Showing papers on "Stopband published in 2000"

A novel 1-D periodic defected ground structure for planar circuits

Abstract: A new one-dimensional (1-D) defected ground unit lattice is proposed in order to improve the effective inductance. Increasing the effective inductance makes it easy to control the cutoff frequency characteristics. The proposed periodic defected ground structure (DGS) provides the excellent cutoff and stopband characteristics. In order to show the improved the effective inductance, three DGS circuits were fabricated with identical periodic and different dimensions. Measurements on the fabricated DGS circuits show that the cutoff and stopband center frequency characteristics depend on the physical dimension of the proposed DGS unit lattice,.

A Novel 1-D Periodic Defected Ground Structure for

Abstract: A new one-dimensional (1-D) defected ground unit lattice is proposed in order to improve the effective inductance. In- creasing the effective inductance makes it easy to control the cutoff frequency characteristics. The proposed periodic defected ground structure (DGS) provides the excellent cutoff and stopband char- acteristics. In order to show the improved the effective inductance, three DGS circuits were fabricated with identical periodic and dif- ferent dimensions. Measurements on the fabricated DGS circuits show that the cutoff and stopband center frequency characteris- tics depend on the physical dimension of the proposed DGS unit lattice.

A novel photonic bandgap structure for low-pass filter of wide stopband

Abstract: In this letter, a novel photonic bandgap (PBG) structure is proposed for increasing the stopband of a low-pass filter without the increasing circuit size for applications in microstrip circuits The proposed structure is connected in two parallel periodic structures which have a different center frequency of the stopband The wide stopband is achieved by two periodic structures of two different stopbands We also show the performance improvement of microstrip patch antenna by etching of the proposed structure in ground plane

Detuned grating multi-section-RW-DFB-lasers for high speed optical signal processing

Abstract: We present a detailed description and a first theoretical study of an improved concept for high-frequency self-pulsations (SPs) in multisection (MS)-DFB lasers with an integrated phase tuning section. The DFB wavelengths of the two DFB sections are spectrally detuned by nearly the stopband width using two gratings with different grating periods. If both DFB sections are operated at lasing conditions and an appropriate phase is chosen, we obtain beating-type SP with a frequency given by the spectral distance of two lasing modes. Good agreement between theory and experiment is obtained with respect to the role of the detuning, the role of the phase section, as well as the synchronization to external injected signals. The modeling shows a strong nonlinear coupling of the two involved modes via the carrier densities. This effect is important for the mutual coherence and for the observed locking of the beating oscillations to external signals. From the results of the calculations, we draw the conclusion that even higher SP frequencies can be obtained based on the new concept.

Theory and design of a class of cosine-modulated non-uniform filter banks

Abstract: In this paper, the theory and design of a class of PR cosine-modulated nonuniform filter bank is proposed. It is based on a structure previously proposed by Cox (1986), where the outputs of a uniform filter bank are combined or merged by means of the synthesis section of another filter bank with smaller channel number. Simplifications are imposed on this structure so that the design procedure can be considerably simplified. Due to the use of cosine modulated filter banks as the original and recombination filter banks, excellent filter quality and low design and implementation complexities can be achieved. Problems with these merging techniques such as spectrum inversion, equivalent filter representations and protrusion cancellation are also addressed. As the merging is performed after the decimation, the arithmetic complexity is lower than other conventional approaches. Design examples show that PR nonuniform filter banks with high stopband attenuation and low design and implementation complexities can be obtained by the proposed method.

Tuneable microstrip device controlled by a weak magnetic field using ferromagnetic laminations

Abstract: The properties of lamellar insulator ferromagnetic on the edge (LIFE) material in a microwave device under a static field are studied. The LIFE composite is manufactured by gluing sheets of a ferromagnetic thin film deposited by physical vapor deposition on a polymeric substrate. The 0.154-μm-thick ferromagnetic material is an amorphous CoNiZr alloy deposited on a 12.7-μm-thick kapton film. According to gyromagnetic model, when an external static field is applied along the easy axis, the gyromagnetic resonance frequency is shifted towards high frequencies. Then, a piece of LIFE composite was integrated in a microstrip line, using a substrate of low permittivity. The displacement of the minimum of the transmission coefficient in the microstrip line due to a static field applied is presented. The operation of a microwave filter with a stopband tuneable in the 2–6 GHz range by a small static magnetic field (<500 Oe) is demonstrated, as well as a magnetic switch.

