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Signal flow graph (SFG) representation of small-signal responses of nonlinear microwave circuits around a large-signal operating point is developed using the X-parameters. It is shown that, unlike the SFGs for linear circuits, negative-frequency nodes need to be included explicitly. The development elucidates the circuit-operational meaning of the elusive T-type small-signal X-parameters, which represent interaction between positive- and negative-frequency components. As an example, such an SFG is used to derive a closed-form expression of the output power of an amplifier as a function of the load reflection coefficient. It is then used to plot approximate load-pull power contours. The result is consistent with the expressions of the optimum load reflection coefficient derived by Root et al. (EuMIC 2017) and of power contours derived by Peláez-Pérez et al. (TMTT 2013). SFGs provide an alternative systematic means to derive closed-form expressions in terms of X-parameters and to gain illuminating insights into the workings of weakly nonlinear circuits.

A broadband noise measurement system is newly developed and demonstrated at temperatures between 3 K and 300 K. Using the system, wideband noise spectroscopy (WBNS) from 20 kHz to 500 MHz is carried out for the first time, revealing that shot noise is the dominant white noise down to 3 K. The paper also suggests, by means of WBNS, the possibility of extracting the baseline noise characteristics, which do not include the noise component that varies a great deal from device to device.

On-wafer evaluation of white thermal and shot noise in nanoscale MOSFETs is demonstrated by directly sensing the drain current under zero- and nonzsero-drain-bias (Vd) conditions for the first time, without recourse to a hot noise source, commonly needed in noise figure measurement. The dependence of white noise intensity on the drain bias clearly shows thermal noise at Vd=0 V and shot noise at Vd>0 V with its gate-bias-dependent suppression. An empirical expression for the Fano factor (shot-noise suppression factor) that is well-behaved even at Vd=0V exactly and suitable for measurement-based evaluation is proposed. The direct measurement approach could allow more accurate and predictive noise modeling of RF MOSFETs than has conventionally been possible.

Signal flow graph (SFG) representation of small- signal responses of nonlinear microwave circuits around a large-signal operating point is developed using the X-parameters. It is shown that, unlike the SFGs for linear circuits, negative-frequency nodes need to be included explicitly. The development elucidates the circuit-operational meaning of the elusive T-type small-signal X-parameters, which represent interaction between positive- and negative-frequency components. As an application example, such an SFG is used to derive a closed-form expression of the output power of a power amplifier as a function of the load reflection coefficient. It is then used to plot approximate load-pull power contours. The result is consistent with and more general than the expression of the optimum load reflection coefficient derived analytically by Root et al. (EuMIC 2017). SFGs provide a systematic means to derive closed-form expressions in terms of X-parameters and to gain illuminating insights into the workings of weakly nonlinear circuits.

A 40-nm CMOS receiver (RX) capable of performing A-to-D-converter-less carrier recovery including frequency and phase tracking and coherent QPSK demodulation is presented. It operates in frequency-acquisition mode, followed by phase-tracking mode. It is meant as a demodulator of a 270-GHz RX operating at an intermediate frequency of 45 GHz. The highest data-rate of 32 Gbit/s was achieved dissipating 351 mW, amounting to an energy-per-bit of 11 pJ/bit.

A 272-GHz CMOS receiver (RX) for IEEE 802.15.3d, capable of an analog BPSK/QPSK demodulation based on a Costas loop, is presented. A QPSK demodulation is realized with the non-linear operation of a phase detector at the BPSK-demodulation Costas loop. An 8-Gbaud BPSK and a 4-Gbaud QPSK demodulation at the carrier frequency of 272.16 GHz (channel 58 of IEEE 802.15.3d) are achieved.

This paper presents a 258-GHz CMOS transmitter with phase-shifting capability for phased-array systems targeting sixth-generation mobile network (6G). Phase shifters are inserted in local oscillator (LO) paths to limit the bandwidth required of the phase shifters. A power detector is used to detect and calibrate the phase difference between a pair of phase shifters in the two power-combined paths of the transmitter. It is fabricated using a 40-nm CMOS technology. A data rate of 16 Gb/s and output power of −6.8 dBm are achieved with quaternary phase-shift keying (QPSK). The calibration procedure of the phase shifters is verified by simulation.

De-embedding is the process of deducing the characteristics of a device under test (DUT) from measurements made at a distance ((Bauer & Penfield, 1974)), often via additional measurements of one or more dummy devices. This article reviews a simple thru-only de-embedding method suitable for on-wafer characterization of 2-port, 4-port, and 2n-port networks having a certain symmetry property. While most conventional de-embedding methods require two or more dummy patterns, the thru-only method requires only one THRU pattern. If the device under measurement is a 2-port and the corresponding THRU pattern has the left/right reflection symmetry, the THRU can be mathematically split into symmetric halves and the scattering matrix for each of them can be determined (Ito & Masu, 2008; Laney, 2003; Nan et al., 2007; Song et al., 2001; Tretiakov et al., 2004a). Once those scattering matrices are available, the effects of pads and leads can be canceled and the characteristics of the device obtained. Themethodwas applied up to 110GHz for characterization of an on-chip transmission line (TL) (Ito & Masu, 2008). In the case of 4-port devices such as differential transmission lines, 4-port THRU patterns with ground-signal-ground-signal-ground (GSGSG) pads or GSSG pads can often be designed to have the even/odd symmetry in addition to the left/right reflection symmetry. In that case, the scattering matrix for a THRU can be transformed into a block-diagonal form representing two independent 2-ports by an even/odd transformation. Then, the 2-port thru-only deembedding method can be applied to the resultant two 2-ports. This 4-port thru-only method was applied to de-embedding of a pair of coupled transmission lines up to 50GHz (Amakawa et al., 2008). The result was found to be approximately consistent with that from the standard open-short method (Koolen et al., 1991), which requires two dummy patterns: OPEN and SHORT. In the above case (Amakawa et al., 2008), the transformation matrix was known a priori because of the nominal symmetry of the THRU. However, if the 4-port THRU does not have the even/odd symmetry or if the device under measurement is a 2n-port with n ≥ 3, the above method cannot be applied. Even if so, the thru-only method can actually be extended to 4-ports without even/odd symmetry or 2n-ports by using the recently proposed S-parameterbased modal decomposition of multiconductor transmission lines (MTLs) (Amakawa et al., 2009). A 2n-port THRU can be regarded as nonuniform multiconductor transmission lines, 2