Showing papers on "Stopband published in 1991"

FIR digital filters with least-squares stopbands subject to peak-gain constraints

Abstract: The use of digital filters with peak-constrained least weighted-squared errors (PCLWSE) is proposed. The emphasis is on PCLWSE filters with equiripple passbands and peak-constrained least-squares (PCLS) stopbands. The stopband energy is minimized subject to a constraint on the maximum stopband gain. A design algorithm is presented, and examples are discussed. Each example provides the unique optimal solution to the corresponding design problem. The tradeoff between the peak stopband gain and the total stopband energy is examined. It is shown that the most inefficient filters have minimax or least-squares stopbands. In particular, the stopband energy for minimax filters can be significantly reduced with almost no change in the peak stopband gain. Also, the peak stopband gain for filters with least-squares stopbands can be significantly reduced with almost no change in the total stopband energy. These results are supported by mathematical analysis, and examples are provided. >

Realization of a 1-V active filter using a linearization technique employing plurality of emitter-coupled pairs

Abstract: A low voltage (1 V), low-power (100 mu W), and low-frequency (9 kHz) fifth-order fully integrated active low-pass filter (LPF) using a bipolar technology is described. Novel highly linear transconductors consisting of N emitter-coupled pairs were designed for low-voltage operation. The linear input range is expanded to about 100 mV/sub p-p/ at 1% error with N=4, which is about twice that of the conventional linearization technique. The filter is basically a gyrator-capacitor type, in which gyrators are implemented by using the linearized transconductors. Large time constants were realized with very low current (540 nA/transconductor) owing to the high transconductance-to-operating-current ratio of the linearized transconductors. Measured results show a passband ripple of 1.5 dB, a minimum stopband rejection of 70 dB, and a dynamic range of 56 dB, despite a very high nominal impedance (400 k Omega ). Practical limitations of this approach are also discussed, such as the sensitivity of the linearized transconductors against process variations, noise, and frequency limitations. >

Theory and practical implementation of a fifth-order sigma-delta A/D converter

Abstract: An 18-bit analog-to-digital converter integrated circuit has been designed which uses a fifth-order loop filter with an unusual loop topology. Implementation of the loop using differential switched-capacitor techniques is described. A one-step decimation filter with 115-dB stopband attenuation is used to remove out-of-band quantization noise. Preliminary measurements indicate a dynamic range of 105 dB, a number that is compatible with the requirements of professional digital audio

Narrow-band distributed feedback reflector design

Abstract: The theory is developed for a narrowband distributed feedback reflector that reflects at the center of the grating stopband and transmits at frequencies to either side. A perturbational method of analysis is presented which simplifies the algebra and provides helpful insight. The approximate analysis is compared with the exact results. It is shown that the approximate solution is good in the operating region of practical devices. The proposed tunable narrowband reflector can perform well at a reasonable bandwidth of about 40 GHz. >

Filter with electrically adjustable attenuation characteristic

Abstract: A tunable bandstop/bandpass filter particularly suitable for use in duplex applications where the transmit and receive bands are closely located, comprises two or more reactively coupled quarter wavelength resonators e.g. dielectric resonators. One end of each resonator is coupled to ground potential. The opposite (open-circuit) end of the resonators is coupled to adjacent resonators via coupling capacitors. Voltage controlled tuning means, e.g. a varactor and series connected capacitor, are coupled in parallel to the open circuit end of each of the resonators respectively. The stopband/passband of the filter can thus be adjusted by varying the voltage applied to the tuning means. Additionally, in the case of a bandpass filter a tunable zero (or "notch") may be introduced into the transmission response by including varactors coupled in series to the open-circuit end of the resonators.

Effects of coefficient inaccuracy in switched-capacitor transversal filters

Abstract: Coefficient inaccuracy effects in the frequency response of finite-impulse-response (FIR) switched-capacitor filters implemented in direct form are investigated. No assumption is made with respect to the filter coefficients, so that the results of the analysis are valid for both linear and nonlinear phase FIR filters. Assuming that the errors in the capacitor ratios realizing the tap coefficients are uncorrelated and have identical Gaussian distributions, an exact probability distribution function is derived for the error in the frequency response. It is shown that this distribution can be characterized by a Rayleigh distribution, which is then used to derive an upper bound for the expected stopband attenuation. Extensive simulation results are shown to support the analysis. >

Narrow bandstop filters

Abstract: The synthesis of narrow bandstop filters with arbitrary stopband and equiripple passband responses is demonstrated. A new transformed frequency variable is used for iterative approximation with automatic bandwidth adjustment and prototype circuit realization. A five-resonator filter is used to illustrate the proposed method. >

Acoustic Bloch Wave Propagation in a Periodic Waveguide

Abstract: : The propagation of linear, dissipative acoustic Bloch waves in a periodic waveguide is investigated theoretically and experimentally. The waveguide under study is a rigid, fluid-filled, rectangular waveguide that is loaded with a periodic array of rigidly terminated rectangular side branches. Conditions for the existence of Bloch waves in the periodic waveguide are presented. Analytic expressions for the dispersion relation, the impedance function, and the Bloch wave function are derived. Measurements verify the predicted passband/stopband structure of the dispersion relation and show good agreement with the theory.

