Transition Bandwidth Research Articles

Chebyshev filter and Butterworth filters: Comparison and applications in different cases

This study focuses on the filter selection problem in signal processing and wireless communication applications. Specifically, addressed two different filter selection problems: the Chebyshev filter and the Butterworth filter. Using MATLAB, in order to design and model these two types of filters. The performance, frequency response, transition band width, filter order, design complexity and target application of Chebyshev filter and Butterworth filter under different parameters are analyzed and compared. The selection of the two filters under different conditions and the reasons for choosing them are discussed. The Chebyshev filter is suited for applications that call for a high frequency response, and Chebyshev filters provide a steeper roll-down slope, which can suppress high-frequency noise and interference signals, according to the test results, it is widely used in communication systems. On the other hand, the Butterworth filter is more suitable for applications that require a flat passband and a wide stopband, such as audio systems.

Performance prediction of industrial robot harmonic reducer via feature transfer and Gaussian process regression

This paper addresses the problem of identifying faults in the harmonic reducers of industrial robots by analysing their vibration signals. In order to solve the problem of obtaining fault data and rotation error from harmonic reducers in service, an accuracy performance prediction method based on transfer learning and Gaussian process regression (GPR) is proposed. The Euclidean distance between the spectral sequence of each component is proposed as the fitness index to optimise the transition bandwidth of the filter banks. The optimised empirical wavelet transform (OEWT) is used for signal decomposition to obtain sensitive frequency bands. A feature transfer method based on semi-supervised transfer component analysis (SSTCA) is proposed to achieve target domain feature transfer under missing data conditions. A prediction model based on GPR is established using the mapped features to predict the performance and accuracy of the harmonic reducer. The effectiveness of the proposed method is verified through model evaluation indicators and degradation experiments.

Design and analysis of highly selective ultrawide stopband lowpass filter using lumped and distributed equivalent circuit models

AbstractAn ultrawide stopband lowpass filter is reported using three stepped impedance resonators with high selectivity. The filter extends the stopband frequency range and attenuation, and two quarter‐wave open stubs and three circular ground slots are introduced. The lumped and distributed equivalent models are derived and analyzed. The corresponding results are validated experimentally in a fabricated prototype. The prototype lowpass filter has a 3 dB cutoff frequency (fc) of 2.9 GHz, and the stopband is extended up to 35 GHz (12.07fc), with an attenuation level better than 20 dB throughout. The passband‐to‐stopband transition (3 dB–20 dB) bandwidth is 0.18 GHz, and the roll‐off factor is 135 dB/GHz at 30 dB. The insertion loss is 0.3 dB at 1.6 GHz. The normalized circuit size of the proposed filter with respect to the guided wavelength is 0.04.

Absorptive/transmissive frequency selective surface with multiple transmission zeros for reduced transition bandwidth

An absorptive/transmissive frequency selective surface (ATFSS) with multiple transmission zeros is proposed, which consists of one lossy layer and two lossless layers separated by air space. As the key features, the slot-line loading and interlayer coupling technologies are adopted in the lossy layer and lossless layers, respectively, to introduce the infinite impedance points and four transmission zeros, thereby simultaneously achieving low insertion loss and high selectivity of the transmission band. Benefiting from the ohmic loss of the lumped resistance in the lossy layer, effective absorption can be readily implemented. A detailed qualitative analysis of the proposed structure is presented through the equivalent circuit theory, surface current, and power loss density distributions. Under normal incidence, the overall structure exhibits two discrete absorption bands over the frequency range of 6.34 to 13.40 GHz, whereas a transmission behavior is obtained from 9.34 to 11.40 GHz with a minimum insertion loss of only 0.14 dB. In particular, there are only 3.9% and 3% transition bandwidths between absorption and transmission functions. Then, a sample prototype is fabricated for demonstration, and the measured results are well consistent with the simulated one. As expected, the proposed ATFSS has the advantage of multiple transmission zeros, loss insertion loss, and narrow transition band, which is of great potential in the application of radar stealth radome.