Photonics-based interference mitigation filters

Abstract: New photonic filter structures for interference mitigation of microwave signals are presented. These novel fibre-based filters have a parallel topology, and overcome the problem of synthesising both a narrow stopband and a very-wide and flat passband. Results for these filters showed a stopband 6-dB width of 10 MHz at a frequency of 1.5 GHz, with flat passband, and a shape factor for -40 dB interference rejection of 7.8, which is the lowest reported for a photonic filter.

Nonlinear disordered media for broad-band optical limiting

Abstract: We analyze broad-band limiting behavior in nonlinear structures that are, on average, periodic. Introduction of a controlled degree of randomness in layer thicknesses results in widening of the stopband. Light at all of the frequencies in this broadened effective stopband of the structure with randomly perturbed layer thicknesses exhibits true optical limiting-clamping of the transmitted intensity below a fixed level independent of incident intensity. We explore the impact of the degree of randomization and the strength of the nonlinear mechanism on the smoothness and regularity of the limiting spectrum and on the localization of the light within these cyclostationary media. Optical limiting in integrable devices is of interest in optical logic, signal processing, and personnel and sensor protection.

Optimization of Tapered Bragg Reflectors in Microstrip Technology

Abstract: The frequency responses of tapered Bragg reflectors made by etching one row of holes on the ground plane of a microstrip line are analyzed, comparing different windows and their effects on the rejection level, the bandwidth, the side lobe level and the abruptness of the main stop band.

Factorable FIR Nyquist filters with least stopband energy under sidelobe level constraints

Abstract: Spectrally factorable Nyquist filters are used in data communications to avoid intersymbol interference. An approach is developed for obtaining a Nyquist filter that is factorable having the smallest stopband energy for a given sidelobe level. The resulting constrained minimization problem is solved efficiently and reliably using the Goldfarb-Idnani (1983) algorithm. Some examples are presented comparing the present method with a previous approach from the literature.

Analysis of Photonic Crystal Filters by the Finite-Difference Time-Domain Technique

Abstract: A special finite-difference time-domain (FDTD) formulation which allows electromagnetic (EM) wave wideband simulations of oblique incidence for periodic media is used for the design and analysis of an infrared photonic crystal filter with dual stopbands at 3–5 and 8–12 μm. The transmission coefficient in the main stopband (8–12 μm) is below −10 dB. Scattering coefficients are calculated for different incidence angles, and the stopbands are shown to exist for different angles of incidence. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 81–87, 2000.

Single-passband single-stopband narrow-band filters

Abstract: Techniques are presented for obtaining an optimum filter response for narrow-band requirements of a single passband and a single stopband. For certain transformed equiripple passband responses, including Chebyshev and elliptic function responses and a new "double n/2 poles" response, the minimum number of resonators can be easily determined, resulting in reduced size and weight relative to more conventional frequency-symmetric bandpass or bandstop filters.

EM analysis of PBG substrate microstrip circuits for integrated transmitter front end

Abstract: In this work, electromagnetic analysis of a novel photonic bandgap (PBG) substrate microstrip line circuit is presented and its applications in an integrated antenna amplifier transmitter front end are discussed. The method-of-moments based Sonnet Suite has been used for full-wave 3D electromagnetic simulation of the microstrip on a high-density substrate having rectangular air blocks. It is shown that a single row of air blocks consisting of only 3-5 elements of optimized dimensions produce a very steep and wide (up to 10 GHz) bandgap for the microstrip mode. The results obtained demonstrate that such a structure has high potential for designing novel low-pass and band-pass filters and integrated amplifier tuning elements. The transmission-line-circuit method has been applied in obtaining analytical conditions of stopband and passband for the circuit considered. The proposed structure can be mass-produced by micro drilling in a conventional high-density substrate.

Novel 1-D photonic bandgap microstrip transmission line

Abstract: A new microstrip transmission line incorporating a photonic bandgap (PBG) structure is proposed. It consists of a periodic array of perforations on the microstrip line itself. By controlling the shape and periodicity of the perforations, the microstrip transmission line exhibits slow-wave and stopband characteristics.

