Improving the Gain-Frequency Performance of Cascaded Single-Stage Distributed Amplifiers with Bandpass Filter Structure

In this paper a bandpass filter structure is proposed for realizing the artificial transmission lines of cascaded single-stage distributed amplifiers (CSSDA) and the basic analysis and design of the bandpass structured CSSDA (BP-CSSDA) is demonstrated. Some of the lower frequency region in the gain-frequency band of the CSSDA is not utilized due to presence of the bias components in traditional design methods. By using the bandpass structure for the realization of artificial transmission lines, the unused portion of the gain-frequency band can be utilized. Therefore, one can obtain more bandwidth using the bandpass type artificial lines in the CSSDA than using the lowpass type lines. The gain of a CSSDA can be increased, by increasing the interstage termination impedance (Zoint) without compromising the bandwidth. In this paper, a graphical method for determining the optimum Zoint is introduced. Simulation results showing the advantage of using the BP structured artificial lines in the CSSDA is provided.