Protective and decoupling shunt switch at LNA input for TDMA/TDD transceivers
First Claim
1. A front-end circuit for a radio transceiver having a receiver, a transmitter and an antenna, said front-end circuitry comprising:
- a. a common signal path connected to said antenna and shared by the transmitter and receiver of the radio transceiver;
b. an RF Transmit/Receive (T/R) switch for alternately coupling the transmitter and receiver to the common signal path, said T/R switch having a first state coupling the transmitter to the common signal path and a second state coupling the receiver to the common signal path via a receive signal path; and
c. a shunt switch connected between said receive signal path and an electronic ground, said shunt switch distinct from said T/R switch and disposed downstream on said receive signal path from said T/R switch, said shunt switch having a first shunt state coupling said receive signal path to ground and a second shunt state not coupling said receive signal path to ground, wherein said shunt switch is placed in said first shunt state during transmission and in said second shunt state during reception.
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Accused Products
Abstract
The invention relates to an improved front-end circuitry for a radio transceiver for which the receiver and transmitter share a common transmission path, which is switched between the receiver and transmitter during operation. An additional switch is placed between the RF switch and the receiver circuitry, and, preferably, in close proximity to the receiver circuitry. The switch is configured to provide a low impedance electrical path to ground for the receiver circuitry input during transmission sequences and an open circuit during receiving sequences. Coupling the receiver input to ground during transmission sequences at a location proximate to the receiver input significantly reduces the amplitude of all unwanted signals appearing at the receiver'"'"'s input during transmission sequences, especially attenuated and/or delayed replicas of the transmitted signal itself. These signals can result in distortion of the transmitted signal due to feedback into the transmitter chain, and/or damage to the sensitive electronics of the receiver.
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Citations
34 Claims
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1. A front-end circuit for a radio transceiver having a receiver, a transmitter and an antenna, said front-end circuitry comprising:
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a. a common signal path connected to said antenna and shared by the transmitter and receiver of the radio transceiver;
b. an RF Transmit/Receive (T/R) switch for alternately coupling the transmitter and receiver to the common signal path, said T/R switch having a first state coupling the transmitter to the common signal path and a second state coupling the receiver to the common signal path via a receive signal path; and
c. a shunt switch connected between said receive signal path and an electronic ground, said shunt switch distinct from said T/R switch and disposed downstream on said receive signal path from said T/R switch, said shunt switch having a first shunt state coupling said receive signal path to ground and a second shunt state not coupling said receive signal path to ground, wherein said shunt switch is placed in said first shunt state during transmission and in said second shunt state during reception. - 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 radio transceiver comprising:
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a. an antenna;
b. a receiver;
c. a transmitter;
d. front-end circuitry coupled between said antenna and said receiver and transmitter, said front-end circuitry further comprising;
i. a common signal path connected to said antenna and shared by the transmitter and receiver of the radio transceiver;
ii. a RF Transmit/Receive (T/R) switch having a first state for coupling the transmitter to the common signal path and a second state for coupling the receiver to the common signal path via a receive signal path; and
ii. a shunt switch between said receive signal path and an electronic ground, said shunt switch distinct from said T/R switch and disposed downstream on said receive signal path from said T/R switch, said shunt switch having a first shunt state coupling said receive signal path to ground and a second shunt state not coupling said receive signal path to ground, wherein said shunt switch is placed in said first shunt state during transmission and in said second shunt state during reception. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A radio transceiver comprising an antenna;
- a receiver;
a transmitter; and
front-end circuitry coupled between said antenna and said receiver and transmitter, said front-end circuitry further comprising;a. a common signal path shared by the transmitter and the receiver;
b. a RF Transmit/Receive (T/R) switch having a first state for coupling the transmitter to the common signal path and a second state for coupling the receiver to the common signal path via a receive signal path; and
c. shunt means, located between said T/R switch and receiver, for shunting said receive signal path to an electronic ground during transmission, said shunt means distinct from said T/R switch and disposed downstream on said receive signal path from said T/R switch. - View Dependent Claims (29, 30, 31, 32, 33, 34)
a. a diode coupled between said receive signal path and ground, and b. a control line adapted to provide a voltage to forward bias the diode during transmission to couple an input of said receiver to ground.
- a receiver;
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30. The radio transceiver of claim 28 wherein said shunt switch comprises:
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a. a transistor switching network coupled between said receive signal path and ground, and b. a control line adapted to provide a voltage to operate said network in a saturation mode during transmission to couple an input of said receiver to ground.
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31. The radio transceiver of claim 28 wherein said shunt switch comprises:
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a. at least one transistor coupled between said receive signal path and ground, and b. a control line adapted to provide a voltage to operate said transistor in a saturation mode during transmission to couple an input of said receiver to ground.
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32. The radio transceiver of claim 28 wherein the receiver includes receiver electronics having an input coupled to said receive signal path, said shunt switch coupled to said receive signal path substantially proximate to said input.
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33. The radio transceiver of claim 32 wherein said shunt switch is coupled to said receive signal path at an electrical distance from the input electronics of the receiver of within about one-eighth wavelength of the radio frequency carrier signal of the radio transceiver.
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34. The mobile radio transceiver of claim 28 wherein said shunt switch is coupled to said receive path an electrical distance from the T/R switch of approximately one-quarter wavelength of a radio frequency carrier signal of the mobile terminal.
Specification