Showing papers on "Stopband published in 1980"

A filter family designed for use in quadrature mirror filter banks

Abstract: This paper discusses a family of filters that have been designed for Quadrature Mirror Filter (QMF) Banks. These filters provide a significant improvement over conventional optimal equiripple and window designs when used in QMF banks. The performance criterion for these filters differ from those usually used for filter design in a way which makes the usual filter design techniques difficult to apply. Two filters are actually designed simultaneously, with constraints on the stop band rejection, transition band width, and pass and transition band performance of the QMF filter structure made from those filters. Unlike most filter design problems, the behavior of the transition band is constrained, which places unusual requirements on the design algorithm. The requirement that the overall passband behavior of the QMF bank be constrained (which is a function of the passband and stop band behavior of the filter) also places very unusual requirements on the filter design. The filters were designed using a Hooke and Jeaves optimization routine with a Hanning window prototype. Theoretical results suggest that exactly flat frequency designs cannot be created for filter lengths greater than 2, however, using the discussed procedure, one can obtain QMF banks with as little as ±.0015dB ripple in their frequency response. Due to the nature of QMF filter applications, a small set of filters can be derived which will fit most applications.

An analytical theory for the scattering of surface acoustic waves by a single electrode in a periodic array on a piezoelectric substrate

Abstract: An analytical theory is presented that leads to the scatter matrix of a sngle electrode for an acoustic surface wave propagating through a periodic array of electrodes on an anisotropic piezoelectric substrate. The scatter matrix elements are obtained analytically as functions of frequency and metallization ratio, considering only the electrical loading by the electrodes; mechanical loading effects are neglected. The results may be used directly in the broad band analysis of surface acoustic wave reflectors and multistrip couplers. Previous works have provided these parameters numerically for electrically shorted and open arrays at stop band frequencies (frequencies where the array period is an integer number of half wavelengths). This work extends the analysis in three ways: (a) the analysis is valid for all frequencies, (b) the external electrical load connected to the electrodes is included as a parameter, and (c) the scatter matrix elements are determined analytically instead of numerically.

On the design of recursive low-pass digital filters

Abstract: The magnitude-squared characteristic of a low-pass filter is approximated, over the finite interval [-1, 1 ], by the ratio φ(x)/[φ(x) + P(x)] of two polynomials. For elliptic filter design, a special case, the polynomials φ(x) and P(x) (of the same order) are chosen such that the ratios P(x)/φ(x) and φ(x)/P(x) approximate, in the Chebyshev sense, the zero function over the passband [x p , 1] and stopband [-1, x s ], respectively. The passband and stopband form two disjoint intervals. The polynominals are determined by repeated applications of Darlington's technique for obtaining a rational function generalization of Chebyshev polynominals.

Behavior of Bleustein-Gulyaev Waves in a Periodically Corrugated Piezoelectric Crystal

Abstract: The propagation characteristics of Bleustein-Gulyaev waves in a periodically corrugated piezoelectric crystal is investigated theoretically and numerically. The exact couple-mode equations governing the nature of Bleustein-Gulyaev wave interactions are derived with the aid of a singular perturbation procedure, and the interesting behavior of the filtering characteristics are shown numerically. It is found that the practically important characteristics such as wide stop-bandwidth and large wave-decay in the stopband can be achieved by choosing a value of the piezoelectric constant suitably, and/or coating the crystal surface with thin conducting material.

Unsolved theoretical problem in design of optimal low-pass filter for harmonic suppression in radio-transmitter output

Abstract: The author offers to cooperate in development of an optimal harmonic-suppression output filter for power amplifiers. The commonly used elliptic-function filter is not optimal for this purpose: less attenuation is needed at higher frequencies in the stopband. An improved design should provide a value of A_{\min} that varies with frequency as the harmonic output of the amplifier varies with frequency.

Dispersion In n Coupled Microstrip Meanders

Abstract: A meander Iine consisting of an even (n), or odd (n-1), number of coupled microstrips has been analyzed for its dispersion and iterative impendance characteristics. In contrast with the unit cell approximation used by other authors, this method takes all the couplings into account and enables correct determination of stopband locations, which is very important in the design of such slow-wave structures. Other periodic structures can also be analyzed by this method, and their possible future applications as filters, etc., can be predicted.

