Current Generator Plane Research Articles

RF Characterization of GaAs HBT under Load Mismatch with Reverse Wave Injection Technique.

RF PAs need to be reliable enough to protect them from damage under load mismatch conditions. This paper investigated the characteristics of GaAs heterojunction bipolar transistors (HBTs) under load mismatch conditions using a novel reverse wave injection technique to realize large VSWR ruggedness measurement with the circle centered at 50 Ohm and optimal impedance separately to analyze the device in real applications. With a real-time waveform measurement system, the RF voltage and current waveform information can be acquired, which provide a more-accurate view of what is occurring at the current generator plane of the HBT device. Thereby, the potential failure mechanisms and load impedance can be identified to design the most-suitable PA circuits in communication systems.

Exploring Feasible Design Space for Multi-Octave Power Amplifier Using Nonlinear Embedding

This brief presents a design space analysis for optimum load trajectory selection in multi-octave continuous class power amplifiers using nonlinear embedding model. The proposed approach solves the major problem associated with the synthesis of a broadband matching network due to the non-foster behavior of load at the device package terminal. The nonlinear embedding model allows the designer direct access at the current generator plane for applying any load apparently creating desired waveforms for any class of operations. These loads are then projected to the package plane using the model for designing the required matching network. For demonstration, a nonlinear embedding model of 25 W GaN HEMT device from Wolfspeed is extracted and utilized to develop multi-octave continuous class F PA operating in 0.5-2.2 GHz band with 60%-73.8% drain efficiency in measurement.

A Broadband Millimeter-Wave Continuous-Mode Class-F Power Amplifier Based on the Deembedded Transistor Model

In this letter, a broadband millimeter-wave (mm-wave) continuous-mode Class-F power amplifier (PA) based on the deembedded transistor model is proposed for the fifth-generation (5G) applications. To design the output matching network at the intrinsic current-generator plane, an $S$ -parameter fitting method is proposed to extract the parasitic parameters of nonpackaged transistors over a wide frequency range. The PA is implemented in the 0.13- $\mu \text{m}$ SiGe BiCMOS process, which occupies only 0.42 mm2. By controlling the even and odd harmonics impedance, the PA achieves a 78.2% −3-dB small-signal gain fractional bandwidth from 21.1 to 48.2 GHz. The −1-dB $P_{\mathrm {sat}}$ bandwidth covers 21–43 GHz (68.8% fractional bandwidth) and the saturated output powers are 17.2–18.1 dBm. Meanwhile, the designed PA provides a 24.1%–32.1% peak power-added efficiency (PAE) over the band.

Exploring the impedance coverage limitation at current generate plane of transistors up to millimeter‐wave band based on comprehensive large signal model

AbstractThe harmonic power amplifiers (PAs) have potential to be used in the millimeter‐wave band, but the sophisticate parasitic network effects on the projection of reflection coefficient coverage from transistor package (TP) plane to current generator (CG) plane is an important challenge. In this work, every typical parasitic element with unique effect is derived theoretically. Thus, in the millimeter‐wave band, the reduced and rotated projection of parasitic network between the two planes becomes clear. The fundamental frequency (20 GHz), second harmonics (40 GHz), and third harmonics (60 GHz) load‐pull simulations using the commercial standard nonlinear transistor modeling are simulated. The simulation and derivation are consistent and show that output power and efficiency become less sensitive to harmonic tuning due to the lossy parasitic network. This work will be helpful for harmonic tuned transistor and PA design in the millimeter‐wave band, in the future.

Analytical Design Space of Power Amplifiers Including the Class-A/B/J Continuum for Dynamic Load Modulation

In this paper, an analytical design space of power amplifiers (PAs) including the Class-A/B/J continuum for dynamic load modulation (DLM) at the current generator plane (CGP) is proposed based on the theory of load modulated (LM) continuous Class-B/J PAs. By introducing a biasing operation factor ρ, the theory of DLM PAs provides an analytical design space for all the operation modes from Class-B/J mode to Class-A mode. The analytical design space of DLM PAs shows that high efficiency is maintained at a large dynamic range of output power back-off (OPBO) with a purely resistive load modulation at the CGP when Class-B/J mode is performed. For deep Class-AB mode, the analytical design space of the DLM PAs shows that a combination of resistive and reactive load modulation at the CGP is used to maintain the high efficiency at the OPBO. The effectiveness of the proposed analytical design space is validated by load-pull measurements of a bare-chip gallium nitride (GaN) device.

