<italic>D</italic>-Band Active Transmission Line With 33-GHz Bandwidth and 13-dB Gain at <italic>f</italic> <inline-formula> <tex-math notation="LaTeX">$_{\text{max}}$</tex-math> </inline-formula>/2

This article presents a <italic>D</italic>-band multisection active transmission line (ATL), where each ATL section consists of a microstrip TL and a cascode <italic>G</italic> <inline-formula> <tex-math notation="LaTeX">$_{\text{m}}$</tex-math> </inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">$f_\text{0}$</tex-math> </inline-formula>. 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 <inline-formula> <tex-math notation="LaTeX">$f_\text{0}$</tex-math> </inline-formula> (i.e., <inline-formula> <tex-math notation="LaTeX">$S_\text{11}=S_\text{22}=\text{0}$</tex-math> </inline-formula> at <inline-formula> <tex-math notation="LaTeX">$f_\text{0}$</tex-math> </inline-formula>). 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 <inline-formula> <tex-math notation="LaTeX">$Z_\text{0}$</tex-math> </inline-formula>, the maximum gain BW (GBW) of each ATL section is achieved when it is terminated to <inline-formula> <tex-math notation="LaTeX">$\text{1.19}Z_\text{0}$</tex-math> </inline-formula> at its input and output ports, leading to <inline-formula> <tex-math notation="LaTeX">$S_\text{21}$</tex-math> </inline-formula> of 1.51 dB, 3-dB and RL BW of 300 GHz, and GBW of 357 GHz around <inline-formula> <tex-math notation="LaTeX">$f_\text{0}=\text{150}$</tex-math> </inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">$f_\text{max}$</tex-math> </inline-formula> of 290 GHz. The prototype circuit features a 13-dB average gain over 136&#x2013;169-GHz BW and supports amplification up to <inline-formula> <tex-math notation="LaTeX">$\text{0.58}f_\text{max}$</tex-math> </inline-formula> of the technology.