Highly Compact GaN-based All-Digital Transmitter Chain Including SPDT Switch for Massive MIMO
48th European Microwave Conference (EuMC 2018), Madrid, Spain, Sep. 25-27, pp. 918-921 (2018).
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This paper presents a fully digital transmitter chain from baseband to antenna, including a modulator, a truly digital (i.e. switch mode) microwave power amplifier and a transmit / receive switch. Both, amplifier and switch MMIC were implemented in a GaN HEMT process. The novel amplifier design provides greatly reduced complexity, needing only three voltage sources. Measurements were conducted using 5MHz and 20MHz wide baseband (BB) signals on a carrier of 900 MHz. For the 5MHz BB signal an ACLR of over 52 dB has been reached, fulfilling the 3GPP specs for base station use while still maintaining a final-stage drain efficiency of 46% at 6.5 dB peak to average power ratio. Full-scale output power at 30V supply voltage was measured to exceed 3W at 80% drain efficiency. Further features of this digital amplifier approach include small form factor and extreme frequency agility, making it an ideal candidate for software defined radio.
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik (FBH), Berlin, Germany
5G mobile communication, power amplifiers, massive MIMO, digital transmitter, Millimeter wave integrated circuits, Switching circuits.