Acoustic loss mechanisms in leaky SAW resonators on lithium tantalate

Abstract: We discuss acoustic losses in synchronous leaky surface-acoustic wave resonators on rotated Y-cut lithium tantalate substrates. Laser probe measurements and theoretical methods are employed to estimate the radiation of leaky waves into the busbars of the resonator and the excitation of bulk-acoustic waves. We find that the escaping waves lead to a significant increase in the conductance, typically in the vicinity of the resonance and in the stopband, but that they do not explain the experimentally observed deterioration of the electric response at the antiresonance. At frequencies above the stopband the generation of fast shear bulk-acoustic waves is the dominant loss mechanism.

Study of Propagating Characteristics for Folded Waveguide TWT in Millimeter Wave

Abstract: Folded waveguide circuit (FWC) is an ideal slow wave structure for broadband power traveling wave tube (TWT) in millimeter wave. But owing to changes of propagating character by reflecting of waveguide bend and electron beam hole, stopband can be formed. On the basis of computation of the stopband, effects of the dimension of FWC on stopband width are analyzed. It is available for design in FWC TWT.

Single-passband, single-stopband narrowband filters

Abstract: Techniques are presented for obtaining an optimum filter response for narrowband requirements of a single passband and a single stopband. For transformed elliptic function responses, the minimum number of resonators can be easily determined, resulting in reduced size and weight relative to more conventional bandpass or bandstop filters.

Waveguide Filters with Improved Stopband Performance

Abstract: A waveguide bandpass filter with improved stopband performance is presented The predicted filter performance shows improved stopband performance and reduced filter dimensions compared with conventional E-plane bandpass filters The validity of the method is confirmed by the measurement of a fabricated five resonator waveguide bandpass filter

Algorithm for the design of transmultiplexers with time-frequency spread criteria

Abstract: A new class of transmultiplexers are designed with the filter responses spread in both the time and frequency domains. In contrast to design algorithms with passband flatness and stopband attenuation criteria, the new algorithm includes a time/frequency property. Transmultiplexers with five users and linear-phase property are experimentally constructed.

The design of peak constrained least squares FIR filters with finite precision coefficients

Abstract: A method for the design of finite precision coefficient (FPC) peak constrained least squares (PCLS) finite duration impulse response (FIR) digital filters based on Adams' optimality criterion and an efficient local search method is presented. Simple quantization of the infinite precision filter coefficients typically leads to filter designs that fail to meet the frequency response and passband to stopband energy ratio (PSR) specifications. It is shown that it is possible to implement computationally efficient filters (with reduced filter FPC wordlengths) that meet the passband and stopband attenuation specifications at the expense of a lower PSR energy ratio.

Dispersion characteristics of microstrip with periodic perturbations

Abstract: Dispersion characteristics of a periodical planar microstrip line are presented in the form of Brillouin diagram together with plot of attenuation constant versus frequency. The dispersion characteristics are the results of the space harmonics deduced from the excited surface currents of the periodical structure. Rigorous theoretical methods and procedure for deembedding the space harmonics are reported and validated. The dispersion characteristics show that, in addition to the familiar forward traveling waves and backward traveling waves, a pair of complex modes is present in the stopband and the space harmonics become leaky waves when operating frequency is sufficiently high.

Low-cost realization of ISM band pass filters using integrated combline structures

Abstract: Low-cost realization of ISM band pass filters using substrate-integrated combline structures has been demonstrated. For the low-cost realization and mass-production, efforts have been concentrated into realizing the combline filter structure as a integrated conductor layer of FR4/epoxy based multi-layer substrates which are widely used as multilayer printed circuit boards (PCB) instead of ceramic. By loading capacitive loads to each side of the combline strips, more reduction of the overall feature size has been achieved. Reasonable stopband and passband characteristics have been achieved. This filter can be used as a RF band pass filter for the wireless network devices of the 2.4 GHz ISM band such as Bluetooth and wireless LAN.

Simulation results for a novel optically controlled photonic bandgap structure for microstrip lines

Abstract: A novel optically controlled one dimensional (1D) photonic bandgap (PBG) microstrip structure is proposed. This device consists of a 50 /spl Omega/ microstrip transmission line and a PBG ground plane both deposited onto a photoconductive substrate. With no optical illumination the structure exhibits a well-defined stopband. When light is focused through the holes in the ground plane and onto the substrate, electron-hole pairs are generated to form a photoinduced plasma. This increases the conductivity of the exposed region of the substrate and forms a complete ground plane. The structure then acts as a conventional microstrip line and the bandstop characteristics are switched off. S-parameter simulation results are presented.

