Bandstop Resonator Research Articles

Broadband bandpass filters using slotted resonators fed by interdigital coupled lines for improved upper stopband performances

This paper proposes new broadband microstrip bandpass filters based on slotted linear tapered-line resonator (SLTR) and slotted step impedance resonator (SSIR) structures for size reduction and improved stopband performances. A comprehensive treatment of slotted resonators and both ends of the resonator with interdigital coupled lines is described. The design concept is demonstrated by two filter examples including one with an SLTR and another one with an SSIR. These filters have not only compact size but also a wider upper stopband resulting from resonator bandstop characteristics. The simulated and experimental results of stopband performances are better than 15 dB for a frequency range up to 25 GHz.

Broad Stopband Microstrip Bandpass Filter with Metamaterial Substrates of Fractal Cantor Distribution

In this paper, microstrip line with metamaterial fractal Cantor distributing substrates is investigated. Transmission matrix method is used to calculating the transmittance and reflectance. Comparing with conventional Cantor distributing substrates, microstrip line with metamaterial fractal Cantor distribution shows broad stopband and little resonance peaks inside bandgap. The resonances in somewhere out of bandgap split and form more peaks with increasing of the number of generation. These peaks are more flat. According to these properties, a novel broad stopband bandpass filter is proposed.

Design of a band‐selective filter for UWB applications and its characteristic when combined with band‐notched antennas

AbstractA compact microstrip band‐selective filter for ultra‐wideband (3.1–10.6 GHz) radio system is proposed. The filter combines an optimum pseudo‐bandpass filter and a coupled resonator bandstop filter on both sides of the meandered 50‐Ω microstrip line. Three coupled resonators are modified to have S‐shape to miniaturize the filter. The measured results show that the filter has wide passband of 146.7% (2.1–10.15 GHz) with low insertion loss and the stop‐band of 7.42% (5.29–5.85 GHz) for 3‐dB bandwidth. The measured group delay variation is less than 0.7 ns within the passband except the stop band. Finally, the filter is combined with band‐notched antennas and then received power levels of the antennas with and without the filter are also examined at the notch frequency. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 98–101, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23019

A Tunable Bandstop Resonator Based on a Compact Slotted Ground Structure

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A new slotted ground structure featuring compact size and spurious-free passband in the context of microstrip lines is proposed. The compactness of the new structure originates from the lengthened coupling gap in the ground. The spurious-free response in a wide passband is a result of combining both narrow and wide slots in the new structure, which effectively forms a stepped-impedance slot resonator. Compared to the previously proposed dumbbell- and H-shaped defected ground structure, over 40% size reduction can be realized in the new structure. The new structure also provides flexibilities in introducing additional functionalities to the bandstop resonators. By embedding varactors in the slotted ground structure, tunable bandstop resonators can be implemented and 13% tuning range centered at 2.36 or 2.67 GHz have been obtained. </para>

Resonant Behavior and Selective Switching of Stop Bands in Three-Dimensional Photonic Crystals with Inhomogeneous Components

We demonstrate that, in contrast with the well-studied photonic crystals consisting of two homogeneous components, photonic crystals comprised of inhomogeneous or multiple (three or more) components may bring new opportunities to photonics due to the discovered quasiperiodic resonant behavior of their (hkl) stop bands as a function of the reciprocal lattice vector. A resonant stop band cannot be switched off for any permittivity of structural components. Tuning the permittivity or structural parameters allows the selective on-off switching of nonresonant (hkl) stop bands. This independent manipulation of light at different Bragg wavelengths provides a new degree of freedom to design selective optical switches and waveguides. Transmission experiments performed on synthetic opals confirmed the theoretical predictions.

Dual bandstop resonator using combined split ring resonator and defected ground structure

AbstractDefected ground structure and split ring resonator are combined to form a compact dual bandstop filter or a dual pole bandstop filter. An equivalent circuit model is developed for the proposed structure and it agrees very well with EM simulation. A dual bandstop resonator was fabricated. Measurements and theoretical predictions are in a very good agreement. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1249–1253, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22464

Compact semilumped bandstop resonators using the capacitively loaded parallel‐coupled microstrip line

AbstractCompact semilumped bandstop resonators are simply designed using parallel‐coupled microstrip line and lumped capacitors. The lumped capacitors loaded in between coupled lines increase the odd mode electrical length, and the frequency of transmission zero can be controlled by the lumped capacitors. For the accurate estimation of the transmission zero frequency, the four‐port impedance parameter is derived using the even/odd mode analysis in an inhomogeneous dielectric medium. Two types of the bandstop resonators are proposed using the coupled line with the length of λg/8 (@2 GHz), and the calculated and measured results of transmission zero frequency are compared in 1–3 GHz ranges. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 367–369, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22135

Microstrip Bandpass Filters with Reduced Size and Improved Stopband Characteristics Using New Stepped-Impedance Resonators

This paper proposes a new microstrip stepped-impedance resonator (SIR) used for bandpass filters with reduced size and improved stopband characteristics. A comprehensive treatment of both ends of the resonator with loaded triangular and rectangular microstrips is described. The design concept is demonstrated by two filter examples including four-resonator parallel-coupled Chebyshev bandpass and compact four-resonator cross-coupled elliptic-type filters. These filters are not only compact size due to the slow-wave effect, but also have a wider upper stopband resulting from the resonator bandstop characteristic. The filter designs are described in details. The simulated and experimental results are demonstrated and discussed.

