Agilent Advanced Design System Research Articles

Unconditional Stability Boundaries of a Three-Port Network

An analytical approach for acquiring the explicit expressions of the boundaries concerning the unconditional stability regions of a three-port network is presented. This approach begins with the expressions for the input reflection coefficients S 11 ' and S 22 ' at ports 1 and 2 of a three-port network having port 3 terminated with ?3 . |S 11 '| = 1 and |S 22 '| = 1 then give two stability circles in the ?3-plane. One can graphically determine that the tangent point of these two stability circles is on the boundary of the unconditional stability region for the terminating port. The explicit expressions of the boundary for port 3 are then acquired. This procedure may be followed for the other two ports in order to fully characterize the unconditional stability boundaries of a three-port network. In addition, issues pertaining to uniqueness and continuity in the plotting of unconditional stability boundaries are addressed. Using the agilent advanced design system software tool, the derived expressions of the unconditional stability boundary for the terminating port and related extreme phase values of reflection coefficients of the other two ports are implemented. These derived expressions can then enhance the computer-aided capability on the stability analysis of a three-port network and provide useful information for the microwave circuit designer.

CALCULATION OF LINEAR AND NONLINEAR SCHRÖDINGER EQUATIONS BY THE EQUIVALENT NETWORK APPROACH AND ENVELOPE TECHNIQUE

In this letter, a technique is introduced which allows calculations of linear and nonlinear Schrödinger equations by commercially available circuit simulators. The results derived using the Circuit Envelope Simulation tool in Agilent Advanced Design System TM are tested by analytical calculations, and good correspondence is demonstrated.

RADANT 렌즈를 위한 평행판 도파관 내에서의 4-비트 다이오드 위상변위기 구현

본 논문에서는 평행판 도파관 내에서 동작하는 X-대역 4-비트(<TEX>$22.5^{\circ}$</TEX>, <TEX>$45^{\circ}$</TEX>, <TEX>$90^{\circ}$</TEX>, <TEX>$180^{\circ}$</TEX> BIT) 다이오드 위상변위기의 설계 개념 및 구현 방법에 관하여 기술한다. 이를 위하여 <TEX>$11.25^{\circ}$</TEX>, <TEX>$22.5^{\circ}$</TEX>, <TEX>$45^{\circ}$</TEX> 유전체 위상 변위 레이어에 대한 CST사의 MWS(MicroWave Studio)와 Agilent사의 ADS(Advanced Design System) 시뮬레이션 결과를 제시하고, 측정 결과와 비교한다. 시뮬레이션 결과는 각각 <TEX>$0.6^{\circ}$</TEX>, <TEX>$0.7^{\circ}$</TEX>, <TEX>$3.5^{\circ}$</TEX>의 위상 오차가 발생하며, 측정 결과는 <TEX>$0.6^{\circ}$</TEX>, <TEX>$2^{\circ}$</TEX>, <TEX>$5.5^{\circ}$</TEX>의 위상 오차가 발생함을 알 수 있다 또한, 이들을 바탕으로 <TEX>$22.5^{\circ}$</TEX> BIT와 <TEX>$45^{\circ}$</TEX> BIT 위상변위기에 대한 시뮬레이션 결과를 비교, 제시함으로써 4-비트 위상변위기의 설계 개념 및 구현 방법의 타당성을 입증한다. In this paper, the design concept and implementation method of the X-band 4-bit(<TEX>$22.5^{\circ}$</TEX>, <TEX>$45^{\circ}$</TEX>, <TEX>$90^{\circ}$</TEX>, <TEX>$180^{\circ}$</TEX> BIT) diode phase shifter in the parallel plate waveguide are introduced. The simulated results of <TEX>$11.25^{\circ}$</TEX>, <TEX>$22.5^{\circ}$</TEX> and <TEX>$45^{\circ}$</TEX> dielectric phase shift layers using CST's MWS and Agilent's ADS are presented, and the measured results are compared with the simulated ones. The simulated phase shift errors at the center frequency are <TEX>$0.6^{\circ}$</TEX>, <TEX>$0.7^{\circ}$</TEX>, and <TEX>$3.5^{\circ}$</TEX>, respectively and the measured phase shift errors at the center frequency are <TEX>$0.6^{\circ}$</TEX>, <TEX>$2^{\circ}$</TEX>, and <TEX>$5.5^{\circ}$</TEX>, respectively. Also, the MWS simulated results of <TEX>$22.5^{\circ}$</TEX> BIT and <TEX>$45^{\circ}$</TEX> BIT phase shifter are presented and compared with the ADS simulated ones to verify the validity of the presented design concept and implementation method.

