Stopband Attenuation Research Articles

Analysis of Dirichlet, Generalized Hamming and Triangular window functions in the linear canonical transform domain

Linear canonical transform is a four-parameter class of integral transform that plays an important role in many fields of optics and signal processing. Well-known transforms such as the Fourier transform, the fractional Fourier transform, and the Fresnel transform can be seen as the special cases of the linear canonical transform. This paper presents a new mathematical model for obtaining the linear canonical transforms of Dirichlet, Generalized “Hamming”, and Triangular window functions. The different window function parameters are also obtained from the simulations. By changing the value of four parameters and then changing the adjustable parameter, the main-lobe width, −3 dB bandwidth, −6 dB bandwidth and correspondingly, the minimum stop-band attenuation of the resulting window functions can be controlled. It has been shown that by using linear canonical transform, we are able to obtain all window parameters successfully as compared to fractional Fourier transform.

Advanced Multilayer Thick-Film System-on-Package Technology for Miniaturized and High Performance CPW Microwave Passive Components

This paper presents advanced multilayer (ML) thick film system-on-package (SOP) technology for realization of ceramic-based embedded coplanar waveguide (CPW) inductors and capacitors library with remarkably high performance and miniaturization. The detailed characterization and modeling of CPW-lumped components in low-cost photoimageable thick film technology is reported. The passive components are developed with impressive measured self-resonance frequency (SRF) of more than 40 GHz. The newly developed inductors are highly miniaturized and measurements in single (2-D) and double layers (3-D) show inductance value from 0.6 nH to as high as 30 nH for one to eight turns, and with SRF >; 40 and 2 GHz, respectively. The quality factor (g) for small value inductors is better than 100 and that for the 30 nH inductor is better than 30. The 30 nH inductor measures only 1.3 mm × 1.3 mm × 0.7 mm and demonstrates highest level of miniaturization in ceramic based multichip module (MCM) technology. Metal-insulator metal capacitors have been designed and modeled, for single and number of pairs of parallel plates employing horizontally, with increased capacitance and high SRF >; 40 GHz. Based on the models developed for the ML lumped components a miniaturized fifth order CPW-based embedded lowpass filter is designed and developed for IF applications with a cut-off frequency of 3.5 GHz. The filter is miniaturized with remarkably low insertion loss of 0.3 dB and stop band attenuation better than 40 dB at 7 GHz. The measured response characteristics are in excellent agreement with the predicted response. This filter represents one of the highest passive component performances ever reported for ceramic-based MCM technology and highly suitable to incorporate in RF module for cost-effective and compact microwave and mm-wave SOP applications.

A Compact V-Band Bandpass Filter in IPD Technology

This work presents a miniaturized bandpass filter in V-band using integrated passive device (IPD) technology with thick metal layers and Benzocyclobutene (BCB) dielectric on a glass substrate. The proposed filter, comprised of two stepped-impedance resonators with quarter-wave short-circuited stubs and floating pads, has low passband insertion loss and high stopband attenuation in a compact size. The fabricated filter has an insertion loss of 2.46 dB at the center frequency of 59 GHz, and a 3 dB bandwidth from 55.7 to 62.2 GHz. The core size of this filter is only 0.32×0.4 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (0.064 ×0.08 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ).

Application of microstrip cavity couplers for wideband bandpass filters

AbstractThis article presents a design for wideband bandpass filters using a microstrip cavity coupler. The broadband nature of the cavity‐coupled designs is fully exploited for this application. Two additional circuits are introduced to improve the stopband performance of the cavity‐coupled bandpass filter. A prototype design example is presented with its center frequency located at 6.28 GHz. The design has the merits of wide bandwith of more than 140%, flat group delay within the passband, good insertion/return loss, and stopband attenuation of nearly 30 dB up to 30 GHz. The validity of the simulation results is verified experimentally. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2814–2817, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26410

A highly linear baseband Gm—C filter for WLAN application

A low voltage, highly linear transconductan—C (Gm—C) low-pass filter for wireless local area network (WLAN) transceiver application is proposed. This transmitter (Tx) filter adopts a 9.8 MHz 3rd-order Chebyshev low pass prototype and achieves 35 dB stop-band attenuation at 30 MHz frequency. By utilizing pseudo-differential linear-region MOS transconductors, the filter IIP3 is measured to be as high as 9.5 dBm. Fabricated in a 0.35 μm standard CMOS technology, the proposed filter chip occupies a 0.41 × 0.17 mm2 die area and consumes 3.36 mA from a 3.3-V power supply.

The Design and Experiment of IIR Lowpass Digital Filters for Airborne Gravity Data

AbstractWe have designed IIR (Infinite Impulse Response) lowpass digital filters based on Butterworth and Chebyshev approximations, and conducted an experiment research of filtering to GT‐1A airborne gravity data. The result shows that: by selecting proper parameters such as passband and stopband attenuation, these IIR lowpass digital filters for airborne gravity data can get satisfactory filtering effect almost as good as that of GT‐1A filtering result.

