This paper presents a study of the effects on polarization induced in a twisted polymer microwave fiber (PMF). PMF is gaining more and more interest for multigigabit data rate communications with the continuous advancement of Radio Frequency Integrated Circuits (RFICs). While bending effects have been studied, twisting effects were only reported for a specific PMF. In this study, isotropic and anisotropic cross-section PMF are both considered in theory. Then, for validation purposes, experiments based on a vector network analyzer (VNA) and time domain spectroscopy (TDS) are introduced considering various PMF geometries. It is demonstrated that for the case of an isotropic cross-section PMF, the polarization is maintained relatively to the absolute coordinates. Though, considering an anisotropic cross-section PMF, the polarization is altered. Understanding of the twisting effect is crucial for an optimal implementation of PMF in future systems to cope with polarization losses and for the design of in-band full duplex PMF systems taking benefit of orthogonal polarizations.

This paper presents the integration of passive components at D-band $(110-170 \text{GHz})$ within the air-filled substrate integrated waveguide (AFSIW) technological platform. First, for interconnection purposes, a wideband transition from WR-6.5 to AFSIW is introduced. It achieves a fractional bandwidth of 26.5% with an average insertion loss (IL) as low as 0.85 dB. Then, the surface roughness losses at D-band of an AFSIW transmission line are studied in theory based on the Hurray model with an experimental validation. Finally, to demonstrate the interest of the AFSIW platform for the integration of passive functions, an AFSIW bandpass filter based on multi-mode and over-mode cavities is designed, simulated, and fabricated. In experiment, it achieves a 23.5% fractional bandwidth centered at $\mathbf{1 4 5 ~ G H z}$ with an average insertion loss of 0.95 dB.

This paper demonstrates a high-efficiency SiGe Power Amplifier (PA) for 5G New Radio (5G-NR) / 6G FR3 application. Four cascode cells are combined through current and pseudo-differential voltage combining at the output matching network to optimize power density, efficiency, and stability. A shunt neutralization inductor was added at the input of commonbase transistors to absorb the C-be parasitic capacitance of the stage and enhance output stability. This PA is implemented in the 55nm BiCMOS B55X process from STMicroelectronics with a total chip area of 1.42 mm(2). The circuit achieves 24.1 dBm peak saturation power with 37.7% peak power-added efficiency (PAE) over the 6.4 to 8.5 GHz band with 49% of 3-dB fractional bandwidth (FBW). Tested at 7.5 GHz with 5G NR FR2 TDD modulated signals, this PA delivers up to 14.3 dBm of P-out,P-avg at 17.5% PAE(avg), with -27 dB of rms EVM and -34.9 dBc of ACPR, for a 1-CC 200 MHz 256 QAM showing 12.9 dB of PAPR.

Future wireless systems are expanding toward multi-gigahertz (GHz) bandwidths and sub-terahertz (THz) frequencies. Conventional solutions struggle with high sampling rates, strong nonlinearities, and the diminishing efficiency gains of analog circuits in complementary metal-oxide-semiconductor (CMOS) technologies. Wideband radio-frequency (RF) architectures require a new signal representation and processing paradigm to address these challenges, enabling energy-efficient wideband access and linearization. The Walsh sequency domain offers such an opportunity: its orthogonal basis enables highly parallel and energyefficient wideband operations, reducing RF signal-processing complexity while remaining fully compatible with CMOS technologies. Operating directly in the Walsh domain allows compact implementations of RF conversion, channelization, and nonlinear compensation. These capabilities have been experimentally demonstrated through proof-of-concept integrated circuits in CMOS fully depleted silicon-on-insulator (FDSOI) technologies, including GHz-range RF conversion, digital pre-distortion (DPD), and channel-aggregation techniques. Furthermore, a Walshnative end-to-end wireless autoencoder shows improved robustness to amplifier nonlinearities while benefiting from reduced sampling requirements. Walsh-based RF processing opens a new design space for multi-GHz bandwidth, energy-efficient, and hardware–algorithm co-design in next-generation artificial intelligence (AI)-assisted communication systems.

This paper presents the implementation of two novel twisted hybrid couplers in GaN technology. The first hybrid coupler is optimized to achieve wide bandwidth operation, by reaching a fractional bandwidth of about 80%, making it suitable for broadband applications. The second coupler exhibits insertion losses of around 0.55 dB with a fractional bandwidth of 15%. Its key advantage lies in its ability to modify its form factor, making it particularly compact. The integration of the twisted coupler within an amplifier is performed using a 150 nm GaN on SiC GH15 technology from United Monolithic Semiconductors (UMS). The power amplifier delivers a saturated output power of 10 W, achieving a maximum power-added efficiency (PAE) of approximately 30 – 38% across the 24 – 31 GHz (5G FR2) frequency band.

