In this article, a scalable large-signal model for SiGe heterojunction bipolar transistors (HBTs) is presented. Compared with SPICE Gummel-Poon model, the proposed model has taken into account the self-heating effects, which is important for large-signal operations. The model includes a new base-collector breakdown description, which has taken the current dependence into account. This model allows exact modeling of all transistor parameters from single emitter size cells to other size devices. The scaling rules are shown in detail. The model is verified by the SiGe HBTs with emitter area of 0.3 × 20.3, 0.3 × 13.9, 0.3 × 9.9, and 0.3 × 1.9 um². Excellent agreement has been achieved between modeled and measured data over a wide range of bias conditions and signal frequencies. The model has been implemented in Verilog-A using the ADS circuit simulator. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

This article reports the design and development of high power, low cross-polarization, and high efficiency circularly polarized microstrip patch array antenna at S-band, proposed for Indian Regional Navigation Satellite System payload. A novel feeding mechanism for truncated corner square patch based on square coaxial line for broadband impedance matching is discussed. Sequential rotation scheme for axial ratio improvement in an array is implemented. High power handling margins in critical regions of square coaxial line for multipaction breakdown is brought out. Measured 19 dB return loss bandwidth of array antenna is 15.6%. Axial ratio of 0.78 dB over global coverage is achieved in the desired frequency band of operation. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

This article describes an implementation of a compact wire model into the three-dimensional transmission-line matrix (TLM) cylindrical mesh for the purpose of an efficient analysis of probe-coupled cylindrical microwave cavity devices. Because of a cylindrical grid structure and empirical nature of the compact model, this implementation has to take into account a change of wire model parameters with a variable cross section of the TLM nodes through which a wire conductor passes. The model accuracy has been experimentally verified and compared with the corresponding results reached by the TLM method based on a rectangular grid in order to consider its advantages. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

This article combines the Galerkin method of moments with the complex image technique to find the current distribution, input impedance, return loss, and frequency bandwidth of a half-wave dipole near a human head. It also finds the specific absorption rate distribution inside the human head which is modeled as three planar layers of lossy dielectrics. Comparisons with IE3D commercial simulator verify the accuracy and speed of the proposed method. It is found that the input resistance of the dipole is significantly reduced as the dipole is brought closer to the human head causing a reduction in the frequency bandwidth. The proposed method can be modified to solve other types of antennas on different human head planar geometries. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

Dynamic differential evolution (DDE) for shape reconstruction of perfect conducting cylinder buried in a half-space is presented. Assume that a conducting cylinder of unknown shape is buried in one half-space and scatters the field incident from another half-space where the scattered filed is measured. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem. The inverse problem is resolved by an optimization approach, and the global searching scheme DDE is then used to search the parameter space. Numerical results demonstrate that even when the initial guess is far away from the exact one, good reconstruction can be obtained by using DDE both with and without the additive Gaussian noise. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

A method for mitigating the return loss and crosstalk corresponding to coupled vias is presented in this article. The method is based on selecting the proper dimensions for the antipad holes related to vias as well as the most adequate distribution of the ground vias, which allows to simultaneously reducing impedance mismatch and undesirable via coupling. The usefulness of the method is demonstrated by improving the performance of a 2 × 3 array of six signal vias. As a result, return loss levels below −45 dB and crosstalk levels below −40 dB are obtained in the 0–50 GHz frequency range. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

Simulation-based optimization has become an important design tool in microwave engineering. However, using electromagnetic (EM) solvers in the design process is a challenging task, primarily due to a high-computational cost of an accurate EM simulation. In this article, we present a review of EM-based design optimization techniques exploiting response-corrected physically based low-fidelity models. The surrogate models created through such a correction can be used to yield a reasonable approximation of the optimal design of the computationally expensive structure under consideration (high-fidelity model). Several approaches using this idea are reviewed including output space mapping, manifold mapping, adaptive response correction, and shape-preserving response prediction. A common feature of these methods is that they are easy to implement and computationally efficient. Application examples are provided. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

