Post-Simulation Results

The parasitic capacitance exists in metal to substrate shown in Fig. 3.19 resulting in difference of input angle shifts to 74 degree as demonstrated in Fig. 3.20.

Fig. 3.19 Parasitic capacitance of transformer

0.0 0.2 0.4 0.6 0.8 1.0

0 15 30 45 60 75 90

Input phase angle (degrees)

N o rm a il iz e d out put v o lt a g e (V )

Fig. 3.20 EM simulation result

2. Stability

Fig. 3.21 and Fig. 3.22 show the stability circle at DC to 14 GHz of load and source plane.

Fig. 3.21 LSB circle

Fig. 3.22 SSB circle

3. Performance of power amplifier

I. Fixed the input offset angle

Simulated output power versus input power at 1.4 GHz is shown in Fig. 3.23.

The output power is saturated at input power if the input power is larger than -3 dBm.

and the gain of the outphasing power amplifier is 11 dB、9 dB and 12.5 dB for TT、

SS and FF respectively.

Fig. 3.24 shows the simulated drain efficiency of outphasing PA versus input power. Drain efficiency is over 38% above at 1dB compression point. Fig. 3.25 illustrates the simulated PAE versus input power. For TT corner, the PAE is over 29%

above at 1 dB compression point.

-15 -10 -5 0 5 10

-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 Pin (dBm)

Po u t (d B m )

TT SS FF

.

Fig. 3.23 Output power versus input power simulation result

0

Fig. 3.24 Drain Efficiency simulation result

0

Fig. 3.25 PAE simulation result

4. Outphasing response

Simulated output power versus input offset angle at 1.4 GHz is shown in Fig 3.26. The maximum power transfer at 80 degrees input offset angle, and the drain efficiency versus input offset angle is given in Fig. 3.27.

-10

Input phase offset (degrees)

P out ( dB m )

TT SS FF

Fig. 3.26 Output power versus input phase difference simulation result

0

Input phase offset (degrees)

D rai n E ffi ci en cy ( %

Fig. 3.27 Drain efficiency versus input phase difference simulation result

5. Frequency response

Fig 3.28 demonstrates the gain of power amplifier versus input frequency. The phase difference of two input signal is 83 degrees and input power is -5 dBm.

0 2 4 6 8 10 12 14

1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Input Frequency (GHz)

Ga in ( d B )

Fig. 3.28 Frequency response

6. Average efficiency

In wireless communication system, we care the average efficiency more than efficiency of power amplifier itself. Therefore, the average efficiency can be calculated base on the probability density function of OFDM modulation signal. Fig.

3.29 illustrates the OFDM phase distribution and corresponding efficiency. In this work the average efficiency is 33.16% under 14 mW dynamic power consumption.

3.7.3 Performance summary

Finally, a performance summary is given in the Table 3.2. The proposed

outphasing class D low-power amplifier achieves system efficiency to 33.16 % under 14 mW dynamic power consumption.

0 10 20 30 40 50 60 70 80 90

OFDM Phase Distribution and Corresponding Efficiency

Distrbution Efficiency Average Efficiency = 33.16%

0 10 20 30 40 50 60 70 80 90 Phase

Fig. 3.29 Average efficiency of OFDM modulation system Table 3.2 Performance summary

Performance This work

System Efficiency (ideal combiner) (%) 13 →50

System Efficiency (%) 33.16 %

DC power (mW) 14

Power Gain (dB) 11

Pout (dBm) 7

3.8 Summary

Outphasing is one of the most popular techniques that improve the efficiency and linearity. It does not need other circuit aid. In this work, the circuit only consumes 14 mW under 1.2V supply voltage in TSMC 180 nm standard CMOS process. It can be used in wireless data communication for biomedical applications. The power combine technique is most critical factor of outphasing power amplifiers. Therefore, the type of combiners and power amplifiers may be chose with modulation signals appropriately.

Chapter IV

Conclusions and Future Work

4.1 Conclusion

In this thesis, two low-power transmitter circuits are implemented and design one is frequency tripler with fundamental cancelling the other is outphasing power amplifier. Both of them are fabricated using 180 nm standard CMOS technology.

The frequency tripler with fundamental cancelling was verified to has 35 dB

HRR

1 which is impressive for frequency multiplier circuit design. The power consumption is another merit compared to other published works. Therefore, this frequency tripler features quadrature signal generation, which is very useful in modern RF transceivers associated with quadrature modulation.

More and more researcher devote to outphasing transmitter which enhance the linearity and efficiency. Although the Chireix combiner provides high linearity but the linearity degrades by adding compensating components. Thus, the combiner should be chose carefully.

4.2 Future Work

The cancellation quantity depends on transistor biasing that is very sensitive result in difficult measurement. Some robust paths could be introduced to suppress the fundamental signal. The poly-phase filter occupied larger area compared to other active technology. Therefore, the quadrature generator could be implemented with active device.

Transformer can be replaced by MEMS inductor that improved the efficiency, and outphasing power amplifier could be used in system verify. Reconfiguration structure could be used in Chireix combiner to improve average efficiency.

Bibliography

[1] Bert Gyselinckx, Chris Van Hoof, Julien Ryckaert, Refet Firat Yazicioglu, Paolo Fiorini, Vladimir Leonov, “Human++: Autonomous Wireless Sensors for Body Area Networks,” CICC 2005.

