This paper presents a switch based on GeTe (Germanium-Telluride) phase-change material (PCM) suitable for millimeter-wave applications. A shunt configuration with indirect excitation through heating is proposed to facilitate the implementation process in integrated circuits and to reduce impact on RF signal. Electromagnetic simulations, from 50 GHz up to 70 GHz, of two parallel switches shunted a CPW transmission line (TL) show an overall ON-state resistance (RON) of 3 Ω with an OFF-state capacitance (COFF) of 7.1 fF. This leads to a high Figure-of-Merit with a cutoff frequency of 7.5 THz. The demonstrated performance is validated through the design of a reflection-type phase shifter (RTPS), where a 3-dB branch-line coupler is loaded with tunable-length lines using those shunt-switches. Simulation results of the RTPS show great precision in terms of phase tunability with an insertion loss (IL) less than 2.7 dB at 60 GHz.

A non-closed-form general mathematical model for CMOS distributed amplifier (DA) for broadband applications is presented. Contrary to the artificial transmission line (TL) assumption made in the conventional analytical models, the proposed model treats the DA as a discrete set of cells connected together, and hence considers propagation and mismatch between inter-cells. This approach provides designers with a much more accurate first sizing of the DA compared to conventional ways and, as a result, leads to a reduced design time and complexity. The model enables both quantitative and qualitative analysis of a DA, for the purpose of aiding the designers in predicting the relations between DA performance and its multi-design parameters, especially in the context of nonuniform designs. In addition, it is well suited to Computer-Automated Design (CAutoD), to help in achieving designs having a given set of performance goals. The validation of the model is demonstrated on two designs, by a comparison with simulations done in Keysight's ADS tool and using STMicroelectronics' 55-nm SiGe BiCMOS design kit. First design is inspired from an already published non-uniform DA design while second one proposes a 100-GHz bandwidth CMOS uniform DA with 8 dB of power gain, after using it in a CAutoD process.

A wideband fully-integrated bias-tee well suited for millimeter waves is presented. Compared to conventional bias-tees, where RF-choke is optimized on the basis of its inductance value, here, the proposed RF-choke takes advantage of its low parasitic capacitance as one of the design parameters. While enabling wideband operation, in particular towards lower frequencies, this bias-tee enables ease-ofimplementation, robustness against resonance, efficient power delivery to the intended wideband circuit and contributes to circuit area reduction on integrated circuit (IC) implementation. As a proof-of-concept, a wideband CMOS distributed amplifier (DA) with a lower-corner frequency (𝑭 𝒍𝒐𝒘𝒆𝒓 ) of 5 GHz and an upper-corner frequency (𝑭 𝒖𝒑𝒑𝒆𝒓 ) close to 100 GHz is implemented in STMicroelectronics' 55-nm technology with the proposed bias-tee connected to its artificial drain line. The implemented bias-tee enabled a bandwidth close to 100 GHz and its RF-choke required a surface area of 82 µm x 82 µm. When integrated along with the DA, the overall chip area remained the same (0.89 mm 2 ). Post-layout simulations showed a DC power overhead (due to inclusion of the on-chip bias-tee) limited to 17% of the DA-only consumption.

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