D-Band Active Transmission Line With 33-GHz Bandwidth and 13-dB Gain at fmax/2

This article presents a {D} -band multisection active transmission line (ATL), where each ATL Section consists of a microstrip TL and a cascode {G} _{\text {m}} cell that senses the TL output and returns a feedback signal to its input. The employed shunt-to-shunt positive feedback compensates the TL loss, amplifies the signal traveling through the TL, and therefore results in a bandpass positive gain with a center frequency of f_{{0}} . The ATL Section can achieve broadband return losses (RLs) of better than 15 dB over 200% fractional bandwidth (BW) when it is perfectly matched at its input and output ports at f_{{0}} (i.e., S_{{11}}=S_{{22}}={0} at f_{{0}} ). The proposed ATL Section is a promising choice to be used as the building block of stagger-tuned amplifiers (STAs) since, unlike the tuned-load stages, it does not introduce a mismatch between the neighboring stages in the chain and hence does not limit the overall RL BW of the STA. Assuming that the TL has a characteristic impedance of Z_{{0}} , the maximum gain BW (GBW) of each ATL Section is achieved when it is terminated to {1.19}Z_{{0}} at its input and output ports, leading to S_{{21}} of 1.51 dB, 3-dB and RL BW of 300 GHz, and GBW of 357 GHz around f_{{0}}={150} GHz. Multiple ATL sections should be cascaded to obtain a reasonable gain and noise-figure (NF) performance. It is shown that a multisection ATL features a better BW compared to a cascade of identical tuned amplifiers and STAs. To verify the theoretical derivations, a proof-of-concept 17-stage ATL is designed and implemented in a 130-nm silicon germanium (SiGe) bipolar complementary metal-oxide semiconductor (BiCMOS) technology with f_{\text {max}} of