A novel composite right-/left-handed transmission line (CRLH TL) and its equivalent circuit model are proposed based on cascaded complementary single split ring resonator (CCSSRR). It features an intrinsically balanced wider band and an additional transmission zero above the right-handed band relative to CRLH TL using complementary single split ring resonator and complementary split ring resonators. Moreover, two single negative (SN) metamaterial (MTM) TLs constructed by using complementary electric inductive-capacitive resonator on the conductor strip and on the ground, respectively, are researched. Both SN MTM TLs exhibit electric resonance above the fundamental magnetic resonance. For application, a monoband (MB) bandpass filter (BPF) covered WLAN band, and a dual-band (DB) BPF covered satellite DMB band and WiMAX band are designed, fabricated, and measured. The SN MTM TLs are adopted for the sake of deep and wide out-of-band suppression while CRLH MTM TLs using square-shaped and Sierpinski-shaped CCSSRR are critical factors of the MB and DB behavior. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

This article demonstrates novel ideas for mitigation of far-end as well as near-end crosstalk in coupled pair microstrip lines (CPMLs) by means of defected microstrip structure (DMS). Simple equations and models for analysis and design of a DMS are presented and extracted. Different configurations of DMS-CPMLs are introduced, and their performances in crosstalk reduction are compared. Finally, the best configuration for far-end crosstalk reduction is fabricated and tested. A maximum of 35 dB reduction in far-end and 38 dB reduction in near-end crosstalk are achieved. The signal integrity performance of the structure is also verified by eye-diagrams. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

In this paper, a design methodology combining coupling matrix representation of filters, neural models and space-mapping techniques is presented for further enhancement of optimization efficency of microwave filters. Neural models are developed for both initial dimension generation and design parameter sensitivity analysis. Combining neural models of filter substructures with space-mapping optimization, the total number of EM simulations of the complete filter structure is significantly reduced. The improvement in efficiency over conventional method is demonstrated using simulation and measurement results of both end-coupled and side-coupled waveguide dual-mode pseudo-elliptic filters. The total CPU times for design and optimization are reduced by 50% to 70 %.© 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

In this study, a new technique is presented to reduce the dimensions of a strip line monopole antenna. A combination of stub-loaded and defected microstrip structure (DMS) methods are employed to design and built a prototype of a reduced planar monopole performing at UHF band (650 MHz). The method allows achieving a size reduction close to 50%, without modifying, significantly, the parameters of the antenna, including gain, radiation pattern, and polarization. The antenna is suitable to perform in personal communications and can be the basis to extrapolate the application to planar arrays. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

The dynamic differential evolution (DDE) is used to synthesize the radiation pattern of the directional circular arc array to minimize the bit error rate (BER) performance in indoor ultrawideband (UWB) communication system. Using the impulse response of multipath channel, the BER performance of the synthesized antenna pattern on binary pulse amplitude modulation system can be calculated. Based on the topography of the circular antenna array and the BER formula, the array pattern synthesis problem can be reformulated into an optimization problem and solved by the DDE algorithm. The novelties of our approach are not only choosing BER as the object function instead of sidelobe level of the antenna pattern but also considering the antenna feed length effect of each array element. The strong point of the DDE algorithm is that it can find out the solution even if the performance index cannot be formulated by simple equations. Simulation results show that the synthesized antenna array pattern is effective to focus maximum gain to the line of site path which scales as the number of array elements. In other words, the receiver can increase the received signal energy to noise ratio. The synthesized array pattern also can mitigate severe multipath fading in complex propagation environment. As a result, the BER can be reduced substantially in indoor UWB communication system. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

