Showing papers on "Prototype filter published in 2008"

Constant time O(1) bilateral filtering

Abstract: This paper presents three novel methods that enable bilateral filtering in constant time O(1) without sampling. Constant time means that the computation time of the filtering remains same even if the filter size becomes very large. Our first method takes advantage of the integral histograms to avoid the redundant operations for bilateral filters with box spatial and arbitrary range kernels. For bilateral filters constructed by polynomial range and arbitrary spatial filters, our second method provides a direct formulation by using linear filters of image powers without any approximation. Lastly, we show that Gaussian range and arbitrary spatial bilateral filters can be expressed by Taylor series as linear filter decompositions without any noticeable degradation of filter response. All these methods drastically decrease the computation time by cutting it down constant times (e.g. to 0.06 seconds per 1MB image) while achieving very high PSNRpsilas over 45 dB. In addition to the computational advantages, our methods are straightforward to implement.

First-order filters generalized to the fractional domain

Abstract: Traditional continuous-time filters are of integer order. However, using fractional calculus, filters may also be represented by the more general fractional-order differential equations in which case integer-order filters are only a tight subset of fractional-order filters. In this work, we show that low-pass, high-pass, band-pass, and all-pass filters can be realized with circuits incorporating a single fractance device. We derive expressions for the pole frequencies, the quality factor, the right-phase frequencies, and the half-power frequencies. Examples of fractional passive filters supported by numerical and PSpice simulations are given.

Low-Loss Two-Pole Tunable Filters With Three Different Predefined Bandwidth Characteristics

Abstract: Low-loss tunable filters with three different fractional-bandwidth variations were designed and fabricated on epsivr = 2.2, 0.787 mm Duroid substrates for 850-1400-MHz applications. A detailed analysis for realizing predefined bandwidth characteristics is presented, and a design technique to take into account the source and load impedance loading is discussed. It is found that independent electric and magnetic coupling makes it possible to realize three different coupling coefficient variations with the same filter structure. The proposed topology is different from the comb-line design in that all three filters have identical electrical lengths, the same varactors, and the same filter Q values. Three different filters are built using Schottky varactor diodes with a tuning range from ~ 850 to ~ 1400 MHz. The constant fraction-bandwidth filter has a 1-dB bandwidth of 5.4%plusmn0.3% and an insertion loss of 2.88-1.04 dB. The decreasing fractional-bandwidth filter shows a 1-dB bandwidth decrease from 5.2% to 2.9% with an insertion loss of 2.89-1.93 dB (this is effectively a 40-45-MHz constant absolute-bandwidth filter). The increasing fractional-bandwidth filter shows a 1-dB bandwidth increase from 4.3% to 6.5% with an insertion loss of 3.47-1.18 dB. The measured Q of the filters are between 53-152 from ~ 850 to ~ 1400 MHz. The measured third-order intermodulation intercept point ranges from 11.3 to 20.1 dBm depending on the bias voltage. To our knowledge, these planar tunable filters represent state-of-the art insertion-loss performance at this frequency range.

Novel Centrally Loaded Resonators and Their Applications to Bandpass Filters

Abstract: This paper presents several novel centrally loaded resonators and their applications to various types of bandpass filters. Based on the theoretical analysis, it is found that the even- mode resonance of the proposed resonators can be conveniently controlled without affecting the responses at the odd-mode resonant frequencies. Benefiting from this feature, the resonator can be utilized to design not only harmonic-suppressed bandpass filters and dual-band bandpass filters but also tunable bandpass filters. The tunable filter offers a fixed passband and a tunable one. The center frequency of the upper passband can be electrically tuned, whereas the performance of the lower one is maintained constant. To demonstrate these applications, four filters using the proposed resonators are implemented. The experiments verify the theoretical predictions and simulations.

Tri-band bandpass filter using stub loaded resonators

Abstract: A tri-band bandpass filter using short and open stubs loaded resonators is presented. The first and the third passband frequencies of the tri-band filter can be flexibly controlled by tuning the lengths of the stubs, whereas the second passband frequency is fixed. A tri-band filter has been implemented with four transmission zeros, the filter has good tri-passband performance at 1.57, 2.4, 3.5 GHz measured results agree well with simulated ones.

