Sharp Roll-off Research Articles

Compact microstrip lowpass filter with wide stopband and sharp transition band using radial stub resonator

This study introduces a compact microstrip lowpass filter that offers a wide stopband and a low transition band. The couple radial stubs are designed for having sharp roll-off. The filter has a −3 dB cut off frequency of 1.6 GHz, with a transition band ranging from 1.6 to 1.7 GHz with attenuation levels of −3 dB and −20 dB, respectively. To ensure a wide stopband, the filter utilizes bended transmission lines with stepped impedance suppressing cells, resulting in a stopband attenuation of 20 dB from 1.7 to 28 GHz. The insertion loss in the passband is less than 0.1 dB, and the overall size of the filter is 0.127 × 0.087 λg2.

Self-Packaged mm-Wave Broadband Air-Filled SIW Filtering Power Divider With Sharp Roll-Off Skirt and High In-Band Isolation

Self-Packaged mm-Wave Broadband Air-Filled SIW Filtering Power Divider With Sharp Roll-Off Skirt and High In-Band Isolation

Compact lowpass filter with vast out-of-band rejection utilizing DGS

A unique low-profile microstrip lowpass filter (LPF) is introduced. It features a broad range of stopband and sharp roll-off. The suggested LPF is built utilizig a T-shaped configuration which includes a stub for resonance and utilizes open stubs as attenuator cells. To further improve the stopband, a double circular ring is engraved into the ground plane. The developed filter features a cut-off frequency of 3 dB at 3.4 GHz, a roll-off rate of 108 dB/GHz, and a stopband range from 3.7 to 22.8 GHz. The attenuation is less than −20 dB. The prospective LPF is designed using a lumped LC circuit model and validated using Keysight Advanced Design System (ADS) simulation and theory. The final design is realized using RT/Duroid 4003C, which boasts a small footprint of 12.4mm×8.69mm×0.8mm. The modelling findings and measurements of the suggested LPF are in fairly good agreement.

A new electric coupling and its applications on millimeter-wave SIW filter with high selectivity and controllable TZs

In this paper, a novel simple horizontal electric coupling (SHEC) structure is proposed, which only requires a single elliptical ring slot to be etched at the top layer of the substrate between the two adjacent SIW cavities. The working mechanism of SHEC is revealed using the equivalent magnetic current theory. The results indicate that the ring slot is divided into two semi-elliptical slots by the via-hole, and the induced electric fields generated by equivalent magnetic current near the slots enhance the extremely weak electric field intensity at the edge of the SIW cavities, resulting in the formation of electric coupling between the adjacent two cavities. As a verification, a fourth-order SIW filter operating at 27.96 GHz was designed based on the SHEC structure. The filter exhibits high selectivity with sharp roll-off of 114/105 dB/GHz and obtains controllable transmission zeros (TZs) by changing the size of the elliptical slot. Additionally, the proposed SHEC design has a regular via-holes arrangement and does not require etching slot on the bottom layer of the substrate, making it easy to accurately process, integrate, and package, providing a new approach for the design of millimeter-wave filters.

Acoustic analysis of video conferencing platforms: Evaluating communication effectiveness for individuals with hearing loss

AIM: This research investigates the impact of video conferencing platforms on the transmitted sound to evaluate their effectiveness in facilitating communication for individuals with hearing loss. The preliminary analysis includes comparing the transmitted sound deviations from source recordings in Teams, Zoom, and Google Meet and exploring differences in audio quality across different settings within each platform (not focused on DSP limitations or audio transmission fidelity). METHODS: In this study, we employed babble noise, BKB speech, and a combination of babble noise and BKB speech (SNR: 9dB) as stimuli. We compared different acoustic features of the received signal, including automatic audio gain adjustments, frequency range, and frequency response, with the source sound. RESULTS: Zoom applies a smooth high-frequency roll-off for speech in a noisy signal, beginning at approximately 14.5 kHz and removing all frequency content above 18 kHz. The roll-off for Teams begins at a relatively low frequency around 7 kHz. Although Google Meet starts the roll-off around 20 kHz, the gain was inconsistent and had a sharp roll-off. CONCLUSION: Each platform exhibited distinct characteristics and introduced noticeable modifications to the stimuli. Results indicated that Zoom with optional audio settings enabled demonstrates the highest fidelity to dynamic range and frequency spectrum.

