Center Frequency F0 Research Articles

Design of parallel coupled‐line microstrip wideband bandpass filter using stepped‐impedance resonators

AbstractIn this article, a parallel coupled‐line microstrip wideband bandpass filter (PCM‐WBF) using stepped‐impedance resonators (SIRs) is designed and implemented on commercial printed circuit board (PCB) of RT/Duroid 5880 substrate. The first two resonant modes of the SIR are coupled together and they are applied to create a wide passband. The proposed filter at center frequency f0 of 5.76 GHz has very good measured characteristics including a bandwidth of 3.63–7.92 GHz (3‐dB fractional bandwidth of 74%) and a low insertion loss of −1 ± 0.9 dB. Experimental results of the fabricated filter show a good agreement with the predict results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 795–798, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22260

UWB bandpass filter with wide stopband using open stubs

AbstractIn this paper, a compact pseudo‐interdigital ultra‐wideband filter using several open stubs to improve the stopband is designed and implemented on FR4 substrate. This filter at center frequency f0 of 4 GHz has presented almost very good measured characteristics, including the bandwidth of 3–5.1 GHz (3‐dB fractional bandwidth of 52%), low insertion loss of −0.6 ± 0.4 dB, sharp rejection due to two transmission zeros in the passband edge created by inter‐stage coupling, and wide stopband rejection greater than 15 dB from 5.3–9 GHz. Experimental results of the fabricated filter show a good agreement with the predict results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 573–575, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22212

Novel compact bandpass filters with wide controllable fractional bandwidth

AbstractIn this letter, a novel compact structure is proposed for bandpass filter (BPF) design. The structure is realized using only one resonator. The resonator is excited by two open microstrip stubs. Further, ground plane aperture technique is used to obtain wide bandwidth. 3‐dB fractional bandwidth can be varied between 1.0 and 90.0% with good in band as well as out of band filter characteristics. The filter has the advantages of compactness, wide bandwidth, low insertion loss (IL), and ease of fabrication. A prototype fabricated filter of FBW 45.1% and passband center frequency f0 = 3.795 GHz shows a maximum passband IL of 2.0 dB. The basic BPF occupying area is less than 0.22 λg × 0.23 λg, where λg is the guided wavelength at f0. A simple stub modification extends its upper stopband at least three times the upper cutoff frequency. Good agreement between measurements and simulations are obtained. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 29–31, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22039

Ferrite-ferroelectric layered structures for electrically and magnetically tunable microwave resonators

It is demonstrated experimentally that a layered structure consisting of ferrite and ferroelectric thin films can be used as an electrically and magnetically tunable microwave resonator. The dual tunability is realized through the application of a bias electric field to the ferroelectric layer (thus changing its dielectric constant), and a bias magnetic field to the ferrite layer. The resonator having central frequency f0≅5GHz and bandwidth Δf=3.5MHz demonstrated a broadband (∼300Δf) tunability through the variation of the bias magnetic field, and a narrow-band (∼2Δf) tunability through the variation of the bias electric field.

Design of sharp-rejection, compact, and low-cost ultra-wideband bandpass filters using interdigital resonators

With the rapid development of broadband communications, sharp rejection and wide bandwidth are very important issues for UWB applications. In this article, a compact pseudo-interdigital ultra-wideband filter using the tapped input/output (I/O) and strong coupling is designed and implemented on FR4 substrate. This filter at center frequency f0 of 3.9 GHz has presented almost very good measured characteristics, including the bandwidth of 3.1–4.8 GHz (3-dB fractional bandwidth of 44%), low insertion loss of −1.6 dB, sharp rejection due to two transmission zeros in the passband edge created by interstage coupling, and low group delay varied between 0.2 and 0.5 ns. Experimental results of the fabricated filter show a good agreement with the predicted results. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2093–2096, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21877

A Multichannel Acoustooptical Deflector with a Planar Delay-Line Structure for Ultrasound Excitation

Results are presented from the development and experimental study of an eight-channel acoustooptical deflector with central frequency f0 = 1000 MHz and bandwidth ΔfΣ = 500 MHz within the limits of a 6-dB nonuniformity of diffraction efficiency, the maximum value of which is η ≈ 0.35%/W. In the deflector, a flat spiral delay-line structure excites ultrasound from the surface of a Z-cut LiNbO3 piezoelectric crystal. The technical parameters of the deflector are discussed, as are the optical, microwave electrical, and acoustical aspects of its construction.

