A Wideband Highly Linear Distributed Amplifier Using Intermodulation Cancellation Technique for Stacked-HBT Cell

In this article, a wideband linearization technique for distributed amplifiers (DAs) is presented. In particular, an auxiliary transistor is employed to create additional intermodulation distortion components that will be feed-forwarded to the output of each gain unit cell to significantly suppress the third-order intermodulation (IM3) distortion. To verify the concept, two DAs are fabricated in an indium phosphide (InP) process. One amplifier employs a conventional stacked-heterojunction bipolar transistor (HBT) gain unit cell, and the other linearized amplifier utilizes the proposed technique. The linearized DA exhibits a measured gain of 10.5 dB with a 3-dB gain bandwidth from dc to 90 GHz. The maximum 1-dB gain compression output power ( P_{\text {1 dB}} ) is 20.5 dBm, and the third-order intercept point (OIP3) is 33 dBm. Compared to the conventional amplifier, the two values are improved by 3.5 and 4.5 dB on average, respectively. Moreover, the linearization technique only increases very little dc power consumption at high power and has the same chip size as compared to the conventional design. To the best of the authors' knowledge, compared to published state-of-the-art DAs, the proposed DA achieves among the highest OIP3 over a wide bandwidth.