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vor 8 Jahren

8-2015

  • Text
  • Komponenten
  • Technik
  • Radio
  • Filter
  • Oszillatoren
  • Quarze
  • Emv
  • Bauelemente
  • Wireless
  • Messtechnik
  • Mikrowellentechnik
Fachzeitschrift für Hochfrequenz- und Mikrowellentechnik

RF & Wireless Figure 7:

RF & Wireless Figure 7: Fundamental load-pull for power, similar to the impedance point for gain in Fig.6 drain-source voltage and current waveforms. This waveform engineering will actually be done via the load-pull wizard to peak up the power, gain, and efficiency. After fundamental frequency source pull has been done with the 50-ohm output load, the next step is to change the setup for fundamental load pull. Again, the goals are power gain and PAE using the optimum input impedance point for each test frequency, as determined by the source pull. Finally, second and third harmonic source pull and load pull will be invoked with the wizard to further improve Figure 8: Load pull with the source tuner set for optimal PAE from the impedance point for gain in Fig. 6 source-pull data. PAE improves from 60.5 percent (source pull only) to 72 percent (both ports matched for PAE at fundamental only) power gain and PAE, ensuring that the best performance is obtained from the device. Of course, when second and third harmonic terminations are included, their impedances will likely have a small effect on the fundamental impedance. Consequently, it will be necessary to iterate around the load-pull loop at least twice to get to that optimum point. The first fundamental source pull for gain is shown in Figure 3. Figure 9: Both ports are loaded for optimal PAE, which improves to >80 percent when the second harmonic is properly terminated. Figure 10: The third harmonic load-pull result has a smaller effect, providing one or two percentage points improvement in efficiency. 50 hf-praxis 8/2015

RF & Wireless PAE. Now it can be seen that the optimum impedance for gain in this case on the load side of the device is not that far removed from 50 ohms - about a two-toone voltage standing wave ratio (VSWR). Figures 7 and 8 show the fundamental load-pull results for power and PAE. The result for power is similar to the impedance point for gain, with a small difference seen for the optimal PAE result. The PAE has improved from 60.5 percent with source pull alone to 72 percent at this point, with both ports matched for PAE at the fundamental only. Figure 11: An ideal Class F input network. PAE has an impedance that is very close to the maximum for both gain and power, which simplifies the matching task considerably. Note that even though the load is directly into 50 ohms, the PAE is already over 60 percent at this point. The next step is load pull for maximum gain (Figure 6), with the source pull set at the impedance that was giving the best Using the load-pull wizard, there are several options for source and load-pull optimization at the second and third harmonics. Figure 9 shows the result with the fundamental source and load impedances set to previous values and, then allowing the wizard to find the optimum second harmonic load pull for maximum PAE. In this case, the PAE has improved to over 80 percent. Adding the third harmonic load pull (Figure 10) has a smaller effect, improving PAE by one or two percentage points. Figure 12: Terminations based on load-pull analysis. The optimum impedance point is automatically calculated through all the converged points by the wizard. Remember, however, that the output of the device is loaded directly into 50 ohms, so although there is quite good power gain of 15.3 dB at the optimum point, the gain decreases (blue contours) away from that optimum point (magenta). Figure 4 shows the results for output power, which are actually quite close to those obtained for power gain, even though the output of the device is loaded into 50 ohms. To some extent, this is due to the fact that the intrinsic load line of the device is not that far from 50 ohms, as will be seen when fundamental load pull is performed. Finally, Figure 5 shows the fundamental source pull for PAE. Again, the optimum point for Figure 13: Harmonic loading: open at second and short at the third. hf-praxis 8/2015 51

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