A Square-Root Nyquist (M) Filter Design for Digital Communication Systems

Abstract: Designing matched transmit and receive filters whose combination satisfies the Nyquist condition is a classical problem in digital communication systems. In this correspondence, we propose a novel method for designing such filters. The proposed method is based on a cost function whose minimization leads to designs that can strike a balance between the stopband attenuation, the residual intersymbol interference (ISI), robust sensitivity to timing jitter, and/or reduced peak-to-average power ratio (PAR). An iterative algorithm for optimizing the proposed cost function is suggested and its excellent performance is shown by presenting a variety of design examples. Compared to the published works, the proposed method offers the following unique advantages. By introducing a symmetry in the filter coefficients, filters with reduced computational complexity can be designed. We also introduce a design parameter that allows one to strike a balance between the PAR and other features of the desired filter.

Coefficient decimation approach for realizing reconfigurable finite impulse response filters

Abstract: A new approach to implement computationally efficient reconfigurable finite impulse response (FIR) filter is presented in this paper If the coefficients of an FIR filter are decimated by M, ie, if every Mth coefficient of the filter is kept unchanged and remaining coefficients are changed to zeros, a multi-band frequency response will be obtained The resulting frequency responses will have centre frequencies at 2pik/M, where k is an integer ranging from 0 to M-1 If these multi-band frequency responses are selectively masked using inherently low complex wide transition-band masking filters, different low-pass, high-pass, bandpass, and bandstop filters can be obtained If every Mth coefficient is grouped together removing the zero coefficients in between, a decimated frequency response in comparison to the original frequency response is obtained In this paper, we also show the design of a reconfigurable filter bank using the above approach

Stopband-Expanded Low-Pass Filters Using Microstrip Coupled-Line Hairpin Units

Abstract: In this letter, a class of stopband-expanded low-pass filters (LPFs) is proposed via attenuation poles of microstrip coupled-line hairpin unit. By centrally tap-connecting this coupled-line unit and adjusting its coupling strength, three attenuation poles can be excited above the desired low passband. A coupled-line-oriented closed-form model is then constructed to provide a physical insight into the excitation of these poles and to execute an efficient synthesis design of this LPF. Two prototype filters with single and two units are finally designed with the specified cutoff frequency at 2.5 GHz. Measured results of the fabricated filters evidently demonstrate good LPF performance, sharp roll-off skirt, and a wide upper-stopband of 3.2 to 11.8 GHz with the insertion loss higher than 20.0 dB.

Ultra-Wideband Bandpass Filter Using Multilayer Liquid-Crystal-Polymer Technology

Abstract: Novel ultra-wideband (UWB) bandpass filters are proposed based on quasi-lumped-element prototypes and implemented with multilayer liquid-crystal-polymer (LCP) technology. In this study, the broadside-coupled microstrip radial stubs and high-impedance microstrip lines are adopted as quasi-lumped elements for realizing compact UWB bandpass filters. By introducing a short-circuited high-impedance microstrip line as a shunt inductor and suitably designing quasi-lumped-element capacitors, a compact six-pole bandpass filter is implemented with the Federal Communications Commission (FCC) defined UWB specifications. To further improve the selectivity and wideband performance, an eight-pole filter of this type is developed by adding two shunt short-circuited microstrip stubs, which introduce a transmission zero at the upper passband edge. The proposed filters are fabricated using multilayer LCP technology. Good agreement between simulated and measured results of these filters are observed. The measured results show that the fabricated six-pole filter has good specifications for the FCC-defined UWB system. The fabricated eight-pole filter has an ultra-wide fractional bandwidth (139%) and a good stopband rejection level, which is higher than 38.1 dB from 10.57 to 18.0 GHz. The proposed filters are attractive for UWB communications and radar systems.

Universal current-mode filters and parasitic impedance effects on the filter performances

Abstract: In this letter, two universal current-mode (CM) filters for simultaneously realizing low-pass, band-pass and high-pass characteristics are proposed. Both of the presented filters can also realize notch and all-pass responses with interconnection of the relevant output currents. They employ second-generation current-controlled conveyors (CCCIIs) and only grounded capacitors. They also have low active and passive element sensitivities along with electronically adjustable angular resonance frequency (ω0) and quality factor (Q). Based on the first developed filter, the parasitic impedance effects of the conveyors on the filter performances are investigated in detail. Simulation results using SPICE simulation program are included to verify the theory. Copyright © 2007 John Wiley & Sons, Ltd.

Improved powder filters for qubit measurements.

