Active Microwave Devices Research Articles

Active and Passive Microwave Devices and Circuits

Active and Passive Microwave Devices and Circuits

Mildly Nonquasi-Static Two-Port Device Model Extraction by Integrating Linearized Large-Signal Vector Measurements

This paper introduces a new procedure, based on linearized large-signal vector measurements, for extracting a nonlinear behavioral model for two-port active microwave devices. The technique is applied to a model structure that assumes a short-term memory condition and is formulated as a parallel connection of a limited number of frequency-weighted static nonlinearities. The proposed method consists of integrating the time-varying linear characterization of the device driven into a nonlinear state by a large signal. The experiment design and measurement setup are based on a large-signal network analyzer and are discussed in detail. In the second portion of this paper, insight is provided on the most meaningful model parameters, along with an extensive independent experimental validation, which considers a GaAs pHEMT as a case study and includes two-tone large-signal data, a wideband code division multiple access signal, bias-dependent -parameters, and dc data.

Small-Signal Modeling of Microwave MESFETs Using RBF-ANNs

This paper presents a comprehensive approach to accurate and efficient modeling of microwave active devices such as metal semiconductor field effect transistors (MESFETs) using artificial neural networks (ANNs). A radial basis function (RBF)-ANN model is developed for S-parameters and equivalent circuit parameters (ECPs) of MESFETs. The training and testing data for these models are obtained from the measured two-port scattering parameters and extracted ECPs of a 0.25 times 200 mum (4 times 50 mum) gallium arsenide MESFET. A four- input eight-output ANN is used to model the S-parameters of a microwave MESFET versus bias, temperature, and frequency, and a three-input eight-output ANN is used to model the ECPs of a microwave MESFET versus bias and temperature. Comparisons of measured and modeled data are presented, and the results show very good agreement. The average relative errors using the RBF-ANN models for the S-parameters and ECPs were 0.81% and 0.77%, respectively, which both represent about 60% reduction in error when compared to backpropagation ANN models of similar parameters of the same device.

An oscillator with low phase noise and superior harmonic suppression characteristics based on uniplanar compact split ring resonators

AbstractIn this paper, we describe a novel microwave oscillator incorporating a CPW‐based split‐ring resonator (SRR) as a resonant component of the circuit. The high quality (Q) factor and spurious‐free SRR contribute to phase noise reduction as well as the harmonic tuning of the oscillator circuit in a very small chip area. The fabricated 5.5‐GHz oscillator showed an output power of 2.774 dBm with a 2nd‐harmonic suppression of −43.04 dB and phase noise of −100.8 dBc/Hz at 100‐kHz offset. The proposed oscillator is believed to be the first application of a metamaterial to the performance enhancement of a microwave active device. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 938–940, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21525

Harmonic solution of semiconductor transport equations for microwave and millimetre-wave device modelling

The hydrodynamic transport equations for charges in a semiconductor have been solved for a periodic excitation by means of a harmonic approach, in order to model microwave and millimetre-wave active devices. The solution is based on the expansion of physical variables in a Fourier series in the time domain, and on discretisation in the space domain. A waveform-balance technique in the TD is used to solve the nonlinear equations system. This approach allows for a longer time step with respect to standard TD solutions for most cases of interest, greatly reducing simulation time by at least two orders of magnitude in typical cases. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 36–48, 2004.

Simple technique for measuring source reflection coefficient while characterizing active devices

The measurement of the source reflection coefficient is fundamental for noise, as well as large-signal testing of microwave active devices. This paper describes a simple yet rigorous technique for fast and accurate determination of a source reflection coefficient when a load-source pull test set is used. The solution consists in measuring the waves at the device-under-test reference plane under two different bias conditions. We have proven that these measurements give enough information to compute the source reflection coefficient with accuracy suitable for most applications. Experimental results are presented and compared to data obtained with more conventional techniques.

Energy model for optically controlled MESFETs

An energy-based transport model for the analysis of illuminated microwave active devices is presented. The model is based on the Boltzmann's transport equation, with optical carrier generation and carrier recombination accounted for. The simulation results are compared with the conventional local-field mobility models based on drift-diffusion formulations. It is shown that the drift-diffusion models lose their applicability in submicrometer gate-length devices. The presented time-domain model has a great potential in the analysis of microwave devices under ac and pulsed illumination conditions.

