Showing papers on "Stopband published in 2002"

A design of the novel coupled-line bandpass filter using defected ground structure with wide stopband performance

Abstract: In this paper, a novel three-pole coupled-line bandpass filter with a microstrip configuration is presented. Presented bandpass filters use defected ground structure (DGS) sections to simultaneously realize a resonator and an inverter. The proposed coupled-line bandpass filter provides compact size with low insertion-loss characteristic. Furthermore, a DGS shape for a microstrip line is newly proposed. The proposed DGS unit structure has a resonance characteristic in some frequency band. The proposed coupled-line filter can provide attenuation poles for wide stopband characteristic due to resonance characteristic of DGS. The equivalent circuit for the proposed DGS unit section is described. The equivalent-circuit parameters for DGS are extracted by using a three-dimensional finite-element-method calculation and simple circuit analysis method. A design method for the proposed coupled-line filter is derived based on coupled-line filter theory and the equivalent circuit of the DGS. The experimental results show excellent agreements with theoretical simulation results.

Parallel coupled microstrip filters with suppression of harmonic response

Abstract: Corrugated coupled microstrip lines are proposed to design planar microwave filters with suppression of spurious response at twice the center frequency (2f/sub o/). The corrugated structure is designed to equalize the phase velocities of the two eigenmodes in the propagation direction. The designed bandpass filters have a wide upper stopband with satisfactory attenuation levels. In addition, the symmetry of the passband response is improved. Measured results of two fabricated circuits show that the idea works very well.

A novel dual-mode bandpass filter with wide stopband using the properties of microstrip open-loop resonator

Abstract: A novel dual-mode microstrip square loop resonator is proposed using the slow-wave and dispersion features of the microstrip slow-wave open-loop resonator. It is shown that the designed and fabricated dual-mode microstrip filter has a wide stopband including the first spurious resonance frequency. Also, it has a size reduction of about 50% at the same center frequency, as compared with the dual-mode bandpass filters such as microstrip patch, cross-slotted patch, square loop, and ring resonator filter.

Wideband bandpass filter design with three-line microstrip structures

Abstract: A systematic procedure is described for designing wideband bandpass filters based on parallel coupled three-line microstrip structures. It starts with modal analysis of a three-line coupled microstrip circuit. A database of modal eigenvoltage coefficients and modal characteristic impedances for a specified value of substrate ɛr is established. The relation between the circuit parameters of a three-line coupling section and an admittance inverter circuit is derived, so that the filters can be synthesised by a standard procedure. As compared with traditional parallel coupled lines, the proposed three-line design has the following two important features for the design of wideband filters: the tight line spacings of end stages can be greatly relaxed; and the stopband rejections are improved. Four filters with fractional bandwidths from 40% to 70% are fabricated on substrates with low and high dielectric constants. Prediction and measurement results are in good agreement.

A compact-size microstrip spiral resonator and its application to microwave oscillator

Abstract: This letter presents a compact size microstrip spiral resonator and its application to a low phase noise oscillator. This resonator has stopband characteristics to be used in the series feedback oscillator topology. The whole circuit area of the proposed resonator is within 1/10 wavelength, which results in the reduction of the circuit area and cost. A 10-GHz oscillator incorporated with this resonator was designed, fabricated and measured. It shows low phase noise performance of -95.4-dBc/Hz at 100 kHz offset.

A novel equivalent circuit and modeling method for defected ground structure and its application to optimization of a DGS lowpass filter

Abstract: In this paper, a novel equivalent circuit and modeling method for a defected ground structure is proposed to design an optimized DGS lowpass filter circuit The equivalent circuit presented in this paper has parallel capacitance to explain the fringing fields due to the defects on the metallic ground plane Several comparisons between the EM-simulations on the DGS circuits and circuit simulations on its equivalent circuits are demonstrated to show the validity of the proposed model Optimization for the DGS circuit is carried out by using the proposed equivalent circuit Simulation and measurements on the fabricated DGS lowpass filter show optimized passband and stopband performance

Stability of traveling-wave amplifiers with reflections

Abstract: The maximum achievable gain in individual sections of helix-type traveling-wave amplifiers is limited by the requirement that the device be stable with respect to the excitation of spurious modes. The excited modes may be of two types: backward waves, which are absolutely unstable, or forward waves, which are unstable in the presence of reflections and regenerative amplification. Whether a specific device is unstable depends on a number of details that must be computed numerically. We will present a model, used in the traveling-wave tube simulation code CHRISTINE, in which stability is determined including a number of important effects. These are: the placement of severs, their reflection and transmission coefficients, the profile of attenuation along the interaction length, the presence of a driven signal, and the coupling of forward and backward waves due to asymmetries in the helix support structure. Asymmetries result in a stopband near the "/spl pi/" point formed by the coupling of the forward and backward waves. For this case, a model is developed to evaluate the maximum stable length.

