Compact Bandstop Filter Research Articles

Design and analysis of quasi‐lumped notch filter with extended upper pass band

AbstractThis paper presents a hybrid technique‐based compact narrow band stop filter design for broadband applications. It provides the rejection of 60 dB at the centre frequency of 2.25 GHz without any stop band harmonics over the required frequency band of operation, i.e. 1–10 GHz. This filter is highly appropriated for the rejection of undesired bands for RADAR, electronic warfare, and military communications.

A wide bandstop filter using negative permeability achieved by complementary electrical L-C resonators

This paper proposes an improved approach for designing a compact microstrip line-based band stop filter (BSF) using a new Z-shaped complementary electrical LC (CELC) resonator with negative permeability. The design offers advantages in terms of compactness and large stopband. The measured insertion loss exhibits a 3 dB bandwidth from 6.7 to 9 GHz, resulting in a relative stopband bandwidth of 28.75% with rejection exceeding 20 dB between 7.5 and 8.2 GHz. Both the simulation and the measurements reveal a high level of selectivity in both the lower and upper transition bands. The final filter has 0.33λg×1.32λg circuit size and is very effective in rejecting unwanted frequency in terms of its selectivity and size.

A filtering patch antenna with reflectionless in a wide frequency range

AbstractA filtering antenna consists of a reflective filtering antenna (RFA) and a bandstop filter (BSF) is presented. Due to the L‐shaped feeding structure, slots etching on the radiator and the ground plane, the RFA obtains good impendence matching, stable in‐band gain, as well as four reflective radiation nulls, and that contribute an operating band of 19% and good frequency selectivity to the proposed filtering antenna. The RFA and BSF are cascaded directly, and the compact BSF is terminated by a resistor to absorb the stopband energy of the RFA, bringing good reflectionless characteristics in a wide frequency range to the proposed filtering antenna. The proposed filtering antenna has a 2‐dB gain bandwidth of 22% (1.78–2.22 GHz), in‐band gain of about 6.81 dBi, radiation suppression levels of higher than 23.4 and 21.4 dB for the lower and upper stopbands, respectively. Within 1.0–3.0 GHz, |S11| ≤ −12 dB, implying slight effect of reflected wave on the devices connected to the proposed filtering antenna.

Non-Bianisotropic Complementary Split Ring Resonator Metamaterial Bandstop Filter Using Cylindrical Metal Vias

This brief presents a bandstop filter using the Non-bianisotropic Complementary Split Ring Resonator (NBCSRR) and cylindrical metal vias, which exhibits electromagnetic bandgap behavior. A compact bandstop filter structure is achieved using NBCSRR sub-wavelength operation. The filter prototype is fabricated and tested, and the measured results agree well with the simulated results. The filter has higher bandstop rejection levels in the X band, which ranges from 8.8GHz to 9.3GHz.

Compact Quadband Bandstop Filter Based on Concentric Split Ring Resonators with Perturbation for Multifunctional Wireless Systems

Bandstop filters play an essential role in many radio frequency (RF) and microwave communication systems to block undesired signals or reject spurious harmonics. This paper presents the design and experiment of a compact quadband bandstop filter centered at 1.2/1.97/2.96/4.78 GHz with a passband insertion loss ranging from 1.07 to 2.9 dB. The overall volumetric size of the proposed filter is 0.197 λ g × 0.197 λ g × 0.01 λ g , where λ g is the guided wavelength at 1.2 GHz. The desired performance is achieved by introducing two diamond-shaped concentric split ring resonators (DSCSRRs) intercoupled and defected ground structure. The metamaterial properties of the DSCSRR have been verified by extracting and analyzing its effective permittivity and permeability. This research shows that DSCSRRs can generate multiband characteristics and yield high selectivity with good band-to-band isolation by generating transmission zeros between passbands. The filter is designed, optimized, and analyzed using High-Frequency Structural Simulator (HFSS). A good agreement is observed between simulated and experimental results. The measured results demonstrate that the proposed quadband banstop filter exhibits a minimum stopband rejection of 11.22 dB and fractional bandwidth greater than 4.51%, which makes it suitable for front-end transceiver components or multifunctional wireless systems to suppress unwanted signals at four separate frequency bands.

