Active Microwave Circuits Research Articles

A 3-D Smith Chart Based on the Riemann Sphere for Active and Passive Microwave Circuits

This letter proposes a spherical 3-D Smith Chart suitable for representing both active and passive microwave circuits. Using the mathematical concept of the Riemann sphere, the extended reflection coefficient plane is transformed into the surface of the unit sphere. Since the proposed Smith Chart compiles the whole complex plane, all possible loads are included. A simple graphic tool is thus obtained that successfully unifies active and passive circuits. In addition, lossy lines with complex characteristic impedances can also be represented. The letter presents the 3-D Smith Chart, provides its main governing equations, and also enumerates its more important properties.

Hybrid Integration of Microwave Circuit Solenoid Inductors and AlGaN/GaN HEMTs Using an SU-8 Photosensitive Epoxy Interposer Layer

Integration of active and passive microwave circuit components onto an inexpensive silicon substrate can be accomplished using photosensitive SU-8 epoxy as the interposer layer. This paper addresses the 3-dimensional integration of AlGaN/GaN high electron mobility transistor's (HEMT's) embedded into deep reactive ion etched (DRIE) pockets on a silicon substrate with gold-plated vias and transmission lines formed in a follow-on layer of SU-8 epoxy over the HEMT's. In addition, modeling, simulation, fabrication and testing of gold-plated, solenoid inductors embedded in SU-8 over the silicon substrate is covered. This integration process may replace variable inductance wire bond connections; with reproducible interconnects to enhance circuit design flexibility and accuracy. The solenoid inductors, whose inductance L and quality factor Q can be further optimized through the addition of ferrite or ferromagnetic cores, will help reduce the overall circuit footprint. This paper is organized into two parts: the solenoid model development and the HEMT integration process and test results.

Active and Passive Microwave Devices and Circuits

Active and Passive Microwave Devices and Circuits

Active Microwave Circuit With Negative Group Delay

In this letter, we report on the design, simulation and implementation of an active negative group delay circuit that operates at 1 GHz with a group delay and a gain, respectively, around 2 ns and 2 dB. Analytical formulas are proposed to demonstrate that the adopted topology is able to simultaneously achieve negative group delay (NGD) and gain while fulfilling active device constraints. The theoretical and simulated results are both validated by frequency measurements of a two-stage active microwave circuit.

A parallel FFT accelerated transient field-circuit simulator

A novel fast electromagnetic field-circuit simulator that permits the full-wave modeling of transients in nonlinear microwave circuits is proposed. This time-domain simulator is composed of two components: 1) a full-wave solver that models interactions of electromagnetic fields with conducting surfaces and finite dielectric volumes by solving time-domain surface and volume electric field integral equations, respectively, and 2) a circuit solver that models field interactions with lumped circuits, which are potentially active and nonlinear, by solving Kirchoff's equations through modified nodal analysis. These field and circuit analysis components are consistently interfaced and the resulting coupled set of nonlinear equations is evolved in time by a multidimensional Newton-Raphson scheme. The solution procedure is accelerated by allocating field- and circuit-related computations across the processors of a distributed-memory cluster, which communicate using the message-passing interface standard. Furthermore, the electromagnetic field solver, whose demand for computational resources far outpaces that of the circuit solver, is accelerated by a fast Fourier transform (FFT)-based algorithm, viz. the time-domain adaptive integral method. The resulting parallel FFT accelerated transient field-circuit simulator is applied to the analysis of various active and nonlinear microwave circuits, including power-combining arrays.

An unconditionally stable extended (USE) finite-element time-domain solution of active nonlinear microwave circuits using perfectly matched layers

This paper proposes an extension of the unconditionally stable finite-element time-domain (FETD) method for the global electromagnetic analysis of active microwave circuits. This formulation has two advantages. First, the time-step size is no longer governed by the spatial discretization of the mesh, but rather by the Nyquist sampling criterion. Second, the implementation of the truncation by the perfectly matched layers (PML) is straightforward. An anisotropic PML absorbing material is presented for the truncation of FETD lattices. Reflection less than -50 dB is obtained numerically over the entire propagation bandwidth in waveguide and microstrip line. A benchmark test on a microwave amplifier indicates that this extended FETD algorithm is not only superior to finite-difference time-domain-based algorithm in mesh flexibility and simulation accuracy, but also reduces computation time dramatically.

Global modelling of microwave active circuits by an efficient iterative procedure

A new rigorous iterative process is proposed for studying a rectangular waveguide which includes the Gunn diode GaAs AH445 (THOMSON). It consists in generating a recursive relationship between a given wave source and reflected waves from the discontinuity plane which is divided into cells. A high computational speed has been achieved by using fast mode transformation (FMT). The theory as well as its implemention procedure are described. Numerical results are successfully compared with experimental published data.