주기적인 금속 스트립 패턴을 갖는 유전체 층이 놓인 평행판 도파관내에서의 전파 특성

본 논문에서는 주기적인 금속 스트립 패턴을 갖는 유전체 층이 놓인 평행판 도파관내에서의 전파 특성에 대하여 기술하였다. CST사의 MWS(Microwave Studio)를 이용하여 금속 스트립 사이에 연결된 PIN 다이오드의 ON/OFF 상태를 금속 스트립의 단락/개방 상태로 각각 시뮬레이션을 하였고, X-대역 4-bit radant lens 위상변위기에 사용될 수 있는 <TEX>$11.25^{\circ}$</TEX>, <TEX>$22.5^{\circ}$</TEX>, <TEX>$45^{\circ}$</TEX> 유전체 층을 설계하였다. 설계된 각 유전체 층의 위상차 시뮬레이션 결과는 <TEX>$11.28^{\circ}$</TEX>, <TEX>$23.2^{\circ}$</TEX>, <TEX>$46.22^{\circ}$</TEX>이었다. 또한, Agilent사의 ADS(Advanced Design System)를 이용하여 각 유전체 층에 대한 동작대역에서의 등가회로를 구현 및 시뮬레이션 하였고, MWS 시뮬레이션 결과와 비교하였다. 최종적으로 <TEX>$11.25^{\circ}$</TEX>, <TEX>$22.5^{\circ}$</TEX>, <TEX>$45^{\circ}$</TEX> 유전체 층을 제작하여 중심주파수에서 각각 <TEX>$9.6^{\circ}$</TEX>, <TEX>$22.4^{\circ}$</TEX>, <TEX>$43^{\circ}$</TEX>의 측정된 위상차를 얻었다. The propagation characteristics in parallel plate waveguide with dielectric layer having periodic metal strip pattern are investigated. PIN diode ON/OFF states are regarded as the short and open circuit, respectively, in the simulation using CST's MWS. The <TEX>$11.25^{\circ}$</TEX>, <TEX>$22.5^{\circ}$</TEX>, and <TEX>$45^{\circ}$</TEX> layers which can be used for X-band 4-bit Radant lens phase shifter, are designed. The simulated results for each dielectric layer are <TEX>$11.28^{\circ}$</TEX>, <TEX>$23.2^{\circ}$</TEX>, and <TEX>$46.22^{\circ}$</TEX>, respectively. Also, the equivalent circuit of each layer at the operating band is realized and simulated using Agilent's ADS. The ADS simulated results are compared with the MWS simulated ones. Measured differential phase shills at the center frequency are <TEX>$9.6^{\circ}$</TEX>, <TEX>$22.4^{\circ}$</TEX>, and <TEX>$43^{\circ}$</TEX>, respectively.

Power combining techniques into unbalanced loads for Class-E and inverse Class-E amplifiers

A power combining strategy for Class-E and inverse Class-E amplifiers operating at high frequencies such that they can operate into unbalanced loads is proposed. This power combining method is particularly important for the inverse Class-E amplifier configuration whose single-stage topology is naturally limited for small-to-medium power applications. Design examples for the power combining synthesis of classical Class-E and then inverse Class-E amplifiers with specification 3 V–1.5 W–2.5 GHz are given. For this specification, it is shown that a three-branch combiner has a natural 50 Ω output impedance. The resulting circuits are simulated within Agilent Advanced Design Systems environment with good agreement to theoretical prediction. Further the performance of the proposed circuits when operated in a Linear amplification using Nonlinear Components transmitter configuration whereby two-branch amplifiers are driven with constant amplitude conjugate input phase signals is investigated.