Novel filter design incorporating asymmetrical stripline Y-junction circulators

Abstract: Theoretical treatments of an asymmetrical stripline Y-junction circulator have been carried out. These include a formulation of the circulation conditions of an asymmetrical circulator as well as its transmission characteristics under wide-frequency-band consideration. It is found that filter designs incorporating circulators are very plausible and give rise to a narrow transmission band around the desired transmission frequency and a wide stopband extending many times the fundamental transmission frequency. In this design, high order mode excitations inherent in other filter designs are attenuated. In addition, owing to the off-resonance operation of the ferrites, present design could be applied under higher power conditions than traditional resonant ferrite filters. >

Modal-S-matrix design of microwave filters composed of rectangular and circular waveguide elements

Abstract: The authors describe the rigorous CAD (computer-aided design) of a class of cavity filters composed of rectangular and circular waveguide structures. Based on the rectangular-to-circular and circular-to-circular waveguide junction key-building block modal S-matrices, the design takes rigorously into account both the finite iris thickness and the higher order mode interaction at all step discontinuities, as well as asymmetric irises. This allows the stopband characteristic to be included in the filter design, and dual-mode resonance effects may be utilized to achieve improved edge steepness and rejection characteristics. The theory is verified by measurements. >

Bandpass digital differentiator design using quadratic programming

Abstract: A novel technique utilizing quadratic programming for the design of bandpass FIR (finite impulse response) digital differentiators of arbitrary order is presented The new differentiators have linear phase and are maximally accurate at the center of the differentiation band Their design is based on a minimization procedure for the integrated square error of the frequency response over designated approximation bands The closed-form solution for the filter coefficients is obtained by the method of Lagrange multipliers The inclusion of stopband in the design process is also discussed This technique has been successfully used by the authors for the design of optimal low pass differentiators The new differentiators are important for applications where the first-, second-, or higher-order derivative of a digital signal is required to be accurate at midrange frequencies >

Tunable bandpass filter

Abstract: A tunable bandstop/bandpass filter particularly suitable for use in duplex applications where the transmit and receive bands are closely located, comprises two or more reactively coupled quarter wavelength resonators (1,2) e.g. dielectric resonators. One end (3b) of each resonator is coupled to ground potential. The opposite (open-circuit) end (3a) of the resonators is coupled to adjacent resonators via coupling capacitors (14). Voltage controlled tuning means, e.g. a varactor (9,9′) and series connected capacitor (10,10′), are coupled in parallel to the open circuit end of each of the resonators respectively. The stopband/passband of the filter can thus be adjusted by varying the voltage applied to the tuning means. Additionally, in the case of a bandpass filter a tunable zero (or "notch") may be introduced into the transmission response by including varactors (15,16) coupled in series to the open-circuit end (3a) of the resonators.

Lattice wave digital filters with simultaneous conditions on amplitude and phase

Abstract: Simultaneous amplitude and phase approximation for low-pass lattice wave digital filters has been developed based on the hidden relationship between the amplitude and phase characteristics of a nonminimum-phase transfer function. The iterative approximation process is based on the factorization of the nonminimum-phase transfer function into a minimum-phase and an all-pass part. Separate algorithms are used to design the minimum-phase and the all-pass part, and these algorithms are carried out alternately. The approximation method results in filters with equiripple amplitude both in the passband and the stopband while the phase characteristic is equiripple with respect to a linear phase. A design example shows the properties of these filters and illustrates the efficiency of the proposed method. >

Enhanced performance mode S interrogator

Abstract: An enhanced performance Mode S interrogator that includes a matched channel receiver. The receiver includes equiripple-phase response filters with finite peaks of attenuation. This new class of filters provides a faster rise of attenuation than all-pole filter while extending the equiripple delay further into the stopband.