Design of Square-Root Domain Filters

In this paper, a square-root domain band-pass filter and biquad filter which are based on the MOSFET square law are proposed. Both of the square-root domain filters operated at 2.5 V supply voltage are constituted by current mirrors, current-mode square-root circuits and capacitors. The circuits presented have been simulated and fabricated using 0.25 ? m CMOS process. Both of simulation and measured results which are in good agreement indicate that the center frequency f0 is not only attainable at megahertz frequencies but also tunable electronically. The proposed circuits have the merits of high frequency operation, tuneability, low power supply voltage operation, low third order intermodulation distortion and low total harmonic distortion.

A novel compact dual-mode circular-patch bandpass filter with improved second spurious response

A novel compact dual-mode circular-patch bandpass filter (BPF) with improved stopband performance is presented. A pair of square etched areas acting as a perturbation element on the circular-patch resonator is used in the proposed structure, so that the two split modes are coupled and the filter structure can be reduced. An open stub is attached at the input/output port in order to improve the stopband performance of the proposed BPF. The proposed BPF is demonstrated with a central frequency f0 = 2.17 GHz, insertion loss of −2 dB, a 3-dB bandwidth of 8%, and a rejection of −35 dB at the 2nd harmonic. The measured results of experimental filter show good agreement with the theoretical simulated results. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 203–206, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21123

Stopband improvement of a dual‐mode ring bandpass filter using DGS

AbstractThis paper presents the improved stopband of a novel dual‐mode bandpass filter (BPF) using an etched H‐shaped defected ground structure (DGS) at 2 GHz. The wide‐stopband characteristic results from the rejection‐band resonant characteristic of the DGS in the harmonic frequency of the dual‐mode BPF. The proposed BPF is designed and fabricated with the following frequency characteristics: central frequency f0 = 2 GHz, 3‐dB bandwidth of 3%, and wide stopband from 2.5 to 5 GHz at −40 dB. The measured results of the fabricated filter show good agreement with the simulation results. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 247–249, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20600

Automatic song-type classification and individual identification of the ortolan bunting (Emberiza hortulana L) bird vocalizations

This paper presents a method for automatic song-type classification and individual identification of the ortolan bunting (emberiza hortulana L). This method is based on hidden markov models (HMMs) commonly used in the signal processing and automatic speech recognition research communities. The features used for classification and identification include both fundamental frequency and spectral characteristics. Fundamental frequency features consist of center frequency f0, relative f0 to moving-average baseline, peak strength, and peak bandwidth. Spectral features are derived from frequency-weighted cepstral coefficients. Using these features one HMM is trained for each type of vocalization both for each individual bird and across the entire population. Preliminary results indicate accuracies of above 90% for both song-type classification and individual identification tasks.

Miniaturized multilayer hairpin bandpass filter with tunable transmission zeros

AbstractA miniaturized multilayer hairpin bandpass filter using tapped‐line I/O with tunable transmission zeros is designed and implemented. This structure provides additional cross‐coupling between two layers, as well as the coupling effect on the same layer. The designed filter demonstrates superior passband characteristics with a central frequency f0= 2.39 GHz, insertion loss S21= −1.45 dB and a return loss S11= −32 dB. Moreover, by combining with two layers and tapped‐line I/O structure, the filter produces two tunable transmission zeros at 2.8 GHz with −48 dB and 3.2 GHz with −43‐dB rejection that the typical elliptic function response can be easily. Experimental results of the fabricated filter measured by network analyzer agree well with the simulation results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 53–55, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20044

