Showing papers on "Stopband published in 1986"

Stopbands in a corrugated parallel plate waveguide

Abstract: The stopband structure of a two‐dimensional periodically corrugated waveguide is investigated by means of the null‐field method. In the numerical examples, the walls are assumed to be hardwalled with symmetric, antisymmetric, or one‐sided sinusoidal corrugations. The interaction pattern and the stopband widths are determined for the lowest modes. The resonances are found to be of the stopband type, and it appears that geometrical symmetries of the boundaries suppress well‐defined sets of resonances.

Analysis of Antipodal Ridge Waveguide Structure and Application on Extremely Wide Stopband Lowpass Filter

Abstract: This paper presents an accurate analysis of antipodal ridge W/G structure. Design parameters like the cut-off frequencies of TE/sub 10/ and TE/sub 20/ modes, characteristic impedance and gap impedance have been calculated. Comparison with exact analysis of such structure reported in Literature, shows very good agreement. Using the fact that antipodal ridge structures provide very large bandwidth (about twice that of double ridge W/G structures), a lowpass filter with extremely wide stopband using evanescent mode-antipodal ridge W/G techniques has been developed and tested. Spurious free response up to at least the sixth harmonic has been achieved.

Evanescent Mode-Serrated Ridge Waveguide Bandpass Harmonic Filters

Abstract: A new class of bandpass harmonic filters with spurious free and extremely wide stopband response is presented. The design concept is based on using evanescent mode waveguide sections as impedance K-inverter, while using serrated ridge waveguide sections as series resonators. Measured results of narrow and wideband filters show an excellent agreement with the theoretical design.

Generalized approximation techniques for selective linear-phase digital and nonreciprocal lumped filters

Abstract: The paper presents expressions for low-pass digital filter transfer functions with finite-band approximation to constant amplitude and delay in the passband, together with an arbitrary number of transmission zeros at half the sampling frequency. The corresponding high-pass filter transfer functions can be obtained by a transformation. The available degrees of freedom can be divided arbitrarily between the passband and stopband responses. The functions are of the nonminimum-phase type, and the corresponding nonreciprocal analog (continuous) filters are also covered; these can be realized in standard active RC structures. The zero-bandwidth cases are obtained, either directly or as limiting cases of the finite-band ones. It is also indicated that there is an upper bound on the number of transmission zeros which may be introduced while maintaining the stability of the filter for a given degree. The technique represents the most comprehensive one available for the solution of the combined amplitude and phase approximation problem, and leads to a large family of stable transfer functions.

Image Parameter Design of Noncommensurate Distributed Structures: An Application to Microstrip Low-Pass Filters

Abstract: The direct application of the image parameter method (IPM) to distributed structures is suggested in order to overcome some limitations of classical design methods for microwave filters. Several advantages are pointed out: 1) Wider degrees of freedom are obtained using noncommensurate structures. 2) The IPM can be applied directly to a microwave structure without any use of lumped prototypes. 3) Possible technological constraints can be easily incorporated in the design procedure. 4) Filters designed according to the IPM can be cascaded together in order to improve their characteristics. An application to the design of a class of microstrip low-pass filters, which have been previously designed on a low-frequency approximation basis, is illustrated in detail. The IPM is shown to provide an effective control of both the passband and stopband, leading to filters with improved characteristics, as demonstrated by the experimental results.

Elliptic Bandpass Filters Using Four TM/sub 010/ Dielectric Rod Resonators

Abstract: Compact elliptic bandpass filters of three types are constructed by using four TM/sub 010/ dielectric rod resonators. Filters designed to have center frequencies of 3 to 5 GHz, relative bandwidths of 2 to 13 percent, insertion losses of 0.3 to 1.6 dB, and minimum stopband attenuations of 40 to 52 dB.

Programmable switched-capacitor low-pass ladder filters

Abstract: Switched-capacitor filters with digitally programmable capacitor arrays (DPCAs) offer a solution to the diverse needs to the market for audio-frequency high-order low-pass filters. Cascading switched-capacitor biquads which contain binary or geometrically weighted DPCAs are not a viable way to produce precision high-order responses, because of the errors introduced by capacitance quantization. To overcome this problem, a ladder-based structure is proposed. It uses DPCAs tailored to provide exactly the capacitances required to realize a restricted but useful set of responses. A simple procedure for synthesizing such filters is presented and illustrated with a detailed example. A CMOS prototype chip which provides eight seventh-order responses was fabricated. A 3-bit word programs its response: elliptic (with four different selectivities), Chebyshev, inverse Chebyshev, Butterworth, or modified Bessel (modified to have stopband notches). Experimental results are included which show that with this design philosophy, performance is not sacrificed for programmability.

