A 36-39GHz Power Amplifier with Built-in Linearizer Using 0.1μm GaAs pHEMT Process

This article introduces a millimeter-wave power amplifier (PA) utilizing monolithic integrated circuits with an integrated linearizer, designed for the 5G millimeter-wave (mm-Wave) phased array front-end operating between 36-39 GHz. The PA is composed of three common- source (CS) stages to achieve adequate gain performance at mm-Wave frequencies. A direct shunt power combining technique utilizing a four-way configuration structure is used to achieve the desired output power. Furthermore, the 5G mobile communication system employs OFDM digital modulation signals to enhance spectrum efficiency. Due to the large peak to average power ratio (PARR) of the OFDM signal, the PA requires power back-off operation to fulfill the linearity criteria. However, efficiency of the mm-Wave PA severely degrades in the power back-off region. To address this issue, a pre-distortion linearizer linearization technique has been developed and integrated into the 36-39 GHz GaAs PA to enhance linearity and minimize the amount of power back-off. The 36-39 GHz PA with an integrated linearizer has been implemented using a 0.1-μm GaAs-based pHEMT fabrication process. The supply is 4 V and quiescent current is 510 mA. From the experimental, the gain of the PA for small signals is 20.5 dB at frequency of 38 GHz. The bandwidth is 3 GHz from 36 to 39 GHz. The saturation output power (Psat) is 28.5 dBm at 38 GHz with power added efficiency (PAE) of 24.2%. After linearization, the output 1-dB compression point (OP1dB) of the PA is 28dBm. To evaluate its linearity, the presented PA has been tested using the OFDM based modulation signals. Under an OFDM signal utilizing 64-QAM modulation with a bandwidth of 250 MHz, the PA has an output power of 19.1 dBm with an error vector magnitude (EVM) of 5.6% (-25 dB) at 38 GHz.