Novel bandpass filter using tapered PBG cells

AbstractA novel bandpass filter using tapered PBG cells is designed and implemented. With the tapered PBG structure inserted between the top layer of two hairpin resonators with symmetric feed‐line tapping and a ground‐plane bottom layer, the passband characteristics are excited and, moreover, a transmission zero on the higher passband edge is produced. The novel bandpass filter using tapered PBG cells demonstrates the frequency characteristics with a central frequency f0 = 2.9 GHz, a 3‐dB bandwidth (FBW) of 9%, and insertion loss S21 of −2.8 dB. Good agreement between the experimental and simulation results is obtained. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 66–68, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20048

Microstrip coupled‐line bandpass filter with a multilayer structure

AbstractA microstrip coupled‐line filter with a multilayer structure is designed and implemented. This structure provides additional overlapped coupling and cross coupling between two layers, except for the coupling effect on the same layer. The designed filter demonstrates the frequency characteristics with central frequency f0 = 2.4 GHz, return loss S11 = −12.2 dB, and insertion loss S21 = −2.49 dB. Moreover, it is found that, due to a transmission zero occurring at 3.14 GHz with −45‐dB rejection, a typical elliptic‐function response can be easily obtained by the proposed structure. Experimental results of the fabricated filter measured by using a network analyzer agree well with the simulation results. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 493–495, 2003

Surface acoustic wave resonator from thick MOVPE-grown layers of GaN(0001) on sapphire

ABSTRACTWe report on fabrication and measurement of a surface acoustic wave resonator prepared on ∼10m thick GaN(0001) films. The films were grown by metal-organic vapor phase epitaxy on a c-plane sapphire substrate. The surface morphology of the films were examined with scanning electron and atomic force microscopy. A metallic bilayer of Al/Ti was subsequently evaporated on the nitride film surface. Definition of the resonator interdigital transducers, designed for a wavelength of λ=7.76m, was accomplished with standard UV lithography and lift-off. S-parameter measurements showed a resonator center frequencyf0=495MHz at room temperature, corresponding to a surface acoustic wave velocity of 3844m/s. The insertion loss at center frequency was measured at 8.2dB, and the loaded Q-factor was estimated at 2200. Finally, measurements of the resonator center frequency for temperatures in the range 25–155°C showed a temperature coefficient of -18ppm/°C. The intrinsic GaN SAW velocity and electromechanical coupling coefficient were estimated at νSAW=383 1m/s andK2=1.8±0.4·10−3.

A new triply rotated quartz cut for the fabrication of low loss saw filters

The dramatic expansion of the cellular phone market has led to a very strong interest in the development of SAW devices devoted to frequency filtering. For intermediate frequency applications (50–500 MHz) and narrow frequency bandwidth (less than 2% of the filter central frequency f 0 ), the ( ST,X ) cut of quartz has been the industrial standard for the design of SAW filters for a long time. Nevertheless, a deeper analysis of the quartz properties shows the existence of unexplored angular domains for which Rayleigh waves can be efficiently excited, exhibiting physical characteristics better than the ones of the (ST,X) cut. This paper presents a family of quartz allowing significant improvements of SAW devices on quartz. A larger number of experiments have been performed, confirming the above mentioned theoretical predictions. A filter built on this cut is presented showing the interest of the proposed crystal orientations. Une nouvelle famille de coupes de quartz pour filtres à ondes de surface. L'explosion du marché des téléphones portables a considérablement favorisée les recherches et développements de composants à ondes de surface pour le filtrage de fréquence. Pour les filtres à bande étroite aux fréquences (50–500 MHz), la coupe ( ST,X ) du quartz s'est avérée l'optimum pour la fabrication industrielle de filtres à ondes de surface depuis plusieurs années. Cependant, une étude approfondie des propriétés physiques des ondes de surface sur quartz montre qu'il est possible d'exciter celles-ci de façon plus efficaces sur certaines orientations jusqu'alors inexplorées que sur la coupe ( ST, X ). Le présent article présente une famille de coupes de quartz répondant à cette définition. De nombreuses mesures expérimentales ont été effectuées, prouvant son intérêt pour les applications de filtrage. La démonstration d'une telle conjecture est finalement faite par la réalisation de deux filtres à vocation industrielle.