The Design and Investigation of the Low-Pass Filter with High Selectivity and Ultra-Wide Stopband

In this work, an ultra-wide stopband low-pass filter (LPF) is proposed using tapered step impedance resonators. The distributed equivalent of the proposed step impedance LPF is extracted, analyzed, and legitimated with simulated and fabricated results. The fabricated prototype has a 3 dB cut-off frequency (fc) of 2.92 GHz and an ultra-wide stop band extended up to 25.7 GHz (8.8fc) with an attenuation level of >20 dB. The transition bandwidth (from 3 to 20 dB) is 0.20 GHz and the roll-off factor is 112 dB/GHz (a reference to 30 dB). The passband insertion loss is 0.32 dB at 1.5 GHz and the normalized circuit size of the filter is 0.055.

Identification of wind turbine gearbox weak compound fault based on optimal empirical wavelet transform

A double modulation phenomenon is found in wind turbine gearbox compound fault signals, consisting of a resonance modulation frequency band and an asymmetric modulation frequency band. The modal aliasing and the double modulation phenomena make it difficult to use empirical wavelet transform to obtain the spectral components in the meshing modulation regions. Our main contribution is to establish an optimal empirical wavelet transform (OEWT) framework for weak feature extraction of compound faults, which incorporates the optimal velocity synchronous linear chirplet transform (OVSLCT) and the simulated annealing (SA) algorithm to obtain the optimal parameters of the filter bank. The frequency boundary of the fault component is obtained through OVSLCT rather than the extreme value of the spectrum. A filter transition band width optimization scheme is proposed in which the optimal transition band width of the filter bank in EWT is optimized by the SA algorithm. Compared with the original EWT and variational mode decomposition, OEWT can better obtain the compound fault characteristic frequency and solve the mode aliasing problem.

Practical method for nullifying ripple effect from FIR-Hilbert transformer

ABSTRACT When an FIR-Hilbert transformer with an even-numbered filter order of N is used in real-time signal processing, a delay line should be placed in parallel to compensate for the delay time of N/2 arising from the FIR-Hilbert transformer. In general, the FIR-Hilbert transformer possesses a ripple governed by a filter order, a transition bandwidth, among others. In contrast, the delay line does not possess any ripple. Then, an issue regarding the ripple is encountered during signal processing. In this letter, a practical method is proposed to nullify the ripple effect in signal processing. A simple solution is that the same ripple exists on the Hilbert transformer and delay line. Subsequently, two Weaver’s modulators for generating the USB signal are placed in parallel, and the real part of one of the two is used for a delay line and the imaginary part of the other of the two is used for a Hilbert transformer. When the same FIR-LPF is introduced into each of the two, the ripple effect can be nullified.

A Dual-Channel High-Linearity Filtering-by-Aliasing Receiver Front-End Supporting Carrier Aggregation

A filtering-by-aliasing (FA) receiver front-end based on a slice-based time-varying architecture was described by Bu and Pamarti (2021). Unlike prior FA architectures, it demonstrated, using a 28-nm CMOS prototype IC, a time-invariant input impedance that enables dual-channel operation with high linearity. Up to 50-dB stopband rejection with a transition bandwidth (BW) of only 3.2 times the RF BW, out-of-band IIP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> of +35 dBm, blocker 1-dB compression point of +12 dBm, and local oscillator (LO) leakage power better than −81 dBm were achieved, using a 0.9-V supply. This article elaborates on the design of this prototype, presents detailed analyses of the slice-based architecture, and shows how it addresses many of the prior FA receivers’ problems.

АНАЛИЗ УПРАВЛЯЕМОСТИ НЕКОТОРЫХ ЦИФРОВЫХ ФИЛЬТРОВ С КОНЕЧНОЙ ИМПУЛЬСНОЙ ХАРАКТЕРИСТИКОЙ

This overview article covers finite impulse response filters and filter banks. The use of these filtersfor hearing aids is considered. Ways to compensate for hearing loss and ways to increase loudnessusing broadband amplification are considered. A schematic diagram of a method for digitalsignal processing using a bank of filters, as well as a technique for synthesizing interpolation filterswith low computational complexity, is presented. Also, the application of the MATLAB system for thesynthesis of narrow-band non-recursive FIR filters, their design procedure, methodology and examplesare considered. Finite Impulse Response (FIR) filters and filter banks have specific propertiesthat guarantee stability. Therefore, they are popular in many applications such as communicationsystems, audio signal processing, biomedical instruments, and so on. Unfortunately, due to the longerwavelength, the cost of implementing an FIR filter is usually not higher than an infinite impulse response(IIR) filter that meets the same requirements. It is well known that the length of an FIR filter isinversely proportional to its transition bandwidth. Therefore, the disadvantage becomes acute when agiven filter has a narrow transition band. The main goal is to consider computationally efficientmethods for designing FIR filters and filter banks. The masking method (FRM) results in significantsavings in the number of multipliers. Next, a 16-band, low group delay, non-equal-spacing digitalFIR filter bank is considered. Overall latency is significantly reduced as a result of a new filter structurethat reduces the interpolation factor for prototype filters. Masking filter may be an interpolatedfinite impulse response (IFIR) filter that helps reduce complexity.