Effects of Directional Coupling on the Magnetostatic Surface Wave Propagation

Abstract: In this report we describe the experimental confirmation of the directional coupling of the magnetostatic surface wave between two parallel YIG films. We also describe a theory to calculate the coupling coefficient and the over-all passband characteristics of the devices. With this technique, a bandstop filter with the minimum insertion loss of 18 dB and the rejection of at least 25 dB from the top of the passband at 7.08 GHz was demonstrated. The stopband width at 10 dEi below the top of the passband was 15 MHz. A narrow bandpass filter was also built. We observed the reduction of up to 75 of the 30 dB passband with the increase of the insertion loss of less than several decibels. This method is useful at higher frequencies because we can choose a material with the lowest intrinsic loss and control the bandwidth by the directional coupling. The experimental results agreed qualitatively well with the theoretical predictions. This will provide a new possibility to the design of magnetostatic signal processing devices.

Multiple real‐pole equal‐ripple rational (MRPER) approximation for lowpass RC‐active filters

Abstract: A new class of lowpass rational transfer functions is defined, with equal-ripple behaviour both in the passband and in the stopband. The proposed functions have a multiple real pole, which allows the realization of lowpass RC-active filters by cascading more (than one) 3rd-order blocks. These new functions, called multiple real-pole equal-ripple rational (MRPER), improve the attenuation performance with respect to a classical solution employing the same number of 2nd-order blocks and hence may allow a reduction in the required number of active elements and, eventually, in power consumption and in noise-to-signal ratio. However, even if the number of active blocks cannot be reduced, the better attenuation performance, which results, allows component tolerances to relax.

Transmission Characteristics and a Design Method of Transmission-Line Low-Pass Filters with Multiple Pairs of Coincident Zeros and Multiple Pairs of Coincident Poles

Abstract: The transmission characteristics and a design method are presented for a transmission-line Iow-pass filter with multiple pairs of coincident zeros in the finite frequency of the passband and multiple pairs of coincident poles in the finite frequency of the stopband and for a transmision-line low-pass filter with Butterworth characteristic in the passband and multiple pairs of coincident poles in the finite frequeney of the stopband. The former transmission-line low-pass filter shows an improved skirt attenuation performance and delay characteristic than a Chebyshev transmission-line low-pass filter in the same network degree. The latter type of transmission-line low-pass filter shows an improved skirt attenuation performance in comparison to a Butterworth transmission-line low-pass filter in the same network degree, it is positioned about in the middle between a Butterworth type and a Chebyshev type, the delay characteristic is improved considerably in comparison to the Chebyshev type, and the characteristic is close to that of the Butterworth type. With this design method, the connecting unit elements in addition to the stubs contribute to the attenuation response. The design example is shown on the basis of a concrete specification, and it is shown that the obtained attenuation strictly fulfills the specification.

Characteristic function of least-mean-square passband filters with finite attenuation poles

Abstract: Characteristic function of low-pass filters with finite attenuation poles approximating a zero passband loss in terms of a weighted least-mean-square norm is derived in explicit form. The number and locations of attenuation poles are subject only to the realizability conditions and can be adjusted by a simple pole placer program to meet either equal-ripple or general stopband requirements. The shape of the passband magnitude response is controlled by a variable parameter which appears in the weight function used to define the error integral. Filters with either Chebyshev, or maximally flat passband magnitude response are shown to be the special cases of the explicit formula derived.

A New Computer Aid for Microwave Filter Design

Abstract: A recent development for the synthesis, as well as the analysis, of microwave filters, multiplexers, and impedance matching circuits is described in this paper. The new program offers interactive design of filter networks constructed by commensurate transmission line stubs and unit elements. Lowpass, highpass, bandpass, linear-phase lowpass and band-reject filters can be specified with maximally flat or equal-ripple passband, having monotonic, equal-minimum or arbitrary stopband specifications. If finite transmission zero locations are not known, the program can compute them by an optimization procedure. Circuit topology may also be specified by the user, or the program can generate it internally. At the command level, all the known network manipulations (Norton Transformations, Kuroda Identities including Levy's Extension, etc.) are readily available; additional unit elements may be inserted at the source or the load side to increase the complexity of an existing network. Filter size may be specified by its degree or by the appropriate stopband specifications.

