Focus Microwaves (Canada)

This paper presents a comparative analysis of onwafer noise figure (NF) measurements at D-band <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(110-170 \text{GHz})$</tex> and G -band <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(140-220 \text{GHz})$</tex> frequencies using cold-source and Y-factor methods. A broadband distributed amplifier fabricated in an advanced BiCMOS process is used as the device under test. The measurement setups employ automated source tuners, bandspecific calibration components, and vector network analyzerbased gain extraction to improve accuracy. Results highlight notable discrepancies in NF and gain measurements across bands, attributed primarily to variations in calibration and gain estimation. The study provides insight into the sensitivity of sub-THz NF metrology to hardware non-idealities, and proposes techniques to mitigate these challenges, with implications for the design and evaluation of future 6 G systems.

This paper presents the characterization results of several new passive millimeter wave circuits integrated on very thin ceramic substrate. The work is focused on the design and characterization of a novel rounded Wilkinson power divider, a 90 hybrid coupler, a rat-race coupler, and of a novel six-port (multi-port) circuit. Measurements show the wideband characteristics, allowing therefore their use for multi Gb/s V-band wireless communication systems.

An in-depth analysis of the continuous inverse Class F power amplifier (PA) accounting for nonlinear input and output active device properties is presented. The analyses show possible ways of exploiting input nonlinearity to improve and maintain PA performance in a broadband operation and propose a flexible source second-harmonic design space which reduces the input matching network (MN) design complexities. Such exploitation of input nonlinearity can also alleviate performance degradation due to dynamic knee behavior of a practical field-effect transistor (FET) in continuous inverse Class F PA operation. The analyses are validated with vector load-pull (VLP) measurements and utilized to implement a broadband PA design. High-drain efficiency (DE) over 75% and output power more than 38 dBm are achieved over 0.8-1.4 GHz at constant 3-dB gain compression.

The Chapter begins with a discussion of the definition of load pull. It goes on to consider scalar and vector load pull, why load pull is needed, load pull methods, reflection on a variable passive load, injection of a coherent (active) signal, impedance tuners, harmonic load pull, fundamental versus harmonic load pull, on wafer integration, base-band load pull, active tuning, and data transfer into CAD and nonlinear models.

This paper compares purely active and hybrid harmonic load pull systems. Purely active systems come in the form of closed active load or open active signal injection. Hybrid systems use active injection and impedance tuners to pre-match the injection power amplifier to the low transistor impedance. Harmonic tuning requires additional sources and/or harmonic tuners. Each approach is scrutinized based on technical and cost criteria.

A slide screw microwave impedance tuner is presented which has four independent carriages, which slide across a low loss slabline. Each carriage has one or two vertical axes and associated stepper motors and gear, allowing the precise positioning of RF probes (slugs) into the slot of the slabline at any horizontal or vertical position. Each RF probe generates wideband reflection when approaching the center conductor. The associated calibration and tuning software can identify combinations of tuner probe positions corresponding to reflection factors such as to create independent tuning at up to four different frequencies. In case of harmonic frequencies the coverage of the RF probes has to be at least two octaves, i.e.: maximum: minimum frequency ¿ 4:1; in practice frequency coverage is higher than 4:1, since most applications require a certain operation bandwidth; in the typical case of a fundamental frequency band of 1.8-2.5 GHz the frequency range covered by the RF probes needs to be 1.8 to 10 GHz, the maximum frequency being 4 · 2.5 GHz = 10 GHz..