Microstrip Substrate Research Articles

Realization of a Second Harmonic Antenna for Rural Communications

In this research, an active antenna operated at the second harmonic frequency is investigated, and is implemented using microstrip antenna material. The antenna consists of a FET oscillator which plays as a fundamental frequency oscillator and a frequency multiplier, and a patch antenna resonated at the second harmonic frequency as the radiator. A maximum second-harmonic output power can be extracted when the load impedance of the oscillator is optimized both at the fundamental and at the second harmonic frequencies. A rectangular patch antenna is used to radiate the second harmonic output power from the oscillator. The patch impedance is matched resistively at the second harmonic frequency. The patch antenna is fabricated using Diclad 522 microstrip substrates (relative permitivity er = 2.5) with a dielectric thickness of 1.57 mm. A GaAs FET AT- 8250 transistor is used as an oscillator and a frequency multiplier and acts as the active component. Fundamental frequency is designed at 2,4 GHz band, so that the second harmonic frequency operates at 4,8 GHz band. The frequency is chosen to facilitate and to extend the needs of communications in rural areas using the unlicensed Industrial Scientific, and Medical (ISM) band. Operating the communication infrastructures intended for the use at 2.4 GHz band at its second harmonic frequency, is intended to alleviate interference levels at 2.4 GHz.

Microstrip Patch Antenna With Defected Ground Structure for Cross Polarization Suppression

A defected ground structure (DGS) is proposed to reduce the cross-polarized (XP) radiation of a microstrip patch antenna. The proposed DGS pattern is simple and easy to etch on a commercial microstrip substrate. This will only reduce the XP radiation field without affecting the dominant mode input impedance and co-polarized radiation patterns of a conventional antenna. The new concept has been examined and verified experimentally for a particular DGS pattern employing a circular patch as the radiator. Both simulation and experimental results are presented.

Temperature-compensated frequency discriminator based on dielectric resonator

A planar circuit realisation of the Pound-type frequency discriminator has been implemented with a dielectric resonator in a microstrip environment. By taking advantage of the nature of the planar geometry, the circuit is further simplified and the original performance is maintained. Various frequency discriminators with centre frequencies around 4.2 GHz have been constructed and tested. It is demonstrated with analytical models and substantiated by measurement results that the dielectric resonator, with its own temperature coefficient of the resonant frequency, offers a degree of freedom that proves to be effective for temperature compensation in the design of the frequency discriminator. A temperature coefficient of 3.6 ppm/°C for the centre frequency is achieved with readily available dielectric resonator and substrate material from commercial sources. Further improvement of the system thermal stability can be obtained by tailoring the thermal property of the dielectric resonator to the chosen microstrip substrate.

Fast calculation of the propagation constants of leaky and Berenger modes of planar and circular dielectric waveguides terminated by a perfectly matched layer

AbstractA fast technique is proposed to determine the complex propagation constants of the leaky and Berenger modes of circular dielectric waveguides terminated by a perfectly matched layer (PML). The method relies on a coordinate transformation in the complex plane and uses the approximate analytical solutions of the dispersion relations as a first estimate. The efficiency of the technique is shown for a microstrip substrate and a VCSEL configuration, both terminated by a perfectly matched layer. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 167–171, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10857

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.

Convergence behavior and acceleration of the Berenger and leaky modes series composing the 2-D Green's function for the microstrip substrate

The Green's functions G/sub A/ and G/sub V/ are calculated for a two-dimensional microstrip substrate by placing the substrate into a closed perfectly-matched-layer waveguide and by performing a modal expansion in Berenger and leaky modes. It is shown that each series composing G/sub A/ and G/sub V/ has a particular convergence behavior when considering small lateral distances between the excitation and the observation points. It is then demonstrated that, by applying the Shanks transform to accelerate each series separately, a more efficient calculation for the Green's functions can be obtained than by direct computation of the series. The theory is illustrated by means of a representative example.

