Large-signal Characterization Research Articles

Advancing LWIR FSO communication through high-speed multilevel signals and directly modulated quantum cascade lasers.

This study investigates the potential of long-wave infrared (LWIR) free-space optical (FSO) transmission using multilevel signals to achieve high spectral efficiency. The FSO transmission system includes a directly modulated-quantum cascade laser (DM-QCL) operating at 9.1 µm and a mercury cadmium telluride (MCT) detector. The laser operated at the temperature settings of 15°C and 20°C. The experiment was conducted over a distance of 1 m and in a lab as a controlled environment. We conduct small-signal characterization of the system, including the DM-QCL chip and MCT detector, evaluating the end-to-end response of both components and all associated electrical elements. For large-signal characterization, we employ a range of modulation formats, including non-return-to-zero on-off keying (NRZ-OOK), 4-level pulse amplitude modulation (PAM4), and 6-level PAM (PAM6), with the objective of optimizing both the bit rate and spectral efficiency of the FSO transmission by applying pre- and post-processing equalization. At 15°C, the studied LWIR FSO system achieves net bitrates of 15 Gbps with an NRZ-OOK signal and 16.9 Gbps with PAM4, both below the 6.25% overhead hard decision-forward error correction (6.25%-OH HD-FEC) limit, and 10 Gbps NRZ-OOK below the 2.7% overhead Reed-Solomon RS(528,514) pre-FEC (KR-FEC limit). At 20°C, we obtained net bitrates of 14.1 Gbps with NRZ-OOK, 16.9 Gbps with PAM4, and 16.4 Gbps with PAM6. Furthermore, we evaluate the BER performance as a function of the decision feedback equalization (DFE) tap number to explore the role of equalization in enhancing signal fidelity and reducing errors in FSO transmission. Our findings accentuate the competitive potential of DM-QCL and MCT detector-based FSO transceivers with digital equalization for the next generation of FSO communication systems.

A General Analysis of Resonant Switched-Capacitor Converters Using Peak Energy Storage and Switch Stress Including Ripple

This work presents a general analytical framework enabling large-signal characterization of resonant switched-capacitor (ReSC) power converters that accounts for passive component voltage and current ripple, for operation at and above resonance. From this, appropriate phase durations for minimized rms currents are derived, in addition to expressions for total passive component volume using an intuitive peak energy method. An example hardware prototype validates both the derived waveforms and timings—as well as total passive volume—through three comparable hardware configurations, one of which minimizes passive component volume. In addition, the proposed technique formulates analytical expressions for both rms currents and peak blocking voltages, facilitating refined loss estimation and component selection. Subsequent calculation of the large-signal Volt–Amp (VA) switch stress metric allows a more accurately quantified trade-off between active and passive components compared to prior work, which has not fully accounted for ripple. Four common ReSC topologies are exemplified throughout, with topology specific parameters documented for reference.

Ion Intercalation Enabled Tunable Frequency Response in Lithium Niobite Memristors

Memristors have emerged as a viable component for developing neuromorphic hardware platforms, which can compete with biological systems in density, accuracy, and energy efficiency. Among contemporary memristive systems, intercalation-driven lithium niobite (LiNbO2) memristors have the advantage of inherent flux-driven large analog conductance tunability ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {R}/{R} &gt;89$ </tex-math></inline-formula> ), a wide resistance range (~10–1E <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7 \Omega $ </tex-math></inline-formula> ) selected via geometry selection, and low-power (~100–150 mV) neuromorphic functionality resembling synaptic weight updates in the synaptic membrane. Emerging neural systems require nonstatic temporal responses to implement temporally diverse architectures, such as recurrent neural networks (RNNs), yet these temporally diverse memristors are rare. There is a gap in understanding of the frequency response of nonvolatile memristors, which is a fundamental characteristic in memristive systems and ultimately dictates the speed of adaptive learning in deployed neural networks and the memory windows available for designers in RNNs. Using both large and small signal characterization methods, these memristors demonstrate up to a decade of span in tunable frequency-dependent response, statically controlled via device geometry and scaling design rules, and dynamically tuned via channel lithium concentration. Thus, the tunable frequency dependence of resistance modulation in LiNbO2 memristors is evaluated, enabling future neural network design rules to be identified for scalable multifunctional memristive systems for neuromorphic computing applications.

