DC to 6.5 GHz highly linear low-noise AlGaN/GaN traveling wave amplifier with diode predistortion

A five-stage linear low-noise uniform traveling wave amplifier (L²NTWA) design fabricated in an AlGaN/GaN 0.25μm monolithic microwave integrated circuit (MMIC) process is presented. The amplifier exhibits a bandwidth of 10 MHz - 6.5 GHz at a constant gain of 15 dB and a minimum NF of 1.5 dB. For small-signal operation only, an on-chip active cold load (ACL) can be optionally connected by a bond-wire to replace the gate-line termination resistor and thus to improve the TWA´s low frequency noise performance. To the author´s best knowledge, for the first time a tunable diode predistortion concept is applied in a TWA to improve linearity by cancellation of the C_GS dependent nonlinearity. Large-signal measurements show a SFDR of larger than 38 dBc at 25 dBm output power and a P_1dB and P_SAT at moderate bias of larger than 29 dBm and 33.5 dBm, respectively. The measured OIP3 is larger than 42 dBm over the full bandwidth. All measurements of the MMIC have been conducted in a custom-made PCB mountable package, including off-chip SMD low frequency extensions, to guarantee optimum electrical and thermal performance of the amplifier.