Suspended Microstrip Research Articles

Computer-aided-design (CAD) of suspended-substrate microstrips: An overview

The arrival of electromagnetic (EM) simulation tools has not eclipsed the relevance of CAD models for microwave and millimeter-wave integrated circuits. In this article, an overview of the existing CAD models for suspended and inverted microstrips is presented. Comparisons of the various CAD models with rigorously obtained theoretical data are presented, followed by comparisons against available experimental data. Areas needing further research are also identified. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.

Simple models based on neural networks for suspended and inverted microstrip lines

AbstractThis paper presents new and simple models based on artificial neural networks (ANNs) to determine the effective permittivities of suspended microstrip (SM) and inverted microstrip (IM) lines. The neural results are in very good agreement with the theoretical and experimental results available in the literature for both SM and IM lines. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 383–389, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11225

Wideband dielectric resonator‐loaded suspended microstrip patch antennas

AbstractExperimental investigations of rectangular and circular suspended microstrip patch antennas with dielectric resonator loading at X‐band are reported. With loading, enhanced impedance bandwidth to about 18% is achieved in a single circular patch as compared to 13% for a single rectangular patch. In both cases, with loading, there is practically no change in the respective 3‐dB beam widths of the radiation patterns in E‐ and H‐planes. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 300–302, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10900

On the design of novel compact broad-band planar filters

On the basis of impedance steps and coupled-line sections as inverter circuits, novel wide-band and very compact filters are presented. The application of alternately high- and low-impedance lines presented to the connected transmission-line resonators partly reduces their lengths to a quarter-wavelength only. In addition, effective techniques are demonstrated to reduce spurious stopband resonance resulting from a remaining half-wavelength resonator. Both suspended stripline (SSL) and microstrip filters were designed, fabricated, and tested, proving this concept in an excellent way. For the prototype filters, center frequencies around 6 GHz were selected. Bandwidths are between 2.5-3.25 GHz, and insertion-loss amounts to around 0.25 dB for the microstrip filters and 0.5 dB (including the transitions to coaxial line) for the SSL filters, respectively. For the selected center frequency and on a substrate with a dielectric constant of 10.8, the smallest microstrip filter is only 15 mm/spl times/5 mm in size.

Fourier transform analysis of a unilateral fin line and its derivatives

A unilateral fin line and its derivatives are analysed utilising the Fourier transform and mode-matching. The image theorem is used to transform a unilateral fin line into an infinite number of suspended substrate microstrip lines. New rigorous dispersion relations are obtained in fast-convergent series, which are efficient for numerical computation. Calculations are performed to illustrate the rate of convergence and accuracy of the series solution.

Broadband suspended patch antennas with ground taper transformer

A novel ground taper has been designed and then fabricated using a laser cutter. The taper is used to match the transition between a suspended microstrip line and a microstrip line. This transition is used in the design of a 25 GHz suspended patch antenna deposited onto a polyimide tape and yields an 18% fractional bandwidth.

Third-order intermodulation distortion inYBa2Cu3O7−δgrain boundaries

Results are presented on the microwave intermodulation distortion (IMD) measured in high-temperature-superconducting ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ engineered grain boundaries fabricated on bicrystal substrates. The two-tone IMD at 4.4 GHz of thin YBCO plain films without engineered grain boundaries and films with engineered bicrystal grain boundaries of misorientation angles from $2\ifmmode^\circ\else\textdegree\fi{}$ to $24\ifmmode^\circ\else\textdegree\fi{}$ was measured as a function of microwave power and temperature in a suspended microstrip resonator configuration. The microwave power dependence of the IMD of the plain films and the films with grain boundaries is compared. The long Josephson-junction effects of high-angle grain boundaries were studied. The connection between the results for the microwave impedance of YBCO grain boundaries and for the IMD has been modeled. We find that for grain boundaries of less than 7.5\ifmmode^\circ\else\textdegree\fi{}, the IMD is indistinguishable from that of the plain film.

