The Linearity-EfficiencyCompromise

Presenter :Yu-Cheng Cheng

Outline

• Energy Balance in an RF Power Amplifier

• Feed-Forward and Feedback Linearizers

• Dynamic Load Modulation LINC and Doherty Architectures

• Envelope Tracking in Current-Mode Pas

• Conclusion

Energy Balance in an RF Power Amplifier

Figure 1. Power relationships in a general electronic amplifier, diagram of a linear class A or class B RF power amplifier.

資料來源 :IEEE期刊Microwave Magazine vol. 11, “THE LINEARITY-EFFICIENCY Compromise”, P45

Energy Balance in an RF Power Amplifier

• it must provide a signal gain, G,

given by

• The amplifier’s power added efficiency can beobtained from

資料來源 :IEEE期刊Microwave Magazine vol. 11, “THE LINEARITY-EFFICIENCY Compromise”, P45

Energy Balance in an RF Power Amplifier

Figure 2. Illustrative (a) input and (b) output I/V characteristics of the active device shown in Figure 1.

資料來源 :IEEE期刊Microwave Magazine vol. 11, “THE LINEARITY-EFFICIENCY Compromise”, P46

Energy Balance in an RF Power Amplifier

Figure 3. (a) Ideal linear and optimized class A and B efficiencies asa function of normalized input voltage amplitude. (b) Normalized input and output spectra of the optimizedclass B amplifier with an output adjacent channel powerratio of 45 dBc

資料來源 :IEEE期刊Microwave Magazine vol. 11, “THE LINEARITY-EFFICIENCY Compromise”, P46

Feed-Forward and Feedback Linearizers

Figure 4. Demonstration of the linearization of the power amplifier (PA) system of its exact predistorter (PD).

資料來源 :IEEE期刊Microwave Magazine vol. 11, “THE LINEARITY-EFFICIENCY Compromise”, P49

Feed-Forward and Feedback Linearizers

Figure 5. Diagram of the basic structure of the feedforwardlinearizer showing the main signal path on the top.

資料來源 :IEEE期刊Microwave Magazine vol. 11, “THE LINEARITY-EFFICIENCY Compromise”, P49

Dynamic Load Modulation LINC and Doherty Architectures

Figure 6. Simplified functional diagram of the linear amplification with nonlinear components.

資料來源 :IEEE期刊Microwave Magazine vol. 11, “THE LINEARITY-EFFICIENCY Compromise”, P50

Dynamic Load Modulation LINC and Doherty Architectures

Figure 7. (a) Functional diagram of the basic Doherty arrangement showing the input 90º power divider, (b) Output power contributions of the carrier and peaking amplifiers for optimized efficiency and linear operation.

資料來源 :IEEE期刊Microwave Magazine vol. 11, “THE LINEARITY-EFFICIENCY Compromise”, P51

Envelope Tracking in Current-Mode PAs

Figure 8. Block diagram of a fully analog envelope tracking system showing thedynamic bias modulator that supplies the RF current-mode power amplifier with the dc power needed to minimize dissipation.

資料來源 :IEEE期刊Microwave Magazine vol. 11, “THE LINEARITY-EFFICIENCY Compromise”, P53

Conclusion

• Wireless transmitter builds systems that are more efficient in terms of both power supply and wireless spectrum allocation

usage.

References

[1] Lavrador, P.M., Cunha, T.R., Cabral, P.M., Pedro, J.C., “THE LINEARITY-EFFICIENCY Compromise”, IEEE Trans. Microwave Magazine vol. 11, pp. 44-58, July. 2010.