Fast and accurate simulations of transmission-line metamaterials using transmission-matrix method

Recently, two-dimensional (2D) periodically L and C loaded transmission-line (TL) networks have been applied to represent metamaterials. The commercial Agilent's Advanced Design System (ADS) is a commonly-used tool to simulate the TL metamaterials. However, it takes a lot of time to set up the TL network and perform numerical simulations using ADS, making the metamaterial analysis inefficient, especially for large-scale TL networks. In this paper, we propose transmission-matrix method (TMM) to simulate and analyze the TL-network metamaterials efficiently. Compared to the ADS commercial software, TMM provides nearly the same simulation results for the same networks. However, the model-process and simulation time has been greatly reduced. The proposed TMM can serve as an efficient tool to study the TL-network metamaterials.PACS Codes:41.20.Jb

Voltage tunable Ba 0.6Sr 0.4TiO 3 thin films and coplanar phase shifters

Not only the ferroelectric properties of Ba 0.6 Sr 0.4 TiO 3 thin films but also the design, fabrication and microwave properties of coplanar waveguide (CPW) phase shifter were investigated. When the applied voltage changes from zero to 20 V range at a frequency of 1 kHz, the dielectric constant, tunability, remanent polarization (2P r ) and coercive electric field (Ec) of the BST films are 1266, 29.5%, 2.29 μC/cm 2 and 22.27 kV/cm, respectively. The structure of CPW phase shifter was designed by ANSOFT High Frequency Structure Simulator (HFSS) and Agilent Advanced Design System (ADS). The designed phase shifter consists of 56 same sections. It is observed from the photograph of the fabricated device that the lines of electrodes are regular and the widths of bottom electrodes overlapped by top electrodes are about 5 μm. It was found that the phase shift gradually increases as the voltage increases from 0 V to 20 V, which may be due to the tunability of BST films varies with external dc field. About 168° phase shift was achieved at 28 GHz with a bias voltage of 20 V.

Hybrid $S$-Parameters for Transmission Line Networks With Linear/Nonlinear Load Terminations Subject to Arbitrary Excitations

We propose a generalized S-parameter analysis for transmission lines (TLs) with linear/nonlinear load terminations subject to arbitrary plane-wave and port excitations. S-parameters are prevalently used to model TLs such as cable bundles and interconnects on printed circuit boards (PCBs) subject to port excitations. The conventional S-parameter approach is well suited to characterize interactions among ports. However, nontraditional port excitations associated with plane-wave coupling to physical ports at TL terminals lead to forced, as well as propagating, modal waves, necessitating a modification of the standard S-parameter characterization. In this paper, we consider external plane-wave excitations, as well as port (internal) sources, and propose a hybrid S-parameter matrix for characterization of the associated microwave network and systems. A key aspect of the approach is to treat the forced waves at the ports as constant voltage sources and induced propagating modal waves as additional entries (hybrid S-parameters) in the S-parameter matrix. The resulting hybrid S-matrix and voltage sources can be subsequently exported to any circuit solver such as HSPICE and Agilent's Advanced Design System for the analysis of combined linear and nonlinear circuit terminations at ports. The proposed method is particularly suited for susceptibility analysis of cable bundles and PCBs for electromagnetic interference evaluations. It also exploits numerical techniques for structural and circuit domain characterization and allows for circuit design optimization without a need to perform any further computational electromagnetic analysis