A Miniaturized wide Stopband Low-pass Filter using T and Modified L Shapes Resonators

A new structure of microstrip-based low-pass filter with wide stopband and sharp roll-off is introduced, in this paper. In the proposed topology, resonators with T and modified L Shapes have been used. To improve the suppression factor and relative stopband bandwidth, the second resonator has been added to the first resonator. The designed filter has been fabricated on a 20 mm thickness RO4003 substrate, which has a loss tangent of 0.0021 and a relative dielectric constant equal to 3.38. All parameters including roll of rate, stopband, bandwidth, return loss, insertion loss, and figure of merit have significant coefficients. Simulation has been ran using advanced design system software. The 3dB cutoff frequency is appropriate. The value of the insertion loss parameter is <0.1 dB and the S11 parameter is −22 dB at this point. The stopband is extended from 2.42 up to 24 GHz, which shows an ultra-stopband. The results of the simulation and experiment are almost similar, which indicates a proper performance of the designed structure.

Design and analysis of a compact microstrip lowpass–bandpass diplexer with good performance for wireless applications

AbstractThis paper presents the design of a novel lowpass–bandpass diplexer with compact size and good performance using microstrip cells. For this purpose, two microstrip lowpass and bandpass filters are separately designed and mathematically analyzed. The proposed microstrip diplexer has a novel and simple structure. It occupies a compact area of 0.037 λg2 (722 mm2), and its insertion loss and S11 at both channels are low. The insertion loss at the lower and upper channels is only 0.047 and 0.16 dB, respectively. Meanwhile, both channels are flat with the maximum group delay of 1.68 ns which is the lowest compared to the previously reported diplexers mentioned in this paper. To design the proposed diplexer, first, a lowpass diplexer with good performance is designed which has low losses and a good figure of merit. It has a flat passband with a sharp roll-off. Then, to achieve the proposed diplexer, a bandpass resonator is added to the lowpass filter without any extra matching circuit, which saves the overall size. The proposed diplexer is designed, simulated, and fabricated, where the simulation and measurement results are close.

Low Complexity Compact Lowpass Filter Using T-Shaped Resonator Loaded With a Stub

A novel miniaturized microstrip low pass filter (LPF) with a wide stopband and sharp roll-off is presented. The designed filter is developed by realizing a T-shaped structure loaded with a stub as a resonator and open-stubs as suppressor cells to achieve a simple structure for ease of fabrication process. The new filter with a symmetrical structure has a 3 dB cut-off frequency of 2.15 GHz, the transition band is 123 dB/GHz from -3 dB to -40 dB, a stopband with an attenuation level better than -20 dB from 2.4 up to 22.1 GHz with a compact size of 0.0132λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>g</i></sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The insertion loss in the passband is less than 0.3 dB and return loss is lower than -20 dB. The filter is fabricated, and the results show agreement between the simulation and measurement.

All-Metal Wideband Frequency-Selective Surface Bandpass Filter for TE and TM Polarizations

