System and method for providing a single-ended receive portion and a differential transmit portion in a wireless transceiver
In an input/output circuit ( 200 ), a differential balun ( 250 ) is provided that has first and second balun inputs and first and second balun outputs. An antenna ( 230 ) is connected to the first and second balun outputs. A differential amplifier ( 220 ) has one output connected to the first balun input, and a second output connected to the second balun input, while a single-ended amplifier ( 110 ) has its input connected to the first balun input. A grounding switch ( 240 ) is connected between the second balun input and ground. During a transmit mode the grounding switch ( 240 ) is open, the differential amplifier ( 220 ) is turned on, and the single-ended amplifier ( 110 ) is turned off. During a receive mode the grounding switch ( 240 ) is closed, the differential amplifier ( 220 ) is turned off, and the single-ended amplifier ( 110 ) is turned on.
1. An input/output circuit for a wireless transceiver, comprising:
a differential balun having first and second differential balun inputs and first and second differential balun outputs;
an antenna connected to the first and second differential balun outputs;
a differential transmitter amplifier having a first transmitter output connected to the first differential balun input, and a second transmitter output connected to the second differential balun input;
a single-ended receiver low noise amplifier having a receiver input connected to the first differential balun input; and
a grounding switch connected between the second differential balun input and ground,
wherein during a transmit mode the grounding switch is open, the differential transmitter amplifier is turned on, and the single-ended receiver low noise amplifier is turned off, and
wherein during a receive mode the grounding switch is closed and the differential transmitter amplifier is turned off, and the single-ended receiver low noise amplifier is turned on.
2. An input/output circuit for a wireless transceiver, as recited in claim 1 , wherein the antenna is unbalanced, the first differential balun output is connected to ground, and the second differential balun output is connected to a radiating surface of the antenna.
3. An input/output circuit for a wireless transceiver, as recited in claim 1 , wherein the antenna is balanced, the first differential balun output is connected to a first radiating surface of the antenna, and the second differential balun output is connected to a second radiating surface of the antenna.
4. An input/output circuit for a wireless transceiver, as recited in claim 1 , wherein the balun comprises first and second parallel signal lines formed in substantially concentric coils, the first parallel line being connected between the first differential balun input and the first differential balun output, and the second parallel line being connected between the second differential balun input and the second differential balun output.
5. An input/output circuit for a wireless transceiver, as recited in claim 4 , wherein a first separation between adjacent coils of the substantially concentric coils is at least four times a second separation between the first and second parallel signal lines.
6. An input/output circuit for a wireless transceiver, as recited in claim 4 , wherein a first impedance between the first and second parallel signal lines is at least 10 times lower than a second impedance between adjacent coils of the substantially concentric coils.
7. An input/output circuit for a wireless transceiver, as recited in claim 4 , wherein the impedance of the balun satisfies a set criteria for an operational frequency range.
8. An input/output circuit for a wireless transceiver, as recited in claim 7 , wherein the set criteria is to be above a set threshold impedance value.
9. An input/output circuit for a wireless transceiver, as recited in claim 1 , wherein the first transmitter output is a non-inverting output and the second transmitter output is an inverting output.
10. An input/output circuit for a wireless transceiver, as recited in claim 1 , wherein the second transmitter output is a non-inverting output and the first transmitter output is an inverting output.
11. An input/output circuit for a wireless transceiver, as recited in claim 1 , wherein the switch is formed in the differential transmitter amplifier.
12. An input/output circuit for a wireless transceiver, as recited in claim 1 , wherein the differential transmitter amplifier further comprises:
a first transistor connected between a source voltage and a first output node, the first transistor receiving a first control signal;
a second transistor connected between a source voltage and a second output node, the second transistor receiving a second control signal;
a third transistor connected between the first output node and ground, the third transistor receiving a third control signal; and
a fourth transistor connected between the second output node and ground, the fourth transistor receiving a fourth control signal,
wherein during a transmit mode the first through fourth control signals bias the first through fourth transistors, respectively, to a linear state, and
wherein during a receive mode the first through fourth control signals turn off the first through fourth transistors, respectively.
13. An input/output circuit for a wireless transceiver, as recited in claim 1 , wherein the differential transmitter amplifier further comprises:
a first transistor connected between a source voltage and a first output node, the first transistor receiving a first control signal;
a second transistor connected between a source voltage and a second output node, the second transistor receiving a second control signal;
a third transistor connected between the first output node and ground, the third transistor receiving a third control signal; and
a fourth transistor connected between the second output node and ground, the fourth transistor receiving a fourth control signal,
wherein the fourth transistor forms the grounding switch,
wherein during a transmit mode the first through fourth control signals bias the first through fourth transistors, respectively, to a linear state,
wherein during a receive mode the first through third control signals turn off the first through third transistors, respectively, and
wherein during a receive mode the fourth control signals turns on the fourth transistor.
14. An input/output circuit for a wireless transceiver, as recited in claim 1 , wherein the wireless transceiver is embodied in an integrated circuit.
15. An input/output circuit for a wireless transceiver, as recited in claim 1 , wherein the wireless transceiver is an ultrawide bandwidth transceiver.
16. A method of receiving and transmitting wireless signals in a transceiver having a differential transmitter, the differential transmitter comprising a differential balun connected between a differential transmitter amplifier and an antenna, the method comprising:
connecting a single-ended receiver low noise amplifier to a first differential input of the differential balun;
connecting a second differential input of the differential balun to ground,
isolating the differential transmitter amplifier from the differential balun;
receiving a wireless signal at the antenna, and passing the signal through the differential balun to the receiver low noise amplifier;
isolating the second differential input of the differential balun to ground; connecting the differential transmitter amplifier from the differential balun; and
transmitting the wireless signal from the differential transmitter amplifier through the differential balun to the antenna.
17. A method of receiving wireless signals, as recited in claim 16 , wherein the step of isolating the differential transmitter amplifier is performed by bringing its output nodes to a high impedance.
18. A method of receiving wireless signals, as recited in claim 16 , wherein the step of connecting the second differential input of the differential balun to ground is performed through the use of a switch connected between the second differential input of the differential balun and ground.
19. A method of receiving wireless signals, as recited in claim 18 , wherein the switch is a transistor switch.
20. A method of receiving wireless signals, as recited in claim 19 , wherein the transistor switch is contained in the differential transistor amplifier.
21. A method of receiving wireless signals, as recited in claim 16 , wherein the method is implemented in an integrated circuit.
22. A method of receiving wireless signals, as recited in claim 16 , wherein the method is implemented in an ultrawide bandwidth transceiver.