Numerical Analysis of Bloch Theory for Acoustic Wave Propagation in One-Dimensional Periodic Composites

Abstract: For applications in high-frequency medical ultrasonics, periodic composite materials made by combining a piezoelectric ceramic and an epoxy have aroused interest because of their high electromechanical coupl ing and low acoustic impedance. Composite transducers therefore have high sensitivity and broad band width. These significant advantages have led to considerable theoretical and experimental work on these kinds of new artificial materials. The general Bloch theory for solving acoustic wave propagation in periodic structures in two- and three-dimensions has already been presented in previous papers. Here, numerical calculations for one-dimensional Bloch coupled equation set will be described. This numerical result calculated using truncated Bloch matrix will be compared with the exact solution using the m atrix transmission line method. The purpose of this comparison is to test the accuracy of the truncated Bloch solution, which can not be done for the n ultidimension case, because no exact solution exists. Of special interest is the wide stopband splitting and material loss, characteristic of ceramic-epoxy compos i t es .

SAW Filters Using Three-Transducer Configuration with Outer Transducers Weighted by Comb-Shaped Characteristics

Abstract: New outer transducers which comprise pairs of elemental transducers with comb-shaped characteristics are studied for 3-transducer configuration to obtain good rejection in the stopband and good triple transit suppression. A designing method is also developed; these outer transducers are arranged to synthesize the passband shape of the filters, while the central transducer is apodized for matching in the pasband. Application of these transducers to a SAW filter of 400 MHz center frequency is discussed. Group delay of less than 10 n secpp is obtained, while a 10 dB loss is obtained in 50 Ω systems.

An alternative approach for designing maximally flat low- pass filters with multiple order imaginary-axis zeros

Abstract: A systematic procedure is introduced to design a maximally flat low-pass filter with multiple order imaginary-axis zeros. The filter characteristics is specified by the passband and stopband edge frequencies, maximum loss in passband and minimum loss in stopband. This approach can lead to an optimal design of this class of filters.

Broadband Frequency Selective Surface

Abstract: Future communication satellites will use dichroic subreflectors to produce multiple focal regions from a single parabolic reflector. This additional focal region will allow for beams operating over different frequency bands to be produced by a single reflector and avoid the feed crowding or mechanical limitations current reflector antennas encounter. This paper presents parametric studies on a selected number of dichroic elements for possible use as a frequency selective subreflector. The theoretical and measured frequency response of tripoles and Jerusalem crosses are presented. This paper also addresses the design of multilayered dichroic panels to achieve improved gain slope and bandwidth. Designs capable of producing a 4:1 stopband and a 1.4:1 band separation for circular polarization and angles of incidence up to 40 degrees are shown.

Digital filter for sampling frequency conversion

Abstract: PURPOSE:To obtain a sufficient band stop attenuation without increasing the filter order and the number of times of multiplication/addition by connecting digital filters having different prescribed characteristics in cascade. CONSTITUTION:After an input X having a sampling frequency fS is converted into an output Y having a sampling frequency 2fS at a filter DF1, the result is converted into an output Z having a sampling frequency 4fS. In the frequencies below the fS of the characteristic I, frequencies below fA give the pass band, frequencies over fS-fA provide the block band and frequencies between the fA and the fS-fA give a transition frequency band with a prescribed slope. In frequencies below 2fS of the characteristic II, the pass band cut-off frequency is between the fA and fS/2, the band stop frequency is between 3fS/2 and 2fS-fA, and the transition frequency band with a prescribed slope is attained between the pass band cut-off frequency and the stop band cut-off frequency. Thus, a sufficient stop band attenuation is obtained without increasing the filter order and the number of times of multiplication/addition.

Experimental and theoretical investigation of characteristics of periodic-loaded fin-lines

Abstract: Slow-wave propagation along fin-lines with periodic-loaded stubs has been investigated by means of both a transmission-line experimental procedure and a three-dimensional spectral domain approach with modal spectra in the guided direction. Some important features such as passband and stopband for passive elements (e.g. couplers and filters) are discussed from the measured and calculated results.

Mutual Interference Between the Guided Wave and the Leaky Wave Regions and its Effects on the Performance of Dielectric Grating Filters

Abstract: In an open periodic structure with finite length, a new interaction between the guided-wave and the leaky-wave regions in the omega - beta diagram does occur. The effect of such an interaction on the characteristics is investigated rigorously by using our network approach already proposed. Numerical calculations show that the finite length of periodic structures significantly affects the stopband characteristics of the first Bragg reflection region, especially in producing a complicated behavior of the return loss due to radiation. This paper also shows that such a return loss behavior can be easily estimated from the radiation characteristics of only the first step discontinuity of the periodic structure.

Printed High Power E-Plane Filters with Spurious-Free Response

Abstract: Conventional high power E-plane metal insert bandpass filters produce spurious responses which appear between the desired passband and twice the midband frequency. This paper presents a design proposal which eliminates all spurious passbands in that frequency range up to more than twice the midband frequency of the operating bandwidth. The solution is based on a series connection of two or more individual E-plane filters which provides significantly improved stopband attenuation up to very high frequencies.

