Compact Lowpass Filter Research Articles

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.

Novel Compact Lowpass Filter Using Dual-Layer Coupled Resonators

This article presents the synthesis and design of a novel compact lowpass filter (LPF) with low insertion loss and significant near-skirt selectivity. The LPF is designed based on a new structure called dual-layer coupled resonators (DLCRs) implemented with striplines embedded in air cavity, thus characterized with high quality factor and low insertion loss. To enhance band-edge selectivity and stopband attenuation, finite-position transmission zeros (TZs) are introduced with DLCRs to form pseudo-elliptical fitter functions. The equivalent circuit of DLCR is provided first, followed by detailed synthesis preconditions and procedures based on element extraction. With the elucidated synthesis process, TZs can be customized and arbitrarily placed at specified frequencies. The proposed synthesis theories are general and applicable to LPFs with arbitrary order and assigned TZs, thus providing effective guidelines for physical implementation. Besides, with smaller needed capacitances and avoided long-length high-impedance lines in TZ-producing resonant pairs, a more compact footprint is achieved with DLCRs. A 13th-order LPF with three TZs is synthesized and fabricated for navigation satellite applications, of which the good measurement results have validated the proposed theories.

A Fast Surrogate Model-Based Algorithm Using Multilayer Perceptron Neural Networks for Microwave Circuit Design

This paper introduces a novel algorithm for designing a low-pass filter (LPF) and a microstrip Wilkinson power divider (WPD) using a neural network surrogate model. The proposed algorithm is applicable to various microwave devices, enhancing their performance and frequency response. Desirable output parameters can be achieved for the designed LPF and WPD by using the proposed algorithm. The proposed artificial neural network (ANN) surrogate model is employed to calculate the dimensions of the LPF and WPD, resulting in their efficient design. The LPF and WPD designs incorporate open stubs, stepped impedances, triangular-shaped resonators, and meandered lines to achieve optimal performance. The compact LPF occupies a size of only 0.15 λg × 0.081 λg, and exhibits a sharp response within the transmission band, with a sharpness parameter of approximately 185 dB/GHz. The designed WPD, operating at 1.5 GHz, exhibits outstanding harmonics suppression from 2 GHz to 20 GHz, with attenuation levels exceeding 20 dB. The WPD successfully suppresses 12 unwanted harmonics (2nd to 13th). The obtained results demonstrate that the proposed design algorithm effectively accomplishes the LPF and WPD designs, exhibiting desirable parameters such as operating frequency and high-frequency harmonics suppression. The WPD demonstrates a low insertion loss of 0.1 dB (S21 = 0.1 dB), input and output return losses exceeding 30 dB (S11 = −35 dB, S22 = −30 dB), and an output ports isolation of more than 32 dB (S23 = −32 dB), making it suitable for integration into modern communication systems.

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.

Compact low-pass filter (LPF) with wide harmonic suppression using interdigital capacitor

Abstract In this article, a compact microstrip low-pass filter (LPF) with low in-band insertion loss and a wide attenuation band is recommended. The structure is modeled using two rectangular-shaped open resonators (ORs) loaded with multiple sections of the interdigital capacitor. The proposed LPF has a cut-off frequency of 1.5 GHz, a passband insertion loss of 0.35 dB, and an electrical circuit size of 0.02 λ g 2. In the ground plane, two dissimilar defected ground structures (DGSs) are introduced to generate additional attenuation poles for enriching the stopband performance of the LPF. The harmonics suppression is achieved up to 15 GHz with tenth harmonic suppression and relative stopband rejection of almost 165%. The EM simulated results show a well-matched behavior with the experimental ones. The proposed LPF can be used for global positioning systems (1500 MHz), telecommunications (1600 MHz), and audio broadcasting (1400 MHz) applications.

Stepped Impedance Hairpin Resonator (SIHR) based Compact Lowpass Filter with Wide Attenuation Band

ABSTRACT In this article, a compact (0.29 λg x 0.10 λg) low-pass filter (LPF) using a trisection stepped impedance hairpin resonator (SIHR) with a low insertion loss and a wide attenuation band is proposed. The microstrip structure is loaded with an L-shaped spur-line resonator and folded T-shaped stub for generating additional transmission zeroes to obtain a wider attenuation band. Moreover, an open stub is introduced into the existing structure to enrich the stopband performance of the LPF with a relative stopband rejection of almost 142 %. The proposed LPF that operates at a cut-off frequency of 1.7 GHz is suppressed up to −46 dB at the resonant frequency with a passband insertion loss of 0.35 dB. The suppression of harmonics is achieved up to 10 GHz with a suppression factor of 2. A well-matched behavior is observed in between the EM simulated, measurement, and circuit simulated results. The proposed LPF is suitable for mobile phones (1850 MHz), a global system for mobile communications (1800 MHz), and LTE communications (1700 MHz).