Multilayer LTCC bandpass filter design with enhanced stopband characteristics

Abstract: Lumped-element bandpass filter structures with enhanced stopband rejection targeted for low temperature co-fired ceramic (LTCC) implementation are proposed. Design equation formulations that take into account the effect of the transmission zeros are presented. For demonstration, RF filters operating at 2.4 GHz are fabricated and characterized. Both simulation and measurement results are shown for comparison.

Photonic bandpass filters with high skirt selectivity and stopband attenuation

Abstract: A new photonic signal processor topology that simultaneously achieves both a high-Q and a high skirt selectivity and stopband attenuation filter response is presented. It is based on a novel dual-cavity bandpass optical structure in which two pairs of active fiber Bragg grating cavities are used with an optical gain offset to control the poles and stopband attenuation characteristics of the filter. This concept enables a large improvement in the filter stopband attenuation, rejection bandwidth, and skirt selectivity to be realized. Measured results demonstrate both a narrow bandpass bandwidth of 0.4% of center frequency and a skirt selectivity factor of 16.6 for 40 dB rejection, which corresponds to a 6.5-fold improvement in comparison to conventional single cavity high-Q structures. To our knowledge, this is the best skirt selectivity reported for a photonic bandpass filter to date. The new photonic filter structure has been experimentally verified and excellent agreement between measured and predicted responses is shown.

Electric-magnetic-electric slow-wave microstrip line and bandpass filter of compressed size

Abstract: This paper presents a novel integrated microstrip low-loss slow-wave line. The new microstrip replaces the conventional metal strip by composite metals paralleling the electric surface and magnetic surface (MS). The MS made of an array of coupled inductors shows a high-impedance state in the stopband, below which the propagation properties can be well controlled by varying the dimensions of the electric surface and MS. The dispersion curves obtained by matrix-pencil analyses closely correspond to those obtained by scattering-parameter extraction. Theoretical results, as confirmed experimentally, indicate that an increase of over 60% in the slow-wave factor can be achieved without sacrificing propagation losses, using the proposed structure. This electric-magnetic-electric (EME) microstrip is insensitive to the alignment position of the periodical structure, and can be constructed using conventional printed-circuit-board fabrication processes and integrated with other microwave components in a multilayered circuit. A compact EME bandpass filter (BPF) with suppressed harmonic responses is presented. The length of the filter is reduced by 26%, and the measured insertion loss and fractional bandwidth is comparable to that of a conventional microstrip BPF on the same substrate.

Experimental studies of a drumlike silencer

Abstract: The theoretical finding of the broadband performance of a reactive silencer is validated experimentally. The silencer consists of two highly stretched membranes lining part of the duct and backed by two long and shallow cavities. The test rig was built with a small square duct of 5 cm in dimension, and each cavity is 5 cm deep and 25 cm long. Two types of metal foils, stainless steel and copper, were used, and the lowest membrane-to-air mass ratio was 1.3. A transmission loss in excess of 10 dB was achieved over more than one octave band. For one configuration close to the optimal parameters, the predicted ratio of the frequency band limits is 2.47, while the experiment gave 2.35. Three spectral peaks were found in the stopband, as predicted, but the peaks were broader than prediction, indicating the presence of significant sound energy dissipation mechanisms. Comparison with theoretical simulation shows that the cavity damping dominates over membrane friction. Tests using heavier membranes and membrane with different levels of tension also agree with predictions. Issues of practical implementation of the concept as a flow-through silencer are also addressed.