This article presents a broadband 5G power amplifier (PA) robust to voltage standing wave ratio (VSWR) variations and featuring high efficiency up to deep power back-off (PBO) in 28-nm FD-SOI CMOS technology. The proposed architecture, based on a quasi-balanced structure and an inductive load, offers an alternative to the conventional Doherty PA to maintain its PAE6dBPBO enhancement up to 3:1 VSWR over a wide bandwidth. A detailed theoretical analysis demonstrates the improved broadband performance that can be achieved with this architecture, as well as its robustness to VSWR variations. Indeed, the degradation of its PAE6dBPBO is kept below 7% between 22 and 44 GHz. The circuit achieves 24% PAE6dBPBO and 16% PAE(9.7dBPBO) at 28 GHz, while guaranteeing linearity in line with the 5G standard. The PA occupies a surface area of 0.82 mm2.

A high data rate polymer microwave fiber (PMF) communication link is described in the Y-band (170-260 GHz). The transmitter and receiver are designed in a 90-nm silicon germanium (SiGe) BiCMOS process. The link includes a waveguide to PMF transition and the PMF has a solid circular cross-section. Link tests were done over a one meter long fiber using a carrier of 230 GHz. Measurements show that it supports 50 Gbps using QPSK modulation with SNR=11.5dB and EVM=26.5%. Using QAM-16 modualation 60 Gbps was reached with SNR=15.7dB and EVM=12.2%.

This article presents a broadband 5G power amplifier (PA) robust to voltage standing wave ratio (VSWR) variations and featuring high efficiency up to deep power back-off (PBO) in 28-nm FD-SOI CMOS technology. The proposed architecture, based on a quasi-balanced structure and an inductive load, offers an alternative to the conventional Doherty PA to maintain its $\text {PAE}_{\text {6dBPBO}}$ enhancement up to 3:1 VSWR over a wide bandwidth. A detailed theoretical analysis demonstrates the improved broadband performance that can be achieved with this architecture, as well as its robustness to VSWR variations. Indeed, the degradation of its $\text {PAE}_{\text {6dBPBO}}$ is kept below 7% between 22 and 44GHz. The circuit achieves 24% $\text {PAE}_{\text {6dBPBO}}$ and 16% $\text {PAE}_{9.\text {7dBPBO}}$ at 28GHz, while guaranteeing linearity in line with the 5G standard. The PA occupies a surface area of 0.82 mm2.

This paper presents the first implementation of two innovative 90 degrees hybrid couplers in Gallium Nitride (GaN) process designed for 5G applications. In a very compact design, both couplers target low insertion loss (IL) and large fractional bandwidth (FBW1dB) to replace conventional couplers. The first coupler exhibits minimum insertion loss of 0.44 dB at 22 GHz with a fractional bandwidth of 31%. The second coupler was optimized to reach a minimum insertion loss of 0.28 dB at 25.5 GHz with a fractional bandwidth of 29%, making it suitable for wideband applications. Both couplers perform with an output phase imbalance of 93 degrees +/- 2 degrees. Both circuits were designed using 150 nm GaN on SiC GH15 technology from United Monolithic Semiconductors (UMS).

This paper presents the first experimental demonstration of fully Walsh-based wideband converters for Radio Frequency Front-End (RFFE) architecture implemented in 28 nm FDSOI CMOS technology. The system integrates a Walsh-based RF digital-to-analog converter (WDAC) and a Walsh-based RF analog-to-digital converter (WADC) designed for digital predistortion (DPD) applications. The WDAC achieves an instantaneous bandwidth of 4.7 GHz with an energy efficiency of 0.57 pJ/bit. The WADC achieves a 2.5 GHz bandwidth while consuming only 4 mW. The experimental demonstration showcase efficient wideband signal processing in the Walsh domain and highlights its potential as a promising paradigm for future low-power, high-throughput wireless transceivers, offering both wideband capabilities and a new order of scale energy efficiency.

This brief proposes a wideband Power Amplifier (PA) integrated in 28nm FD-SOI CMOS technology dedicated to sub-6 GHz 5G with controlled PAEmax based on a variable harmonic load across its operating bandwidth. The PA achieves a gain between 31 and 34 dB, a $P_{sat}$ from 20.5 to 22 dBm in the operating bandwidth from 2.9 to 6.1 GHz. Thanks to the PAE control, a PAEmax between 27 and 35% is achieved along the entire operating bandwidth. Modulated 5G-NR FR1 signal measurements are performed with a Walsh-based DPD using an intra-band carrier aggregation scenario to showcase the PA robustness for contiguous carriers. For the first time to the best author's knowledge, PAEmax control is demonstrated over a relative bandwidth of 71%.