Circuit model and full wave analysis of a compact wideband quadrature hybrid

AbstractA printed, compact, and wideband quadrature hybrid is simulated and fabricated by utilizing the multi‐section technique for bandwidth enhancement and equivalent transmission line technique for size reduction. The compact quadrature hybrid has a size reduction of 50% as compared with the conventional quadrature hybrid. The compact hybrid achieves over 50% bandwidth at a centre frequency of 2 GHz. A circuit model and a full wave model are introduced and analyzed using Agilent Advanced design system. Excellent agreement between the simulated and the fabricated hybrid is achieved, which indicates that the circuit and full wave models are indeed a good representation of the fabricated compact wideband quadrature hybrid. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1650–1652, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22519

From circuit topology to behavioural model of power amplifier dedicated to radar applications

A new behavioural model of a power amplifier (PA) at system level is presented, dedicated to radar applications. This model, which is able to take into account output loading impedance mismatch, is based on a similar topology to the PA's circuit. The model, implemented in Agilent Advanced Design System (ADS), is validated for different loading impedances, until VSWR=2 (voltage standing wave ratio), on the PA's bandwidth. This approach permits an extraction, resulting from simple CW measurements or simulations, and easy model implementation. This work has been supported by DGA (French Defense and Security Agency).

Frequency Agility of Broadband Antennas Integrated With a Reconfigurable RF Impedance Tuner

This letter demonstrate the frequency agility that can be achieved when an broadband antenna is integrated with a reconfigurable RF tuner as na impedance matching circuit. The reconfigurable tuner uses a microstrip loaded line structure with four stubs that are each terminated by a varactor diode. The spectral response can be varied by changing the capacitance of the diodes. Input impedance data obtained from measurements on commercially available antennas were used in an agilent advanced design system (ADS) model of the four-stub tuner. The results show that adding the reconfigurable tuner can facilitate excellent frequency agility of the return loss of the broadband antenna over several narrow frequency subbands

Microwave Bandstop Filters Using Novel Artificial Periodic Substrate Electromagnetic Band Gap Structures

Novel microwave and millimeterwave (mm-wave) bandstop filters using artificial periodic substrate electromagnetic bandgap (EBG) are investigated in this paper. Three types of microstrip structures using periodically modified trace width, patterned dielectric substrate, and periodically modified ground plane are treated, respectively. By periodically modifying either the width of the conductor trace, the substrate height, or the dielectric constant of a standard microstrip transmission line, it has been possible to design microwave bandstop filter functions with wide stopband characteristics and reduced size, compared to conventional microwave/RF filter structures. Commercial electronic design automation (EDA) and computational electromagnetic tools such as Agilent's advanced design system (ADS) and CST Microwave Studio are used in the design and simulations of these filter structures. The effects of the physical parameters of the structures on the filter characteristic are studied. The design procedure and simulation results are described and possible applications of these filter structures are discussed in this paper. A particularly wide stopband is achieved by the circuits presented in this paper, which use only a few cell elements. A significant performance improvement of microstrip patch antenna has been observed by implementing one of the presented EBG periodic substrate structures.

Design and optimisation of one-port RF MEMS resonators and related integrated circuits using ANN-based macromodelling approach

The authors propose a modelling methodology which combines finite element method (FEM) and artificial neural networks (ANNs) techniques for the design and optimisation of integrated circuits (ICs) incorporating one-port radio frequency microelectromechanical systems (RF MEMS) resonating structures. The FEM is employed to predict the electro-mechanical performance of MEMS resonators. ANNs are utilised to model complex relationships between the physical parameters of the MEMS resonator and the corresponding electrical equivalent circuit parameters. These parameters are extracted directly from the FEM analysis and used for training the ANNs. It is shown that the relative error of the ANN model for a single MEMS device is less than 0.5% while the computational time is more than 40 times reduced compared to the FEM. To extend the capabilities of the proposed methodology, the developed ANN model is implemented into a commercially available circuit simulator, Agilent's Advanced Design System (ADS). This allows a seamless modelling process for the design and optimisation of MEMS resonators embedded ICs at both the device and circuit levels. As an example, a 30 MHz Pierce oscillator with the ANN model of a free-free beam MEMS resonator is optimised within the circuit simulator.

