Microstrip Lowpass Filter Research Articles

A microstrip lowpass filter with sharp roll-off using arrow-shaped resonators and high-impedance open stubs

In this paper, an efficient microstrip low pass filter (LPF) using arrow-shaped resonators has been proposed. For attenuating undesired harmonics in stop band, stepped-impedance attenuators have been applied. To suppress components in frequency band of 6–10 GHz, two single-base high-impedance stubs have been exploited. To analyze the proposed structure accurately and define the role of each element in the filter, L-C equivalent circuit has been presented. Using this L-C equivalent model, poles and zeros of transfer function can be calculated and discussed. The structure design is based on reducing the coupling effect of elements on each other and neglecting these effects in obtaining the transfer function. Two symmetric arrow-shaped resonators with high-length basis provide 3-dB cut-off frequency as 1.447 GHz. The proposed filter has flat pass band with insertion loss as −0.08 dB and wide stop band with relative stop-band bandwidth (RSB) equal to 1.728. The figure of merit (FOM) is 113,355 which is much interesting compared to other similar works in this field as shown in simulation results.

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.

Analysis, Design, and Actual Fabrication of a Hybrid Microstrip-SIW Bandpass Filter Based on Cascaded Hardware Integration at X-Band

In this paper, the Microstrip-Substrate Integrated Waveguide (M-SIW) bandpass filter is designed, simulated, and fabricated based on the theoretical analysis. The Substrate Integrated Waveguide (SIW) highpass filter and the microstrip lowpass filter are combined in a hybrid design to achieve the M-SIW bandpass filter in the X-band. This design is more comprehensible and easier to achieve a bandpass filter at a desired frequency. The SIW highpass filter and the microstrip lowpass filter are connected in series to achieve the bandpass filter. To the measured results of the fabricated M-SIW bandpass filter, the center frequency is 10.20 GHz and the bandwidth is 2.40 GHz. When the analytical and measurement results are compared, the frequency change in the cut-off frequency is 6.02 % and the frequency change in the bandwidth is 8.74 %. It is generally seen that analytical, simulation, and measurement results are compatible with each other. The M-SIW bandpass filter can be broadly used in radar, Worldwide Interoperability for Microwave Access (WiMAX), and satellite technologies. The filters are simulated in Computer Simulation Technology (CST) Studio Suite.

Design and fabrication of MEMS lowpass filter exploiting space mapping algorithm

AbstractA high‐performance microstrip lowpass filter with coplanar waveguide as the ports is proposed and analyzed. By cascading asymmetric hairpin resonators, a compact elliptic function low‐pass filter with wide stop band was realized. The filter was optimized using aggressive space mapping algorithm, and finally a filter with a cut‐off frequency of 11.8 GHz was obtained. Stop bandwidth with attenuation level better than −27 dB extends from 15.6 to 36 GHz. Also, the maximum insertion loss in the passband is 0.9 dB and the return loss is better than −22 dB. The filter is manufactured on the silicon wafer using micro‐electromechanical systems process, and the measured results in good agreement with the simulation results.

Compact and very sharp roll-off low-pass filter using folded flag resonator

In this paper, a microstrip low-pass filter (LPF) using folded-flag-shaped resonators is designed and presented. Its base resonator length is 12.4 mm, and the proposed low-pass filter has a sharpness of 0.08 GHz. The filter cut-off frequency is 1.44 GHz, and the return loss is reduced to a level of −17 dB, indicating a flat pass-band. Also, the suppressing cell is used to weaken the disturbing harmonics by a stepped impedance structure and two high-impedance stubs with an L-shaped structure, which results in a bandwidth of 17.78 GHz. The circuit area of the LPF is 20.9 × 7.5 mm2, which it has created a suitable normalized circuit size (NCS) rate due to the −3 dB cut-off frequency. The figure of merit (FOM) of the proposed filter is 114450, and it indicates that the microstrip LPF responses are optimal as compared to previous works.

Design and fabrication of a microstrip lowpass filter with wide tuning range as harmonic suppression with application in Wilkinson power divider

In this article, a tunable lowpass filter (LPF) with a hexagonal stepped impedance resonator and multi open stubs is designed. The − 3 dB cut-off frequency for the proposed LPF is 2.2 GHz. Insertion loss (IL) and return loss (RL) in the passband zone are 0.3 dB and 15 dB, respectively. The frequency response slope (roll-off rate) for the proposed LPF is very sharp and equal to 142.4 dB/GHz. The tuning range of − 3 dB cut-off frequency for the presented LPF is very wide and equal to 2.7 GHz [from 0.5 to 3.2 GHz (84.3%)]. To achieve the desired structure and harmonics suppression, a conventional power divider was designed initially, then the transmission lines (with length of λ/4) were replaced with two LPFs. The isolation, IL, and input RL for the proposed modified Wilkinson power divider are better than 20.1 dB, 3.1 dB and 21.2 dB, respectively, at operating frequency of 1.8 GHz (GSM band). The proposed modified Wilkinson power divider eliminates the 2nd–11th harmonics with high levels of attenuation. The feature selective validation method depicts that the simulation and measurement results for the proposed LPF are in good agreement with each other.