Miniaturized microstrip suppressing lowpass cell for hybrid applications

In this paper, a very small microstrip low-pass filter (LPF) has presented for utilization in microwave systems. This device is composed of mirrored stepped impedances with two boxes at each side. A transfer function has been extracted from the relevant LC circuit, which expresses the function of this design. The operating frequency of the LPF is located at 3.5 GHz. The proposed LPF blocks a wide rejection with a rejection level of −20 dB or stronger. The return loss of 33 dB is another competence of the LPF. The overall size of the fabricated prototype is 9.5 mm × 5.8 mm (56 mm2). These dimensions maybe give the most compact lowpass filter operating in such frequency among the published work until now. The measurement results mimic the simulations.

A Compact Low-Pass Filter Using Dielectric-Filled Capacitor on SISL Platform

This letter proposes a compact low-pass filter (LPF) using dielectric filled capacitor based on the substrate integrated suspended line (SISL) platform. A dielectric filled capacitor with high capacitance density is presented for the first time. Using this type of capacitor, a three-order lumped element LPF with a cutoff frequency of 120 MHz is designed, fabricated, and tested. The measured results agree with the simulated ones. The circuit size of the implemented SISL LPF is only 0.005 λg × 0.013 λg, which is very small when compared to the state of art. The measured insertion loss of SISL LPF in the passband is 0.12 dB and the stopband is from 0.35 to 2.27 GHz with a suppression level greater than 20 dB. A seven-order LPF is also designed to further demonstrate the good property of the proposed capacitor.

A compact lowpass filter for satellite communication systems based on transfer function analysis

This paper presents a very efficient design procedure for a high-performance microstrip lowpass filter (LPF). Unlike many other sophisticated design methodologies of microstrip LPFs, which contain complicated configurations or even over-engineering in some cases, this paper presents a straightforward design procedure to achieve some of the best performance of this class of microstrip filters. The proposed filter is composed of three different polygonal-shaped resonators, two of which are responsible for stopband improvement, and the third resonator is designed to enhance the selectivity of the filter. A holistic performance assessment of the proposed filter is presented using a Figure of Merit (FOM) and compared with some of the best filters from the same class, highlighting the superiority of the proposed design. A prototype of the proposed filter was fabricated and tested, showing a 3-dB cut-off frequency (fc) at 1.27 GHz, having an ultrawide stopband with a suppression level of 25 dB, extending from 1.6 to 25 GHz. The return loss and the insertion loss of the passband are better than 20 dB and 0.25 dB, respectively. The fabricated filter has a high FOM of 76331, and its lateral size is 22.07 mm × 7.57 mm.

A Microstrip Lowpass Filter With Wide Tuning Range and Sharp Roll-Off Response

In this brief, a compact lowpass filter (LPF) with wide stopband, very sharp roll-off response and wide tuning range is presented for microwave diode detector applications. It employs two hexagonal-shaped resonators and multiple open-end stubs as suppression cells. The results of the proposed hexagonal-shaped resonator and LC circuits are in good agreement. The 3 dB cut-off frequency for the proposed LPF is 2.2 GHz and the roll-off-rate (ROR) parameter for the proposed LPF is very sharp and equal to 308.6 dB/GHz. Furthermore, insertion loss (IL) and return loss (RL) in the passband region are better than 0.3 dB and 18 dB, respectively. Moreover, the stopband is wide, ranging from 2.34 to 18 GHz, with a 22 dB rejection level. The tuning range of 3 dB cut-off frequency is also wide, equal 0.48 to 1.7 GHz (71%). As an application demonstrator, an envelope detector was designed and fabricated. The proposed detector (with LPF) highly suppresses any harmonics of the fundamental frequency. The proposed LPF and microwave detector is designed, simulated, fabricated and measured. The results of simulation and measurement are in good agreement.

A Novel 183 GHz Solid-State Sub-Harmonic Mixer

This paper proposes a novel sub-harmonic mixing topology. Based on the proposed topology and the precise three-dimensional electromagnetic model of the Schottky barrier diode; a novel 183 GHz solid-state sub-harmonic mixer is designed and measured. By adding a compact low-pass filter near the ground of the mixer’s circuit, the effect on the mixer’s RF performance of the random error of the conductive adhesive in assembling is effectively decreased. The test results show that the optimal single-sideband conversion loss of the mixer is 8.1dB@183GHz when the local oscillator signal is 4mw@91GHz. In the RF bandwidth from 173 GHz to 191 GHz, the single-sideband conversion loss is less than −10.6 dB. At the same time, the RF port return loss is less than 9.8 dB.