Compact Dual Bandstop Filter Using Folded Lines and Genetic Algorithm

A novel method for creating a dual band bandstop filter with a meandering architecture is presented. Proposed bandstop filter shows two notch bands, one at 5.6 to 7.2 GHz and the other at 8 to 11 GHz. The designed filters simulated on HFSS software and fabricated on FR-4 substrates, filter dimensions have been optimized using GA. Filter shows S11 of 1dB and S21 of -18 dB at notch frequency 6.4 GHz and S11 of 1.2dB and S21 of -38 dB at notch frequency 9 GHz. The suggested filter has two pass bands one is up to 5 GHz for wireless communication and another is from 7.4 to 7.9 GHz for C band applications.

A Compact Bandstop Filter Design Using DMS-DGS Technique for Radar Applications

In this study, a novel compact bandstop filter (BSF) by utilizing the defected ground structure (DGS) and defected microstrip structure (DMS) techniques are presented. DGS, DMS, and compensated capacitors are used on both bottom and top layers to obtain sharp transition and wider stopband. The operating frequency bandwidth of the filter can be comfortably regulated by tuning the dimensions of the etched structures. In addition to parametric studies, an equivalent circuit model of the proposed filter is extracted. The BSF has an insertion and return losses better than –1.6 and –17 dB in the passband, respectively. Moreover, the developed filter covers X-band frequency range and has stop bandwidth of 10.8–11.8 GHz with the rejection of better than 20 dB. Furthermore, the measurement and simulation results are in compliance with the suggested method. The proposed BSF has a very small size of 14.28 mm ×× 4 mm ×× 0.508 mm and has the potential to be used for radar applications with its high compactness, low cost, and high harmonic rejection performance.

Design & Simulation of S Band Planar Microwave Filter for Wireless Application

Reducing the size of today’s wireless communication systems has become an important criterion in filter design with minimal possible value of filter parameters. To achieve this goal in wireless communication system, filter design is the most important part of the signal transmission process. Conventional filters are very important for modern wireless communication systems as they do not provide the desired miniaturization and results. Recently, using metamaterials and dielectric resonators, the filter size has been drastically reduced to a very small size for practical applications. This filter is flat and lightweight. It consumes very low power consumption. In this proposed work, a compact S-band microwave band stop filter was designed using a simple technique. These filters are small in size and light in weight. The design covers the S-band and is suitable for the desired frequency for Wi – Fi and wireless LAN application.

A q uasi‐analytic synthesis methodology for spiral defected microstrip compact bandstop filters

A q <scp>uasi‐analytic</scp> synthesis methodology for spiral defected microstrip compact bandstop filters

Compact and wideband microwave bandstop filter for wireless applications

Compact, tunable and wide band stop filter (BSF) for wireless application is presented. The proposed filter is composed of compact rectangular microstrip open loop resonator with stub loaded resonator as building blocks of the filter. First, two vertical lumped capacitors are inserted in the open loop resonator from top to bottom of the substrate at the place which has maximum electric field to decrease the resonance frequency which in turn miniaturize the filter size. The resonance frequency of the fundamental mode is shifted from 5.5 to 4.2 GHz when lumped capacitors of 0.2 pF are added. Second, the capacitance of the open-ended stub can be changed to control the second resonance mode of the filter. Also, by inserting another vertical capacitor at the end of the open-ended stub, the second resonance mode can be controlled and reduced. Finally, by properly selecting the capacitance of the third lumped capacitor, the second resonance mode can be designed to be close to the fundamental mode and hence wide band stop filter can be achieved. The proposed BSF has some appropriate features such as compact size (its size has more than 40% size reduction), wide stopband and most importantly tunability of stopband. The band stop filter has a center frequency of 6.2 GHz, a stop band from 3.5 to 9 GHz, insertion loss lower than − 30 dB, and a return loss higher than 0.4 dB is accomplished inside the stop band. The measured results have good matching with the simulated results.