A Wideband High-power Low-loss Power Divider Using Half-height Pin Gap Waveguide Technology

In this paper, for the first time, a wideband low -loss high-power equally splitting power divider based on the new half-height pin form is introduced with bandwidth from 10 to 13.5 GHz centered at 11.75 GHz. Also, for the first time, a wideband transition from coaxial line to half-height pin gap waveguide with no need of any matching sections with excellent results at the band of (10:20 GHz) was achieved. The proposed transition shows excellent return loss which is lower than 30 dB (measured) at the transition bandwidth center frequency which is (15 GHz) with 0.2 dB (measured) insertion loss and return loss lower than 20 dB (measured) with 0.55 dB insertion loss at the rest of the bandwidth. The proposed transition and power divider designs were validated using circuit and 3D full-wave simulations and confirmed using experimental measurements with all agreements. The power divider has simple manufacturing due to the new pin form; hence, it is suitable for low-cost mass production of high-power mm-wave power dividers.

Design of a novel CEM‐FRM‐based low‐complexity channelised radar transmitter

With the development of the radar technology, it is required that a radar has wider bandwidth and can transmit multiple signals simultaneously. The polyphase digital channelised transmitter structure can transmit multiple signals simultaneously and increase the bandwidth of the output signal. However, in order to reduce the frequency aliasing and improve the spectrum utilisation, the prototype filter needs to have sharp transition bandwidth. The design of the prototype filter directly affects the performance of the radar transmitter. Using the complex-exponential modulation frequency-response masking (CEM-FRM) approach to design the prototype filter can obtain both sharp transition bandwidth and low complexity. The application of a polyphase structure can further reduce the complexity of the filter bank and make the sampling rate of the output signal several times the field programmable gate array operating frequency. The proposed CEM-FRM-based low complexity polyphase channelised radar transmitter is verified by MATLAB simulation and the theoretical complexity of the proposed CEM-FRM-based channelised radar transmitter structure is compared with other methods.

Analysis performance of wavelet OFDM in mobility platforms

Wavelet orthogonal frequency division multiplexing (OFDM) is one of the medium access techniques recommended by the IEEE 1901 working group for broadband communications over electrical networks, and is under consideration for IoT applications. This standard provides a flexible architecture supporting integrated access, smart grid, building, in-home, and mobility platform (vehicle) applications. Wavelet OFDM is a filter bank multicarrier system based on the extended lapped transform, in which the transmitting and receiving filters are obtained from a waveform provided by the standard. In this paper, we explore system performance when other waveforms are employed, studying the trade-off between stopband attenuation and transition band width. Furthermore, an alternative and more efficient way of obtaining the theoretical expressions of the achievable data rate is shown, assuming realistic power line communication noise other than additive white Gaussian noise. To demonstrate the capabilities of wavelet OFDM, the results of simulation of the symbol error rate and the data rate in several systems in platform scenarios (in-vehicle and in-aircraft) are shown.