In this article, we present an efficient technique for the accurate design of wideband substrate integrate waveguide directional couplers. By tapering the coupling section, the bandwidth of substrate integrated waveguide (SIW) directional couplers can be enlarged. Two design aspects are involved in this approach. First, the even-mode propagation constant in the tapered coupling section is accurately extracted with the help of a numerical thru-reflect-line calibration technique. Then, it is fitted into the model of a uniform dielectric-filled rectangular waveguide and thereafter extrapolated to the operation range of the odd mode. Second, equivalent circuit models of the waveguide bifurcation effects are also presented together with parametric values. Based on the results of extraction, a 90° 3-dB directional coupler is developed to validate the proposed design approach. To achieve the reverse phasing at two output ports, the prototyped 90° 3-dB directional coupler is subsequently integrated with a novel broadband fixed phase shifter developed with the SIW technology, of which a systematic synthesis procedure has been proposed in this article. Measured performance of both 90° and 180° 3-dB couplers confirms the accuracy of our proposed design approach. This kind of wide-band directional coupler can find applications in wideband power dividing/combining circuits within a single-layer platform. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

A novel single probe-fed circularly polarized (CP) microstrip antenna design for global positioning system application is proposed. To achieve good CP radiation at 1575 MHz, two circular slots of dissimilar sizes are embedded separately into the radiating element and the ground plane. This CP design possesses the advantages such as simple in structure, uncomplicated fine-tuning technique, and ease in manufacturing tolerances. Parametric studies via simulation are carried out to comprehend the vital parameters that will affect the impedance matching and frequency of the CP radiation. Prototypes of the proposed antenna have been constructed and experimentally studied. The measured results show a 10-dB bandwidth and 3-dB axial ratio bandwidth of 2.28 and 0.89%, respectively. Furthermore, stable gain variation at around 3.6 dBic is also observed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

This article proposes a new method to estimate and compensate for the in-phase and quadrature (IQ) imbalance errors of the quadrature modulator (QM) and demodulator (QDM) without interrupting the transmission. It uses two groups of captured signals, which transmit through two feedback loops with different propagation delays, to separate and estimate the IQ imbalance errors. In comparison with the previous methods, the greatest advantage of the proposed method is that both compensators of the QM and QDM can be obtained without additional feedback loop, and then the digital predistorter can be designed without the disturbance of IQ imbalance errors. This method can improve the compensation performance of digital predistortion with lower costs and less complexity. Experimental results show the correctness and effectiveness of the proposed method. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

A compact realization of composite low-pass filter is presented in this article. The filter is realized using on-chip spiral inductors and metal–insulator–metal capacitors and features an attenuation pole near the cutoff frequency leading to a sharper attenuation response. As well, it offers good matching properties in the passband. Space-mapping-based algorithm is used in the design/optimization of spiral inductors toward achieving high quality factors at the filter cutoff frequency. The realization of the proposed filter is compact in size, suitable for monolithic microwave integrated circuit applications, and exhibit broad upper stopband frequency characteristics. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

This article emphasizes cooperative work between a public research laboratory (XLIM) and an industrial company specialized in space technologies (Thales Alenia Space) for the development of advanced computer-aided design (CAD) solutions. In particular, the article reviews two computer-aided techniques that have been developed through collaborative research programs then integrated into industrial design flows. The first technique is devoted to the design of microwave filters and is based on coupling parameter extraction from simulated/measured data. The second technique consists in developing a CAD library of generic elements based on artificial neural networks for the packaging of multichip modules. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

A robust algorithm for simulation-driven design optimization of microwave structures evaluated using CST MICROWAVE STUDIO^® is described. The algorithm exploits gradient information obtained using adjoint sensitivity (if available) or finite differentiation. It also uses trust region approach that ensures good convergence properties and improves the overall performance. The efficiency of our approach is demonstrated using several examples of microwave structures. We also discuss an extension of the algorithm where the sensitivity of complex-valued responses rather than of the real-valued ones is used. A performance comparison with other optimization techniques is also provided. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