Energy model for optically controlled MESFETs

An energy-based transport model for the analysis of illuminated microwave active devices is presented. The model is based on the Boltzmann's transport equation, with optical carrier generation and carrier recombination accounted for. The simulation results are compared with the conventional local-field mobility models based on drift-diffusion formulations. It is shown that the drift-diffusion models lose their applicability in submicrometer gate-length devices. The presented time-domain model has a great potential in the analysis of microwave devices under ac and pulsed illumination conditions. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 48–52, 2000.

Pulsed bias/pulsed RF characterization measurement system of FET at constant intrinsic voltages

For the first time to our knowledge, a pulsed measurement system has been developed which supports the simultaneous measurement of pulsed Ids(Vds, Vgs) and pulsed scattering parameters of FETs at constant intrinsic voltages. This tool is very useful for the development of nonlinear electrical models of microwave active devices. Indeed, the nonlinear electrical models predefined in the commercial software impose on the user the need to determine the behavior of the active devices at constant intrinsic voltages. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 349–352, 1999.

Bipolar transistor epilayer design using the MAIDS mixed-level simulator

In this paper, we address the epilayer design of the bipolar transistor using the one-dimensional (1-D) mixed-level simulator MAIDS (microwave active integral device simulator). MAIDS facilitates simulation of the electrical behavior of bipolar (hetero) junction transistors with various doping profiles and under different signal conditions in a realistic circuit environment. MAIDS as implemented within Hewlett Packard's microwave design system is a useful and promising tool in the development of bipolar transistors for large-signal conditions. Using MAIDS, we have identified the dominant bipolar transistor distortion sources with respect to the biasing conditions. Simulation results are compared with small- and large-signal measurements for the BFQ135 transistor, which has been developed for cable television (CATV) applications. By analyzing the measured and simulated data, we have developed an optimum epilayer design map for third-order intermodulation distortion that has proven to be particularly useful in the epilayer dimensioning of transistors for CATV applications.

Wideband on-wafer noise measurement setup for noise characterization of active devices in the low VHF band

This paper addresses a new wideband on-wafer measurement test set designed for noise characterization of microwave active devices over the frequency range of 300 kHz to 150 MHz. Noise parameters obtained from the multiple impedance technique on a GaAlAs/GaAs heterojunction bipolar transistor (HBT) from 300 kHz to 70 MHz are reported and compared with low-frequency noise data. Investigation of the excess noise sources of III-V HBT's is performed well above the 100 kHz frequency limit of standard dynamic signal analyzers and noise modeling of these devices is reported.

Pulsed laser deposition of electronic ceramics

High quality thin films of electronic ceramics are currently being deposited by pulsed laser deposition (PLD) for a variety of applications. Examples of these applications include ferroelectric thin films for active microwave electronics and rare-earth doped manganite thin films for uncooled infrared focal plane arrays (IRFPAs). Single phase and oriented Sr x Ba (1− x TiO 3 films have been deposited by PLD onto (100) substrates of LaAlO 3 for active microwave devices. The dielectric properties of these films has been measured using gold interdigital capacitors deposited on top of the film. A 2 : 1 change in the capacitance can be achieved using a 40 V bias across a 5–10 μm capacitor gap. The dissipation factor (measured at 1 MHz) depends on film composition and temperature. Rare-earth manganite (RE x M 1− x MnO δ) thin films have also been deposited by PLD for use in uncooled IRFPAs. The temperature dependence of the resistivity has been measured for La 0.67Ca 0.33MnO 3 and La 0.67Sr 0.33MnO 3 thin films deposited onto LaAlO 3 substrates. Film properties depend strongly on composition and post-deposition processing conditions to vary the oxygen stoichiometry. The temperature coefficient of resistance (TCR) has been measured to be between 2 and 15%. Based on preliminary measurements, these films will increase the sensitivity of the uncooled IR detector to be comparable or greater than a cooled detector based on HgCdTe.

Neural Network Approach for the Characterisation of the Active Microwave Devices

Small-signal and noise behaviour of an active microwave device is modeled through the neural network approach for multiple bias/configurations.Here ,the device is modelled by a black box whose small signal and noise parameters are evaluated through a neural network,based upon the fitting of both of these parameters for the multiplebias or configuration. The concurrent modelling procedure does not require to solve device pbysics equations repeatedly during optimization. Compared to the existing device modelling techniques, the proposed approach has the capability to make bighdimensional models for higbly nonlinear devices.