Design and preparation of single-chip HTS coplanar waveguide bandpass filters

An extremely low-loss, sharp cut-off, single-chip high-temperature superconducting (HTS) coplanar waveguide (CPW) bandpass filter (BPF) was designed and prepared; such filters are useful for future telecommunications systems. A nine-pole CPW BPF having a centre frequency (f0) of 10 GHz and fractional bandwidth of 1.5% (whose chip size is less than 10 mm square) was designed, and confirmed by a computer simulation (HP-Momentum). In order to realize fully two-dimensional HTS filters, we make use of meanderline geometry and interdigital capacitance coupling. In order to make the BPF compact, we clarify the cross-coupling between meanderlines and modelling of the corner bend of the transmission lines. Experiments with a prototype miniaturized CPW BPF (three-pole) on 10 mm square YBCO film are also presented.

A synthesis of an LC simulation—type double‐tuned circuit adjustable by a single parameter

AbstractIn this paper we derive a double‐tuned, narrow‐band transfer function and illustrate its LC simulation‐type active realization with low element sensitivity. First, a new double‐tuned function that is adjustable by a single parameter is derived for a circuit using mutual induction. Next, the basic circuit that generates negative feedback with RLC elements and controlled sources is derived. This basic circuit can have a low element sensitivity within the passband, as confirmed by the numerical analysis. As an example of the implementation for the basic circuit, an active RC circuit with the center frequency f0 = 455 kHz and Q = 30 is constructed; transistor gyrators are used for L element simulation; and a single variable resistor is used for the coupling coefficient adjustment. The experimental tuned characteristics for several coupling coefficients are in good agreement with the calculated values.

Antenna decoupling requirements in a gyrotron collective Thomson scattering diagnostic (CTS)a)

The required rejection ratio of the stray light in a CTS, respect to the launching power is investigated, for obtaining useful signal‐to‐noise ratio. This problem is faced considering the central gyrotron frequency f0, as well as the in‐band stray light raising from the spurious mode of the gyrotron and amplified cyclotron emission (the so‐called gyrotron noise), falling into the scattered light spectrum. The statistical nature of the gyrotron noise in the scattering band is important because the required decoupling is obtained using the S/N formula where the fluctuation of the plasma radiation and the gyrotron noise fluctuation appears. It turns out that the total decoupling required at f0 is of the order of or greater than 80 dB, while in the scattering band could be less than 40 dB.

Antenna decoupling requirements in a gyrotron collective Thomson scattering diagnostic (CTS) (abstract)a)

The required rejection ratio of the stray light in a CTS, respect to the launching power is investigated, for obtaining useful signal-to-noise ratio. This problem is faced considering the central gyrotron frequency f0, as well as the in-band stray light raising from the spurious mode of the gyrotron and amplified cyclotron emission (the so-called gyrotron noise), falling into the scattered light spectrum. The statistical nature of the gyrotron noise in the scattering band is important because the required decoupling is obtained using the S/N formula where the fluctuation of the plasma radiation and the gyrotron noise fluctuation appears. It turns out that the total decoupling required at f0 is of the order of or greater than 80 dB, while in the scattering band could be less than 40 dB.

EFFECTS OF POROSITY ON SEISMIC ATTENUATION

Effects of porosity on the attenuation of wave propagation are studied. The effects of pore fluids and porous structures are significant on changing the shapes of propagating wavelets. The waveform change of a propagating wavelet is much more sensitive to porosity than intrinsic attenuation. The attenuation occurred in natural rocks may largely due to these porous effects in addition to the internal friction of the solid represented by the intrinsic quality factor Q. The waveform of a propagating wavelet is quantitatively associated with attenuation, porosity, and fluid content, and is characterized by three parameters: the porosity ϕ, the quality factor Q, and the center frequency f0. Estimations of attenuation, porosity, and fluid content can be made by optimal wavelet analysis. High-resolution mapping of subsurface structures can be achieved by solving the integral equation with the nonlinear optimization of the time-variant wavelets. The inversion and the optimization schemes have been applied to study the porous sea floor and the crustal axial magma chamber (AMC) on the East Pacific Rise. These results provide porosity, attenuation information, and the highly resolved wave events, for further evaluation of compressional and shear wave velocities and other physical properties such as crack density and aspect ratio.