Compact, narrow bandwidth, lumped element bandstop resonators

This letter describes the design and simulation of novel, highly compact, lumped element bandstop resonators. The resonators are fabricated using copper microstrip lines, with resonant frequencies around 5GHz but with areas of only 1.075mm /spl times/ 1.275mm. Each resonator consists of 8 interdigital capacitive fingers in parallel with a straight line inductor. The new design offers at least a 40% size reduction compared with similar resonators , . Furthermore, adjustment of the input and output feed line geometries enables resonator tuning at the design stage over a bandwidth of approximately 100MHz. The measured characteristics show good agreement with the simulated responses. Ultimate performance of this type of bandstop resonator is achieved using superconducting thin films, and to conclude a 20-finger, superconducting resonator (of area 1mm /spl times/ 0.41mm) is described and simulated.

Characteristics of a packaged laser‐diode module without band‐stop resonance

AbstractCircuit parameters for an equivalent circuit model of a laser diode were extracted with an impedance analyzer. Impedance matching can be achieved by eliminating inductive components of the leads in the package by using lumped chip capacitors, whereas it shows resonance dip in the low‐frequency band. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 347–349, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20300

Resonances in 1-3 piezocomposite rings

Lead zirconate titanate (PZT)/epoxy 1-3 piezocomposite rings with PZT volume fraction φ ranging from 0.58 to 0.93 have been fabricated. They have sufficiently small epoxy width (∼77–81 μm) and can be treated as effective homogeneous media. Stopband resonances (fS1, fS2) can be observed in the spectra and their locations are close to the theoretical predictions. Mode coupling theory and a finite element model (FEM) are applied to estimate the thickness (fT), lateral (fL), radial (fR), and wall-thickness (fW) resonances of the composite rings. As the frequencies and electromechanical coupling coefficients play a significant role in the performance of a composite transducer, it is important to know how these parameters change with φ. Good agreements are found between the experimental results and the FEM simulations. It is observed that the fR and fW vibrations greatly deteriorate at low values of φ. To avoid unwanted modes from coupling to fT, the thickness and aspect ratio of the PZT elements in the rings should be optimized. By using the FEM, effects of the ring dimensions on the lateral resonances can be predicted.

Emittance Limitation in Cooled Hadron Beams

We identify an essential factor that limits the lowest achievable temperature of a stored hadron beam when it is cooled. Two different numerical techniques, i.e. the particle-in-cell and molecular dynamics methods, are employed to simulate the collective beam behavior in a storage ring. It is demonstrated that a cooling process can be strongly interrupted by linear and nonlinear resonance stopbands. In particular, a serious tune locking occurs when a second-order coherent resonance is encountered during cooling. We show that, in order to reach the space-charge limit by means of a strong dissipative force, the design phase advance per lattice period must be smaller than 90 degrees.

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.

Parametric resonances in intense one-dimensional beams propagating through a periodic focusing channel

We study parametric resonances in arbitrary periodic lattices, incorporating the effect of space-charge self-fields. The linearized Vlasov approach is employed to provide an analytic description of resonant beam instability. Neglecting the momentum dispersion and image charges, we obtain an eigenvalue equation that determines the frequencies of collective modes in a one-dimensional waterbag beam. Approximate formulae for the resonance stopbands, growth rates, etc. are given. The theoretical predictions are compared with multi-particle simulation results. The effect of error fields is also analytically explored in the present paper.

Mode coupling in lead zirconate titanate/epoxy 1–3 piezocomposite rings

Lead zirconate titanate (PZT)/epoxy 1–3 piezocomposite rings were fabricated with PZT volume fractions φ ranging from 0.82 to 0.94 and with a small epoxy width of 77 μm in order to investigate their resonance characteristics and to reveal the mode coupling. Four major resonance modes were observed, namely the coupled longitudinal-thickness fH and lateral fL1 and fL2 mode resonances of individual PZT elements inside the rings as well as the radial fR and wall-thickness fW mode resonances of the whole rings. No stopband resonances were observed in the frequency range of 1 to 10 MHz. fH was found to increase linearly with the decrease in element height while fL1 and fL2 remained constant. When the height and width of the elements became comparable, coupling of fH with fL1 and fL2 occurred. The observed fH, fL1, and fL2 for all samples agreed with those calculated by the mode-coupling theory. fR and fW were almost independent of the ring thickness but increased as φ increased. A guide of operating fH in the rings without causing mode coupling was presented to optimize the composite structure for transducer design.