Modernization of the filtration system for the Doppler reflectometry diagnostics of the L-2M stellarator for operation in regimes high-power ECR heating

The commissioning of the MIG-3 gyrotron complex at the L-2M stellarator has made it possible to reach a record power density input into plasma of 3.4 MW/m3 during the ECR heating of the plasma. This power input, however, resulted in noisy Doppler reflectometry signals (with a high-amplitude component at the gyrotron working frequency of 75.3 GHz), which could not be processed and analyzed. We modernized the filtering system of the Doppler reflectometry diagnostics, which had consisted of two pin-type band stop waveguide filters. Another pin-type filter was added to the filter system and a new compact bandstop filter was designed based on the Fabry-Perot resonator (BFFPR) to provide high suppression at the frequency of 75.3 GHz and low attenuation at the 30–40 GHz diagnostic frequency. We optimized the cavity length of the filter and calculated the characteristics of filters with different numbers of resonators by using numerical simulations. The filter layout was designed, and its characteristics were measured. The results of experimental measurements and numerical simulations have a good match. The redesigned filters were used to suppress the noise from the MIG-3 gyrotron complex.

Tunability of metamaterial compact band-stop filters using YIG substrate

ABSTRACTIn this paper, the design of a tunable and compact metamaterial microstrip band-stop filter is proposed. The device is designed to operate in the X band, it is based on a metamaterial pattern (single-turn square planar resonator) implemented on a ferrite substrate. The study focuses on the metamaterial band-stop filter and on the way to tune its frequency properties. For this reason, the magnetic material is a perfect solution, using YIG (Yttrium Iron Garnet) substrates. As a result, the central frequency of the filter can be tuned by varying the magnetic bias applied to the YIG substrate. A tunability up to 10.81% is obtained. The size of the proposed filter is electrically reduced to 3.7 mm2.

Compact bandstop filters using coupled lines and open/short stubs with multiple transmission poles

A compact bandstop filter (BSF) using parallel-coupled lines and open stubs with four transmission poles (TPs) is proposed. Through theoretical equation deduction, the positions of these four TPs can be obtained. Good roll-off skirts and stopband suppression characteristics of the BSF can be realised with the help of multiple TPs. To improve transition band roll-off rates, another BSF with five TPs is designed, where a short-circuited T-stub is loaded on the middle of the above BSF circuit structure. For demonstration, two filter examples with centre frequencies at 2 and 1.8 GHz are implemented with generation of four and five TPs, respectively, for theoretically calculated certification. Good agreement between simulated and measured results validates the design method.

Compact multiple bandstop filter using integrated circuit of defected microstrip structure (DMS) and dual-mode resonator

In this article, a compact bandstop filter (BSF) with desirable four attenuation narrow bands is developed for multiple wireless network systems. The developed filter composes of two microstrip circuits. In the first microstrip circuit, stepped-impedance and two open-circuit stubs in defected microstrip structure (DMS) are analyzed to generate the first and the second rejection bands. The third and the fourth stopbands are realized using a second microstrip circuit consist of two dual-mode resonators. This circuit are capacitively coupled to the DMS-circuit. The filter attitude is very well explained using a coupling mechanism diagram. To demonstrate the developed concept, dual and quad-bandstop filters are designed, fabricated, and measured to supress the frequencies of (2.4 GHz and 5 GHz WLAN) and (1.56 GHz GPS, 2.4 GHz WLAN, 3.5 GHz WiMax, and 5.25 GHz WLAN) respectively. The measured results agree with the predicted ones closely. The measured responses improved that the quad-BSF can apply 10 dB attenuation bandwidths of 81 MHz, 73 MHz, 60 MHz, and 129 MHz centred at 1.56 GHz, 2.4 GHz, 3.5 GHz, and 5.25 GHz respectively. The designed filter has overall circuit area of 125 mm2 excluding the feeding ports.

Compact dual-band bandstop filter based on coupled open-ended Hilbert resonators

ABSTRACTIn this paper, the design procedure of a compact dual-band bandstop filter (DBBSF) based on coupled open-ended Hilbert lines is proposed. The proposed filter topology consists of two pairs of coupled open-ended lines bended in the shape of the Hilbert fractal curves and a stepped-impedance line section (SIS). In that manner, tree transmission paths are crated allowing the independent control of filter characteristic in both bands. To obtain appropriate coupling between resonators, and the independent control of the center frequencies and in-band characteristics of the filter, the SIS is introduced as matching section. Design rules are derived using lossless transmission line model and even/odd analysis. To validate the design concept, two compact DBBSFs have been designed, fabricated, and measured. The proposed filters exhibit excellent in-band characteristics, high selectivity, and small dimensions.