Electromagnetic and semiconductor device simulation using interpolating wavelets

A MESFET and a two-dimensional cavity enclosing a cylinder are simulated using a nonuniform mesh generated by an interpolating wavelet scheme. A self-adaptive mesh is implemented and controlled by the wavelet coefficient threshold. A fine mesh can therefore be used in domains where the unknown quantities are varying rapidly and a coarse mesh can be used where the unknowns are varying slowly. It is shown that good accuracy can be achieved while compressing the number of unknowns by 50% to 80% during the whole simulation. In the case of the MESFET, the I-V characteristics are obtained and the accuracy is compared with the basic finite difference scheme. A reduction of 83% in the number of discretization points at steady state is obtained with 3% error on the drain current. The performance of the scheme is investigated using different values of threshold and two types of interpolating wavelet, namely, the second-order and fourth-order wavelets. Due to the specific problem analyzed, a tradeoff appears between good compression, accuracy, and order of the wavelet. This represents the ongoing effort toward a numerical technique that uses wavelets to solve both Maxwell's equations and the semiconductor equations. Such a method is of great interest to deal with the multiscale problem that is the full-wave simulation of active microwave circuits.

Development of microwave multilayer plastic-based multichip modules

We present the design and development of multilayer plastic-based multichip modules (MCM) at microwave frequencies. A vertical feed-through interconnect, which consists of embedded copper wires in plastic, has been developed to transport RF/microwave and dc signals from the first to the second packaging level. The development of this vertical feed-through enables plastic modules to be configured in a surface mount topology that can be interfaced with low cost FR-4 boards using ball grid arrays (BGA). The experimental analysis results demonstrate that this vertical feed-through used with BGAs has ultra-low parasitics and achieves a return loss of greater than 20-dB at 4-GHz. In addition, we demonstrate a number of packaged active microwave circuits including a switch, a low noise amplifier (LNA) and a power amplifier using the plastic module technology at microwave frequencies.

A Special 3-Mirror Quasi-Optical Power Combining System

A special quasi-optical power combining system of millimeter wave has been proposed and developed in this paper. It can be classified into two categories: power combiner of a Multiple oscillators and power combiner of a Multiple device oscillation. The combining condition, the input and output coupling factor and combining coefficient are treated, based field theory of guided-wave and an eigenfunction approach for active microwave circuit respectively. The validity of the descriptions given for this combining has already been experimentally verified.

Electro-optic S-parameter and electric-field profiling measurement of microwave integrated circuits

An S-parameter measurement system based on electro-optic sampling for the on-wafer testing of microwave integrated circuits is presented. Conventional network-analyser measurements on passive circuits up to 20 GHz are used to establish a calibration and measurement procedure to allow S/sub 21/ measurement on further circuits with 0.5 dB uncertainty. Extension of these rules to the noninvasive testing of active microwave circuits, coupling waveguides and digital circuits is demonstrated with a spatial resolution of 8 /spl mu/m and submillivolt sensitivity.

An improved extended FDTD formulation for active microwave circuits

An improved extended finite-difference time-domain formulation for the analysis of active linear and nonlinear microwave circuits is presented in this paper. Here, we have selected the current source approach and have tried to update all the electric-field components on the active sheet. Central-difference approximation has been used for the discretization of the resultant set of state equations. The equivalent circuit of the device has been treated as a zero-dimensional circuit with respect to the wave propagation. The results based on this formulation show good agreement with analytically obtained data for circuits like amplifiers and oscillators.

A global finite-element time-domain analysis of active nonlinear microwave circuits

An extension of the finite-element time-domain (FETD) method for mixed electromagnetic and circuit simulation of complex active microwave circuits is proposed in this paper. The passive distributed part of the circuit is analyzed using FETD and its interaction with lumped passive/active linear/nonlinear components is modeled via an equivalent-current generator whose value and internal capacitive admittance are computed at each time step by the FETD solver. Benchmark tests on a microwave amplifier and a injection-locked oscillator indicate that this extended FETD is not only superior in mesh flexibility, but also gives more accurate results than the similar FDTD-based algorithm.

Efficient numerical CAD technique for RF and microwave amplifiers

The real frequency technique (RFT) is an efficient numerical method to design the matching networks of microwave active circuits. It provides several advantages over most of the usual techniques. By directly including measured scattering and noise parameter data, it does not require any rational functions or circuit models. Moreover, a predetermined matching circuit topology is not necessary. The described method also allows the design of stability-guaranteed broadband circuits when employing potentially unstable transistors. With the Levenberg–Merquardt algorithm, the RFT can be applied to simultaneously optimize transducer power gain, input and output VSWRs, noise figure, and group delay of a multistage microwave active circuit. Applications as different as low-noise amplifier, active filter, or broadband amplifier are possible. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 131–141, 1998.

