Digital PA Lab

Future wireless communication infrastructure requires a more efficient power management and highest flexibility. The microwave power amplifiers together with the modulation of the input signal determine the overall system efficiency and thereby the operating cost. Given the system requirements and the growing demands regarding flexibility, the long-term target is the complete digital transmitter.

At FBH, new digital modulation schemes and amplifier designs are developed in the framework of a Leibniz project to fabricate integrated power amplifier circuits and modules for the microwave range. They are realized in GaN-HEMT technology and target applications in mobile base stations. Furthermore a new DFG granted project investigates the potential of a digitally designed supply modulator in an envelope-tracking system. The goal is to build an energy-efficient PA at 28 GHz with extreme signal bandwidths of more than 1 GHz for future 5G applications. 

Furthermore, for the first time, the digital concept is transferred to the sub-THz-region based on FBH InP-DHBT technology to develop efficient PAs for very high signal bandwidths in the course of 5G. 

  • Digital Microwave Power Amplifier MMIC
    [+] Highly efficient and compact: novel GaN-based digital power amplifier MMIC (3 stages)
  • Digital PA Module for 900 MHz
    [+] Novel concept reaches highest PAE (40 %) over 10 dB power back-off range at 900 MHz
  • Highly linear digital PA Module for 900 MHz
    [+] Highest linearity reached: using push-pull drivers the digital PA achieves more than 50 dB ACLR (after DPD)

Topics

  • Design of an optimized modulator to encode analog input signal
  • Switch-mode amplifiers and related concepts for next-generation transmitter architectures (e.g., class S, D)
  • Digitale design approaches for highly efficient supply modulators providing extreme signal bandwidths for envelope tracking
  • Novel high-Q filter architectures for recovery of wanted signal at output

Achievements

Modulator

  • Novel digital modulation scheme based on a wave-table approach featuring highest linearity (ACLR > 60 dB, EVM ~ 1%), maximum coding efficiency and built-in DPD for minimized system losses (pending patent)

Amplifier

  • 8 W single-band class-S amplifier for 800 / 900 MHz with up to 60% PAE and 40 dB large-signal gain
  • Novel driver topology closes the gap to state-of-the-art: more than 40% PAE over 10 dB power back-off range reached
  • 14 W class-S amplifier in H-bridge topology, by applying the digital Doherty concept peak final-stage drain efficiencies at 6 dB and 12 dB power back-off of 75% (6 dB) and 40% (12 dB)  are achieved
  • Several multi-band (dual-/triband) class-S PAs covering 0.8 ... 2.6 GHz
  • Concept transfer to W-Band for high speed communication with ultra-high bandwidth
    • First demo (95 GHz): 14.4 dBm output power and peak PAE of 31%