Compact Bandstop Half-Mode Substrate Integrated Waveguide Filter Based on a Broadside-Coupled Open Split-Ring Resonator

A shunt RLC resonant circuit obtained from a broadside-coupled open split ring resonator (BC-OSRR) is proposed. This BC-OSRR cell allows a parallel connection with planar waveguides. Hence, it has been applied to a half-mode substrate integrated waveguide (HMSIW) section. The analysis of the frequency response and electromagnetic field distribution of the HMSIW structure loaded with an appropriate BC-OSRR cell have shown two main behaviors. The first characteristic is a high-pass frequency response inherent to the HMSIW and the second is a transmission zero in the passband of the HMSIW, which is due to the resonance of the BC-OSRR cell. The First- and second-order prototypes have been designed and fabricated. The measured bandstop HMSIW filters using BC-OSRR achieve a 3-dB stopband bandwidth around 10% with more than 21-dB insertion loss. This BC-OSRR cell with low undesired radiation loss can be a new alternative for the implementation of compact bandstop filters in the planar technology.

A New Compact and Wide-band Band-stop Filter Using Rectangular SRR

This paper proposes a novel compact band-stop filter based on Rectangular SRR unit cell. The BSF structure consists of modified microstrip line connected to 50 Ω feed line on both sides and Rectangular-SRR which has been added and located in the center of the proposed design. The R-SRR dimensions are chosen and optimized in order to achieve a resonant frequency in the undesired band. This filter is designed, simulated and optimized using two electromagnetic solvers. The circuit performances have been investigated and found to have an excellent BSF characterized by high power rejection level in the stop-band, low insertion loss in the both pass-bands and compact size. The experimental results illustrate that the proposed BSF achieves a wide fractional bandwidth of 72 % at 2.2GHz.

A novel compact bandstop filter with interdigital and spiral structure

AbstractA compact bandstop filter (BSF) based on frequency‐selecting coupling structure (FSCS) is presented. Quarter‐wavelength FSCS with an open‐circuited resonator is used to implement a BSF. Spiral and interdigital structures are finely designed to realize a further miniaturization. The performance of this filter is evaluated in both simulations and measurements. The operating frequency is 4.3 GHz with an insertion loss (IL) below 15.2 dB and a 3 dB fractional bandwidth of 94.2%. The stopband frequency contains 2.45 and 5.8 GHz, which can be widely used in Wi‐Fi and other applications. There is a good agreement between the simulation and measurement results. The size of the proposed filter is 4.6 × 8.79 mm2.

Electronically tunable microstrip bandstop filters using a varactor-loaded open ring resonator (VLORR)

A compact microstrip bandstop filter (BSF) with a wide electronically tunable frequency range and a constant absolute bandwidth is presented. It consists of an open ring resonator (ORR) loaded with a varactor diode and connected to a section of a microstrip transmission line. As a reverse bias is applied to the proposed varactor-loaded ORR (VLORR), the value of the resulting capacitor is controlled and the resonant frequency can be varied to the desired position. The measured tunable BSF achieves 92.6 \(\,\%\) tuning range with a constant 15 dB absolute bandwidth of 0.27 GHz and a minimum rejection level of 37 dB. This reconfigurable microstrip BSF can be useful in microwave communication systems.

Compact triple-band bandstop filter using folded, symmetric stepped-impedance resonators

A compact bandstop filter composed of eight folded stepped-impedance resonator cells for triple-band stopband is presented. Based on the analysis of unit structure’s characteristic and parametric analysis, it is found that the result of input output connecting lines with proposed stepped-impedance resonator cells exhibits three transmission zeros. Through tuning the geometry parameters in a small range, the design flexibility of transmission zeros is depicted. Then, the influence of different amounts of folded, symmetric resonator cells is researched for the sake of getting the characteristic of triple-band rejection. Via optimization, a compact triple-band bandstop filter adopting eight stepped-impedance resonator cells has been fabricated and measured. Three center frequencies at 3.8, 6.7 and 9.5GHz are reported corresponding to the attenuation level of 54.3, 37.4 and 27.5dB with return losses of 0.11, 0.25 and 0.71dB. Additionally, there are two transmission poles on the right and left sides of each stopbands for better selectivity. Owing to the folded shape, the totally size of the proposed structure gets reduced.