Modeling of microwave active devices using the FDTD analysis based on the voltage-source approach

This letter describes a voltage-source-based formulation of the extended finite-difference time-domain algorithm for the purpose of modeling microwave devices. The device-wave interaction is fully characterized by replacing the lumped devices with equivalent voltage sources in the device region, which in turn generate electromagnetic fields according to Faraday's law. This formulation is applied to the analysis of a typical microwave amplifier, which includes a three-terminal active MESFET device. Simulation results are in good agreement with measured data.

Signal–noise neural network model for active microwave devices

A new method for concurrently modelling the small-signal and the noise performance of active microwave devices is proposed. Here, the device is modelled by a black box whose small signal and noise parameters are evaluated through a neural network, based upon the fitting of both of these parameters over the operational bandwidth of the device. On using the concurrent modelling procedure, it has been found that, not only can the small-signal performance be simulated accurately, but also the prediction of noise performance is in much better agreement with measurements than those of recent published models.

SrxBa(1−x)TiO3 thin films for active microwave device applications

Abstract Thin (0.3–50 μm) films of SrxBa(1−x)TiO3 (SBT) with x=0.35 − 0.8 have been deposited by pulsed laser deposition onto single crystals of MgO, LaAlO3 and thin films of YBa2Cu3O7−δ. The SBT films were characterized morphologically, structurally and electrically at frequencies ≤ 13 GHz. On MgO, smooth, oriented single phase films were obtained at substrate temperatures ≥ 825°C. Films as thick as 10 μm were exclusively (100) oriented. At thicknesses approaching 50 μm SBT films were phase pure but polycrystalline. The dielectric constant of SBT films, as determined from patterned structures using microstrip geometries, was ∼20% of that observed in bulk SBT (εmax(film)=1100 for x=0.5 at 200 K). The temperature dependence of the dielectric constant was broad in comparison to the sharply peaked behavior of the bulk material. The ferroelectric thin film properties described, while significantly different from bulk material, are very encouraging for use in active devices at microwave frequencies.

Nonlinear Dielectric Thin Films For Active and Electrically Tunable Microwave Devices

AbstractWe have prepared electrically tunable and active microwave devices incorporating (superconducting YBa2Cu3O7-x)/(nonlinear dielectric SrTiO3) or (normal metal Au)/(nonlinear dielectric Sr0.5Ba0.5TiO3) bilayers. The dielectric layer thickness for these samples varied between 0.5 μm and 2 μm. The top electrode layer for each sample was patterned into a coplanar waveguide device structure. We have configured these devices as voltage-tunable resonators, voltage-tunable phase shifters, voltage-tunable mixers, and voltage-tunable filters. Under dc voltage bias, these prototype devices have exhibited up to 30% resonant frequency modulation, about 1°/mm-GHz phase shift, more than 40 dB change in mixed microwave power, and finetunable symmetric filter profile with less than 2% bandwidth and more than 15% adaptive range.

Novel hardware and software solutions for a complete linear and nonlinear microwave device characterization

While S-parameter test sets are well suited for linear active device characterization, many problems are still unsolved for a complete large-signal characterization. In this paper a test set, which performs measurements of S-parameter and load-pull characteristics at the fundamental and harmonic frequencies, is used to produce a set of data (constant gain, constant output power, efficiency, and so on), which completely describes the linear and nonlinear transistor behavior. The goal is reached by means of a special design of the test set which quickly makes the measurements with a particular tracking algorithm for load-pull contours. The high speed and the accuracy that can be achieved make the test set particularly useful for production testing of microwave active devices and for power amplifier design.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Unified small-signal-noise model for active microwave devices

A new method for modelling, concurrently, the small-signal and the noise performance of active microwave devices is proposed. Here the determination of the element values in a device equivalent circuit is no longer dependent only on the scattering parameters, but also on the device noise parameters. In other words, the device noise performance is treated as an intrinsic set of characteristics of a device like the S-parameters themselves and influences the determination of element values in the device equivalent circuit. On using the concurrent modelling procedure suggested in this paper, it has been found that, not only can the small-signal performance be simulated accurately, but also the prediction of noise performance is in much better agreement with measurements than those of recent published models [1, 2]

A superconductive dual-control active microwave device

In this article we review the background material necessary for the understanding of the operation of superconducting flux flow transistors. A new microwave flux flow device is then presented which exhibits behavior analogous to that of a dual-gate FET. Equivalent circuits and experimental results are presented.