Numerical modeling of microstriplines with substrates with arbitrarily varying thickness with the use of the TLM method

AbstractThe symmetrical condensed‐node TLM method is used for the analysis of microstrip lines with substrates of arbitrary varying thickness. This numerical technique has been efficiently used for the computation of the propagation constant and the characteristic impedance of this structure. Moreover, it has been demonstrated that the shape of the microstrip substrate is also an important parameter for controlling the values of its characteristic impedance. The validity of the obtained results is proved by comparisons with those obtained from the literature. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 48–51, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10369

A fast technique based on perfectly matched layers to model electromagnetic scattering from wires embedded in substrates

A two‐dimensional integral equation formulation is used to model electromagnetic scattering from metallic structures embedded in substrates. The new method involves a fast evaluation scheme for the Green's function of the substrate by using perfectly matched layers to obtain closed‐form expressions as a series of leaky and Berenger modes. Efficient summation of these series is performed by means of the Shanks transform. The modal series can be applied to calculate all interactions, except for the self‐patch contribution. The latter can be approximated with good accuracy by using the closed‐form quasi‐static part of the Green's function. The new technique is illustrated by studying scattering from wires embedded in a microstrip substrate.

Singular behavior of the Berenger and leaky‐modes series composing the 2D Green's function for the microstrip substrate

AbstractThe singular behavior of the modal expansions is examined in Berenger and leaky modes for the Green's functions GA and GV of a 2D microstrip substrate. When the excitation point approaches the source point, and both are lying in the microstrip substrate, the Green's function exhibits a singularity that corresponds to the open configuration without a perfectly matched layer. This observation remains valid when one or both points are lying on the substrate–air interface, unless GA is being considered for a nonmagnetic (μr = 1) substrate. In the latter case a different singularity is obtained when both excitation point and source point are lying on the interface. That singularity is of a higher order and depends on the characteristics of the PML. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 87–93, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10244

Berenger and leaky modes in microstrip substrates terminated by a perfectly matched layer

In this paper, it is shown that the dispersion relation of a microstrip substrate terminated by a perfectly matched layer (PML) allows two sets of zeros. For a strongly absorbing PML, the first set does not depend on the characteristics of that layer. Within a good approximation, it corresponds to the leaky modes of the microstrip substrate. The second set is not influenced by the microstrip substrate. Since it mainly depends on the characteristics of the PML, this set of modes are called the Berenger modes. Analytic expressions are derived for these two sets of zeros in the quasi-static limit.

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.

3-D Green's functions of microstrip separated into simpler terms-behavior, mutual interaction and formulas of the terms

Green's functions of microstrip substrate are important for microwave integrated circuit (MIC) analyses. Much work has been done by many researchers with successes over the years in gaining greater insight and simplifications into this complicated problem. This paper continues this trend with further simplification by arriving at formulas with insight for the Green's functions, both scalar and vector. Each Green's function is separated into three terms, namely: the quasi-dynamic, leaky wave, and surface wave. Practical MIC circuits require low surface-wave loss. This means that the formulas are constructed for frequencies low enough that with only the fundamental TM/sub 0/ surface-wave mode propagating. Formulas of dominant terms are emphasized. The formulas are accurate, with estimated errors from 1% to 2%. An important behavior observed is that the surface wave rises rapidly with frequency, at the four power even at low frequencies.

Small H-shaped antennas for MMIC applications

A small short-circuited H-shaped GaAs monolithic microwave integrated circuits (MMICs) patch antenna is presented. Resonant at 5.98 GHz, it is the lowest frequency MMIC patch antenna reported that we are aware of and is intended for short-range communications (e.g., vehicular). Initial experimental and theoretical characterization of the proposed structure has been carried out on soft microstrip substrates. It has been shown that the size of an H-shaped patch antenna can be reduced to as low as one tenth of that of a half wavelength patch antenna resonant at the same frequency, saving valuable substrate space. The resonance frequency, radiation patterns and gain have been investigated. Ground plane truncation effects, which are important for MMIC applications, have been examined using the finite-difference time-domain (FDTD) method.

