【正文】 , Finland, in 1980. He received the . degree in Electrical Engineering from the University of Oulu, Oulu, Finland, in 2005, and is currently working toward the at the University of Oulu. His technical interests lie in the field of analysis and modeling of switching RF power amplifiers.J。 Rutledge, D. (2006). Stability analysis andstabilization of power amplifiers. IEEE Microwave Magazine,7(5), 51–65. doi:Simo Hietakangaswas born in Alaha168。 Tabisz, W. (1989). Class ce highefficiency tuned power amplifier. Circuits and Systems, IEEE Transactions on, 36(3), 421–428. doi:10. Hietakangas, S., Typpo, J., amp。 Rahkonen, T. (2006). 1 ghz class erf power amplifier for a polar transmitter. In Proc. 24th norchipconference(pp. 5–9). doi:7. Hietakangas, S., Rautio, T., amp。 Sokal, A. D. (1975). Class e–a new class of high efficiency tuned singleended switching power Journal of SolidState Circuits, 10(3), 168–176.4. Mury, T., amp。=).The increase of chip decoupling capacitors (4470 pF) in the case of amplifier A did lower the resonance from around100 MHz into 30 MHz region. Inside the177。30 MHz. The probable reason for this lies in different drain bypassing as the amplifier D had less supply capacitance (4470 pF less). The effect of this was studied by simulating from input to load transmission (S21) in the drain bias and matching network. The circuit from amplifier D shows resonance at around 93 MHz as shown in Fig. 21(a), while in the amplifier A the drain resonance is at 27 MHz frequency as shown in (b). As a reference, a measured spectrum of amplifier A’s output is shown in , where the markers one and four are at177。 Schwarz FSQ 40 VSA. Tuning of the amplifier In the first measurements the amplifier did not meet the simulated response. Measurements gave only W of output power at 1575 MHz when the simulated figures were W of output power and drain efficiency of 70%,all at supply voltage of V. Our suspicion directed towards a scribe line that passed very close to the output resonator structure and possibly could couple the output to the input of the amplifier. The scribe line was cut with an UVlaser but this had no effect to the frequency measured DC current of the amplifier was considerably higher than simulated, suggesting that the load impedance of the switching stage was too low. The impedance seen at the drain was increased by replacing a pair of pF highQ ceramic capacitors (Amplifier A, inTable1) in the external output matching network with one pF capacitor (Amplifier B, in Table1). This modification increased the output power to 2 W and the drain efficiency to 56% at the frequency of 1625 MHz. The output power and efficiency in the frequency range – GHz is shown in . The output power is maintained within dB in the desired frequency range(– MHz) as shown in Fig. 13. Within that same frequency band the drain efficiency stays above53% while the highest efficiency, 56%, is achieved at1626 MHz. By adjusting the supply voltage the efficiency of the amplifier can be increased even more, which can be seen from . Drain efficiency increases steadily when supply is lowered. At a supply voltage of V and frequency of 1625 MHz, the amplifier has a drain efficiency of 65%. This implies that the amplifier can maintain an efficient operation also when used in an envelope elimination and restoration (EER) system. The high peaks in at lowest supply voltages in Fig. 14are caused by drive signal feedthrough that sums into the output signal. Load pull measurements Measurements were performed with load pull system GHz spot frequency to several modified amplifiers. The differences between the amplifiers are shown in the next chapters we will mainly concentrate on amplifiers C and D for reasons that will be apparent later on. Let us now discuss the amplifier C which is very similar to amplifier B measured earlier. Tuners of the load pull system were connected to the outputs and inputs of the amplifier C. The load tuning of fundamental, second harmonic and third harmonic resulted in about W of output power ( dBm) while maintaining about % drainefficiency at this peak power spot. The fundamental load impedance in terms of power was at slightly higher impedance than the optimum drain efficiency point as shown in , where the 1 dB output power points (triangles) and5% unit efficiency points(circles) are shown. The peak efficiency point in the figure is (a) (%) and peak power is (b) ( dBm). The optimum efficiency area is rather large. Both of the load harmonics were even more relaxed, and differences for example in output power had to be measured in tenths of decibels rather than in decibels. Further,the efficiency differences were measured in one or two percentage units instead of five to ten. As an example, the third harmonic optimum output points within dB from maximum (triangles) and efficiency points within 2% units from maximum (circles) are shown in Fig. 16. As it can beseen, the third harmonic impedance is not as critical as the fundamental tone. The optimum efficiency is marked with(a) and maximum output power is marked with (b). It should be noted that the adjustment of the third harmonic did not increase output power on the absolute scale nor the drain efficiency. The peak output power value remained within dB of the peak value of the fundamental load pull and the drain efficiency rose from only to %shown at the Smith chart point (a) in . The insensitivity of the amplifier to harmonic tuning is caused by the long drain bias line that is low impedance at the second harmonic and the low pass matching network at the output that attenuates the third harmonic. Source pull measurementsThe source pull of the fundamental impedance did increase the output power and efficiency of amplifier C slightly. The optimum drain efficiency (circles) and output power points(triangles) (a) and (b), respectively, are shown Fig. 17. The power points are within the li