Input impedance of probe‐fed multilayer rectangular microstrip patch antenna using the modified Wolff model

AbstractThe modified Wolff model (MWM)‐based cavity model is presented for the simple and accurate computation of the input impedance of a probe‐fed multilayer rectangular microstrip patch antenna. Results of the MWM are compared with both the experimental data and data of the MoM, with agreement within 1.5% for resonance frequency and within 0.15 for normalized input impedance. Further results are presented on the input impedance of a suspended rectangular microstrip patch antenna with a two‐layer superstrate. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 237–239, 2001.

Fast microchannel plate detector with an impedance matched anode in suspended substrate technology

Fast particle detectors with subnanosecond pulse widths are key elements in modern time-of-flight mass spectrometers. Typically, an impedance matched transmission line from the extended anode to the coaxial cable is necessary to obtain fast pulses. We present an approach using a planar geometry for the transmission line. Thereby, the impedance match is realized with a transition from a 50 Ω suspended substrate microstrip line to a coaxial 50 Ω line. A prototype with an active area of 1.8 cm diameter including a strategy to reduce peak ringing was built and tested. The mean pulse width measured with a 1 GHz analog oscilloscope was 520 ps (full width at half maximum) with a rise time of 380 ps. The robust, compact, and low-weight design of the detector is well suited for an application in space, where weight, space, and power consumption are very limited resources.

Microwave and millimeter‐wave high‐Q micromachined resonators

Alternative techniques for integrating high-quality factor resonators using micromachining techniques have been investigated. Two methods are presented which include suspending microstrip lines on thin dielectric membranes, resulting in an effective dielectric constant of near unity, and integrating three-dimensional micromachined waveguide cavity resonators with planar feedlines. These resonators show large improvements in quality factor over conventional techniques, and more importantly, allow for planar integration in complex systems. Resonators were fabricated in suspended microstrip at 29, 37, and 62 GHz with quality factors of over 450 with very close agreement between simulated and measured results. An integrated micromachined cavity resonator was also fabricated with a TE011 resonance quality factor of 1117 at 24 GHz and a TE021 resonance quality factor of 1163 at 38 GHz. To the authors' knowledge, these are the highest quality factor planar resonators without the use of superconductive materials, and can be used in microwave and millimeter-wave low-loss filters and low-phase-noise oscillators. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 326–337, 1999.

Microwave and millimeter-wave high-Q micromachined resonators

Alternative techniques for integrating high-quality factor resonators using micromachining techniques have been investigated. Two methods are presented which include suspending microstrip lines on thin dielectric membranes, resulting in an effective dielectric constant of near unity, and integrating three-dimensional micromachined waveguide cavity resonators with planar feedlines. These resonators show large improvements in quality factor over conventional techniques, and more importantly, allow for planar integration in complex systems. Resonators were fabricated in suspended microstrip at 29, 37, and 62 GHz with quality factors of over 450 with very close agreement between simulated and measured results. An integrated micromachined cavity resonator was also fabricated with a TE011 resonance quality factor of 1117 at 24 GHz and a TE021 resonance quality factor of 1163 at 38 GHz. To the authors' knowledge, these are the highest quality factor planar resonators without the use of superconductive materials, and can be used in microwave and millimeter-wave low-loss filters and low-phase-noise oscillators. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 326–337, 1999.

Ku-band double-sided suspended substrate microstripcoupled-line bandpass filter

A Ku-band double-sided suspended substrate microstrip (DSSSM) coupled-line bandpass filter with less than 2 dB insertion loss is presented. The design utilises five sections and is specified to be centred at 15 GHz with a moderate 10% bandwidth which is fabricated on an alumina substrate (ɛr = 9.9, h = 0.381 mm and airgap = 0.381 mm). The versatile configuration of the DSSSM provides a significant size reduction with easily realisable bandwidths due to a wider range of couplings obtainable from the overlapping (nonoverlapping) sections as compared to conventional suspended substrate microstrip.