Co-layered integration and interconnect of planar circuits and nonradiative dielectric (NRD) waveguide

A concept of hybrid integration between planar circuits and a nonradiative dielectric (NRD) waveguide is proposed in this paper with preliminary experiments. This approach utilizes co-layered arrangement of the two dissimilar structures, which allows the NRD-guide in direct contact with (or surface mounted on) the planar circuits. Two basic building-block schemes are presented that involve microstrip line and coplanar waveguide (CPW) with the NRD-guide. The first is to deposit the NRD-guide on the top of a relatively thin microstrip substrate, thus forming unbalanced NRD-guiding hybrid circuits, while the second is to design CPW circuits directly etched on the ground planes of the NRD-guide. The unbalanced NRD-guide is subject to a certain leakage loss, but at a negligible level, and it may even be suppressed completely in certain circumstances. Such an integration technique is found consistent with the concept of low loss interconnects at millimeter-wave frequencies. In other words, the NRD-guide can be used for viable interconnects of co-layered planar circuits with a simple "put and cover" procedure. Measured results of several co-layered hybrid transitions/baluns indicate that satisfactory transmission properties can readily be achieved. The new building blocks are expected to provide an alternative design approach to three-dimensional multilayered millimeter-wave circuits and systems.

Broadband microstrip to dielectric image line transitions

Novel broadband microstrip to dielectric image line (DIL) transitions have been developed. A conducting strip is flared linearly from the microstrip line to the DIL. The DIL and microstrip substrate are on the same side of their common ground plane. Theoretical simulation results, obtained by using the finite-difference time-domain method, agree well with experimental results. The transitions should have applications in the integration of the dielectric image line with microwave integrated circuits (MICs) and monolithic microwave integrated circuits (MMICs).

Study of a dielectric‐loaded slot antenna fed by a finite‐width substrate microstrip line

A dielectric‐loaded slot antenna fed by a finite‐width substrate microstrip line is studied theoretically and experimentally by using the spatial dyadic Green's functions. Emphasis is placed on the analysis of the new feeding method, the finite‐width substrate microstrip line, which is a versatile microstrip structure and can be made as a stand‐alone device. The dielectric load is a hemisphere placed over the slot. The volume equivalence theorem is used to establish the theoretical model of the microstrip line. A simple excitation method for the microstrip line is introduced and modified to fit our problem. The spatial domain multilayered dielectric sphere dyadic Green's functions are used to obtain the scattered electromagnetic fields from the hemispherical dielectric load. The microstrip‐line current, the microstrip‐substrate electric field, and the equivalent magnetic current on the slot are obtained and used to calculate the impedance and the radiation pattern of the antenna. Computed impedances of the unloaded slot antenna and the loaded slot antenna show good agreements with either published data or measurement values. Analysis shows that the permittivities of the microstrip substrate have a significant effect on the impedance level of the antenna. It is found that electrically dense (high permittivities) substrates can give better impedance‐matching between the feeding microstrip line and the slot antenna. The reduction of the antenna impedance by using a thinner substrate has also been demonstrated in our investigation.

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.

The temperture dependence of substrate parameters and their effect on microstrip antenna performance

In the common approach to the design of microstrip antennas, the designers rely on data provided in the manufacturers' specifications, even though such specifications are confined to standard environmental conditions. In practice, the electrical parameters of the substrates may deviate from the manufacturers' data, thus making the antenna designer adopt a deficient design strategy. In the study reported, microstrip substrates were exposed to large temperature variations and their temperature dependent properties were measured in a specialized laboratory for dielectric materials. The results include plots of the dielectric constant and dissipation factor for wide temperature ranges equivalent to those in airborne applications. On the basis of this experimental data, the substrates were divided into four categories according to their dielectric constant value and its temperature dependence. Using both manufacturers' data and the measured values, a series of microstrip dual-feed aperture-coupled patch antennas were designed for the four categories of substrates and the sensitivity of their electrical performance due to temperature variations was fully investigated.

An efficient series expansion for the 2D Green's function of a microstrip substrate using perfectly matched layers

A new efficient technique is proposed to derive a series representation for the two-dimensional (2-D) Green's function of a planar substrate. A perfectly matched layer (PML) is used to turn the original open configuration into a closed one. The resulting structure is regarded as a waveguide and the resulting-analytically known-discrete set of eigenmodes is then used to expand the Green's function. The method turns out to be elegant and efficient for distances larger than 0.1/spl lambda/ away from the source.

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.