[2] Jessi E. Johnson, G. R. Branner, and John-Paul Mima, “Design and Optimization of Large Conversion Gain Active Microwave Frequency Triplers,” IEEE

Microwave and Wireless Components Lett. , vol. 15, no. 7, pp. 457-459, July

2005

[3] Donald G. Thomas, Jr. and G.R. Branner., “Optimization of Active Microwave Frequency Multiplier Performance Utilizing Harmonic Terminating Impedances,” IEEE Trans. Microwave Theory and Techniques, vol. 44, no. 12, pp. 2617-2624, Dec. 1996

[4] Jui-Chieh Chiu et al., “A 12-36GHz PHEMT MMIC Balanced Frequency Tripler,” IEEE Microwave and Wireless Components Lett., vol. 16, no. 1, pp.

19-21, Jan. 2006

[5] You Zheng and Carlos E. Saavedra, “A Broadband CMOS Frequency Tripler Using a Third-Harmonic Enhanced Technique,” IEEE J. Solid-State Circuits, vol.

42, no. 10, pp. 2197-2303, Oct. 2007.

[6] Brad R. Jackson, Francesco Mazzilli, and Carlos E. Saavedra, “A Frequency Tripler Using a Subharmonic Mixer and Fundamental Cancellation,” IEEE Trans.

Microw. Theory Tech., vol. 57, no. 5, pp. 1083-1090, May 2009.

[7] Chien-Nan Kuo, Huan-Sheng Chen, and Tzu-Chao Yan, “A K-band CMOS Quadrature Frequency Tripler Using Sub- Harmonic Mixer,” accepted in revise, IEEE Microw. Wireless Compon. Lett.

[8] M. Danesh, F. Gruson, P. Abele, and H. Schumacher, “Differential VCO and Frequency Tripler Using SiGe HBTs for the 24GHz ISM Band,” in IEEE RF Integrated Circuits Symp., Philadelphia, PA, June 2003, pp. 277–280.

[9] Ali Boudiaf et al., “A High-Efficiency and Low-Phase-Noise 38-GHz pHEMT MMIC Tripler,” IEEE Trans. Microwave Theory and Techniques, vol. 48, no.

12, pp. 2546-2553, Dec. 2000

[10] Behbahani, F.; Kishigami, Y.; Leete, J.; Abidi, A.A, “CMOS mixers and polyphase filters for large image rejection”, IEEE Journal of Solid-State Circuits, Volume: 36 Issue: 6, Page(s): 873 -887, June 2001

[11] P. B. Kenington, High-Linearity RF Amplifier Design. Norwood, MA: Artech House, 2000.

[12] J. Cha, J. Yi, J. Kim, and B. Kim, “Optimum design of a predistortion RF power amplifier for multicarrier WCDMA applications,” IEEE Trans. Microw. Theory Tech., vol. 52, no. 2, pp. 655–663, Feb. 2004.

[13] Y. Y. Woo, Y. Yang, J. Yi, J. Nam, J. Cha, and B. Kim, “A new adaptive feedforward amplifier for WCDMA base stations using imperfect signal cancellation,” Microw. J., vol. 46, no. 4, pp. 22–44, Apr. 2003.

[14] S. C. Cripps, RF Power Amplifiers for Wireless Communications. Norwood, MA: Artech House, 1999.

[15] P. B. Kenington, High-Linearity RF Amplifier Design. Norwood, MA: Artech House, 2000.

[16] Y. Kim, Y. Yang, S. H. Kang, and B. Kim, “Linearization of 1.85 GHz amplifier using feedback predistortion loop,” in IEEE MTT-S Int. Microwave Symp. Dig., Baltimore, MD, 1998, pp. 1675–1678.

[17] H. Chireix, “High power outphasing modulation,” Proc. IRE, vol. 23, no. 11, pp.

1370–1392, Nov. 1935.

[18] X. Zhang, L. E. Larson, and P. M. Asbeck, Design of Linear RF Outphasing Power Amplifiers. Boston, MA: Artech House, 2003.

[19] A. Birafane and A. Kouki, “On the linearity and efficiency of outphasing microwave amplifiers,” IEEE Trans. Microw. Theory Tech., vol. 52, no. 7, pp.

1702–1708, Jul. 2004.

[20] Y. Jaehyok, Y. Yang and B. Kim, "Effect of efficiency optimization on linearity of LINC amplifiers with CDMA signal," in IEEE MTT-S Int. Microwave Symp.

Dig., vol. 2, May 2001, pp. 1359-1362.

[21] Birafane, A. Kouki, A.B.,” Sources of linearity degradation in LINC transmitters for hybrid and outphasing combiners,” IEEE Electrical and Computer Engineering, 2004. Canadian Conference, vol.1 2-5 May 2004, pp 547- 550

[22] F. H. Raab, “Maximum efficiency and output of class-F power amplifiers,” IEEE Trans. Microw. Theory Tech., vol. 49, no. 6, pp. 1162–1166, Jun. 2001.

Vita

姓名:蔡建忠 Chien-Chung Tsai 出生日期: 1983/10/23

出生地:嘉義,台灣 教育程度:

2004/09~2007/06

國立台北科技大學電機工程系 學士

2007/07~2009/9

國立交通大學電子工程研究所 碩士

在文檔中 應用於射頻發送端之低功率電路 (頁 71-0)