Design of broad-band matching network with lossy junctions using the real-frequency technique

A computer-aided design (CAD) procedure based on the real-frequency technique (RFT) is introduced for treating the matching of an arbitrary load to a complex generator. In this paper, the method has been applied to the design of interstage matching networks for microwave active circuits. The RFT provides several advantages over most of the usual techniques. It requires neither any transistor model because it directly includes measuring scattering- and noise-parameter data, nor a predetermined matching-circuit topology is necessary. A low-noise amplifier (LNA) design proceeding directly from experimental data is presented. Moreover, a new idea for treating the broadband matching problem leads to the use of an equalizer topology containing cascaded transmission lines with lossy junctions. Thus, gain-flatness and stability are satisfied by designing the input and the output matching circuits by the line-segment technique. An example is presented for the matching of a 0.1-5 GHz amplifier.

Transient analysis of microwave active circuits based on time-domain characteristic models

A modular method is presented to speed up transient simulation of microwave active circuits which consist of linear components and active devices that are often nonlinear. Firstly, the linear components and active devices are individually characterized by time-domain characteristic models (TDCM's) and lumped equivalent circuits, respectively, to reduce the computer memory. Then, based on deconvolution, the TDCM's of linear components are synthesized from the terminal voltages and currents of step voltage excitation, which are simulated by the finite-difference time-domain (FDTD) method. Finally, transient analysis of a one-dimensional (1-D) discrete-time system is applied to obtain the terminal responses of the microwave active circuits, in which a larger sampled step is chosen to reduce the simulation time. This method is employed to two realistic circuits to validate its efficiency and accuracy. The results are in good agreement with the time-consuming direct FDTD simulation of entire circuits.

Full-wave analysis of packaged microwave circuits with active and nonlinear devices: an FDTD approach

This paper presents a comprehensive full-wave analysis of packaged nonlinear active microwave circuits by applying the extended finite-difference time-domain (FDTD) method. Based on the approach of using equivalent sources, the device-wave interaction is characterized and incorporated into the FDTD time-marching scheme. As a consequence, analysis of linear and nonlinear properties, including harmonic generation and intermodulation, can be accomplished by employing a large-signal device circuit model. The implementation is first validated by comparing results of FDTD and HP MDS simulation of the circuit without the packaging structure. The analysis then goes beyond the capability of the circuit simulator to include the packaging effect. This analysis is useful in circuit design involving electromagnetic compatibility/electromagnetic interference (EMC/EMI) problems.

TLM modelling of multilayer coupling structures for microwave PCS antennas

This paper presents a multilayer architecture applicable to integrated planar active array antennas in personal communication systems (PCSs). The configuration uses a combination of microstrip and stripline transmission lines on stacked substrates to integrate printed patch antennas, microwave active circuits, signal-distribution networks, etc., into a compact multilayer system. A general-purpose EM simulator based on the transmission-line matrix (TLM) has been developed to model some vertical interconnections in a multilayer construction. Good agreement is obtained between measurements and numerical results of a monolithic microwave integrated circuit (MMIC) via hole, a novel broadband stripline coupler, and an aperture-coupled dielectric resonator antenna.

Modeling of dispersive microwave FET devices using a quasi‐static approach

AbstractIn the design of active microwave circuits nonlinear device models are of great importance to allow one to predict the reliability of circuit performance. This article reflects our experimental approach in nonlinear FET modeling. Consistent bias‐dependent model elements of the FET small‐signal equivalent circuit are obtained by a recently developed unique multibias extraction procedure which permits the reduction of the nonlinear analysis to the inner part of a FET device. A dispersive nonlinear FET model with current and charge sources being integral functions of the bias‐dependent small‐signal model parameters is proposed. A bias‐dependent difference transconductance and difference channel conductance are introduced as relevant dispersion parameters. The proposed nonlinear FET model is verified on the basis of our signal waveform measurement technique using combined frequency‐ and time‐domain signal detection.

Small-sized MMIC amplifiers using thin dielectric layers

Miniaturized MMIC amplifiers utilizing a multilayer structure composed of thin film transmission lines are presented. The fundamental characteristics of the thin film transmission lines for use in microwave active circuits are discussed through calculations by numerical analysis. A two-stage low-noise amplifier, a single-stage wideband amplifier, and a balanced amplifier are designed within very small areas, while good performance is maintained. The results include that a Ka-band single-stage amplifier is fabricated in a 0.8 mm/spl times/0.6 mm area with a gain of 8.0-9.5 dB in the frequency range of 16-26.5 GHz and input/output return losses of better than 8 dB at 26.5 GHz. The proposed amplifier configurations can be applied to high density integration of one-chip MMIC modules.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>