Resonance characteristics of lead zirconate titanate/epoxy 1–3 composite rings

Lead zirconate titanate (PZT)/epoxy 1–3 composite rings with PZT volume fractions ø ranging from 0.82 to 0.94 are fabricated, and their resonance characteristics are studied. These composite rings have sufficiently small epoxy width (∼ 77 μm) and can be treated as effective homogeneous media in which stopband resonances are not observed in the frequency band of interest (< 4 MHz). A mode coupling theory is applied to predict the longitudinal-thickness fH and lateral fL mode resonances of PZT elements inside the rings. By thinning the rings and by measuring the resonance peaks using an impedance analyzer, fH is observed to increase linearly with the decrease in element height while fL remains constant. When the height and width of the elements become comparable, mode coupling occurs. To avoid spurious modes being coupled to fH , the rings cannot be too thin in order to keep fH smaller than fL . In the lower frequency regime, they cannot be too thick to avoid coupling of fH with the wall-thickness fW and radial fR mode resonances. fW and fR are found to be independent of ring thickness but increase as Ø increases.

Diffraction effects in guided photonic band gap structure

The concept of the photonic band gap (PBG) structures stems from ideas of Yablonovitch. The idea is to design components so that they affect the properties of photons, in much the same way that ordinary semiconductor crystals affect the properties of electrons. In fact, the PBG structures forbid propagation of photons for a particular range of energy. They can be used to realise optical filters with large stop band and sharp transmission resonance. In the guided PBG structures, the existence of diffractive effects in the vertical dimension could limit the quality factor of such filters. In this paper, we have investigated the origin of diffraction losses in one-dimensional guided PGB structures using 2D and 3D numerical tools. We propose an analytical approach based on Bragg diffraction relation to explain these losses phenomenon. From this approach, the influence of some design parameters on the electromagnetic behaviour and the spectral response of PBG resonators will be explained.

Frequency selective Bragg filters based on (Mg,Zn) (S,Se) waveguides for the visible spectral range

Bragg grating transmission filters were fabricated on ZnMgSSe-ZnSSe-ZnMgSSe planar optical waveguide structures using a high resolution electron-beam lithographic process. Varying the grating geometry, the filter characteristics like resonance wavelength, modulation contrast, and stopband width can be adjusted. For example, for a L=600-/spl mu/m-long grating with a period of /spl Lambda/=120 nm, we achieve 16% residual transmission and a spectral width of 4 /spl Aring/ for the designed resonance wavelength of 603 mm. The experimental data can be explained quantitatively with a transfer matrix calculation assuming a coupling coefficient of 40 cm/sup -1/.

Influence of the biasing scheme on the performance of Au/SrTiO3/LaAlO3 thin film conductor/ferroelectric tunable ring resonators

The performance of gold/SrTiO3/LaAlO3 conductor/ferroelectric/dielectric sidecoupled, tunable ring resonators at Ku-band frequencies is presented. The tunability of these rings arises from the sensitivity of the relative dielectric constant (εr) of SrTiO3 to changes in temperature and dc electric fields (E). We observed that the change in εr which takes place by biasing the ring up to 450 V alters the effective dielectric constant (εeff) of the circuit resulting in a 3λ resonant frequency shift of nearly 12% at 77 K. By applying a separate dc bias between the microstrip line and the ring, one can optimize their coupling to obtain high Q bandstop resonators with δfn −1 = f0/Δf3dB as high as 12,000. The 3λ resonance was tuned from 15.75 to 17.41 GHz while keeping δfn −1 above 768 over this range. The relevance of these results for practical microwave components will be discussed.

Improved water and lipid suppression for 3D PRESS CSI using RF band selective inversion with gradient dephasing (BASING).

A T1 insensitive solvent suppression technique-band selective inversion with gradient dephasing (BASING)-was developed to suppress water and lipids for 1H magnetic resonance spectroscopy (MRS). BASING, which consists of a frequency selective RF inversion pulse surrounded by spoiler gradient pulses of opposite signs, was used to dephase stopband resonances and minimally impact passband metabolites. Passband phase linearity was achieved with a dual BASING scheme. Using the Shinnar-Le Roux algorithm, a highpass filter was designed to suppress water and rephase the lactate methyl doublet independently of TE, and water/lipid bandstop filters were designed for the brain and prostate. Phantom and in vivo experimental 3D PRESS CSI data were acquired at 1.5 T to compare BASING with CHESS and STIR suppression. With BASING, the measured suppression factor was over 100 times higher than with CHESS or STIR causing baseline distortions to be removed. It was shown that BASING can be incorporated into a variety of sequences to offer improved suppression in the presence of B1 and T1 inhomogeneites.