Characterization of Nanocrystalline Flake Ribbon for High Frequency Magnetic Cores

This letter reports characterization of the novel nanocrystalline flake ribbon (NFR) soft magnetic material. The comparative analysis among the ferrite N87, N27, and the NFR is presented at different temperature, frequency, and peak magnetic flux density, respectively. Experimental results prove that the NFR has lower loss density, higher magnetic flux density saturation, and better temperature stability from 85 to 300 kHz. A <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> resonant tank based circuit is employed for large signal characterization. The mass-based stacking factor of the NFR core is adopted to describe the core structure. This letter suggests that the NFR is a good alternative to the ferrite for high power magnetic cores due to its superior performance and flexibility structures.

RF Small and large signal characterization of a 3D integrated GaN/RF-SOI SPST switch

AbstractThis paper presents the radio frequency (RF) measurements of an SPST switch realized in gallium nitride (GaN)/RF-SOI technology compared to its GaN/silicon (Si) equivalent. The samples are built with an innovative 3D heterogeneous integration technique. The RF switch transistors are GaN-based and the substrate is RF-SOI. The insertion loss obtained is below 0.4 dB up to 30 GHz while being 1 dB lower than its GaN/Si equivalent. This difference comes from the vertical capacitive coupling reduction of the transistor to the substrate. This reduction is estimated to 59% based on a RC network model fitted to S-parameters measurements. In large signal, the linearity study of the substrate through coplanar waveguide transmission line characterization shows the reduction of the average power level of H2 and H3 of 30 dB up to 38 dBm of input power. The large signal characterization of the SPST shows no compression up to 38 dBm and the H2 and H3 rejection levels at 38 dBm are respectively, 68 and 75 dBc.

A Robust on-Wafer Large Signal Transistor Characterization Method at mm-Wave Frequency

Accurate on-wafer large signal characterization of RF transistor is crucial for the optimum design of wireless communication circuits. We report a novel and systematic measurement method for the accurate acquisition of input and output power of on-wafer transistors up to 40GHz. This method employs external couplers to extract the travelling waves, combined with a novel large signal calibration algorithm to calculate the power at on-wafer probe tip. The accuracy of this method was bench marked versus conventional approaches in a real measurement bench, and further been verified by characterizing the large signal response of a 0.25μm GaN HEMT device. It is concluded that the measurement uncertainty has been greatly decreased with this new method, especially at mm-wave frequencies.

Large-signal vector characterization of LDMOS devices for analysis and design of broadband Doherty high-power amplifiers

AbstractWe present a novel broadband large-signal vector characterization technique, suitable for high-power broadband Doherty amplifiers (DPAs). It consists of characterizing the DPA three-port sub-circuit composed of the main and peak power devices that are inter-connected by the input network. We discuss a suitable way to extract the three-port X-parameters of a DPA sub-circuit, which is based on a pair of high-power Silicon Laterally Diffused MOSFETs (LDMOSs) for UHF applications. It is then applied to the analysis of a high-power broadband DPA developed on the basis of the same DPA sub-circuit. This technique permits the broadband analysis of the operation of the DPA, as well as to get insight on the load modulation for both the peak and main devices, while they mutually interact through the input network. Measurements and simulated data in the 700–960 MHz bandwidth are compared so as to demonstrate the feasibility of three-port X-parameters characterization for high-power DPAs in UHF band.

