Power amplification apparatus of portable terminal
View Patent ↗The present invention relates to a power amplification circuit of a mobile device for improving the efficiency and the linearity properties of the power amplifier. In one embodiment, the power amplifier improves these properties by controlling the input voltage of the supplemental amplifier so that the power amplifier operates as the Doherty mode in the low output power mode depending on the magnitude of the output power from the output unit and so that the input voltage of the supplemental amplifier may be increased up to satisfy the non-linear operational requirements of a power amplifier in the high output power mode. Moreover, because only the input voltage of the supplemental amplifier is controlled, the power amplifier can be implemented in a simple manner. Thus, the size of the power amplifier becomes small, which in turn reduces the cost of the power amplifier, among other things.
1. A power amplifier in a mobile handset comprising: a phase difference compensation means, coupled to an input terminal of a carrier amplifier and an input terminal of a peak amplifier, for compensating a phase difference by equalizing a phase of a carrier output power signal from the carrier amplifier and of a peak output power signal from the peak amplifier at a power amplifier output stage; an output matching unit for transmitting the carrier output power signal and the peak output power signal; and a voltage control means for detecting a level of the power amplifier output power signal transmitted to the power amplifier output stage and controlling an input DC-bias voltage applied to the input of the peak amplifier in accordance with the detected level of the power amplifier output power signal.
2. The power amplifier according to claim 1 , wherein the phase difference compensation means is a 3 dB hybrid coupler for distributing certain input powers to the carrier amplifier and the peak amplifier, minimizing interference between the carrier amplifier and the peak amplifier and transmitting signals in such a manner that a phase of an input power signal applied to the peak amplifier is substantially 90.degree. out-of-phase from a phase of an input power applied to the carrier amplifier.
3. The power amplifier according to claim 2 , wherein the 3 dB hybrid coupler is implemented with lumped elements.
4. The power amplifier according to claim 2 , wherein the 3 dB hybrid coupler is implemented by the Low Temperature Co-fired Ceramic (LTCC) method.
5. The power amplifier according to claim 1 , wherein the phase difference compensation means includes a phase difference compensator, coupled between an input stage of the power amplifier and the input terminal of the peak amplifier, for delaying the phase of input signal applied to the peak amplifier by 90.degree. from the phase of input signal applied to the input terminal of the carrier amplifier.
6. The power amplifier according to claim 5 , wherein the phase difference compensator is implemented with a transmission line.
7. The power amplifier according to claim 5 , wherein the phase difference compensator is implemented with lumped elements.
8. The power amplifier according to claim 1 , wherein the output matching unit is implemented with lumped elements.
9. The power amplifier according to claim 1 , wherein the output matching unit is implemented by the Low Temperature Co-fired Ceramic (LTCC) method.
10. The power amplifier according to claim 1 , wherein the voltage control means comprises: an envelope detector for detecting the level of the power amplifier output power signal transmitted from the output matching unit to the power amplifier output stage; a comparison and determination unit for determining by comparison whether the output power level detected by the envelope detector deviates from the low output power range; and a voltage controller for controlling an input DC-bias voltage applied to the peak amplifier according to the resultant comparison of the determination made by the comparison and determination unit.
11. The power amplifier according to claim 1 , wherein the voltage control means: if the level of power amplifier output power signal transmitted from the output matching unit to the power amplifier output stage is within the low output power range, the voltage control means controls an input DC-bias voltage applied to the peak amplifier in such a manner that the power amplifier is operated in a Doherty amplification mode; and if the level of power amplification output power signal transmitted from the output matching unit to the power amplifier output stage deviates from the low output power range, the voltage control means controls input DC-bias voltage applied to the peak amplifier in such a manner that the input DC-bias voltage applied to the peak amplifier is increased up to a point that a non-linearity characteristic of the power amplifier is satisfied.
12. The power amplifier according to claim 1 , wherein the carrier amplifier and the peak amplifier have different gain characteristics.
13. A mobile handset including a power amplifier for transmitting wireless communication signals, the power amplifier comprising:
a carrier amplifier having a carrier input terminal and a carrier output terminal;
a peak amplifier having a peak input input terminal and a peak output terminal;
an output matching circuit having a first input, a second input and an output;
an envelope detector having an input coupled to the output of the output matching circuit;
a comparator matching circuit to determine whether the output power level of the power amplifier is in a range other than a low output power range, the comparator having a comparator input coupled to an output of the envelope detector; and
a peak amplifier controller having an controller input coupled to an output of the comparator and a controller output coupled to the peak amplifier, the peak amplifier is configured to vary at least one characteristic of the power amplifier.
14. The mobile handset of claim 13 , wherein the output matching circuit comprises:
A first transformer having an input coupled to the carrier output and an output coupled to the output terminal of the peak amplifier; and
A second transformer having an input coupled to the output of the first transformer, and an output as an output for the power amplifier.
15. The mobile handset of claim 13 , wherein the at least one characteristic of the power amplifier is linearity.