Stability Analysis of Bandpass Sigma–Delta Modulators for Single and Dual Tone Sinusoidal Inputs

In this paper, the stability boundaries of higher order 1-bit bandpass (BP) Σ-Δ modulators for single- and dual-sinusoidal inputs are determined using quasi-linear modeling together with the describing-function method. Closed-form mathematical expressions are derived for the stability curves for different quantizer gain values. The stability prediction for the maximum stable input limits for eighth- and tenth-order (i.e., effective fourth- and fifth-order) inverse-Chebyshev- and Butterworth-based BP Σ-Δ modulators for different stopband attenuation and bandwidths are established. The theoretical results are shown to be in good agreement with the simulation results for a variety of input amplitudes, bandwidths, and modulator orders. The proposed mathematical models of the quantizer will immensely help speed up the design of higher order BP Σ-Δ modulators.

The Influencing Factors in Acoustic Nonlinearity Parameter B/A Measurement

In this paper, the nonlinearity parameter B/A of ethanol has been measured under different emitted voltages, temperatures, multiple frequencies and stop-band attenuations. The experimental apparatus and technique used to measure B/A in ethanol was the finite amplitude insert-substitution method. This method was applied within the emitted voltages from 30.0 to 150.0V and at temperatures of between 22 and 45°C, and different frequencies at 1.0MHz, 2.25MHz, 3.5MHz, 5.0MHz and in attenuations from 30.0 to 120dB. Experimental results (Fig.4, Fig.5, Fig.6, Fig.7) show that: (1) The value of B/A has almost a linear increase with temperature and a linear decrease with frequency. (2) Parameter B/A is independent of the stop-band attenuations and has a little decrease with different emitted voltage.

A simple design method for the cosine-modulated filter banks using weighted constrained least square technique

This paper presents a simple and efficient design method for cosine-modulated filter banks with prescribed stopband attenuation , passband ripple , and channel overlap. The method casts the design problem as a linear minimization of filter coefficients such that their value at ω = π /2 M is 0.707, which results in a simpler, more direct design procedure. The weighted constrained least squares technique is exploited for designing the prototype filter for cosine modulation (CM) filter banks. Several design examples are included to show the increased efficiency and flexibility of the proposed method over the exiting methods. An application of the proposed method is considered in the area of sub-band coding of the ECG and speech signals.

An Improved and Simplified Approach for Designing Cosine Modulated Filter Bank Using Window Technique

An improved and simplified approach is presented for design of nearly perfect reconstructed cosine-modulated (CM) filter banks with prescribed stopband attenuation and channel overlapping. The method employs Kaiser window technique to design the prototype filter for filter banks with the novelty of exploiting spline functions in the transition band of the ideal filter instead of using the conventional brick-wall filter based on linear optimization of filter coefficients such that their value at frequency (??=??/2M) is 0.707. The simulation results illustrate the proposed method and its improvement over other existing methods in terms of amplitude distortion (e am ), number of iterations (NOI), aliasing distortion (e a ) and computation time (CPU time).

A Linear Optimization of Dual-Tree Complex Wavelet Transform

In this paper, a linear optimization of the dual-tree complex wavelet transform (DTCWT) based on the least squares method is proposed. The proposed method can design efficient DTCWTs by improving the design degrees of freedom and solving the least square solution iteratively. Because the resulting DTCWTs have good approximation accuracy of the half sample delay condition and the stopband attenuation, they provide precise shift-invariance and directionality. Finally, the proposed DTCWTs are evaluated by applying to non-linear approximation and image denoising, and showed their effectiveness, compared with the conventional DTCWTs.

Suppression of microstrip filter spurious responses using frequency-selective resistive elements

The spurious responses of microstrip filters were suppressed to extend the stop band. Even-order spurious resonances are suppressed using resistive loads at the voltage nodes of the fundamental resonance, which are the antinodes at the spurious frequency. Odd orders are removed using additional resonators which are deliberately lossy, and whose fundamental resonant frequency is equal to the spurious resonance of the main resonators. Equations for initial estimates for losses and required coupling coefficients are given. Of three filters designed and measured, two show 30 dB stop band attenuation, at the cost of only a small increase in pass-band loss and a small increase in substrate area.

EXPERIMENTAL INVESTIGATIONS ON A SURFACE MICROMACHINED TUNABLE LOW PASS FILTER

In this paper, a surface micromachined microwave tunable low pass fllter, consisting of tunable shunt capacitors and series inductors, has been realized. The fllter exhibits insertion loss of less than 1dB (up to 10GHz), stop band attenuation of 20dB at 20GHz, and cut-ofi frequency is changed to 8GHz with the application of DC actuation voltage in the structure. The fllter has an overall dimension of 5:5mm£2mm. The characteristics of tunable fllter are investigated with and without packaging.

Improvement of SIW filter upper stopband performance using bypass coupling substrate integrated circular cavity (SICC)

A novel method of using bypass coupling SICC resonator to generate transmission zeros (TZs) in filter stopband to improve upper stopband attenuation is presented. A SIW quasi-elliptic function filter with bypass coupling SICC resonators is designed and fabricated to validate the method. The results show the method is effective to improve the filter stopband performance.