Distortion in Gaussian pulse on microstrip-like transmission lines

Distortion in the Gaussian pulse on the shielded, suspended, and composite substrate microstrip line has been analyzed by using newly developed closed-form expressions. Practically distortion-free pulses could be obtained on the suspended microstrip line, and in the practical range of interest, the thickness of the passivation layer has no effect on the distortion in the pulse on the GaAs–polyimide substrate. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 253–255, 1998.

On the analysis of three parallel-coupled suspended strip lines and microstrip lines in an inhomogeneous isotropic medium

A variational method in the Fourier-transform domain is used to analyze three coupled symmetric suspended strip lines and microstrip lines having different strip widths in an inhomogeneous isotropic medium. Variational expressions characterizing the capacitances per unit length of the three-coupled-line structure are derived. Numerical results for the mode characteristic impedances and effective dielectric constants are presented and discussed. Results for the special case of three open microstrip lines with equal widths are compared with published data to confirm the analysis. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 16: 307–312, 1997.

A closed-form dispersion model for millimeter-wave suspended microstrip lines

A closed-form dispersion model for millimeter-wave suspended microstrip lines

A general formulation for connecting sources and passive lumped-circuit elements across multiple 3-D FDTD cells

A previous extension of the finite-difference time-domain (FDTD) method to include lumpedcircuit elements is further extended to model lumped-element circuits connected across multiple FDTD cells. This formulation is needed to model many kinds of circuits, like those with a transistor or other active device connected across a transmission line with more than one dielectric. The FDTD analysis of a shielded suspended microstrip transmission line excited by a current source in parallel with a resistance illustrates the usefulness of the formulation.

CAD models for suspended and inverted microstrip

The accuracies of CAD models for suspended and inverted microstrip are examined, and new models are proposed. The models are compared over the range of 0.1/spl les/w/h/spl les/10 and for /spl epsiv//sub r/ values of 3.78 and 12.9. Of the three models examined, the Tomar and Bhartia (T&B) model is shown to be the most accurate. For /spl epsiv//sub r/=12.9 (the worst case), the T&B model shows maximum and average errors of 2.94 and 1.28% respectively over its valid range. New CAD models are presented which demonstrate significantly improved accuracy and range of convergence. For suspended and inverted microstrip, the new models demonstrate worst case errors of 0.65 and 1.02%, respectively, and average errors of 0.23 and 0.27%, respectively. Further, the new models are valid for the full 0.1/spl les/w/h/spl les/10 range, and unlike the other models, converge for the limiting cases of either complete substrate filling or a zero thickness substrate.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis, synthesis, and experimental validation of a new type of microstrip transition

This paper presents the theoretical analysis, synthesis, and experimental validation of a wideband transition between a conventional microstrip line and a microstrip line printed on a double-layer substrate. This transition is useful to link conventional microstrip circuits to certain special configurations fabricated on double-layer substrates. A particular case of generic interest is the transition between microstrip and suspended microstrip technologies. The analysis is carried out by using an enhanced version of the spectral domain analysis (SDA) that leads to computer codes quick enough to be used in an optimization design program. >

Determination of the open‐end discontinuity and resonance frequency of a suspended microstrip using the slr technique

AbstractThis article presents a model, called the EKJK model, to determine the open‐end discontinuity of a suspended microstrip line. The accuracy of the model is confirmed within 2% compared to the computed resonance frequency by this model and by the SDA. The effects of the width of the line and top shield on the resonance frequency of the suspended line resonator are also reported. © 1994 John Wiley &amp; Sons, Inc.

Design of impedance-transforming microstrip-balanced stripline tapered transitions

An improved approach to the computer-aided modelling of impedance-transforming microstrip-balanced stripline tapers used in microwave doubly balanced mixers is presented. The spectral domain method has been used to determine the parameters of a suspended microstrip with finite ground plane width. Calculations show that dispersion effects in the analysed structure are insignificant. The designed and realised 50–100ω transition on a 1.5mm thick alumina substrate exhibited very good or acceptable performance up to 10 and 15GHz, respectively. A method to suppress undesired modes appearing in the case of shielded transitions has been proposed and experimentally verified.