A $G$ -Band Broadband Balanced Power Amplifier Module Based on Cascode mHEMTs

The first full $G$ -band power amplifier module demonstrated in GaAs metamorphic high electron mobility transistor (mHEMT) technology has been developed for use as a driver amplifier in instrumentation. The circuit integrated in this module uses a compact balanced cascode topology and is based on a 35-nm mHEMT technology in a grounded coplanar waveguide environment. High compactness is achieved due to the use of a small ground-to-ground spacing of $14~\mu {\mathrm{ m}}$ and an advanced process with three metallization layers. The millimeter-wave integrated circuit exhibits a linear gain higher than 15.3 dB and return losses better than 10 dB from 118 to 236 GHz, which represents an ultrabroad relative bandwidth (RBW) of 67%. A peak output power of 10 dBm is achieved at 200 GHz. The WR-5 module uses broadband transitions, which show insertion losses of less than 1.5 dB. It demonstrates a small-signal gain that exceeds 13.4 dB in the whole $G$ -band (RBW ≥ 54%). Large-signal characterization exhibits power levels higher than 3.6 dBm from 130 to 210 GHz (RBW = 47%). This module achieves the highest bandwidth in $G$ -band and the highest output power when comparing it with modules based on similar technologies.

Design and Large-Signal Characterization of High-Power Varactor-Based Impedance Tuners

This paper presents a new systematic and efficient method for the design of high-power varactor-based impedance tuners. By incorporating the varactor losses and voltage handling capabilities, the method allows the impedance tuning range to be maximized and losses to be minimized under high-power operating conditions. A 2.2-GHz large-signal double-stub tuner has been designed using the proposed methodology and SiC varactor diodes. Using comprehensive large-signal measurements, a 25-W input power handling is demonstrated up to $\Gamma _{\max } \approx ~0.8$ . Two-tone linearity measurements show an input third-order intercept point exceeding 50 dBm for most impedances. These results clearly demonstrate the feasibility of the proposed technique for the design of high-performance large-signal tuners.

A Prepulsing Technique for the Characterization of GaN Power Amplifiers With Dynamic Supply Under Controlled Thermal and Trapping States

The asymmetry between capture and release time constants associated with charge-trapping phenomena observed in the electrical characteristics of microwave gallium–nitride (GaN) field-effect transistors (FETs) introduces distortion in GaN-based power amplifiers (PA). The PAs that operate with supply modulation to increase efficiency are particularly affected by this phenomenon, since the GaN FET trap state exhibits a nonlinear dependence on the voltage applied to the device terminals. In this paper, a measurement approach and the setup are presented for a large-signal characterization of GaN-based PAs operated with dynamic bias supply: a new prepulsing technique is introduced, which enables the characterization of the PA in controlled charge-trapping and thermal states. The characteristics obtained with this technique are shown to give an accurate description of the PA performance in the actual application working conditions. The proposed approach is validated by using the measured data for the direct computation of predistortion functions for the linearization of a 9.7-GHz envelope tracking 10-W GaN monolithic microwave integrated circuit PA for amplitude-modulated pulsed radar transmitters. Additional research on the PA trap-induced performance degradation is also presented and can be explored to predict the PA performance for different parameters of the operative regime or for the formulation of the PA behavioral models.

Performance Analysis of Reconfigurable Bandpass Filters With Continuously Tunable Center Frequency and Bandwidth

This paper presents a comparison and performance evaluation of three different technologies for the implementation of tunable filters utilizing semiconductor varactors, commercially available barium strontium titanate (BST) thin film and screen-printed BST thick-film varactors. To identify the most suitable technology for applications in low power receiving up to high-power transmitting stages, the performance evaluation is carried out with the same tunable hairpin filter design. While the center frequency of the proposed tunable filter structure is tuned by varactors loading the filter resonators, the bandwidth is controlled by coupling varactors between adjacent resonators. The filters are designed for a center frequency range from 700 MHz to 1 GHz and for bandwidth tuning from 60 to 150 MHz. The tunable filters are evaluated and compared with regard to their tunability, quality factor, linearity (intermodulation products of third order), and power handling capability. In conclusion, the tunable hairpin filter based on semiconductor varactor diodes offers the largest center frequency tuning range of 390 MHz with a transmission between −1.5 and −7 dB, whereas the BST thin- and thick-film-varactors-based filters exhibit high linearity with an IIP3 between 39 and 60 dBm. Moreover, large signal characterization reveals that the BST thick-film-varactors-based filter structure has the best power handling capability of up to 41dBm.

