Tunable microwave network and application to transmit leakage cancellation circuit in an RFID interrogator
First Claim
1. A radio transceiver which concurrently transmits and receives 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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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.
16 Citations
20 Claims
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1. A radio transceiver which concurrently transmits and receives 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 radio 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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20. A coupling means for coupling both a transmitting element output and a receiving element input to a common radiating element in such a fashion that the transmitting element output signal of said transmitting element output experiences substantial attenuation from said transmitting element output to said receiving element input, said substantial attenuation exceeding the attenuation from the common radiating element to said receiving element input, comprising:
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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 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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Specification