RF Performance and Modeling of Si/SiGe Resonant Interband Tunneling Diodes

The RF performance of two different Si-based resonant interband tunneling diodes (RITD) grown by low-temperature molecular beam epitaxy (LT-MBE) were studied. An RITD with an active region of B /spl delta/-doping plane/2 nm i-Si/sub 0.5/Ge/sub 0.5//1 nm i-Si/P /spl delta/-doping plane yielded a peak-to-valley current ratio (PVCR) of 1.14, resistive cutoff frequency (f/sub r0/) of 5.6 GHz, and a speed index of 23.3 mV/ps after rapid thermal annealing at 650/spl deg/C for 1 min. To the authors' knowledge, these are the highest reported values for any epitaxially grown Si-based tunnel diode. Another RITD design with an active region of 1 nm p+ Si/sub 0.6/Ge/sub 0.4//B /spl delta/-doping plane/4-nm iSi/sub 0.6/Ge/sub 0.4//2 nm i-Si/P /spl delta/-doping plane and annealed at 825/spl deg/C for 1 min had a PVCR of 2.9, an f/sub r0/ of 0.4 GHz, and a speed index of 0.2 mV/ps. A small signal model was established to fit the measured S/sub 11/ data for both device designs. Approaches to increase f/sub r0/ are suggested based on the comparison between these two diodes. The two devices exhibit substantially different junction capacitance/bias relationships, which may suggest the confined states in the /spl delta/-doped quantum well are preserved after annealing at lower temperatures but are reduced at higher temperature annealing. A comprehensive dc/RF semi-physical model was developed and implemented in Agilent advanced design system (ADS) software. Instabilities in the negative differential resistance (NDR) region during dc measurements were then simulated.

Characterization of a Low-Noise Linearized Microwave Power Amplifier Module

An X-band, low-noise, linearized microwave power amplifier module consisting of a low-noise solid-state amplifier (SSA), predistortion linearizing circuit, and low-gain helix traveling wave tube (TWT) is designed and tested in order to demonstrate both reduced noise figure and suppressed intermodulation distortion ratio. Two-tone intermodulation distortion (IMD) ratios are predicted from simulations obtained from modeling of the TWT, linearizing circuit, and SSA by the use of Agilent's Advanced Design System simulation code. Simulated IMD ratios are in good agreement with measured results. Measurements show a noise figure of 2.2 dB at 9.5 GHz and the third-order IMD ratio of -53 dBc at 10 dB input back off from the input P1dB point. It is found that both noise figure and IMD ratio are significantly improved compared with conventional helix-TWTs and microwave power modules.

Analytical expressions, modeling, and simulations of intensity and frequency fluctuations in directly modulated semiconductor lasers

Analytical expressions for the intensity and frequency/phase noise of single-mode semiconductor lasers based on quantum- mechanical rate equations are derived. Correlated photons, electrons, and phase Langevin noise sources and their auto and cross-correlation relations are presented, along with a novel self-consistent normalized laser model that includes the laser's correlated noise sources. A symboli- cally defined device (SDD) is constructed using the proposed normalized model and implemented in Agilent's advanced design system (ADS) CAD tool. Dynamic laser characteristics are predicted using the SDD implementation for 1300-nm InGaAsP/InP lasers. The results of time do- main dynamic simulations of photons, carriers, optical output power, and phase—with and without the effects of noise—are presented. Simulation results are used to show the effects of random noise on both the phase and optical power output of semiconductor lasers. Simulation results are analyzed to demonstrate the resonance frequency shift dependence on the bias current levels, the relation between the frequency response and the bias current, and the dependence of the laser line width broadening on the frequency fluctuations. Comparison between the presented re- sults and other published results (simulations and measurements) show good agreement while achieving simulation time enhancement. The suit- ability of the proposed models for the study and characterization of the performance of complete systems in both circuit and system simulations is examined. © 2004 Society of Photo-Optical Instrumentation Engineers.