| Currently, the wireless communication technology develop rapidly and the wireless communication technology using for long and short distance change our life constantly. WiFi technique is used more and more widely as it can transmit wireless, short distance, and high speed data. At the same time, the transmitter require higher linearity of the power amplifier, it brings great challenge to our design. So it is significant to study high linear power amplifier which meets IEEE 802.11ac standard. Based on these, the paper designs a 2.4GHz WiFi power amplifier which meets IEEE 802.11ac based on GaAs HBT process, which pave the way for the 5GHz WiFi PA.The paper analyses the linearity requirement of the linear power amplifier, including 1dB compression point, intermodulation, and error vector magnitude, at the same time it expatiates GaAs HBT process which has the characteristic of high linearization, linear topology structure including class A, B and AB, and linearization technique such as power back off, adaptive bias and feedback circuit. Basing on the whole design requirement of power amplifier and theory of linearization, we use high linearity, high power density GaAs HBT process, apply three cascaded amplifier structure, and we design adaptive bias circuits, harmonic depression circuits, and apply the power back off so as to improve the linearity.We optimize the design and the power of center frequency can reach 28.3dBm when IM3 is under-35dBc and IM5 is lower than -45dBc basing on two-tone signals. Combined with test data, the power of power amplifier can reach 28.3dBm at 2.4GHz, and has 27.6dBm at 2.5GHz, the result and the design is consistent. When the input signal with 256QAM,40MHz bandwidth, MCS9 and EVM is under -35dBc(1.8%), the power of the power amplifier is 24.9dBm at 2.4GHz, has 24dBm power at 2.5GHz, the second, third and other order harmonic power are below -35dBm, and other indicators meet the requirements of 2.4GHz WiFi IEEE 802.11ac. |
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