Ultra-wide stopband HTS LPF with closed-loop cross-coupled microstrip structure

A compact high-temperature superconducting (HTS) low-pass filter (LPF) with an ultra-wide stopband and a sharp transition band is designed by integrating the fifth-order low-pass filter branch and closed loop cross-coupled (CLCC) microstrip structure. The fifth-order low-pass filter consists of two radial-stubs (RSs), one butterfly-shaped stub (BSs), and two T-shaped stubs (TSs), which can introduce five transmission zeros (TZs) with independently controllable frequency and position, so as to obtain good sideband suppression or upper stopband characteristics. The CCLC microstrip circuit is composed of cascaded high and low impedance microstrip lines, which can widen the width of the upper stopband and realize the ultra-wide stopband characteristic. The operating mechanism of the fifth-order LPF resonator and the CLCC microstrip structure are analyzed by theLCequivalent circuit models. The implemented LPF on a 0.5-mm thick MgO wafer with double-sided YBCO films demonstrates 1-dB cut-off frequency (fc) at 2 GHz and 0.12 GHz narrow transition bandwidth from −1dB to −40 dB. The measured results show a 30-dB harmonic suppression from 1.08fc to 11.7fc i.e., above 23 GHz, a steep roll-off rate of 326 dB/GHz, an in-band insertion loss (IL) <0.10 dB, and a miniaturized size of 0.24λgc × 0.08λgc (λgc is the guided wavelength at the cut-off frequency).

Direct Broadband Dielectric Spectroscopy of Liquid Chemicals Using Microwave-Fluidic Two-Wire Transmission Line Sensor

A novel robust approach for permittivity measurements of liquid materials in a wide frequency range is proposed. A high-sensitivity microwave-fluidic sensor is developed enabling direct determination of liquid samples' permittivity from the measured sensor's propagation constant. Importantly, neither sensor calibration using liquid standards nor sensor's geometry (except length) information is required, which is very advantageous for industrial applications. This is achieved through the sensor's geometry, which is a two-wire transmission line (TWL) encapsulated in a 3-D printed container, and thus, the liquid-under-test fully encloses the propagating electromagnetic waves. The measurement setup comprises the sensor cascaded between two microstrip-to-TWL transitions for which a simplified de-embedding procedure is proposed using only a THRU standard. For demonstration, a setup was developed with transitions operating within 1-10 GHz and tested up to 18 GHz by measurement of a set of alcohols to produce useful data within the transition bandwidth, which can be extended at the cost of increased uncertainty by postprocessing. Finally, the measurement error study has shown that a relatively low uncertainty and error with respect to the reference is obtained, verifying the usability of the developed measurement technique.

Narrowband aperture coupled waveguide to microstrip transition for space applications

Background/Objectives: To design, analyze and fabricate aperture coupled waveguide to microstrip transition for Ka-Band where energy is coupled through slot in ground plane and a metal patch placed over the substrate. Methods: Impedance matching approach has been adopted for transition design. Microstrip line is inserted into the waveguide through aperture acting as a probe. Followed by inductive line and transformer line for impedance translation between waveguide and microstrip line. Waveguide transition has been designed using Ansoft High Frequency Structure Simulator (HFSS) full-wave EM simulator. Findings: Designed transition shows return loss performance better than 15 dB and insertion loss better than 0.5 dB for back to back configuration over a frequency band of 34 – 36 GHz. Transition is fabricated on RT5580 Duroid substrate (2r= 2:2) with substrate thickness 0.254 mm. Measured results show return loss better than 25 dB and insertion loss less than 1 dB over a frequency band of 34-36 GHz. Table 2 shows comparison of present design with previously reported designs in terms of performance. Novelty/Applications: Comparison of the presented transition shows superior performance to previously reported transition designs in terms of transition bandwidth and insertion loss. Aperture coupled transitions can be widely used for space applications where hermetic sealing is required and it saves extra effort for sealing. Certain RF circuit applications require narrowband waveguide transitions to attain required performance, in this case aperture coupled transition can be a good option and its integration with RF circuits is also easy. Fabricated transition design results show good agreement with simulated results so it can be concluded that design is tolerant to fabrication errors. Transition has been fabricated using standard PCB process so production of such transition can be done easily without requirement of any special facility for fabrication. Keywords: Aperture coupled transition; waveguide; microstrip; kaBand;hermetically sealed

