Digital PA Lab

Future wireless communication infrastructure requires a more efficient power management and highest flexibility. The microwave power amplifiers 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 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, 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 Power Amplifier
    [+] Four-stage GaN chip of a digital power amplifier
  • H-Bridge Digital Power Amplifier
    [+] Flexible regarding modulation schemes - digital class-S power amplifier for future mobile communication
  • Suspended Substrate Stripline Bandpass Filter
    [+] High-Q Suspended Substrate Stripline Bandpass Filter for 1.8 GHz


  • 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)
  • Novel high-Q filter architectures for recovery of wanted signal at output



  • 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)


  • 8 W single-band class-S amplifier for 800 / 900 MHz with up to 60% PAE and 40 dB large-signal gain
  • 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%