Photoacoustic study of the transmission of wide-band ultrasonic signals through periodic one-dimensional structures

Abstract: The propagation of wide-band acoustic pulses in one-dimensional periodic structures consisting of alternating plexiglas and water layers is studied theoretically and experimentally. The experiment is carried out with the use of the wide-band photoacoustic spectroscopy based on the laser excitation of ultrasound and a wide-band signal detection. The fact that the transmission spectrum of a periodic structure has alternating pass and stop bands is confirmed experimentally. The width and localization of the stop bands strongly depend on the thickness of the layers and on the phase velocity of ultrasound in them. It is demonstrated that defects of the structure periodicity give rise to one or several local transmission maxima in the stop band and to a modification of the pass band. The amplitude and position of a local maximum in the stop band strongly depend on the position of the defective layer. The experimental data agree well with the results of numerical simulation.

Method of tuning thin film resonator filters by removing or adding piezoelectric material

Abstract: The present invention provides a method for tuning a thin film resonator (TFR) filter comprising a plurality of TFR components formed on a substrate. Each of the TFR components has a set of resonant frequencies that depend on material parameters and construction. TFR bandpass filter response for example can be produced by shifting the set of resonant frequencies in at least one of the series branch TFR components so as to establish the desired shape of the bandpass response and the desired performance of the filter. The shifting may be advantageously performed by removing piezoelectric material from the series branch TFR component, providing a TFR filter with bandwidth and attenuation advantages over that conventionally achieved by down-shifting resonant frequency sets of the shunt TFR components by adding metal material. Additionally, the above method can be used to produce a stopband TFR filter with a desired response by removing piezoelectric material from the shunt branch TFR component, to up-shift the shunt TFR components' set of resonant frequencies with respect to the series branch TFR components.

Design of Weighted Reflectors and Their Application to Surface Acoustic Wave Bandpass Filter

Abstract: This paper proposes a method of designing surface acoustic wave (SAW) weighted reflectors using an adaptive nonlinear least-squares algorithm. In the method, the total reflector length, the weighting function, the film thickness and pitch of the grating electrodes are all simultaneously optimised. The optimally designed reflector possesses the stopband width of 4 MHz at the centre frequency of 200 MHz with very steep response in the transition region and off-stopband reflectivities of nearly -80 dB. The electrode width-weighted reflectors were fabricated and applied to filter devices employing a multistrip coupler. The experimental result was in good agreement with theoretical prediction.

A very low power channel select filter for IS-95 CDMA receiver with on-chip tuning

Abstract: A channel-select filter with on-chip PLL tuning for CDMA IS-95 has been integrated in a 0.35-/spl mu/m digital CMOS technology. To achieve both low power and robustness, dynamic range scaling is implemented on an elliptic ladder prototype. The dynamic range scaling is based on the special requirement for the wireless receiver. A new method to analyze the trade-off between filter noise and power consumption is presented. The filter and PLL dissipate 2.9 mW and 1.6 mW from a 3-V supply, and the die area is 1.06 mm/sup 2/. The filter achieves 61 dB stopband rejection, 0.05 dB/0.2/spl deg/ I/Q gain/phase mismatch, 100 /spl mu/Vrms input-referred noise, 20 dBm IIP3, and 58 dB SFDR.

FFT-based analysis of periodic structures in microacoustic devices

Abstract: Periodic structures utilized as transducer or reflector elements play an important role in microacoustic wave devices. Such structures can be described using approximate analytical models. However, to obtain the accuracy required for reliable device simulation, numerical methods have to be employed. In this contribution, we present an efficient numerical approach to calculate the dispersion curves associated with microacoustic modes propagating in periodic structures; the method is demonstrated for the case of Love wave modes. The computational efficiency is related to the utilization of the FFT algorithm in a hybrid Method of Moments (MoM)/Mode-Matching analysis. From the obtained dispersion curves, characteristic parameters such as the stopband width can be obtained which can be used in a coupling-of-modes (COM) model of the structure.

Coefficient quantization in nearly perfect-reconstruction cosine-modulated filter banks

Abstract: This paper presents one possible implementation structure for nearly perfect-reconstruction (NPR) cosine-modulated filter banks (CMFBs). The effect of straightforward coefficient quantization on the performance of the filter bank systems is studied. In multicarrier systems, these filter banks can be used in the transmultiplexer (TMUX) configuration. The performance is evaluated by using parameters like intercarrier interference (ICI), intersymbol interference (ISI), and stopband attenuation.