Geometric effects on the stopband structure of 2-2 piezoelectric composite plates

Abstract: Piezoelectric composites have become an important part of medical transducer design over the past several years. A critical issue in the proper design of these materials is an understanding of the stopband edge resonances which produce a net piezoelectric response. Previous work has been done showing the stopband structure for 2-2 composite plates which have a unit cell length greater than the plate thickness (d>t). A simple model for predicting the stopband resonance frequencies in 2-2 composite plates with the length of the unit cell smaller than the plate thickness (d >

High-silica cascaded three-waveguide couplers for wideband filtering by flame hydrolysis on Si

Abstract: Simply by the proper choice of the interaction length and number of cascaded three-waveguide directional couplers (3WC), appropriately connected, it is possible to design suitable spectral responses for filtering operations, tuning the passbands and achieving high stopband rejection. We report on the realization of low-loss, cascaded 3WCs for wideband filtering, based on high-silica waveguides on Si. The devices have been fabricated by a combination of Flame Hydrolysis Deposition, photolithographic patterning and reactive ion etching. The design has been directed towards the filtering of the amplified spontaneous emission in Nd-doped fluoride fibre amplifiers operating at 1.3 [?m], which limits the magnitude of the amplifier gain and requires wideband filtering operation to be suppressed. However, a similar arrangement would also find useful application in other devices such as a multi/demultiplexer for widely spaced channels or when wider rejection bandwidths are required to cover the wavelength variation of laser sources in practical conditions.

High order FIR digital filter realization in distributed arithmetic

Abstract: For FIR digital filters implemented in distributed arithmetic, the exponential growth of the memory size with the impulse response coefficients has always been considered to be a fundamental drawback of implementation. With higher-order section cascade structures it is possible to reduce the memory size requirements at the same speed of operation as in the basic distributed arithmetic implementation, since no additional adders are needed. The simulated results for frequency response calculations with stopband attenuation, passband gain, and passband ripple are presented for several digital filters. >

High frequency, low loss, fundamental mode STW resonators used for stable oscillator design

Abstract: The results of a development effort to design high-frequency, low-loss, fundamental-mode surface transverse wave (STW) resonators for use in stable oscillator applications are presented. Several devices have been fabricated with a resonant frequency below the grating stopband center in order to investigate the effects of this resonant frequency shift on the insertion loss of a two-port STW device. Both theoretical and experimental results are presented along with a discussion of STW design considerations for stable oscillator applications above 2 GHz. >

Imaging of the wave field of surface acoustic wave devices

Abstract: An optical measurement technique for the phase preserving imaging of elastical wave fields of surface acoustic wave devices was developed. This technique uses short pulses from a mode-locked picosecond laser, harmonic mixing, and coherent detection to achieve a measurement bandwidth beyond 1 GHz. It is therefore well suited to perform measurements on surface acoustic wave devices of even the highest frequencies where modeling becomes increasingly difficult. The detection capability for surface displacements of 1 pm/ square root Hz allows a minimum dynamic range of about 40 dB for the determination of amplitude profiles of surface acoustic wave devices. As an example of a practical application, results of measurements on a bandpass filter are presented. The generated wave profiles have been determined at several different distances from the transducer both in the passband and in the stopband of the device. The measurements are in excellent agreement with computer simulations obtained with an angular spectrum of waves model. >

Inline optical filter using lifted-off GaAs/AlGaAs multilayer

Abstract: A new inline optical filter is reported. A GaAs/AlGaAs multilayer interference filter was lifted off its GaAs substrate by selective etching, and was sandwiched between two gradient-index rod lenses. Near-theoretical performance was obtained, with over 20 dB rejection in the stop band and less than 0.5 dB insertion loss at transmission peaks. This type of filter could be extremely useful in wavelength division multiplexed systems.

Band pass filter

Abstract: PURPOSE:To eliminate the need for an excess additional circuit for blocking a band by providing a throughhole penetrating a dielectric material supporting a strip line conductor at a midpoint where the current distribution of a microstrip line conductor of lambda/2 in length being a component of a resonator is maximized. CONSTITUTION:A throughhole 3, 4 penetrating a dielectric base having a microstrip line is provided at a midpoint (equivalent short-circuit point) where a current distribution of a lambda/2 wavelength resonator 1, 2 is maximized without any shape working such as tapering or projection to a resonance line. Thus, the band pass filter is realized, in which only the fundamental frequency at a pass band is used for the resonance frequency and other harmonic frequencies are not used. Thus, no excess additional circuit is required to prevent the deterioration in the stop band characteristic and the filter design is facilitated.

Toward a unified efficient algorithm for characterizing planar periodic waveguides and their applications to MIC and MMIC circuits

Abstract: A modified three-dimensional spectral-domain approach is presented in detail to analyze the characteristics of planar periodically loaded structures. Mode propagation in both symmetrically and asymmetrically loaded periodic structures is described, and some physical mechanisms are clarified. Slow-wave and loss properties as well as passband and stopband characteristics related to the cutoff and resonant frequencies are discussed. Numerical results are compared with measured results obtained by transmission line experimental procedures. >

