Radio frequency switch circuit

1. An apparatus comprising:

a first amplifier configured to receive a first radio frequency (RF) signal and to amplify the first RF signal on a first path during a first mode of the apparatus;

a second amplifier configured to receive a second RF signal and to amplify the second RF signal on a second path during a second mode of the apparatus, wherein the second amplifier has a different gain than the first amplifier, and wherein the first and second paths intersect at a junction node;

a switching device coupled with the second amplifier to switch the apparatus between the first mode and the second mode; and

a matching circuit coupled between the junction node and the second amplifier to:

convert, at a fundamental frequency of the second RF signal, an output impedance at an output terminal of the second amplifier to a junction impedance at the junction node; and

present an open circuit at a third harmonic of the first RF signal.

2. The apparatus of claim 1 , wherein the first mode is a high-power mode (HPM) and the second mode is a low-power mode (LPM), and wherein the first amplifier has a higher gain than the second amplifier.

3. The apparatus of claim 1 , wherein the matching circuit includes an inductor and a capacitor coupled with one another in parallel along the second path.

4. The apparatus of claim 3 , wherein the matching circuit further comprises a shunt capacitor coupled in shunt with the second path.

5. The apparatus of claim 3 , wherein the inductor and the capacitor are configured to resonate at the third harmonic of the first RF signal.

6. The apparatus of claim 1 , wherein the matching circuit is a first matching circuit, wherein the apparatus is configured to output an amplified RF signal at an output terminal, and wherein the apparatus further comprises a second matching circuit coupled between the junction node and the output terminal to match the junction impedance at the junction node to an output impedance at the output terminal.

7. The apparatus of claim 1 , wherein the switching device includes a transistor coupled between the second transistor and the junction node wherein the transistor is configured to receive a control signal to switch the apparatus between the first mode and the second mode.

8. The apparatus of claim 1 , wherein the matching circuit is further configured to pass through RF signals at a second harmonic of the second RF signal.

9. The apparatus of claim 1 , wherein the first amplifier is configured to receive a bias voltage to turn on the first amplifier when the apparatus is in the first mode and to turn off the first amplifier when the apparatus is in the second mode, wherein the switching device is configured to control the bias voltage.

10. The apparatus of claim 9 , wherein the bias voltage is a first bias voltage, and wherein the second amplifier is configured to receive a second bias voltage to turn off the second amplifier when the apparatus is in the first mode and to turn on the second amplifier when the apparatus is in the second mode, wherein the switching device is configured to control the bias voltage.

11. A circuit comprising:

a first amplifier configured to receive a first radio frequency (RF) input signal and to amplify the first RF signal on a first path during a first mode of the circuit;

a second amplifier configured to receive a second RF signal and to amplify the second RF signal on a second path during a second mode of the circuit, wherein the second path and first path intersect at a junction node;

a switching device coupled with the second amplifier to switch the circuit between the first mode and the second mode;

a matching circuit coupled between the junction node and the second amplifier to convert an impedance at an output terminal of the second amplifier to an impedance at the junction node at a fundamental frequency of the RF signal and to present an open circuit at a third harmonic of the first RF signal, the matching circuit including:

an inductor coupled between an output terminal of the second amplifier and the switch;

a first capacitor coupled in parallel with the inductor; and

a second capacitor coupled between the output terminal of the second amplifier and a ground terminal.

12. The circuit of claim 11 , wherein the inductor and the first capacitor are configured to resonate at the third harmonic of the first RF signal.

13. The circuit of claim 11 , wherein the first mode is a high-power mode (HPM) and the second mode is a low-power mode (LPM), and wherein the first amplifier has a higher gain than the second amplifier.

14. The circuit of claim 13 , wherein matching circuit is a first matching circuit, wherein the circuit is configured to output an amplified RF signal at an RF output terminal, and wherein the circuit further comprises a second matching circuit coupled between the junction node and the RF output terminal to match the impedance at the junction node to an impedance at the RF output terminal.

15. The circuit of claim 11 , wherein the switching device includes a transistor coupled between the second amplifier and the junction node.

16. The circuit of claim 11 , wherein the first amplifier is configured to receive a first bias voltage to turn on the first amplifier when the apparatus is in the first mode and to turn off the first amplifier when the apparatus is in the second mode, wherein the second amplifier is configured to receive a second bias voltage to turn off the second amplifier when the apparatus is in the first mode and to turn on the second amplifier when the apparatus is in the second mode, and wherein the switching device is configured to control the first and second bias voltages.

17. A system comprising:

one or more antennas;

a transceiver; and

a power amplification module coupled with the one or more antennas and the transceiver, the power amplification module configured to receive radio frequency (RF) signals from the transceiver and provide amplified RF signals to the one or more antennas, wherein the power amplification module is switchable between a high-power mode and a low-power mode, and wherein the power amplification module includes:

a high-power amplifier configured to receive a first RF signal and to amplify the first RF signal on a first path during the high-power mode;

a low-power amplifier configured to receive a second RF signal and to amplify the second RF signal on a second path during the low-power c rode, wherein the first and second paths intersect at a junction node;

a switch coupled between the low-power amplifier and the junction node, the switch configured to be dosed during the low-power mode and open during the high-power mode; and

a matching circuit coupled between the low-power amplifier and the junction node to:

convert an output impedance at the low-power amplifier to a junction impedance at the junction node at a fundamental frequency of the second RF signal; and

present an open circuit at a third harmonic of the first RF signal.

18. The system of claim 17 , wherein the matching circuit includes:

an inductor coupled in series with the second path;

a first capacitor coupled in parallel with the inductor; and

a second capacitor coupled in shunt with the second path.

19. The system of claim 17 , wherein the matching circuit is a first matching circuit, and wherein the power amplification module further comprises a second matching circuit coupled between the junction node and an output terminal of the power amplification module to match the junction impedance at the junction node to an output impedance at the output terminal.

20. The system of claim 17 , wherein the system is a user equipment configured to transmit the amplified RF signals over a wireless communication network using the one or more antennas.