This paper presents the first experimental demonstration of a fully Walsh-domain Radio Frequency Front-End (RFFE) architecture implemented in 28nm FDSOI CMOS technology. The system integrates a Walsh-based RF digital-to-analog converter (WDAC) and a Walsh-based RF analog-to-digital converter (WADC) for digital predistortion (DPD) purpose. The WDAC achieves an instantaneous bandwidth (BW) of 4.6875 GHz with an energy efficiency of 0.38 pJ/bit. The WADC supports a 2.5 GHz BW and consumes only 4 mW. This experimental demonstration showcases wideband and power-efficient signal processing and highlights the potential operating entirely in the Walsh basis as a compelling approach for future low-power, high-throughput wireless systems, combining both energy efficiency and wideband performances.

This paper presents the design and measurement results for a wideband SiGe front-end module operating from 24.25 GHz to 30.5 GHz, which integrates a passive phase shifter (PS), a variable gain and phase-inversion amplifier (VGA) with low impedance and minimal phase variation, and a linear power amplifier (PA) designed for beamforming systems. The PS with the VGA provides a full 360 degrees tuning with a resolution of 5.6 degrees, while the gain control spans 17 dB in 0.5 dB increments. Measurements present a maximum gain of 27 dB, P-sat of 21 dBm, PAE(max) of 31.2% at 27 GHz. Developed with 130nm SiGe BiCMOS technology, the circuit occupies an area of 0.53mm(2) excluding pads.

This paper presents a theoretical and experimental study of the effects of a twist on the hybrid HE11V and HE11H mode propagations of X-shaped plastic waveguides. Plastic waveguides, providing a light-weight and low-cost alternative to optical fibers and copper lines for high data rate transmissions, are of high interest, particularly for applications in data centers and emerging autonomous cars. While the bending effects on plastic waveguides have been reported in the literature, to the best of the authors' knowledge, twisting effects were not addressed. The X-shaped plastic waveguide optimizing the sensitivity and loss trade-off compared to solid and hollowed circular plastic waveguides is considered in this study. First, the effects of a twist are analyzed in theory and simulation with an experimental validation. Then, the case of a twisted bent waveguide is investigated. The study concludes that for the X-shape topology, the polarization direction remains invariant (i.e., it does not rotate) in the two considered cases despite the twist.

In this paper, several plastic fiber for high-speed mmW communications are measured in the sub-THz range using waveguide transitions specifically designed for its characterization. These waveguide transitions have the advantage of being low cost and very broadband. First, rectangular to circular waveguide transitions are introduced. Then circular to plastic waveguide transitions are presented. These transitions are designed and measured at D-band (110-170 GHz) and H-band (220- 330 GHz). Next, the characterization of plastic waveguides of different shapes and in both frequency bands is carried out. Within the two considered bands, the proposed transitions achieve both simulated and measured insertion losses (IL) as low as 1 +/- 0.2 dB and 2 dB, respectively. For the plastic fibers, a good agreement between theoretical model and experimental results are obtained with loss per meter varying between 4 and 20 dB/m depending on the fiber geometry and operating frequency.

This paper presents a broadband 5G power amplifier robust to VSWR variations and featuring high efficiency up to deep power back-off in 28nm FD-SOI CMOS technology. The proposed architecture, based on a quasi-balanced structure and an inductive load, offers an alternative to the conventional Doherty PA to maintain its PAE 6dBPBO enhancement up to 3:1 VSWR over a wide bandwidth. Indeed, the degradation of its PAE 6dBPBO is kept below 7% between 22 and 44 GHz. The circuit achieves 24% PAE 6dBPBO and 16% PAE 9.7dBPBO at 28 GHz, while guaranteeing linearity in line with the 5G standard. The PA occupies a surface area of 0.82 mm 2 .

Exploring millimeter-wave bands presents fresh opportunities for new high data rates communication standards, yet confronts technological challenges like power amplification. Digital predistortion (DPD) offers a solution to enhance the linearity of the amplification while keeping high efficiency. Since Envelope Transient simulations (ET) are time-consuming during circuit design, designers often restort to experimental DPD verification instead. This paper proposes two co-simulation workflows to simulate modulated signals on Integrated Circuits (IC) Power Amplifiers (PA) with an application of DPD. Simulation results indicate that the computational modeling of power amplifiers enables 99% faster schematic and post-layout (PLS) ET simulations, reducing the time needed from months to minutes while maintaining comparable output accuracy.