Stopband performance improvement of rectangular waveguide filters using stepped-impedance resonators

Abstract: Rectangular waveguide stepped-impedance resonators (SIRs) are analyzed and employed in the design of an X-band filter with center frequency f/sub 0/ = 10 GHz and a bandwidth of 100 MHz. An attenuation of 80 dB is held up to 23.1 GHz and, compared to standard uniform-impedance-resonator filters, a reduction in length of 55 % is achieved at the expense of an increased insertion loss from 0.6 to 1.5 dB. The second resonance of the fundamental TE/sub 10/ mode can be controlled by adjusting the length and impedance ratio of each resonator. A design procedure that takes into account step discontinuities is described and applied to the design of a number of SIR filters. Finally, the presented theory is supported with experimental results.

Nonreciprocal microwave band-gap structures.

Abstract: An electrically controlled nonreciprocal electromagnetic band-gap material is proposed and studied. The new material is a periodic three-dimensional regular lattice of small magnetized ferrite spheres. In this paper, we consider plane electromagnetic waves in this medium and design an analytical model for the material parameters. An analytical solution for plane-wave reflection from a planar interface is also presented. In the proposed material, a new electrically controlled stop band appears for one of the two circularly polarized eigenwaves in a frequency band around the ferrimagnetic resonance frequency. This frequency can be well below the usual lattice band gap, which allows the realization of rather compact structures. The main properties of the material are outlined.

Tunable photonic band gap in self-assembled clusters of floating magnetic particles

Abstract: We fabricated a 3D photonic crystal consisting of metal coated disk-shaped magnetic particles floating at the liquid-air interface inside a stack of containers. The particles self-assemble into an ordered crystal whose in-plane lattice constant can be varied by external magnetic field in very broad limits. This crystal exhibits photonic stopband at microwave frequencies. The stopband can be continuously tuned by external magnetic field until complete disappearance.

Record tuning range of InP-based multiple air-gap MOEMS filter

Abstract: Continuously tunable Fabry-Perot filters based on multiple InP/air-gap MOEMS technology are presented. Record wavelength tuning >112 nm with an actuation voltage of only 5 V is demonstrated. The FWHM remains constant over the entire tuning range. The stopband covers both the second and third optical telecommunication window (1250-1800 nm).

Improved performance of photonic band-gap microstripline structures with the use of Chebyshev distributions

Abstract: Conventional uniform circular-patterned photonic band gaps (PBGs) have constraints in the broadband passband and stopband performance because of the high ripple heights in S parameters. This Letter suggests a novel configuration with nonuniform dimensions of circular-patterned PBG to improve both pass- and stopband bandwidths and the ripples. The dimensions of the circles are varied proportionally to the relative Chebyshev amplitudes of a 10-element PBG array, and the dispersion characteristics are analyzed. It is seen that the Chebyshev distribution of the circular-patterned PBG line produces excellent performance by suppressing ripples and yielding better selectivity at cutoffs. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 1–5, 2002; DOI 10.1002/mop.10212

Evanescent-mode ridged waveguide bandpass filters with improved performance

Abstract: New types of evanescent-mode bandpass filters based on the ridged waveguide sections are considered. Insertion of additional inductive strips between the ridge sections enables one to reduce the longitudinal filter size, increase the cross section of the ridged waveguide housing, and achieve a sufficient improvement of stopband characteristics. Results of designing the millimeter-wave filters and comparison with the measured data are presented.

Thin-film design : modulated thickness and other stopband design methods

Abstract: This text presents several new thin-film design methods that can produce multiple stopbands as well as passbands. It is written for thin-film designers and students with advanced knowledge of multilayer, optical thin-film coatings. The text focuses on coatings that have high reflectance performance requirements in more than one spectral wavelength band or region. Relatively basic exercises are provided for students as well as challenging ones for researchers.

Radiation from ground plane photonic bandgap microstrip waveguides

Abstract: This paper presents an analysis of radiation of photonic bandgap (PBG) microstrip structures along with the pass and stopband behavior. Simulations are compared with measurements performed on a PBG microstrip waveguide with circular slots in the ground plane, designed to have a broad stop-band centered around 10 GHz. Radiation can be significant at some frequencies for a microstrip PBG and should be considered when designing filters, harmonic terminations and antenna feeds. Radiation of -3.4 dB was measured at 15 GHz relative to the input power in the passband. Measurement data agree well with simulations.

