configured to adjust a capacitance of the first and second tunable capacitive elements.
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Accused Products
Abstract
A tunable microwave network and its application in a radio transceiver transmit signal cancellation network is described. The tunable microwave network realizes a large set of reflection coefficients over a predefined area in the complex reflection coefficient plane for the purpose of reflecting a variable cancellation signal which, when properly configured, results in the substantial attenuation of transmit reflection and transmit leakage signal at the radio transceiver receiver input. A relevant building block of the proposed tunable microwave network is a shunt tunable capacitive element coupled to another shunt tunable capacitive element through a phase shifting element with phase shift greater than 30 degrees divided by a quantity substantially similar to the total number of said tunable capacitive elements and less than 60 degrees at a predefined frequency.
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Citations
19 Claims
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1. A RFID interrogator transceiver comprising:
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an antenna; a directional coupler comprising an input port, a transmitted port, a coupled port, and an isolated port, the transmitted port being operatively coupled to the antenna; a signal source operatively coupled to the input port to provide an output signal through the antenna; a signal receiver operatively coupled to the isolated port to receive an input signal from the antenna; a tunable microwave network operatively coupled to the coupled port, the tunable microwave network comprising; a phase shifting element operatively coupled to the coupled port; a first tunable capacitive element operatively coupled to the coupled port through the phase shifting element in a shunt configuration between the phase shifting element and ground; and a second tunable capacitive element operatively coupled to the coupled port, in a shunt configuration between the phase shifting element and ground, wherein at least one of the first tunable capacitive element and the second tunable capacitive element comprises; a coarse tunable capacitive element; a fine tunable capacitive element subranging the coarse tunable capacitive element; and an impedance transforming network, wherein the fine tunable capacitive element is electrically coupled to said tunable microwave network through the impedance transforming network; and a control unit configured to adjust a capacitance of the first and second tunable capacitive elements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for operating a RFID interrogator transceiver, the method comprising:
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emitting a first microwave signal through an antenna; receiving a second microwave signal with the antenna, the second microwave signal comprising a RFID tag signal generated in response to receiving the first microwave signal; receiving an intrinsic internal-reflection signal generated by other components of the RFID interrogator transceiver in response to the first microwave signal; measuring the combined received signal comprising the second microwave signal and the internal-reflection signal to estimate at least one component of the internal-reflection signal; and automatically adjusting at least two tunable capacitive elements, comprising a first tunable capacitive element and a second tunable capacitive element, operatively coupled to each other through a series phase shifting element and operatively coupled to the antenna to generate a cancelling internal-reflection signal to substantially attenuate the intrinsic internal-reflection signal in response to the first microwave signal, wherein at least one of the first tunable capacitive element and the second tunable capacitive element comprises; a coarse tunable capacitive element; a fine tunable capacitive element subranging the coarse tunable capacitive element; and an impedance transforming network, wherein the fine tunable capacitive element is electrically coupled to said tunable microwave network through the impedance transforming network. - View Dependent Claims (17, 18, 19)
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Specification