A novel technique to design a low-cost frequency-selective surface (FSS) bandpass filter is presented in this article. Wideband polarization-independent FSS bandpass filters are predominantly made of multiple microwave dielectric substrates or noncommercially available composite materials with or without active components, contributing to a very high manufacturing cost. The presented FSS filter has neither microwave substrates, nor any active devices, while it has a large controllable operational frequency band, which can support all polarizations, due to its symmetrical configuration. To the best of our knowledge, such a polarization-independent wideband bandpass response has never been achieved by any low-cost fully metallic FSS filter. The proposed FSS filter is made of three thin metal sheets composed of an engineered metallic substrate (EMS) and a metallic orthogonal dipole resonator (ODR). The EMS is responsible for ensuring the mechanical integrity of the filter without imposing electromagnetic (EM) restrictions throughout the desired frequency band. The integration of EMS and ODRs realizes a fully controllable wideband bandpass verified thorough circuital and modal analyses. According to the predicted and measured results, the FSS filter has a large bandwidth of around 31&#x0025;, extending from 8.76 to 11.96 GHz with sharp roll-offs for the normal incidence. Simulated and measured results show a low sensitivity of the FSS filter response to oblique angles of incidence for both TM and TE polarizations.

Tunable liquid crystal metamaterial filter with polarization-insensitive characteristic

ABSTRACT In this paper, a systematic design method for polarization-insensitive tunable liquid crystal (LC)-based metamaterial filter with the passband of flat-top and sharp roll-off is proposed. A compact LC-based bandpass metamaterial filter unit cell with a dimension of 0.09 λ × 0.09 λ is designed. The metamaterial filter element consists of a pair of planar pinwheel-shaped metallic structures with four symmetrically distributed isosceles triangular patches. LC is sandwiched in this pair of metallic structures. The metal pattern on each layer is 90° rotationally symmetrical leading that the LC-based metamaterial filter is insensitive to the polarization of incident waves. In order to obtain the transmission characteristics of flat top and sharp roll-off, a double-layer LC-based metamaterial filter structure is proposed. Full-wave simulations show that the central frequency of the metamaterial filter is tuned from 10.88 GHz to 11.78 GHz, and the tuning range reaches up to 7.9%. Meanwhile, under TE and TM polarizations, the double-layer LC-based metamaterial filter structure achieves filtering characteristics with a flat-top passband of not less than 997 MHz and sharp roll-off for arbitrary LC states. Moreover a prototype sample is designed, fabricated, and measured to verify the proposed design method.

A New Method for Designing Modified Compact Microstrip LPF with Sharp Roll-Off and Wide Stopband

A New Method for Designing Modified Compact Microstrip LPF with Sharp Roll-Off and Wide Stopband

Designing and Validation of Miniaturized CPW Based Microwave Notch Filter Using Loaded Modified Multiple Split Ring Resonator (MSRR)

In this article, a coplanar waveguide (CPW) based compact low loss notch filter (NF) with sharp roll–off is proposed. At the beginning, the proposed NF is designed using an array of conventional Multiple Split Ring Resonator structure (MSRR), then it is replaced by modified MSRR structure in array to improve the sharpness factor in dB/GHz. This array of modified MSRR structure is behaving like a metamaterial unit cell. The proposed NF operates at resonant frequency of 2.56 GHz with 3 dB fractional bandwidth (FBW) of 4.68%, a roll-off factor (ROF) of 672 dB/GHz, and passband insertion loss of 0.35 dB. A parametric study has been done to obtain the relationship between the ring perimeter of the MSRR and the resonant frequency of the NF. Finally, a dual-band notch filter (DBNF) is designed by using an array of four modified MSRR structures. The EM simulated, circuit simulated, and measurement results of the proposed structure are in good agreement with each other. The proposed CPW based NF is useful for various applications like LTE (2600 MHz), Wimax (2500 MHz), and FCC ID (2.68 GHz).

Tunable liquid crystal frequency selective surface with the compact unit cell, large tuning range, and the passband of flat-top and sharp roll-off