We propose a new parametric macromodeling technique for complex electromagnetic (EM) systems described by scattering parameters, which are parameterized by multiple design variables such as layout or substrate feature. The proposed technique is based on an efficient and reliable combination of rational identification, a procedure to find scaling and frequency shifting system coefficients, and positive interpolation schemes. Parametric macromodels can be used for efficient and accurate design space exploration and optimization. A design optimization example for a complex EM system is used to validate the proposed parametric macromodeling technique in a practical design process flow. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

In this article, we propose a sensitivity based correction model that improves the accuracy of the neural model keeping the structure of artificial neural network (ANN) simple. The proposed approach is applied to the modeling of RF transistors, spiral inductors, and microstrip antennas. Results are compared with conventional ANN and a recent technique referred to as correction model that is assisted by the regula-falsi method. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

An RCLK modeling technique has been proposed for intended and parasitic inductance in silicon ICs, providing rapid extraction times. To tackle netlist size and passivity issues, passivity enforcement techniques are presented in this article based on eigenvalue decomposition and bandwidth reduction of the inductance matrix. Runtime performance of the RCLK modeling method is reported for the first time, applied to realistic 65 nm CMOS circuits, while the computational overhead of passivity enforcement is given. The proposed techniques can reduce netlists between 41% and 96% in the cases presented, while runtimes for passivity enforcement can be improved by 85% or better, compared with eigenvalue decomposition of a full inductance matrix. These results indicate that full inductance modeling of silicon circuitry becomes practical, resolving the bottleneck facing other known electromagnetic simulation methods. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

A new constrained space mapping algorithm is presented. This algorithm is based on aggressive space mapping type algorithm. Orthogonal projection is used to handle the constraints. The new method has advantage of simplicity without sacrificing mathematical robustness of space mapping. Proof of the convergence of the proposed method for convex constraints case is presented. Modified Broyden's method is used to improve the method's stability. The proposed algorithm is used to optimize a multilayer low-temperature cofired ceramic bandpass filter. Parameter extraction is done using circuit tuning based on physical augmentation. The results show the proposed algorithm is effective and efficient. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

In this article, we introduce an effective approach for dynamic impedance tuning of antenna matching circuits in both the transmitting and receiving modes. The tuning problem is described mathematically by a system of two nonlinear equations. These nonlinear equations are constructed by perturbing the tunable components of the matching circuit. We introduce a closed form solution to the proposed system of equations in addition to a numerical one. The outcome of our algorithm is the exact calculation of the instantaneous antenna input impedance. This impedance is then used to determine the optimal matching circuit values. The proposed algorithm takes place on the handset in real-time. Additionally, it does not limit the number of tunable components of the tunable matching circuit as the computational overhead is independent of their cardinality. The proposed approach can also be expanded to the case of real-time broadband tuning of antennas in a dynamic environment. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

A sectoral Sierpinski Gasket fractal (SSGF) antenna is proposed for dual-band operation with wide-bandwidth covering GPS, DCS-1800, PCS-1800, UMTS, IMT-2000, Wireless broadband Internet Services (WiBro), Bluetooth, and WLAN bands. The SSGF antenna consists of volume 65.5 × 27 × 1.6 mm³. To analyze its performance, measurements are carried out. The proposed antenna model exhibits resonances in 1.51–3.39 GHz (2:1 VSWR BW 76.6%) and 5.31–6.32 GHz (2:1 VSWR BW 17.3%) bands with 2.5–5 dBi gain. Very good agreement is obtained between simulation and experimental results. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

Two different tri-band microstrip patch antenna designs are presented. Antennas are designed and simulated using the commercial simulation Sonnet Suites [(Sonnet Software, version: 12.56 www.sonnetsoftware.com (2009)] and simulated results are compared against measurements in detail. Target application of the first design is radar systems in IEEE 802.11, wireless communications in wireless local area network and worldwide interoperability for microwave access bands. The second tri-resonance antenna is designed to operate in the 9–13 GHz band and comparisons between simulations and measurements are presented. Results show three resonance frequencies at which design presented herein achieves return loss better than 30 dB with the maximum 10 dB return loss bandwidth of 4%. Resonance frequencies are 9.52, 10.66, and 12.60 GHz, which meets the design specification of covering the X-band. A detailed parametric study of the geometry, dielectric thickness, and dielectric constant is also provided. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