An improved large-signal model by artificial neural network for the MOSFETs operating in the breakdown region

An improved large-signal breakdown model establishment applying an artificial neural network (ANN) approach is presented for metal-oxide-semiconductor field-effect transistors (MOSFETs) operating in the breakdown regime for the first time. A neural network program with the feed-forward back propagation algorithm and Levenberg Marquardt optimization is utilized to obtain the MOSFET large-signal model for breakdown operation. When compared with the conventional model without the breakdown effects considered, more accurate large-signal characteristics in the breakdown regime can be obtained by incorporating the avalanche network using the ANN approach. The breakdown network is demonstrated to be significant for large-signal characterization at high bias according to the analysis of minimum acceptable error. Besides, the divergence problem due to the neglected avalanche network can be avoided during ANN training in the avalanche regime. The accuracy of the presented model can keep about 2% error. The presented ANN approach can be applied to device large-signal modeling in the impact ionization regime.

Large-Signal Analysis and Characterization of a RF SOI-based Tunable Notch Antenna for LTE in TV White Space Frequency Spectrum

Large-Signal Analysis and Characterization of a RF SOI-based Tunable Notch Antenna for LTE in TV White Space Frequency Spectrum

Power Measurement Setup for On-Wafer Large Signal Characterization Up to Q-Band

We report on the development of a nonlinear vector network analyzer power measurement setup for on-wafer large signal device characterization up to the Q-band. The setup can be used with various types of load pull (active, passive or hybrid) and enables measurements both in continuous wave and pulsed modes (1- $\mu \text{s}$ pulsewidth and a duty cycle of 1%). Subsequently, state-of-the-art power results at 40 GHz have been achieved on sub-10 nm barrier AlN/GaN high electron mobility transistors. Pulsed load-pull measurements allowed reaching an output power density at such high frequency above 6 W/mm together with high efficiency up to a drain voltage of 30 V while avoiding self-heating effects and thus gate leakage current degradation.

A 210-GHz SiGe Balanced Amplifier for Ultrawideband and Low-Voltage Applications

This letter presents a low-voltage balanced amplifier for millimeter-wave radio systems. An ultrawideband of operation is demonstrated from 155 to 210 GHz, which corresponds to a 30% relative bandwidth. Over this band, the system provides 10-dB gain for a power consumption of only 16.8 mW. For the employed 0.8 V voltage supply, the large-signal characterizations demonstrated a maximum iP $_{\mathrm {\mathbf {1 {}dB}}}$ of −17.1 dBm and oP $_{\mathrm {\mathbf {1 {}dB}}}$ of −10.2 dBm. The measured input and output return losses are above 10 and 20 dB for the whole band. The described features are enabled by the balanced common-base architecture, the ad hoc designed multistub matching networks, and the employed high performance 450-GHz SiGe BiCMOS fabrication technology. The realized amplifier compares well against reported SiGe BiCMOS designs operating above 200 GHz by showing the widest demonstrated bandwidth as well as the lowest voltage supply and power consumption.