Design of FIR Half-Band Filter With Controllable Transition-Band Steepness

Maximally flat (MAXFLAT) half-band filters usually have wider transition-band than other filters although the frequency response is maximally flat (i.e., no ripples) in the passband and stopband. This is due to fact that the maximum possible number of zeros at z = ±1 is imposed in half-band close form solution, which leaves no degree of freedom, and thus no independent parameters for direct control of the frequency response. This paper describes a novel method for the design of FIR half-band filters with an explicit control of the transition bandwidth. The proposed method is based on a generalized Lagrange half-band polynomial ( $g$ -LHBP) with coefficients parameterizing a 0 -th coefficient $h_{0}$ and allows the frequency response of this filter type to be controllable by adjusting $h_{0}$ . Then, $h_{0}$ is modeled as a steepness parameter of the transition-band and this is accomplished through theoretically analyzing a polynomial recurrence relation of the $g$ -LHBP. This method also provides explicit formulas for direct computation of design parameters related to choosing a desired filter characteristic (by a reasonable trade-off between the transition-band sharpness and passband & stopband flatness). The examples are shown to provide a complete and accurate solution for the design of such filters with relatively sharper transition-band steepness than other existing half-band filters.

A Broadband Transition From Ridge Gap Waveguide to Microstrip Using Suspended Line Coupling

This letter proposes an inline, ultrawideband, and low loss transition from microstrip line (MSL) to ridge gap waveguide (RGW). An efficient conversion between operational mode of RGW and the quasi-TEM mode of MSL is presented by using suspended line patch as a bridge. Furthermore, the effect of loading a capacitive iris on the transition matching performance is studied and a methodology to tune the transition bandwidth is proposed. In order to validate the presented solution, a back-to-back transition prototype is developed and investigated experimentally. The measured results show an insertion and return loss of 0.4 and 15 dB, respectively, over 107% relative bandwidth in the range of 6.2–20.1 GHz.

Periodically Time-Varying Noise Cancellation for Filtering-by-Aliasing Receiver Front Ends

This article presents a periodically time-varying (PTV) noise cancellation technique for filtering-by-aliasing (FA) receivers. The key to the proposed technique is the use of a time-varying transconductance (G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ) cell to sense the noise generated by the PTV resistor in an FA receiver while maintaining the sharp filtering offered by FA. A prototype IC fabricated in a 28-nm CMOS process improves the noise figure (NF) by about 3 dB while achieving over 67-dB stopband rejection with a transition bandwidth (BW) of only four times the RF BW. A minimum in-band NF of 3.2 dB and an average in-band NF of 4.2 dB are demonstrated. With an upfront N-path filter to further enhance the linearity, the measured out-of-band IIP3 is +18 dBm and the blocker 1-dB compression point is +9 dBm. The whole chip, including digital control circuitry, operates under a 0.9-V supply, while consuming 61-mW power at 500-MHz LO.

Design of narrow transition band variable bandwidth digital filter

This study presents a novel implementation technique for linear phase variable bandwidth finite impulse response (FIR) filters with a noticeable reduction in transition bandwidth as well as hardware complexity. In this proposition, concept of Farrow structure based design technique is effectively utilised; whereas the fixed sub-filters are constructed from a generalised interpolated bandpass method based low-pass FIR filter by means of different techniques such as interpolation, up-sampling and masking. Simulation results have shown the frequency response characteristics of several variable bandwidth FIR filters, designed with the help of the proposed architecture. Simulation results have shown a drastic reduction of transition bandwidth resulting from the proposed variable bandwidth FIR filters of up to ∼70–80%, when compared with other state-of-the-art filtering techniques, with a significant reduction in hardware complexity of up to ∼50%.

A Design of a low-pass FIR filter using Hamming Window Functions in Matlab

The reduction and filtering of the input components of an original signal in one or more frequency bands using a finite impulse response, better known as FIR, is designed using a function of the Hamming window. Although there are various window functions such as the Blackman window function, the Hanning window function and the rectangular window functions that can be used as digital filters, the Hamming window function was used in this study for the reason of its minimum damping/decibel of the stopband with a reduced transition bandwidth. Among the other three widow functions that can be used, the Blackman window function is closest to the Hamming window function in terms of minimum bandstop attenuation/decibel, since both have a dB value greater than -50. However, in terms of transition bandwidth (Δω), the Hamming window has a narrower bandwidth than the Blackman window, making it more appropriate to use in this FIR filter design. This type of filter is important for analyzing the different types of signals that are essential in a world where digital filters play a major role in DSP applications. This research paper offers a Matlab-based low-pass FIR digital filter that uses Hamming window functions. Keywords: FIR filters, Hamming window, Blackman window Hanning window, Matlab. DOI: 10.7176/CEIS/11-2-04 Publication date: February 29 th 2020