Design of a compact LPF and a miniaturized Wilkinson power divider using aperiodic stubs with harmonic suppression for wireless applications

In this paper a miniaturized low pass filter (LPF) with 2.5 GHz cut-off frequency and a novel compact, harmonics suppressed Wilkinson power divider (WPD) at 0.7 GHz is proposed. The proposed divider consists of two multi-stub LPFs and three open stubs at each port. The presented open stub at port one suppresses the second harmonic and other two open stubs at output ports, suppress the third harmonic. To suppress high order harmonics a novel 12 sections LPF based on aperiodic stub is proposed. This filter is designed to suppressed 4th to 15th harmonics. The cut off frequency of applied filter is 2.5 GHz, which creates 12 transmission zeros and suppresses corresponding 4th–15th harmonics of the proposed divider. The proposed WPD not only has perfect harmonics suppression, but also extremely decreases the circuit size. The overall size of the fabricated divider is only 0.116 λg × 0.044 λg, which shows more than 73% size reductions, compared to the 0.7 GHz conventional WPD.

On the Filtering of Spurious Oscillations in the Numerical Simulations of Convection Dominated Problems

This paper presents the numerical filtering as a valuable tool used for the removal of spurious oscillations in the numerical solution of some specific fluids flows. The qualitative results based on the application of two distinct representative filters are discussed. The compact low-pass filters and the digital Total Variation Diminishing (TVD) filters are described as examples of the filtering approach. Their use is shown on selected one-dimensional advection problems, demonstrating the essential behavior of the filtered solution. Finally an example of a more realistic biomedical problem solved using finite-volume scheme is discussed including the effect of the digital filter. The conclusions sum up some of the experience from the application of both filtering techniques.

Compact Lowpass and Dual-Band Bandpass Filter With Controllable Transmission Zero/Center Frequencies/Passband Bandwidth

A simple and compact filter structure for lowpass and dual-band bandpass response with controllable transmission zeros/center frequencies/3-dB bandwidth is proposed in this brief. The proposed filter structure uses two-unit cells, which contains ${{\lambda }}$ /5 length of folded coupled line and open circuited L-shape strip. A lowpass and a bandpass response has been realized by a unit cell due to formation of LC series and shunt tank circuit. Another bandpass response has been achieved by connecting two-unit cells with a strip. In literature, there are very few designs which can achieve two different type of filtering responses. The proposed design is compact as compared to the state-of-the-art and also the two filtering responses have been achieved with improved selectivity and impedance matching due to formation of additional tank circuit. The size of the filter excluding feed line is $0.13{{\lambda }}_{g}\times 0.06{{\lambda }} _{g}$ (15.5 mm $\times $ 7.2 mm) at the 3-dB cut-off frequency (1.05 GHz) of the lowpass filter. The position of transmission zeros/center frequencies and 3-dB bandwidth characteristics can be separately controlled by varying the physical parameter of designed filter structure. The filter performance has been validated through electromagnetic simulation and experimental measurements. The metamaterial properties of designed filter has been verified by its dispersion diagram.

A novel compact lowpass filter with sharp roll-off and wide stopband

AbstractIn this paper, a microstrip lowpass filter adopting two main resonators with steep transition band and wide rejection band has been introduced. The first main resonance cell consists of meandered transmission lines which are loaded by modified T-shaped patches. The second main resonator is composed of high-impedance lines loaded by polygon patches. To obtain a steep skirt performance, the first and second resonators have been combined. Moreover, employing eight high–low impedance folded stubs and two rectangular open-stubs as suppressing cells has resulted in improving the stopband features. To comprehend the frequency behavior of the employed resonators and also their combination, the formulas of the transmission coefficient, reflection coefficient, and the transmission zeros of their equivalent LC circuits have been extracted, separately. According to the measurement results, the −3 dB operating frequency of this filter is 1.65 GHz. Moreover, a relative stopband bandwidth equal to 166% with a corresponding attenuation level of 23 dB and a sharp roll-off rate (393.61 dB/GHz) have been achieved. In the passband region from DC to 1.632 GHz, the insertion loss and return loss are better than 0.0763 and 15.85 dB, respectively, proving an acceptable in-band performance. Finally, the implemented structure brings about a high figure-of-merit equal to 81 672.