In this paper, a design method for tunable liquid crystal (LC)-based frequency selective surface (FSS) with the compact unit cell, large tuning range, and the passband of flat-top and sharp roll-off is proposed. A very compact LC-based bandpass FSS unit cell with the dimension of 0.077 λ × 0.077 λ is designed based on a pair of planar vortex-shaped metallic structure with two large parallel patches, between which the LC is sandwiched. Results show that the central frequency of the FSS is tuned from 11.56 to 12.58 GHz, and the tuning range reaches up to 8.5%. In order to obtain the transmission characteristics of flat-top and sharp roll-off, a double-layer structure is proposed and combined with the LC-based FSS design. Theoretical analyses are conducted to declare the working principle of the double-layer LC-based FSS. A prototype sample for the double-layer LC-based FSS is designed and fabricated. Results show that the double-layer LC-based FSS structure achieves frequency selective characteristics with a flat-top passband of about 450 MHz and sharp roll-off for arbitrary LC states with −15 dB rectangle coefficient of 2.44 for arbitrary LC states. Moreover, stable frequency responses of the double-layer LC-based FSS under various incident angles from 0° to 45° are obtained for arbitrary LC states.

Design of low pass filter with ultra-wide stopband based on DGS and SIRs

This paper presents a novel compact design of a low pass filter (LPF) with a vast rejection band, low insertion loss (IL), and sharp roll-off. The prospective LPF is fed using a modified E-shape microstrip line to improve the higher frequencies rejection band. Two ring slots are engraved in the ground plane and linked to the feeding line through metallic via to provide further improvement in the rejection band. Three coupled stepped impedance resonators (SIRs) are jointed between the I/O ports to improve the filter roll-off. The proposed LPF provides cutoff frequency at 2.8 GHz, and stopband ranges from 3.2 to 20 GHz with an attenuation level less than −20 dB. The lumped RLC circuit model of the proposed LPF is introduced and confirmed by simulation and theory using Keysight Advanced Design System (ADS). This LPF is designed and fabricated on Rogers RT3006 with compact size 13 mm × 8.2 mm. The measurements of the proposed LPF are in good agreement with the simulated results.

UWB dual-notched planar antenna by utilizing compact open meander slitted EBG structure

In this paper, an ultra-wideband (UWB) dual-notch planar antenna is presented. The antenna, in its structure, utilizes a compact electromagnetic bandgap (EBG) structure with new open meander slits to notch two frequency bands at around 3.5 and 5.5 GHz. The main idea is to place the new slitted mushroom-type EBG structure at the vicinity of the feedline to achieve filtering ability for the antenna. The presented EBG structure has many benefits, like notched bands with sharp roll off, independent control over the notched bands, little effects on antenna performance, easy switching configuration and reduction of the required number of EBG cells. The fabricated antenna shows −10 dB bandwidth of 2.63 up to 13 GHz with dual-notched in the frequency bands of 3.11–4.01 GHz and 5.15–5.98 GHz. Simulation and experimental results exhibit a close agreement with each other. The proposed UWB antenna with a flat transfer function and a constant group delay at the notched bands is a suitable choice for compact UWB communication systems.

X-Band Miniature Filters Using Lithium Niobate Acoustic Resonators and Bandwidth Widening Technique

This work presents a class of micro-electromechanical system (MEMS)-driven radio frequency filters in the X-band. The X-band center frequencies are achieved by resorting to the third-order antisymmetric Lamb wave mode (A3) in a 650-nm-thick Z-cut lithium niobate thin film. A novel bandwidth (BW) widening technique based on using the self-inductance of the top interdigital transducers and bus lines is proposed to overcome the limitations set by the electromechanical coupling (k <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> ) and satisfy the demands in miniaturization and wide BW. Four different designs of the filters are designed and fabricated to show the trade-off among BW, insertions loss (IL), out-of-band rejections, and footprint. Due to the spurious-free and highQ performance of the A3 lithium niobate resonators, the fabricated A3 lithium niobate filters have demonstrated small in-band ripples and sharp roll-offs. One of these fabricated has demonstrated a 3-dB BW of 190 MHz, an IL of 1.5 dB, and a compact footprint of 0.56 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Another design is fabricated to demonstrate a 3-dB BW of 170 MHz, an IL of 2.5 dB, an outof-band rejection of 28 dB, and a compact footprint of 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Compact microstrip lowpass filter with very sharp roll-off using meandered line resonators