Stopband optimised E-plane filters with multiple metal inserts of variable number per coupling element

Abstract: Improved stopband attenuation of E-plane filters is achieved by replacing merely a few of the conventional single insert coupling elements by triplets or quintuplets of metal inserts. The method of field expansion into suitable eigenmodes used considers the effects of finite insert thickness and the mutual higher order mode interaction of all inserts. Calculated stopband attenuations of more than 50 dB up to about 30 GHz, or 60 GHz respectively, have been attained, although the passbands of the corresponding filter examples are chosen to operate at the upper waveguide band limit of the mount (at 18 GHz for Ku-band and at 40 GHz for Ka-band respectively). The results demonstrate that high stopband conditions can be satisfied by designs with only a modified number of multiple inserts. This helps to maintain the low-loss and low-cost qualities of E-plane filters and also provides for improved stopband demands. The thickness of all inserts of t = 190 µm makes possible accurate metal-etching fabrication.

Metal-insert filters with improved characteristics

Abstract: A computer-aided design is introduced for E-plane filters with single and double metal inserts within a reduced-width or increased-width waveguide section, respectively. This design achieves filter performances with high peak attenuation in a broad second stopband. The theory described includes both the higher-order mode interaction of all discontinuities and the finite thickness of the inserts. The step-wall discontinuity effect is included in the optimisation process as an additional parameter to be optimised. Ka-band (26.5?40 GHz) design examples demonstrate the good stopband attenuation behaviour of this type of filters. Moreover, this design only requires thin strips, which are very appropriate for technical realisation.

Metallic E-plane filter with cavities of different cutoff frequency

Abstract: A planar integrated circuit filter with multiple all-metal inserts and multiple abrupt waveguide step-wall discontinuities is introduced which achieves broadband high attenuation in the second stopband. The design is based on field expansion into suitably normalised eigenmodes which yield directly the modal S-matrix. This theory allows the immediate inclusion of both the higher-order mode interaction at all discontinuities and the finite thickness of the inserts. Computer-optimised design data for a five-resonator Ka-band prototype filter at 27 GHz midband frequency provide a minimum stopband attenuation of 50 dB between 27.5 and 44.5 GHz.

Acoustic surface leaky wave propagation under periodic metal grating

Abstract: The properties of LSW propagation under periodic metal grating have been investigated by using a new method of field analysis that leads to a satisfactory solution fitting the electrical boundary conditions. The detailed dispersion relations and the curves of attenuation constant for LSW on 49°Y-X LiNbO3 are presented. The discussion and comparison between the theory and experiment for the first stopband are also made.

On the design of FIR digital filters with prescribed stopband or passband deviation

Abstract: The utility of the constrained Chebyshev approximation for the design of FIR filters is discussed in this letter. This method can often replace an iterated execution of the classical Parks-McClellan program and has more flexibility for a number of applications.

On the design of FIR digital filters with prescribed stopband or passband deviation

Abstract: The utility of the constrained Chebyshev approximation for the design of FIR filters is discussed in this letter. This method can often replace an iterated execution of the classical Parks-McClellan program and has more flexibility for a number of applications.

Effects of metallic‐grating upon leaky saw propagating on 36° YX‐liTaO3

Abstract: Propagation characteristics of leaky SAW under a metallic-grating structure (grating mode) on 36° YX-LiTaO3 (36-LTO) are analyzed and compared with experimental results. First, the velocity dispersion and attenuation for the grating mode are theoretically analyzed. The results show that although the velocity dispersion is similar to that for an SAW, the stopband width of the grating changes with the electrical boundary of the grating. The attenuation depends on how strongly the grating mode couples to bulk waves and leaks its energy into the bulk. The interaction of the grating mode with slow shear waves is markedly weak on 36-LTO. Hence, the attenuation due to bulk wave radiation is negligible at frequencies where the grating mode couples only to slow shear waves. However, the attenuation increases at frequencies slightly higher than the stopband, where the grating mode strongly couples to fast shear waves. Next, transmission and reflection characteristics are experimentally investigated about the stopband of a metallic-grating fabricated on 36-LTO. The results are in good agreement with the theoretical prediction.

Two Path Cutoff Waveguide Resonator Filters with Attenuation Poles

Abstract: We propose here a new idea to design filters which consist of low permittivity dielectric resonators placed in the two paths which are realized by a partial H-plane bifurcation in a rectangular waveguide. This type of filters is regarded as the parallel connection of two evanescent - mode waveguide filters. This paper will try to design such a filter with the Chebyshev's passband response and also with the stopband response with attenuation poles at desired frequencies, and practical performance aspects of this type of filters will be discussed from the view points of both analytical methods and experiments in the X-band.

Two-Octave Stopband Microstrip Low-Pass Filter Design using Butterfly Stubs

Abstract: The application of a new design technique using non commensurate elements combined with the use of the butterfly stub permits lowpass filters with exceptional performances to be realised in microstrip configuration. Very compact microstrip filters exhibiting very high cutoff rates, two octave stopband widths, and stopband attenuations of 40 dB have been designed, fabricated and measured.

Equidistant linear phase functions with improved selectivity and stopband attenuation

Abstract: The letter describes a technique to manipulate the parameters governing Rhodes equidistant linear phase functions, so that two finite transmission-zero pairs can appear on the imaginary axis of the complex plane. An increase in the amplitude selectivity and stopband attenuation occurs, with little degradation of the passband ripple and group delay, especially for higher-degree transfer functions.