Transmit-receive front end

1. A transmit-receive (TR) front end, comprising:

a low-noise amplifier (LNA);

a power amplifier (PA);

a transformer, coupled to the PA, for increasing a voltage swing and a power transmission of the PA; and

a TR switch, coupled to the transformer at a first end and coupled to the LNA at a second end, wherein the first end is capable of being coupled to an antenna;

wherein the LNA is single ended and the transformer is not on a path between the antenna and the LNA.

2. The TR front end of claim 1 , wherein the LNA, the PA, the transformer and the TR switch are on-chip.

3. The TR front end of claim 1 further comprising:

an antenna; and

a matching network, for optimizing a load impedance of the PA and maximizing an output power of the PA transmitted to the antenna;

wherein the antenna and the matching network are off-chip.

4. The TR front end of claim 1 , wherein the TR switch is not in a path from the PA to the antenna.

5. The TR front end of claim 1 , wherein the TR switch is switched off to provide isolation between the PA and the LNA during a transmission interval.

6. The TR front end of claim 1 , wherein the TR switch comprises:

a first transistor, comprising a first terminal, a second terminal, and a control terminal;

a second transistor, comprising a first terminal, a second terminal, and a control terminal, the first terminal coupled to the second terminal of the first transistor;

a first resistor, coupled to the control terminal of the first transistor;

a second resistor, coupled to the control terminal of the second transistor;

a third resistor, coupled to the first terminal of the first transistor;

a fourth resistor, having one terminal coupled between the second terminal of the first transistor and the first terminal of the second transistor;

a fifth resistor, coupled to the second terminal of the second transistor; and

a first capacitor, having one terminal coupled to the transformer, and another terminal coupled between the first terminal of the first transistor and the third resistor.

7. The TR front end of claim 6 , wherein the TR switch further comprises a second capacitor, having one terminal coupled to the LNA, and another terminal coupled between the second terminal of the second transistor and the fifth resistor.

8. The TR front end of claim 6 , wherein the first transistor and the second transistor are N-type metal oxide semiconductor (MOS) transistors, and the first terminal, the second terminal, and the control terminal are a drain, a source and a gate, respectively.

9. The TR front end of claim 6 , wherein the first transistor and the second transistor are P-type metal oxide semiconductor (MOS) transistors, and the first terminal, the second terminal, and the control terminal are a source, a drain and a gate, respectively.

10. The TR front end of claim 1 , wherein the TR switch is switched on during a reception interval, and an inductance of the transformer nullifies parasitic capacitance at an operating frequency.

11. A transmit-receive (TR) front end, comprising:

a low-noise amplifier (LNA);

a power amplifier (PA);

a transformer, coupled to the PA, for increasing a voltage swing and a power transmission of the PA; and

a TR switch, coupled between the transformer and the LNA, comprising:

a first transistor, comprising a first terminal, a second terminal, and a control terminal;

a second transistor, comprising a first terminal, a second terminal, and a control terminal, the first terminal coupled to the second terminal of the first transistor;

a first resistor, coupled to the control terminal of the first transistor;

a second resistor, coupled to the control terminal of the second transistor;

a third resistor, coupled to the first terminal of the first transistor;

a fourth resistor, having one terminal coupled between the second terminal of the first transistor and the first terminal of the second transistor;

a fifth resistor, coupled to the second terminal of the second transistor; and

a first capacitor, having one terminal coupled to the transformer, and another terminal coupled between the first terminal of the first transistor and the third resistor.

12. The TR front end of claim 11 , wherein the TR switch further comprises a second capacitor, having one terminal coupled to the LNA, and another terminal coupled between the second terminal of the second transistor and the fifth resistor.

13. The TR front end of claim 11 , wherein the first transistor and the second transistor are N-type metal oxide semiconductor (MOS) transistors, and the first terminal, the second terminal, and the control terminal are a drain, a source and a gate, respectively.

14. The TR front end of claim 11 , wherein the first transistor and the second transistor are P-type metal oxide semiconductor (MOS) transistors, and the first terminal, the second terminal, and the control terminal are a source, a drain and a gate, respectively.

15. The TR front end of claim 11 , wherein the LNA is single ended and there is no transformer between the LNA and the TR switch.

16. The TR front end of claim 11 , wherein the LNA, the PA, the transformer and the TR switch are on-chip.

17. The TR front end of claim 11 further comprising:

an antenna; and

a matching network, for optimizing a load impedance of the PA and maximizing an output power of the PA transmitted to the antenna;

wherein the antenna and the matching network are off-chip.

18. The TR front end of claim 11 , wherein the TR switch is not in a path from the PA to the antenna.

19. The TR front end of claim 11 , wherein the TR switch is switched off to provide isolation between the PA and the LNA during a transmission interval.

20. The TR front end of claim 11 , wherein the TR switch is switched on during a reception interval, and a inductance of the transformer nullifies parasitic capacitance at an operating frequency.