In this paper, a new compact size microstrip lowpass filter (LPF) with a very sharp roll-off is presented to apply in the modern wireless networks. The proposed LPF is designed using the series main resonators with meandered lines based on inductor-capacitor (LC) equivalent circuit analysis. The main goal is to achieve maximum-sharp roll-off by maintaining a wide stopband bandwidth and high return loss (RL). The main resonator of the proposed filter is consisted of two meandered line hairpin resonators (MLHR), and a meandered line T-shaped resonator (MLTR). The designed suppressor is composed of two coupled radial stubs to create a wide stopband. Low return loss in the passband, which has been created by the main resonator, is resolved by the suppressor structure with high return loss. The measured results show a − 3 dB cut-off frequency of 1.93 GHz. The very sharp transition band starts at 1.93 to 1.97 GHz (from − 3 to − 20 dB). The stopband is from 1.97 to 19.9 GHz (with the suppression level of − 20 dB). Also, the total size of the proposed LPF is only 13.3 × 10.1 mm2.

Evolution of Low-Profile Ultra-Wideband Frequency Selective Surface with a Stable Response and Sharp Roll-Off at Lower Band for C, X and Ku Band Applications

Evolution of Low-Profile Ultra-Wideband Frequency Selective Surface with a Stable Response and Sharp Roll-Off at Lower Band for C, X and Ku Band Applications

Novel configuration of ultra‐wide band uni‐planar configuration of complementary split ring resonator composite right/left‐handed based band pass filter with sharp roll off and good stopband attenuation

In this paper, a compact novel simple design of ultra-wide bandpass filter with high out of band attenuation is presented. The filter configuration is based on combining an ultra-wide band composite right/left-handed (CRLH) band pass filter (BPF) with simple uni-planar configuration of complementary split ring resonator (UP-CSRR). By integrating two UP-CSRR cells, the ultra-wideband CRLH filter roll-off and wide stopband attenuation are enhanced. The filter has 3 dB cutoff frequencies at 3.1 GHz and 10.6 GHz with insertion loss equals 0.7 dB in average and minimum and maximum values of 0.48 dB and 1.05 dB, respectively over the filter passband. Within the passband. The transition band attenuation from 3 dB to 20 dB is achieved within the frequency band 1.9 GHz to 3.1 GHz (48%) at lower cutoff and the frequency band 10.6 GHz to 11.4 GHz (7%) at upper stopband. Moreover, the filter has a wide stopband attenuation >20 dB in frequencies 11 GHz to 13.6 GHz (21%) and ends with 3 dB cutoff frequency at 14.8 GHz. Furthermore, the designed filter size is very compact (23 × 12 mm2) whose length is only about 0.17 λg at 6.85 GHz. The filter performance is examined using circuit modeling, full-wave simulations, and experimental measurements with good matching between all of them.

Reconfigurable Low-Pass Filter With Sharp Roll-Off and Wide Tuning Range

A miniaturized reconfigurable low-pass filter (LPF) with a sharp roll-off, wide tuning range, and extended stopband is presented in this letter. The proposed LPF consists of two fixed low-pass (LP) cells and a tunable bandstop (BS) cell loaded with two pairs of varactor diodes. The BS cell with tunable stopband edges is employed to achieve the reconfigurable cutoff frequency and sharp roll-off characteristics in the whole LPF. The fixed LP cells are utilized to suppress the high passband of the BS cell, which obtain the tunable LP filtering response and wide stopband. For experimental demonstration purposes, a microstrip prototype of the proposed reconfigurable LPF with a wide fractional tuning range of 78.8% and roll-off rate over 103 dB/GHz is simulated, fabricated, and measured. The wide stopband is extended up to 10 GHz with a rejection level better than 15 dB, and the overall dimension is $0.078\lambda _{\mathrm {g}} \times 0.08\lambda _{\mathrm {g}}$ . This physical size is comparable to more compact, prior art reconfigurable LPFs while featuring among the sharpest roll-off rate ever reported.