Optimum design and implementation of IIR SC filters using small-order FIR cells

Abstract: A novel approach for designing infinite impulse response (IIR) switched-capacitor filters, based on the optimum allocation of poles and zeros of a transfer function, implemented by a direct-form topology using finite-impulse response (FIR) cells as basic building blocks is presented. As a consequence, low sensitivity with respect to capacitance ratio errors in both passband and stopband frequencies, low power consumption, and improved group delay response are achieved. Comparisons with classical IIR and linear-phase FIR filter designs are made. An illustrative design example including simulation and experimental results obtained with a prototype filter are provided.

Rare-earth element anti-Stokes emission from three inverse photonic lattices

Abstract: The fabrication of a two-dimensional photonic lattice of ZrO2:Er3+ on a silicon substrate and two three-dimensional photonic lattices, ZrO2:Eu3+ and TiO2:Er3+, are described It is demonstrated that, for the two-dimensional lattice, photonic properties dependent on the lattice are not present, although another effect that was dependent on the structure is discussed For the two three-dimensional photonic lattices, the position of the photonic stopband relative to the emission bands of the anti-Stokes phosphors is shown to be crucial in controlling emission properties In the case of the ZrO2:Eu3+ lattice, where the stopband was close to both the emission and the exciting wavelengths, the intensities of both were affected However, for the TiO2:Er3+ lattice, where the stopband was far from the exciting and emission wavelengths, no such effect was seen It was concluded from this work that it should be possible to prepare unconverting photonic lattices with stopbands that extend the lifetimes of certain exc

Novel reduced-size coplanar-waveguide bandpass filter using the new folded open stub structure

Abstract: Proposes a novel folded skill and a simpler method than that of older methods. The advantages of this new structure reveals a better skirt factor than that of the conventional folded /spl lambda//4 series open stub, and it reduces the folded area of the conventional structure by at least 50%. Besides, by using the new folded /spl lambda//4 open stub to realize a bandpass filter, the size of the circuit will be reduced greatly and achieve better stopband rejection.

Combined acoustic-electromagnetic simulation of thin-film bulk acoustic wave filters

Abstract: A method for simultaneously modeling acoustic and electromagnetic (EM) behaviour of thin-film BAW RF filters is described. The inclusion of EM effects is important for fully understanding both passband loss and stopband rejection. Two lumped equivalent-circuit EM models are described. These are compared with measurement of solidly-mounted resonator (SBAR) filters up to 10 GHz.

Stepped impedance resonator bandpass filters with tunable transmission zeros and its application to wide stopband design

Abstract: Bandpass filters with a very wide stopband are designed using parallel coupled stepped impedance resonators (SIR), which have advantageous resonance harmonic characteristics. The singly loaded Q (Q/sub si/) of a tapped SIR is derived, so that the relation between Q/sub si/ and the position of the tap point can be established. It is known that a single resonator with tapped input can create an extra zero. It is found that, with proper tapping at the first and last SIR's of a bandpass filter, two zeros can be created and tuned independently over a wide frequency range. By exploiting both the advantageous resonance characteristics of SIR and tapped-line input, a bandpass filter with high selectivity and/or wide stopband can be realized. The experimental results show good agreement with the simulated prediction.

Transmission Zeros and Its Application to Wide Stopband Design

Abstract: Bandpass filters with a very wide stopband are designed using parallel coupled stepped impedance resonators (SIR), which have advantageous resonance harmonic characteristics. The singly loaded Q (Q,,) of a tapped SIR is derived, so that the relation between Q, and the.position of tap point can be established. It is known that a single resonator with tapped input can create an extra zero. It is found that in this paper, with proper tapping at the first and the last SIR's of a bandpass filter, two zeros can be created and tuned independently over a wide frequency range. By exploiting both the advantageous resonance characteristics of SIR and tapped-line input, a bandpass filter with high selectivity and/or wide stopband can be realized. The experimental results show a good agreement with the simulated prediction.

