Design of an RF PA and Linear Dynamic Supplies for Power Envelope Tracking (PET) on Gate and Drain
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This thesis is about the design and production of a class AB power amplifier, gate tracker circuit and drain tracker circuit. A newly developed envelope tracking (ET) technique called Power Envelope Tracking (PET) is evaluated and tested by using the manufactured designs. The designed power amplifier (PA) has a small signal gain of 13.0dB and a 1dB bandwidth of 450MHZ around a center frequency of 2.4GHz. Peak power added efficiency (PAE) is 53.3% at an output power of 40.5dBm. The 3rd order intermodulation distortion (IMD) is -17dBc at an output power of 37dBm. The designed drain tracker has a controllable gain of 0 to 50, with a -6dB gain bandwidth of 200MHz. The frequency where the first 180 degree phase shift occurs is 100MHz and the output impedance at 50MHz is (5.5 + j2.8)Ohms. For the gate tracker, the controllable gain is 0 to 10, with a -6dB gain bandwidth of 250MHz. The frequency where the first 180$ degree phase shift occurs is 250MHz and the output impedance at 50MHz is (14.6 + j56.2)Ohms. Simulations and measurements of the PET technique show that there are clear benefits by using the technique. Compared to the more traditional ET technique, the PET technique achieves better linearity and almost the same efficiency at a much lower required bandwidth. Simulations show that the bandwidth required for ET is 3 times larger than the bandwidth required for PET. When comparing a PA that uses PET to modulate the supply voltages with a PA that uses constant supply voltages there are great benefits. For a 1MHz QAM signal, the PAE is 9.4% higher, the EVM is 2.4% lower, the ACPR is on average 8.3dBc lower and the signal to total distortion ratio (STDR) is 7.7dB higher.