SAW Bandpass Filter Design for 1.6-GHz PCM Timing Tank Applications

Abstract: A 1.6-GHz surface acoustic wave (SAW) timing tank for a self-timed regenerative repeater for an ultrahigh-speed PCM optical fiber transmission system is described. A SAW narrow bandpass filter with 0.74-mu m linewidth interdigital transducers with double electrode geometry and 20-nm aluminum metallization on AT-quartz substrate is realized by conventional optical photolithography. Typical performance obtained is as follows: center frequency f/sub 0/ is 1.5993 GHz; insertion loss is 22 dB; stopband attenuation is above 23 dB with respect to the passbaand; stability is |2Q/sub L//spl dot/Delta f /f/sub 0/| < 0.1, where Q/sub L/ is loaded Q value and Delta f is mistuning due to temperature effects. It is demonstrated that SAW quartz transversal filters can be made into new practical filters which have both high Q value and high stability fn the GHz range and are satisfactory from the standpoints of precise design, fabrication technique, and performance.

A Simple Method for Spacing the Adjacent Passbands of a Coupled-Line Filter

Abstract: A bandpass filter using two coupled transmission lines is considered. Two ports of the coupled-line four port are both short-circuited (or open-circuited); the other two ports are terminated in the characteristic impedances of the lines (e.g., 50 Omega). For a constant coupling along the coupling section l the attenuation poles are fixed at l/lambda = n/2 (n = 0,1,2,...). If, however, the coupling changes along the coupling section in three steps with the coupling factors k/sub 1/, k/sub 2/, k/sub 3/ = k/sub 1/, the stopband between two adjacent passbands can be extended for certain values of k/sub 1/ and k/sub 2/. A simple calculation method for the coupling factors k/sub 1/ and k/sub 2/ is described. A practical design example shows good agreement with theoretical results.

A SAW Ring Filter with a Phase Matching Electrode

Abstract: A low insertion loss SAW ring filter containing a phase matching electrode was constructed on a Y-cut lithium niobate substrate and successfully operated at 282 PIHz. The filter had an insertion loss of 5 db, passband ripples of less than 1 db, stopband rejection of 75 db, and a 3-db bandwidth of 3 MHz. The passband ripples and losses caused by a phase difference of the surface waves were measured and compared with theoretical ones. The phase matching electrode was effective in reducing the ripples and losses of the ring filter in a high frequency range.

Design of bandstop filters by reactance transformation

Abstract: The usual method for designing bandstop filters is the reactance transformation from a lowpass prototype. When the filter specifications do not satisfy geometrical symmetry, the choice of stopband central frequency constitutes an interesting problem. This letter shows that the mean square of the stopband edges is the stopband central frequency that leads to the lowest selectivity parameter of the prototype.

Design of filters with prescribed time response and Chebyshev stopband attenuation

Abstract: This paper presents a new class of low pass filters with Chebyshev stopband attenuation which are intended for pulse applications and characterized by very small values of the dominant polo Q-factor, Their transfer functions are obtained by computational optimization in the time domain of either step response or impulse response under the constraint of double or higher-order multiplicity of the dominant pair of poles. The comparison with Schussler filters, which are known for their excellent rise-time-overshoot characteristics, reveals that the new filters yield superior frequency and time domain characteristics and yet they have much smaller values of the dominant pole Q-factor. The pole locations and other important frequency and time-domain parameters are tabulated for optimum step response and for optimum impulse response for n = 5, 6, 7, 8 and several values of the maximum tolerable overshoot.

Equiripple stopband characteristic for circularly symmetric 2-D recursive filters

Abstract: A circularly symmetric 2-D recursive digital filter whose magnitude-squared response approximates a Gaussian function in the two frequency variables has a separable transfer function. Such a circularly symmetric filter has a monotonic frequency response. One may, therefore, want to sharpen the response in the transition band. Due to the separability feature, it is shown how to obtain an equiripple characteristic in the stopband without affecting the circular symmetry in the passband. This reduces the transition bandwidth.