New-Tech Europe | July 2018

source soldered down as shown in Fig. 4 (a). Passive Measurements Prior to assembling the complete RFPA the impedances of the INMAT and OUTMAT circuits, as presented to the transistor tabs, were measured to correlate modelled vs measured datasets. The measured data shows an excellent agreement between modelled impedance and measured impedance over an extended bandwidth of 1000 – 3000MHz with no tuning, as shown in Fig. 4 (b). An additional measurement of the INMAT and OUTMAT was performed from 20MHz to 10GHz and still showed very good agreement between modelled and measured datasets as shown in Fig. 5. With the aid of such a demountable jig, the impedances seen by the device can be measured directly and accurately without using mechanically awkward probes that also introduce electrical parasitics, notably stray inductance at the attachment point. The jig is not the production version of the amplifier, but its use is seen as an important stage of the design flow which conforms to the theme of eliminating uncertainties at every possible stage of the design. Small Signal Measurements Initial small signal gain measurements were carried out using a drain bias of Vds = +28V and an Idq = 90mA. A high degree of correlation between measured and modelled gain and match was observed as shown in Fig. 6 with an input return loss of >7.5dB over the operating band. Additionally, the RFPA exhibited no instability under practical stability tests such as varying the drain rail voltage and using an external tuner to vary the source impedance seen by the device.

Figure 4: (a) Fabricated RFPA on jig showing individual INMAT and OUTMAT measurement jigs and copper center section, (b) Measured vs modelled INMAT and OUTMAT 1000 - 3000MHz. (a) (b)

Figure 5: Measured vs modelled INMAT and OUTMAT 1000- 10000MHz.

Large-Signal

Measurements

a maximum P3dB of 40.6 dBm, maximum drain efficiency of 59.1 percent, and a maximum gain of 15.7 dB. The results in Figure7 show a high degree of agreement between modelled and measured datasets. It should also be noted that the RFPA delivered ≥10 W down to 1300 MHz and up to 2900 MHz, extending its range to a fractional bandwidth (BW) of 76.2 percent. To evaluate the efficiency in output back-offmodeand the intermodulation sideband performance, a 2.5 MHz channel BW COFDM signal with 9.5 dB PAPR was used over the band 2.0 – 2.5 GHz. In single-ended form at +34.5 dBm output, the average efficiency was 34 – 35.9 percent, with a linearity of 30 dBc measured at fcenter +/-1.25 MHz as shown in Fig.8. Similar results were obtained

(Continuous Wave) The large signal measurements were carried out using a drain bias of Vds = +28V and an Idq = 90 mA. A continuous wave (CW) signal source was fed into a driver amplifier prior to being fed into the amplifier under test. The RF input and RF output power measurements were corrected for any compression occurring in the driver stage. The three performance parameters measured were power gain, drain efficiency and power delivered to the load. In order to provide a reference these were all evaluated at the 3dB compression point. Modelled results showed a P3dBmax of 40.99 dBm, maximum drain efficiency of 63.2 percent, and a maximum gain of 16.41 dB. Measured results showed

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