Compact low‐pass/band‐pass filters based on quarter‐mode substrate integrated waveguide and a connected network of CSRRs

In this study, a compact low-pass filter (LPF) and two compact dual-wideband band-pass filters (BPFs) are proposed based on a connected network of complementary split-ring resonators (CSRRs) and open CSRRs (OCSRRs). The LPF is designed based on microstrip structure, and then the structure is changed to quarter-mode substrate integrated waveguide for designing the dual-band BPFs. The 3 dB cutoff frequency of the LPF is 1.84 GHz and its size is 0.094λ g × 0.094λ g , where λ is the guide wavelength at 3 dB cutoff frequency. The LPF has a wide stop-band, up to 16 GHz. The first proposed dual-wideband BPF has the centre frequencies of 3.85 and 8.03 GHz, with 3 dB fractional bandwidths of 31.69 and 13.7%, respectively. Finally, a sharper dual-band BPF is obtained by cascading two proposed dual-wideband BPFs and optimising them for the desirable response. The measured centre frequencies of the second dual-band BPF are 3.65 and 7.15 GHz with 3 dB fractional bandwidths of 28.21 and 12.52%, respectively. The measurement results of the fabricated filters are in good agreement with the simulation ones. The filters are compared with similar reported filters in the literature, which confirm the compactness of the proposed filters..

Synthesis of the compact low pass filter using dumbbell-shaped slot resonators

Synthesis of the compact low pass filter using dumbbell-shaped slot resonators

Design of a Modified Wilkinson Power Divider with Size Reduction and Harmonics Suppression using Triangle-Shaped Resonators

In this study, a miniaturized microstrip Wilkinson power divider (WPD) with harmonic elimination using low pass filter is proposed. In proposed design, two large conventional quarter wavelength transmission lines are replaced with compact low pass filters. Applied low pass filters are consisted of three triangle resonators, which result in harmonics suppression and size reduction of the proposed WPD. The proposed WPD has 56% size reduction compared to the conventional one. The proposed divider correctly works at 2 GHz and suppresses second to eighth harmonics with more than 20 dB attenuation level. According to the experimental results the insertion loss of the proposed design is less than 0.1 dB n pass band. The return losses at all ports and output ports isolation parameters are better than 20 dB and 26 dB, respectively, which shows good performance of the proposed device.

A compact microstrip lowpass filter with wide stopband using rectangular resonator and high impedance elements

AbstractIn this paper, a microstrip lowpass filter using rectangular resonators is designed. To weaken the undesired harmonics from 10 to 20 GHz, a stair-shaped suppressing cell and also high impedance elements at the edges are utilized. It should be noted that for analyzing the proposed filter, an LC model is used and the design is done in such a way that the coupling effects of the close-up lines are reduced as much as possible, so that they are ignored in the circuit analysis. The designed filter has a cut-off frequency of 1.01 GHz and the transition band is only 0.1 GHz. In addition to compression of dimensions, the stopband bandwidth is 18.7 times the cut-off frequency (18.7 × fc). The attenuation rate in the passband reaches 0.081 dB which indicates that the passband is flat. In the stopband, disturbing harmonics have been dampened to −23.5 dB and a good bandwidth is achieved. The figure of merit of the proposed filter is 180 387 and it is a good benchmark for the overall comparison of the proposed filter with the previous works.

A compact lowpass filter with ultra-high figure-of-merit for integrating with Class-F/F−1 power amplifiers

This Paper presents a microstrip lowpass filter (LPF) with compact size, and ultra-wide stopband. The structure consists of a semi-circular shaped resonator (SCSR) and circular patches as the suppressing cell. The proposed LPF has a − 3 dB cutoff frequency at 1.53 GHz. It also has suitable performances such as an extended stopband width from 1.62 to 19.1 GHz (with the attenuation level of more than − 20 dB), ultra-sharp transition-band of 0.09 GHz (from − 3 to − 20 dB). Low insertion loss, high return loss and flat group delay in the region of the passband are very significant properties of this LPF. A proper agreement between the simulation and measurement results has been achieved after the fabrication and testing. Proposed LPF has an ultra-high figure-of-merit (FOM) of 126168, showing its strong efficiency. Forasmuch as harmonic control circuits (HCCs) play a key role in designing Class-F/F−1 power amplifiers (PAs); the asymmetric high performance LPFs can be used at the input and output of these PAs in the HCC section. Therefore, the proposed LPF can be suggested for this application.