Adaptive Complex-Coefficient 2D FIR Trapezoidal Filters for Broadband Beamforming in Cognitive Radio Systems

A novel design method is proposed for an adaptive discrete-domain beamformer for the beamforming of temporally broadband-bandpass signals in cognitive radio (CR) systems. The method is based on a complex-coefficient 2D finite impulse response (FIR) filter having a trapezoidal-shaped passband. The temporally broadband-bandpass signals are received by a 1D uniformly distributed antenna array (1D UDAA), where the outputs of the antennas are complex-quadrature sampled by the front end of the CR system. This CR system is based on a software defined radio (SDR) architecture and can be instantly reconfigured by the control system to select the appropriate frequency band and the required sampling rate. The subsequent beamforming enhances the spectral components of the desired temporally broadband-bandpass signals by arranging for the asymmetric trapezoidal-shaped passband of the 2D filter transfer function to closely enclose the region of support (ROS) of the spectrum of the desired signal, whereas the ROSs of the spectral components of the interfering signals are enclosed by the stopband. The proposed novel closed-form design method facilitates instant adaptation of the shape and orientation of the passband of the beamforming 2D FIR trapezoidal filter in order to match the time-varying frequency band and the time-varying bandwidth of the signal, as well as to track and enhance received signals with time-varying directions of arrival (DOAs). Simulated results confirm that, compared with previously reported methods, the proposed method achieves the best overall tradeoff with respect to the instantaneous adaptations of the operating frequency band, the bandwidth, and the time-varying DOAs, the distortion of the desired passband signal, and the stopband attenuation of interfering signals.

An improved closed form design method for the cosine modulated filter banks using windowing technique

This paper presents an improved closed form method for designing cosine modulated filter banks with prescribed stopband attenuation and channel overlap. The proposed method is based on optimum passband frequency, which is calculated using empirical formulas instead of using time consuming single or multivariable optimization. Different window functions are employed to design the prototype filter with the novelty of exploiting spline functions in the transition region of the ideal filter. Several design examples are included to show the increased efficiency of the proposed method over other exiting methods in terms of computation time, amplitude distortion ( e am) and aliasing distortion ( e a). An application of the proposed method is considered in the area of subband coding of the ECG and speech signals.

Microwave photonic notch filter based on a dual-Sagnac-loop structure

A new single-wavelength, coherence-free microwave photonic notch filter is presented. The concept is based on a dual-Sagnac-loop structure that functions with a new principle in which the two loops operate with different free spectral ranges, and which generate noncommensurate taps. It has the ability to generate a narrow notch response and can operate to high frequencies. Experimental results demonstrate a notch filter with a narrow notch width, a flat passband, and high stop-band attenuation of over 40dB.

Nyquist Filters with Alternative Balance between Time- and Frequency-Domain Parameters

Designing matched pulse shaping filters with their cascade satisfying the Nyquist condition for minimum intersymbol interference constitutes an important task for almost all digital data radio transceivers processing an incoming data signal on the sample-by-sample basis. Despite their practical importance, there are only few sets of Nyquist filter definitions and design techniques to devise digital filter coefficients available for a designer. In this paper we propose a set of Nyquist filters that balance the time- and frequency-domain parameters in favor of a filter stop-band attenuation and residual intersymbol interference compared with the already existing Nyquist filter sets. Using a number of filter examples, this paper shows that the proposed Nyquist filters can be a good option for applications that need to fulfill strict limits of adjacent and alternate channel power attenuation while providing a low level of residual intersymbol interference and group delay of the digital filter.

Simple Formulas for Stopband Attenuation Characteristics of Asymmetric Helical Slow-Wave Structures of Traveling-Wave Tubes

Simple closed-form formulas for the estimation of the π-mode stopband and the stopband attenuation in an azimuthally asymmetric helical slow-wave structure (SWS) are developed, following the coupled-mode analysis of multiple reflections. The formulas are simple and amenable to easy computation, and also allow the use of the dispersion characteristics of the structure obtainable from any standard electromagnetic modeling, thereby accruing the accuracy of 3-D electromagnetic analysis. The analysis is benchmarked against published results with close agreement. Based on the analysis, SWS configurations that would reduce the deleterious effects of asymmetry and also would improve TWT efficiency are suggested.

Coherence-Free High-Resolution RF/Microwave Photonic Bandpass Filter With High Skirt Selectivity and High Stopband Attenuation

A new coherence-free high-resolution RF/microwave photonic bandpass filter with high skirt selectivity and high stopband attenuation is presented. It is based on a frequency shifting amplified recirculating delay line loop with a wavelength dependent element at the output. The amplitudes of the delayed optical signals at the output of the frequency shifting loop are windowed by a wavelength dependent element to improve the signal processor frequency response performance. The frequency shifting amplified recirculating delay line enables a large number of taps to be generated using a simple structure for high-resolution signal processing. It has no coherent interference and phase-induced intensity noise limitations, and can be inserted into conventional fibre optic links. Experimental results demonstrate a high-resolution bandpass filter having a high performance with a shape factor of only 3.1 and an extremely high stopband attenuation of over 70 dB.