Front-end architecture for transmitter

1. An apparatus for mixing local oscillator signals with baseband signals, the apparatus comprising:

a mixer configured to mix a local oscillator signal with a baseband signal and output a radio frequency (RF) signal;

a first load coupled to the mixer and configured to operate at an operating frequency;

a second load coupled to the mixer and tuned to a predetermined multiple of the operating frequency; and

at least one switch configured to switch between the first load and the second load based on a power level of the apparatus.

2. An apparatus for mixing local oscillator signals with baseband signals, the apparatus comprising:

a mixer core configured to receive and mix a local oscillator signal with a baseband signal and output a differential RF signal;

a first load coupled to the mixer core and configured to operate the first load at an operating frequency;

a second load coupled to the mixer core and configured to tune the second load to a predetermined multiple of the operating frequency; and

at least one switch configured to switch between the first load and the second load based on a power level of the apparatus.

3. The apparatus of claim 2 , wherein the first load comprises

a first pair of cascode transistors coupled to the mixer core and the at least one switch.

4. The apparatus of claim 3 , wherein the at least one switch comprises

a first switch coupled to gate terminals of the first pair of cascode transistors.

5. The apparatus of claim 2 , wherein the second load comprises

a second pair of cascode transistors coupled to the mixer core and the at least one switch.

6. The apparatus of claim 5 , wherein the at least one switch comprises

a second switch coupled to gate terminals of the second pair of cascode transistors.

7. The apparatus of claim 5 , wherein the second load comprises a notch filter coupled to the second pair of cascode transistors and configured to tune the second load to the predetermined multiple of the operating frequency.

8. The apparatus of claim 7 , wherein the predetermined multiple of the operating frequency is three times the operating frequency.

9. The apparatus of claim 2 , wherein the mixer core comprises

a transconductance unit configured to receive and convert the baseband signal from a voltage signal to a current signal.

10. The apparatus of claim 2 , wherein the mixer core comprises:

first and second pairs of differential transistors configured in a cross-coupled architecture to process and mix in-phase components of the local oscillator signal with in-phase components of the baseband signal; and

third and fourth pairs of differential transistors configured in the cross-coupled architecture to process and mix quadrature phase components of the local oscillator signal with quadrature phase components of the baseband signal.

11. The apparatus of claim 2 , further comprising:

a driver amplifier configured to receive and amplify the output differential RF signal from the mixer core; and

a third load coupled to the driver amplifier and the first load, the third load configured to convert the output differential RF signal to a single-ended RF signal.

12. The apparatus of claim 11 , wherein the driver amplifier comprises:

a pair of input transistors coupled to the mixer core; and

a pair of cross-coupled transistors coupled to the pair of input transistors.

13. The apparatus of claim 12 , further comprising

at least one switch coupled to gate terminals of the pair of input transistors, the at least one switch configured to switch between a ground voltage, a supply voltage, and the output differential RF signal from the mixer core.

14. The apparatus of claim 12 , further comprising:

a pair of capacitors cross-coupled between gate terminals and drain terminals of the pair of cross-coupled transistors; and

at least one resistor coupled between the gate terminals of the pair of cross-coupled transistors.

15. The apparatus of claim 14 , further comprising

at least one switch coupled to the at least one resistor to bypass the at least one resistor.

16. The apparatus of claim 11 , wherein the third load comprises:

a balun having a primary winding and a secondary winding;

a first capacitor coupled to the primary winding; and

a second capacitor coupled to the secondary winding.

17. An apparatus for mixing local oscillator signals with baseband signals, the apparatus comprising:

mixing means configured to mix a local oscillator signal with a baseband signal and output an RF signal;

first loading means coupled to the mixing means and configured to operate at an operating frequency;

second loading means coupled to the mixing means and tuned to a predetermined multiple of the operating frequency;

amplifying means configured to receive and amplify the output RF signal from the mixing means; and

at least one switching means configured to switch between the first loading means and the second loading means based on a power level of the apparatus.

18. The apparatus of claim 17 , wherein the second loading means comprises

filtering means to tune the second loading means to the predetermined multiple of the operating frequency.

19. The apparatus of claim 17 , further comprising

third loading means coupled to the amplifying means and the first loading means, the third loading means configured to convert the output RF signal to a single-ended RF signal.

20. The apparatus of claim 1 , further comprising

at least one switch configured to switch between the first load and the second load based on a power level of the apparatus.