Low Distortion CATV Power Amplifier Using GaAs HJFET and GaN FET Cascode Distortion Cancellation Technique

We have successfully developed broadband low distortion cable television (CATV) power amplifier with AlGaN/GaN hetero-structure field-effect transistor (HFET) capable of high voltage operation for high output power. To realize low distortion characteristics required for modern CATV system, we investigated low distortion cascode configuration composed of GaAs hetero-junction FET (HJFET) for first stage and GaN FET for final stage. The third-order distortion characteristics were improved by realizing distortion cancellation between GaAs HJFET and GaN FET with optimized transconductance (gm)-profile employing Volterra distortion analysis on load-line based on pulsed I-V characteristics. The developed CATV power amplifier demonstrated, to our knowledge, the lowest composite triple beat (CTB) characteristics less than -72 dBc at low drain current condition of 380 mA under 53.7 dBmV at 865 MHz, 11.7 dB tilt, 132 channels.