Waveguide band rejection filter using yttrium iron garnet films

Abstract: This paper describes the theoretical and experimental characteristics of the band reject filter made of a waveguide loaded with yttrium-iron-garnet (YIG) films. First, the problem of reflection and transmission of the plane electromagnetic wave from a semiinfinite YIG film is described. Next, it is noted that the electromagnetic wave of the TE10 mode in a waveguide loaded with an isotropic medium can be expressed as a superposition of these plane waves. Their treatment is applied in an approximate approach to the waveguide loaded with a YIG film. The band rejection characteristics are investigated in which the center frequency varies depending on the dc magnetic field applied. Further, it is shown that a good characteristic is obtained as a band reject filter if YIG films are stacked as a multilayer. Finally, an experiment is carried out at the × band so that the forementioned characteristics are confirmed experimentally. When a dc magnetic field of 2.818 kOe is applied, the observed filter characteristics are such that the center frequency is 10.0 GHz, the insertion loss is 1.0 dB, the bandwidth is 144.7 MHz and the maximum attenuation within the stopband exceeds 60 dB.

Design of partial response data transmission filters with specified stopband attenuation

Abstract: In the paper, a method for optimal design of class 1 partial response filters with low intersymbol interference (ISI) is described. The filter selectivity and stopband attenuation can be easily specified or controlled. It is shown that ISI can be reduced by introducing rolloff around the Nyquist frequency at the expense of a small increase in spectral inefficiency. Class 4 partial response signals are obtained by using class 1 partial response filters. Design examples are given to show that the design method is appropriate for applications.

Parameters of Butterworth, Tschebyscheff, and elliptic prototype reference transfer functions in discrete-time frequency transformations

Abstract: Explicit relationships are presented for the parameters of the normalized lowpass discrete-time prototype reference transfer function suitable for the derivation of denormalized lowpass, highpass, bandpass, and bandstop discrete-time transfer functions having Butterworth, Chebyshev, and elliptic loss-frequency characteristics. These parameters include the required order of the discrete-time prototype reference transfer function as well as the required passband and stopband edge frequencies for its loss-frequency characteristics. >

Wide rejection band multidemultiplexer at 1.3-1.55 mu m by cascading high-silica three-waveguide couplers on Si

Abstract: A novel configuration for an optical guided-wave wide rejection band multidemultiplexer at 1.3 and 1.55 μm is reported. For a stopband rejection loss of 20 dB, a rejection bandwidth of 160 nm is achieved by cascading and appropriately connecting three high-silica three-waveguide directional couplers on Si. The cascading concept behind the rejection bandwidth improvement is simple and straightforward, and lends itself to a systematic approach for the synthesis of spectral responses for wideband filtering operations.

Design of 2-D digital filters with octagonal passband and stopband boundaries

Abstract: A method for the design of 2-D digital filters with octagonal passband and stopband boundaries is described. The method involves cascading four 1-D FIR (finite impulse response) or IIR (infinite impulse response) digital filters. Consequently, it is easy to apply and leads to fast, economical, and efficient designs. By choosing appropriate passband- and stopband-edge frequencies for the 1-D filters, 2-D filters with approximately circular or elliptical passband and stopband boundaries can readily be designed. Additionally, it is possible to realize causal 2-D IIR filters with linear-phase passbands by using 1-D IIR filters having linear-phase passbands. >

A transformation method for the design of two-dimensional circularly-symmetric FIR digital filters

Abstract: A new transformation method for the design of 2-D FIR digital filters with circular band boundaries is proposed. The method involves a simple transformation on an optimal 1-D FIR prototype filter design which is followed by a 2-D windowing operation. The method results in designs with excellent band-boundary circularity, even for high-frequency band boundaries. As shown by the examples, the approximation errors in the passband and stopband are nearly optimal and are typically within 10% of the optimal L/sub infinity / solution. Since the designs are nearly optimal, it is expected that the method may also be useful for generating an initial estimate for optimization methods. An additional result of this work is a technique for estimating the required order of 2-D FIR digital filters that meet prescribed specifications. >

Practical design of wide-stopband filters utilizing asymmetric circulators

Abstract: Wide-stopband filters in which the stopbands extend two octaves of the fundamental transmission frequencies have been realized in terms of asymmetrical Y-junction circulator designs. These filters have been tested at microwave frequencies from 0.05 to 18 GHz. The calculated biasing field requirement, insertion loss, isolation, and stopband frequency range are in reasonable agreement with the corresponding measured values. Since this filter is an off-resonant device, high power handling capability may be assumed. The filters show two octaves of stopband and, hence, can be used extensively as stopband filters in radome applications. >

Enhancement of transmission characteristics in elliptic filter design

Abstract: In filter design, the delay characteristic becomes flatter as the values of the pole-Q decrease. For elliptic filters there exists a method by which one may continuously decrease Q values by increasing a single parameter within the design specifications. It is demonstrated that the pole Q can be lowered by increasing omega /sub s/ (the stopband frequency where the stopband begins). As a consequence the step response in the time domain as well as the delay characteristic in the frequency domain improves. >