Cylindrical Waveguide with Axially Rippled Wall

Abstract: Axially corrugated cylindrical waveguides with wall radius described by R0(1 + ² cos 2¼z=L), where R0 is the average radius of the periodically rippled wall with period L and amplitude ², have been largely used as slow-wave structures in high-power microwave generators operating in axisymmetric TM modes. On the basis of a wave formulation whereby the TM eigenmodes are represented by a Fourier-Bessel expansion of space harmonics, this paper investigates the electro- dynamic properties of such structures by deriving a dispersion equation through which the rela- tionship between eigenfrequencies and corrugation geometry is explored. Accordingly, it is found that for L/R0 > 1 a stopband always exists at any value of ²; the condition L/R0 = 1 gives the widest first stopband with the band narrowing as the ratio L/R0 increases. For L/R0 = 0:5 the stop- band sharply reduces and becomes vanishingly small when² < 0:10: Illustrative example of such properties is given on considering a corrugated structure with L/R0 = 1, R0=2.2 cm and ² = 0:2, which yields a stopband of 1.5 GHz width with the central frequency at 8.4 GHz; it is shown that in a ten-period corrugated guide the attenuation coefficient reaches 165dB/m, which makes such structures useful as an RF filter or a Bragg reflector. It is also discussed that by varying L/R0 and ² we can find a variety of mode patterns that arise from the combination of surface and volume modes; this fact can be used for obtaining a particular electromagnetic field configuration to favor energy extraction from a resonant cavity.

Transmission characteristics of metallodielectric photonic crystals and resonators

Abstract: K/sub u/ band Fabry-Perot type resonances have been observed in the stop band of a metallodielectric photonic crystal by transmission measurements at microwave frequencies. The metallodielectric photonic crystal has a face centered cubic Bravais lattice structure with a lattice constant of 15 mm. Metallic spheres with 6.35 mm diameter are placed at the lattice sites. The metallodielectric photonic crystal displayed a directional bandgap with a lower band edge of 13.0 GHz, an upper band edge of 21.5 GHz and a center frequency of 17.25 GHz, corresponding to a stop bandwidth center frequency ratio of 50%. The maximum rejection at the band center is 35 dB, corresponding to a 7 dB per unit cell rejection ratio. The Fabry-Perot type resonance in the K/sub u/ band has a quality factor of 200, with a maximum transmission peak of -5 dB.

Multilayer resonators and a bandpass filter fabricated from a novel low-temperature co-fired ceramic

Abstract: The main objective of this study was to make components from a novel low-loss, low-temperature Co-fired ceramic (LTCC) dielectric, which was also compatible with a high-conductivity silver paste. The multilayer-component fabrication procedure is presented together with a composition for a tape-casting slurry, choice of conductor paste, and LTCC process parameters. A good Q factor, >100 at 2 GHz, using the novel material system has been achieved for λ/2 resonators operating in the frequency range 1.7–3.7 GHz. An excellent frequency response for a 2 GHz bandpass filter has also been achieved; the insertion losses in the passband were less than −2 dB (bandwidth 60 MHz) and the attenuation more than 25 dB in the stopband located 190 MHz higher.

Extracted Pole Bandpass Filters Based On The Slotted Irises

Abstract: A new design of directly coupled bandpass filter that provides extracted stopband poles is presented by the example of a capacitive iris filter. The attenuation poles are introduced by cutting in iris strips additional slots parallel to the wider waveguide wall. This way of extracted poles implementation does not require spatially developed elements (in particular overmoded ones). The K-inverter corresponding the modified iris changes slightly and may be easily fine-tuned. Additional slot dimensions determine the location and Q-factor of the attenuation poles, which may be placed in the parasitic passband or on a required skirt of the main one. Numerical examples for the three-section filter in WR90 waveguide demonstrate the possibility to increase the skirt selectivity or to improve the stopband attenuation without any extension of the filter dimensions, keeping the same return loss within the passband.

Ball-lens based optical add-drop multiplexers: design and implementation

Abstract: Two types of ball-lens based optical add-drop multiplexers (OADMs) are designed and implemented. Insertion losses as low as 0.5 to 0.6 dB for the reflection light-path, and 1.2 to 1.5 dB for the transmission light-path are demonstrated. The 0.5-dB passband is 44% to 50% of the channel spacing and 30% to 33% of the -30-dB stopband for 100- and 200-GHz OADMs. The reflection path has an isolation of 15 dB. In addition to the distinct cost advantage of ball lenses over gradient index lenses, the ball-lens based OADMs also offer a significant simplification in packaging. The external diameter of the package is 5.5 mm.