Abstract: We designed and fabricated miniature low-pass metal powder filters suitable for noise-sensitive measurements at cryogenic temperatures. In comparison with previous powder filters, our filters have a much better frequency response and significantly smaller dimensions (0.7cm3 including the plugs) and can also be used as hermetic feedthroughs at low temperatures. Their transmission characteristics are smooth, contain no ripples, and have a steep decay above the cutoff frequency. At 4.2K the cutoff frequency of a single filter is fc=1MHz and the roll-off is −50dB per decade. All of the fabricated filters have identical frequency responses at 4.2K and their characteristics are reliably reproducible.

Design of Triple-Passband Microwave Filters Using Frequency Transformations

Abstract: This paper introduces a synthesis method for triple-passband microwave filters A frequency transformation is developed for finding the locations of poles and zeros of the triple-passband filter The poles and zeros obtained as such are optimized to achieve a transfer function with a reduced number of transmission zeros in order to reduce the number of cross-couplings Six- and 12-pole triple-passband filters are synthesized for validation of this proposed method A 12-pole triple-passband filter is fabricated with a microstripline structure and shown to provide good agreement between synthesis and measurement results Finally, the frequency transformation for asymmetric triple-passband filters is briefly discussed

Filter design for grid connected PV inverters

Abstract: This paper proposes filter design guideline for single-phase grid-connected PV inverters By analyzing the instantaneous voltage applied on the filter inductor, the switching ripple current through the filter inductor is precisely calculated Therefore, filter inductance can be designed accurately which guaranties the switching ripple current under the target value Proposed filter design method is verified by experiment

A Dual Wideband Filter Design Using Frequency Mapping and Stepped-Impedance Resonators

Abstract: A dual-wideband filter design implemented by stepped-impedance resonators, which involves the frequency mapping approach, is presented in this paper. The dual-band filter can be divided into two parts: the wideband virtual passband filter and the narrowband virtual stopband filter. Both filters are designed by conventional synthesis methods, under the assumption that the common connecting lines serve as J- and K-inverters simultaneously. The basic building resonators formed by paralleling open- and shorting-stubs are implemented by unbalanced stepped-impedance resonators, exhibiting the desired resonating frequencies and susceptance slope parameters at these two bands. Two filters are tested to validate this design.

Design of sharp-rejection, compact, wideband bandstop filters

Abstract: A general procedure is described to design a sharp-rejection wideband bandstop filter by using interference of the signals propagating through two parallel transmission line segments having different electrical lengths and characteristic impedances. Bandwidth and rejection level of the filters can be controlled by changing the impedances of the lines. A simple transmission line model is used for filter analysis. Design graphs are presented. Theoretical prediction is verified by fabricating two filters in microstrip technology. Good agreements is obtained among theoretical prediction, full-wave simulation and measurements.

Compact Broadband Dual-Band Bandpass Filters Using Slotted Ground Structures

Abstract: Dual-band bandpass filters featuring compact size and flexible frequency choice are demonstrated using resonators based on slotted ground structures. Two resonators based on slotted ground structures form the basis of the filter design. The resonators allow the back-to-back and face-to-face embedding configuration, hence, greatly reduces the physical size of the filters. By changing the sizes of the two resonators independently, the lower and upper resonance frequencies can be adjusted to the desired values. A dual-band broadband bandpass filter was implemented with good compactness and low insertion loss. A good agreement is obtained between the simulation and measurement results.

Classical Circuit Theory

Abstract: This book begins with the basic principles of circuits, derives their analytic properties in both the time and frequency domains, and states and proves the two important theorems. It then develops an algorithmic method to design common and uncommon types of circuits, such as prototype filters, lumped delay lines, constant phase difference circuits, and delay equalizers. The material also discusses the relation between gain and phase, linear and minimum phase functions, group delay, sensitivity functions, scattering matrix, synthesis of transfer functions, approximation of filter functions, all-pass circuits, and circuit design by optimization. This book fills a need for a modern text on the mathematical foundations of passive circuits in general and passive filter design in particular. The mathematical foundations are what classical circuit theory, which is the subject of this book, is all about. It is old, but it has survived the test of time and it is still relevant today because it is basic.