Large-signal characterization of millimeter-wave IMPATTs: effect of reduced impact ionization rate of charge carriers due to carrier-carrier interactions

In this paper, we study the effect of energy loss of charge carriers due to carrier-carrier interactions prior to impact ionization on the static and large-signal characteristics of double-drift region impact avalanche transit time (IMPATT) diodes based on Si designed to operate at millimeter-wave (mm-wave) atmospheric window frequencies such as 94, 140, and 220 GHz. The above mentioned effect has been incorporated in the simulation by taking into account a recently reported generalized analytical model of impact ionization rate of charge carriers based on multistage scattering phenomena in the base semiconductor. Results are compared with static and large-signal signal simulation results of the same diodes that we have reported earlier by taking into account the empirical relation of ionization rates fitted from the experimental data (experiment was carried out on IMPATT structures suitable for operating near 100 GHz). It is observed that both the large-signal RF power output and DC to RF conversion efficiency of the diodes are deteriorated significantly due to reduced ionization rates as a consequence of carrier-carrier collision events prior to the impact ionization. This effect is found to be more pronounced in 140 and 220 GHz diodes due to the enhanced carrier-carrier collisions within those diodes having greater background doping densities as compared to 94 GHz diode. The simulation results presented in this paper found to be in closer agreement with the experimental results as compared to the results that we have reported earlier.

Large-Signal Characterization of pHEMT Under Different Load Conditions by Using X-Parameters

In this letter, output power of pseudomorphic high electron mobility transistors (pHEMTs) under different load conditions and output impedance under large-signal drive are investigated by using novel X-parameters. By further considering the X <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sup> terms of X-parameters, characterization of fundamental output power at different load can be more accurate when compared with the results by using conventional hot-S-parameters without X <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sup> terms. Good agreement between measured fundamental output power of pHEMTs obtained from load-pull measurements and calculated results from the X-parameters under different load conditions is achieved. Besides, output impedance X <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2121</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</sup> under large signal drive incorporating with the X <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sup> and X <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sup> terms can be more accurate for output impedance characterization than the conventional hot-Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2121</sub> without the X <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sup> coefficients considered. This analysis of large-signal characterization can be beneficial to power amplifier designs.

A Low-Voltage 35-GHz Silicon Photonic Modulator-Enabled 112-Gb/s Transmission System

We present a silicon photonic traveling-wave Mach–Zehnder modulator operating near 1550 nm with a 3-dB bandwidth of 35 GHz. A detailed analysis of traveling-wave electrode impedance, microwave loss, and phase velocity is presented. Small- and large-signal characterization of the device validates the design methodology. We further investigate the performance of the device in a short-reach transmission system. We report a successful 112-Gb/s transmission of four-level pulse amplitude modulation over 5 km of SMF using 2.2 ${\rm V}_{{\rm p} - {\rm p}} $ drive voltage. Digital signal processing is applied at the transmitter and receiver. 56-GBaud PAM-4 and 64-Gb/s PAM-2 transmission is demonstrated below a pre-FEC hard decision threshold of $4.4 \times 10^{-3}$ .

Large-Signal Characterization of Power Inductors in EV Bidirectional DC–DC Converters Focused on Core Size Optimization

This paper is focused on core size optimization of power inductors in bidirectional dc-dc converters. It presents an experimental large-signal characterization procedure for power inductors in electric vehicle applications and a method to obtain an inductance reference value for the power inductor in dc-dc converters' simulation studies. It discusses the importance of the inductor design project by describing important constraints such as core size and saturation. The main contribution of this paper is related to the proposed dc flux cancelation technique in the bidirectional converter. A variable inductor prototype is used to replace the power inductor in order to decrease core size by improving the ripple content of the inductor current. The saturation level of the core is controlled by means of an auxiliary winding whether the converter operates in buck or boost mode. Experimental results validate the proposed methodology showing more than 50% reduction in magnetic material for similar current levels.

Dynamic systems behaviour analysis and design based on the qualitative theory of differential equations: the Boost power converter case

This paper uses the qualitative theory of differential equations to analyse/design the dynamic behaviour of control systems. In particular, the Poincaré compactification and the Poincaré--Hopf theorem are used for analysing the local dynamics near the finite and infinite equilibrium points. As an application, a large signal characterisation of a Boost type power converter in closed loop, including its equilibrium/bifurcation points and its global dynamics, which depends upon the value of the load resistance, is studied.