Optimization of broadband drain modulation in GaN HEMT devices

This paper focuses on the optimization of broadband envelope termination for reliable device characterization for future UMTS-LTE systems. Drain bias modulation is suppressed in 8times500 mum GaN HEMT using compensation network overcoming the parasitic effects of the DC feed, generally ignored during broadband measurements. Drain modulation index (DMI) metric is defined for quantifying the extent of drain voltage modulation as a function of carrier spacing and up to 80% reduction in DMI is achieved after drain bias compensation. Further, based on the experimental analysis, a simple bias tee is designed which can overcome improper DC feed conditions. Under 2-carrier CW and W-CDMA excitation, maximum of 19 dB and 18 dB IMD3 suppression together with the minimization of IMD asymmetry, were achieved using in- house bias tee, emphasizing the importance of broadband bias network design.