Single-ensemble-based eigen-processing methods for color flow imaging - Part I. The Hankel-SVD filter

Abstract: Because of their adaptability to the slow-time signal contents, eigen-based filters have shown potential in improving the flow detection performance of color flow images. This paper proposes a new eigen-based filter called the Hankel-SVD filter that is intended to process each slow- time ensemble individually. The new filter is derived using the notion of principal Hankel component analysis, and it achieves clutter suppression by retaining only the principal components whose order is greater than the clutter eigen- space dimension estimated from a frequency-based analysis algorithm. To assess its efficacy, the Hankel-SVD filter was first applied to synthetic slow-time data (ensemble size: 10) simulated from two different sets of flow parameters that model: (1) arterial imaging (blood velocity: 0 to 38.5 cm/s, tissue motion: up to 2 mm/s, transmit frequency: 5 MHz, pulse repetition period: 0.4 ms) and 2) deep vessel imaging (blood velocity: 0 to 19.2 cm/s, tissue motion: up to 2 cm/s, transmit frequency: 2 MHz, pulse repetition period: 2.0 ms). In the simulation analysis, the post-filter clutter- to-blood signal ratio (CBR) was computed as a function of blood velocity. Results show that for the same effective stopband size (50 Hz), the Hankel-SVD filter has a narrower transition region in the post-filter CBR curve than that of another type of adaptive filter called the clutter- downmixing filter. The practical efficacy of the proposed filter was tested by application to in vivo color flow data obtained from the human carotid arteries (transmit frequency: 4 MHz, pulse repetition period: 0.333 ms, ensemble size: 10). The resulting power images show that the Hankel-SVD filter can better distinguish between blood and moving- tissue regions (about 9 dB separation in power) than the clutter-downmixing filter and a fixed-rank multi-ensemble- based eigen-filter (which showed a 2 to 3 dB separation).

Robust switching vector median filter for impulsive noise removal

Abstract: We present an order-statistics-based vector filter for the removal of impulsive noise from color images. The filter preserves the edges and fine image details by switching between the identity (no filtering) operation and the vector median filter operation based on the robust univariate median operator. Experiments on a diverse set of images and comparisons with state of the art filters shows that the proposed filter combines simplicity, flexibility, excellent filtering quality, and low computational requirements.

Low-temperature cofired ceramic LC filters for RF applications [Applications Notes]

Abstract: Over the past few years, a great amount of effort has been spent on LTCC filters or related research [21]?[28]. Some of these components have more advanced functionalities, such as a combination of filter and balun, or a complete front-end module with balun, filter, and matching network. At the same time, advanced methodologies have also been developed to design these components [29]. All the enjoyment of miniaturized RF components or modules is due to the promising three-dimensional design flexibility of LTCC technology. It is expected that a variety of functionally complex components will be continuously available on the market such that the cost and size of the overall wireless terminal can be further reduced. Various aspects of designing miniaturized LTCC LC filters have been briefly discussed here. Conventional coupled LC resonators are commonly used in LTCC filters for RF applications because of their compact size advantage. The shunted parallel resonator in this type of filter can be realized directly as a lumped-element or distributed quarter- wavelength stripline with or without loaded capacitors. Filters with distributed resonators in general have better passband insertion loss performance. Moreover, there are many ways to improve the rejection performance in an LTCC filter design; for example, by modifying the resonators or admittance inverters so as to introduce transmission zeros at the stopband. It was demonstrated, through a design example, that by making use of the flexibility of LTCC technology, a compact LC bandpass filter can be realized for various RF applications.

Digital filter spectrum sensor

Abstract: A spectrum sensing method includes (a) receiving an incident radiation simultaneously through a filter array composed of multiple bandpass filters, (b) digitizing spectral responses of the filter array, and (c) generating an estimate of spectral profile of the incident radiation based on digitized spectral responses of the filter array.

Voltage-mode FDCCII-based universal filters

Abstract: Three new voltage-mode universal biquadratic filters configuration are proposed. The first proposed high-input impedance universal filter with single input and five outputs, which can simultaneously realize voltage-mode lowpass (LP), bandpass (BP), highpass (HP), bandstop (BS) and allpass (AP) filter responses employing all grounded passive components. The second proposed high-input impedance universal filter with three input and single output, which also can realize all the standard filter functions without requiring any inverting input voltage signal. The third proposed universal filter with three inputs and five outputs, which can be used as either a three-input single-output or a two-input five-output universal filter. Moreover, each of the proposed circuits still enjoys (i) the employment of only grounded capacitors, and (ii) no requirement with the component choice conditions to realize specific filtering functions.

