Wideband distributed choke inductor for distributed power amplifiers
A method to design a wideband, low-loss, and high-current choke inductor suitable for use in a distributed power amplifier (DPA) is presented. The choke inductor is composed of several parallelled low-current inductors with small parasitics placed in a distributed manner. High-frequency gain-limiting parasitic shunt capacitors of these inductors are absorbed by the series inductors already present between the transistor drain terminals of the distributed amplifier. We also provide an analytical procedure to determine the widths of stage transistors of a non-uniform distributed power amplifier (NDPA). Several example designs are presented to demonstrate the use of our method. The measurement results of a 2–18 GHz NDPA designed using a distributed choke inductor with an equivalent DC resistance of 0.32 Ω are given. The MMIC has fully integrated with the on-chip DC blocking capacitors and bias inductors. The results of the CW mode measurement for the MMIC at 28 V supply voltage show greater than 10 dB of small signal gain, 6 W to 12 W output power, and 15% to 28% power-added efficiency in the bandwidth.