Nonlinear-Embedding Design Methodology Oriented to LDMOS Power Amplifiers

In this paper, we apply for the first time the nonlinear-embedding technique to the design of power amplifiers (PAs) based on laterally-diffused metal-oxide-semiconductor (LDMOS) field-effect transistors. Such a design technique is based on setting the transistor load line at the intrinsic current-generator plane, according to well-known theoretical guidelines. Then, the selected operating condition can be transposed at any design frequency at the extrinsic transistor terminals, by means of a model of the device nonidealities, such as the nonlinear intrinsic capacitances and the linear parasitic effects. A harmonically-tuned high-efficiency class-F and a wideband class-AB PAs operating within the FM broadcasting band 88 ÷ 108 MHz based on a 10-W LDMOS are then designed and realized. To definitely assess the validity of the proposed approach for the LDMOS technology, we compare the measured performance on the fabricated PAs with the expected predictions.

Evaluation of Uncertainty in Temporal Waveforms of Microwave Transistors

We evaluate the uncertainty in on-wafer vector-calibrated nonlinear measurements with the National Institute of Standards and Technology (NIST) Microwave Uncertainty Framework. We include in our analysis uncertainties in the passive calibration standards, power meter, NIST-traceable phase calibration reference, cable bending, and probe alignment. These uncertainties are propagated first to the electrical quantities across the terminals of the device-under-test, which was an on-wafer microwave transistor. Next, we propagate uncertainties to the transistor current-generator plane, whose temporal voltage/current waveforms and impedances are of interest for the design of power amplifiers.

X-Band GaN Power Amplifier for Future Generation SAR Systems

A X-band GaN monolithic microwave integrated circuits (MMIC) High Power Amplifier (HPA) suitable for future generation Synthetic Aperture Radar systems is presented. The HPA delivers 14 W of output power, more than 38% of PAE in the frequency bandwidth from 8.8 to 10.4 GHz. Its linear gain is greater than 25 dB. For the first time an MMIC X-band HPA has been designed by directly measuring the transistor behavior at the current generator plane. In particular, optimum device load-line has been selected according to the chosen performance tradeoffs.

A Load–Pull Characterization Technique Accounting for Harmonic Tuning

A novel methodology for the characterization of the nonlinear dynamic behavior of electron devices (EDs) is presented. It is based on a complete and accurate ED characterization that is provided by large-signal low-frequency I/V measurements, performed by means of a low-cost setup, in conjunction with any model-based description of the nonlinear reactive effects related to ED capacitances. The unique feature of the proposed technique is that a fully harmonic control of waveforms at the current generator plane is achieved, and as a consequence, high-efficiency operation can be simply investigated. Different experimental data are presented on GaAs and GaN transistors, and to definitely verify the capability of the new approach, the design of a class-F GaN power amplifier is deeply investigated as a case study.

Nonlinear embedding and de-embedding techniques for large-signal fet measurements

The manuscript presents a comparison between two nonlinear procedures oriented to the investigation of the intrinsic I/V dynamic characteristics at a transistor's current-generator plane. These approaches, without the need of modeling device trapping and thermal effects, allow to obtain information at the current-generator reference plane that is more strictly linked to the device performance in terms of output power and efficiency. Experiments carried out on a 800-μm GaN HEMT are reported. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2835–2838, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27169

Waveforms-Only Based Nonlinear De-Embedding in Active Devices

A novel nonlinear de-embedding procedure based on only the use of low- and high-frequency vector large-signal measurements is proposed. The nonlinear Q-V characteristics, along with the parasitic network, are here determined by combining vector measurements with numerical optimization. Consequently, the knowledge of their contributions allows one to retrieve the actual waveform at the current generator plane starting from any high-frequency load line.