A novel design for a 3 dB Lange coupler based on complementary deformed omega structure (CDOS) is proposed. Observations, from parametric study for the CDOS based Lange coupler, are provided to aid in the design process. A functional linked artificial neural network has been used to determine the dimensions of the CDOS. Electromagnetic simulations have been validated with experimental results obtained from fabricated prototypes. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

This article aims at the industry interest on automated design tools that are able to take into account manufacturing effects. First, an efficient design strategy for bandpass waveguide filters including the rounded corners arising from low-cost manufacturing procedures is presented. This technique is based on a recent enhanced prototype and synthesis methodology able to consider the real structure parts. Using the resulting electromagnetic (EM)-based synthesis technique, an excellent structure is extracted, which requires, at most, only a slight final EM optimization. Second, this article presents analytical expressions providing error estimates for the different filter performances in terms of manufacturing tolerances. From such expressions, designers can determine the tolerance to be requested for a tuning-less implementation. Moreover, they can also be used to set the convergence criterion for the synthesis procedure. A fully automated design tool of bandpass waveguide filters able to consider manufacturing impairments has been developed and integrated in the commercial software Full-wave EM Simulation Tool 3D (FEST 3D). © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

Package and PCB-system aware IC co-design and verification entail early awareness of the impact of signal integrity, power integrity, timing, and electromagnetic interference (EMI) impact on functionality and performance. Higher frequencies, along with stringent EMC regulations, are driving the need for developing EMI-aware design methodologies in early and sign-off phases of design cycles. This article discusses the significant challenges of scale, connectivity, turnaround time, and accuracy needed in developing such a flow. In particular, the numerical effect of violating established EMI guidelines is quantified in the flow, enabling cutting-edge designs that are less conservative and still satisfy EMI constraints. The role of rigorous large-scale 3D full-wave electromagnetic simulation in developing such a full-system EMI prediction and early design flow is discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

In this article, an efficient full-wave-mode algorithm has been developed to efficiently address industrial needs for rigorous characterization of electromagnetic compatibility shielding effects in anisotropic high-temperature superconducting microwave devices on lossy anisotropic dielectric substrates in multilayer configuration. Finite thickness and conductivity as well as anisotropy of the superconducting films have been investigated. The proposed formulation uses the spectral domain dyadic Green's functions for stratified media. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

Approximate closed-form expressions for the propagation characteristics of a microstrip line with a symmetrical aperture in its ground plane are reported in this article. Well-known expressions for the characteristic impedance of a regular microstrip line have been modified to incorporate the effect of this aperture. The accuracy of these expressions for various values of substrate thickness, permittivity and line width has been studied in detail by fullwave simulations. This has been further verified by measurements. These expressions are easier to compute and find immense use in the design of broadband filters, tight couplers, power dividers, transformers, delay lines, and matching circuits. A broadband filter with aperture in ground plane is demonstrated in this article. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

In this article, the quasi-TEM approach is successfully used to analyze coupled-microstrip lines of finite length, which are usually used for the coupling between the source/load and resonators in microstrip filters. First, an orthogonal expansion method is used to extract the per-length inductance and capacitance matrices. The authors then obtain the impedance matrix or admittance matrix, which relates the voltages and currents at both ends of coupled-microstrip lines. To verify our theory, an example is presented, i.e., a Y-shaped dual-mode bandpass microstrip filter, for which, the equivalent circuit model based on the quasi-TEM analysis of coupled-microstrip lines is accurately set up. The approach in this article is applicable to planar microstrip lines with arbitrary number of conductors, under the quasi-TEM assumption. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.