Coupled resonator filter with single-layer acoustic coupler

Abstract: We discuss the operation of novel coupled-resonator filters with single-layer acoustic couplers. Our analysis employs the physical Mason model for acoustic resonators. Their simpler fabrication process is counterbalanced by the high acoustic attenuation of suitable coupler materials. At high levels of attenuation, both the phase and the acoustic impedance must be treated as complex quantities to accurately predict the filter insertion loss. We demonstrate that the typically poor near-band rejection of coupled resonator filters can be improved at the die level by connecting a small capacitance between the input and output of the filter to produce a pair of tunable transmission minima. We make use of these theoretical findings to fabricate coupled resonators filters operating at 2.45 GHz.

An Analytic Design Method for Microstrip Tunable Filters

Abstract: This paper describes an analytic design procedure for microstrip tunable filters. Step-impedance resonators are employed and loaded with varactors for achieving agility in the filter response. Fixed lumped capacitors are utilized as admittance inverters in order to minimize the number of varactors in the filter. An analytic approach for filter design makes it possible to achieve a tunable filter showing the same frequency response when the center frequency is adjusted. A two-pole microstrip tunable filter whose center frequency can be adjusted from 1.1 to 1.5 GHz is designed to demonstrate the validity of design theory. A prototype tunable filter operating from 2.1 to 2.7 GHz is also designed and measured. A good agreement between the measured and simulated results is shown. Finally, three- and four-pole tunable filters are designed to show straightforward application of the presented design method to higher order tunable filter design.

A New Class of Low-Loss High-Linearity Electronically Reconfigurable Microwave Filter

Abstract: A novel electronically reconfigurable microwave bandpass filter based on a switched delay-line approach is presented. In contrast to conventional tunable filters, the approach enables the lossy and nonlinear switching elements to be used as part of the coupling elements rather than within the resonators. Therefore, the filter distinguishes itself through its ability to provide a wide tuning bandwidth with low passband loss and high linearity. Theoretical analysis of the approach is presented in this paper. The feasibility of the approach has been experimentally verified with microstrip circuit prototypes. The filter produced a maximum passband loss of 1.7 dB and a third-order intercept point of >32 dBm with 35% tuning bandwidth.

A Generalized Window Approach for Designing Transmultiplexers

Abstract: This paper proposes a computational, very efficient, approach for designing a novel family of M-channel maximally decimated nearly perfect-reconstruction cosine-modulated transmultiplexers. This approach is referred to as the generalized windowing method for transmultiplexers because after knowing the transmission channel a proper weighted sum of the inter-channel and inter-symbol interferences can be properly taken into account in the optimization of the window function, unlike in other existing windowing techniques. The proposed approach has also the following two advantages. First, independent of the number of subchannels and the common order of the subchannel filters, the number of unknowns is only four. Second, the overall optimization procedure is made considerably fast by estimating the above-mentioned sum in terms of two novel measures, namely, the signal to inter-symbol and the signal to inter-channel interferences, which are very easy to evaluate. Furthermore, when the transmission channel is not considered in the design, a table is provided, which contains the parameters for designing the prototype filter directly by using the windowing method without any time-consuming optimization. When comparing the resulting transmultiplexers with the corresponding perfect-reconstruction designs (the same number of subchannels and same prototype filter order), the levels of interferences are practically the same. However, when the system is affected by a strong narrowband interference, the proposed transmultiplexers outperform their PR counterparts. Design examples are included illustrating the efficiency of the proposed design approach over other existing techniques based on the use of the windowing method.

Universal resistorless current-mode filters employing CCCIIs

Abstract: In this paper, four different-type second-order current-mode filters, employing second-generation current-controlled conveyors (CCCIIs) and two capacitors, are proposed. The first two of the presented filters can simultaneously realize high-output impedance low-pass, band-pass and high-pass responses. Also, the two filters can provide notch and all-pass filter responses with interconnection of the relevant output currents. The first developed one needs no critical active and passive element matching conditions and-or cancellation constraints. The second and third introduced ones employ only grounded capacitors. The fourth proposed filter derived from the third one uses only plus-type single output CCCIIs (CCCII+s). The fifth filter can be constructed using commercially available active devices such as AD844s along with additional resistors instead of CCCII+s of the fourth proposed filter to perform experimental test easily. All of the proposed filters have low active and passive element sensitivities. Time and frequency domain analyses are performed for the first, second and third realized filters using SPICE simulation program. Also, experimental test is achieved for the fifth filter. In this study, stability problems attributed to non-ideal gains of the CCCIIs and signal limitations of the first, second and third introduced filters due to restricted power supply voltages are investigated. Copyright © 2007 John Wiley & Sons, Ltd.