Wide Band Stop Response Using Interdigital Capacitor/CSRR DGS in Elliptical Microstrip Low-Pass Filter

Abstract In this paper, a compact elliptic-response microstrip low pass filter (LPF) is presented with a wide stop-band using stepped impedance resonators. With high attenuation in the stop-band, the overall size reduction of the proposed filter is achieved using a novel defected ground structure technique using an interdigital capacitor and complementary split ring resonator (CSRR). A 4.2 GHz LPF is designed and simulated on FR4 substrate and a stop band of 8.8 GHz is obtained by utilizing interdigital and complementary split ring resonator. Results further show that the use of U-shaped high impedance line on the top layer of filter enhances the stop-band bandwidth by 2.2 GHz. In the final design, the passband insertion loss is found below 0.5 dB, and –10 dB is obtained over a band from 5.06 GHz to 17.06 GHz between input and output ports. The normalized circuit size of the filter is 0.417× 0.202 and the figure of merit is calculated about 55 at the cut-off frequency. These proposed LPFs have promised significant advantages in the stop-band characteristics with an acceptable roll-off rate for spurious-free communications.

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.

Analysis and Design of Microstrip Filters Using Photonic Band Gap Ground Plane with Fractal Periodic Pattern (Dept.E)

In the present work, four different techniques are used in designing the microstrip low pass filters (LPF). These techniques include LPF with fractal defected ground structure (DGS), LPF with continuous minkowiski fractal element, multi-stop band filter with discontinuous minkowiski element, and finally a wide multi-stop filter with separated interdigcap shape. A microstrip PBG filter of minkowiski element and interdigcap shape was designed to operate as a multifrequency band stop filter. With an appropriate fractal geometry of minkowiski and interdigcap elements, a wide stop-band at different frequencies are obtained. A continuous sinusoidal fractal slots are designed to work as a wide LPF. A novel fractal DGS for the microstrip LPF is proposed. The proposed fractal DGS can provide better band gap, and slow-wave characteristics. The numerical results show that a LPF of continuous and discontinuous fractal minkowiski elements in ground plane is obtained with a bandwidth 0 - 3 GHz for a slot width 0.5mm. However, if the slot width is taken equal 0.2 mm, the bandwidth is increased up to 10 GHZ. With suitable choice of number of elements, one can control the filter bandwidth. With a discontinuous fractal minkowiski and interdigcap element in ground plane, the filter response is forced to have a stop band at resonance frequency of fo and repeated at 2fo, .. etc. The numerical results obtained using an analytical technique with the aid of a numerical package (Sonnet) which is used in microstrip analysis.

Optimization of Microstrip Lowpass Filters with Three-Dimensional Stubs

Introduction. Lowpass filters (LPFs) are used to suppress unwanted harmonics and spurious signals. Microstrip LPFs are widely used in various electronic systems. New, more stringent system requirements demand increased LPF selectivity. In the previous work, we considered the calculation of the fifth-order microstrip LPF with three-dimensional (3D) stubs. According to the results of 3D modeling, the LPF frequency response (FR) has a steepness close (but slightly worse) to the steepness of the FR LPF based on lumped elements. In the presented paper the optimization of the LPF with 3D stubs is performed, the experiment results for 3D stub and LPF are given. Optimized LPF has a steeper FR than LPF based on lumped elements. 1 Features of the fifth-order LPF with 3D stubs. The quasi-lumped inductance is made by a through hole in the dielectric with an overhead conductor above it, and the quasi-lumped capacitance is made by a blind metallized hole on the signal conductor side. In addition to the use of 3D reactive elements, the LPF has the following differences from traditional solutions: 1) the stub is connected to the line by a small contact pad; 2) the stubs are placed on different sides relative to the direction of wave propagation. 2 Optimization of the LPF. Value of the stub’s rejection frequency is affected by the stub-line T-junction parasitic inductance connected in series with the stub. Parasitic inductance value depends on the depth of the stub hole and the contact pad sizes. If the LPF stubs contact pads are different in sizes, their rejection frequencies will be different. This will widen the LPF suppression band. Thus, by choosing stub holes depth and contact pads sizes, you can optimize steepness and suppression band width the LPF FR. As a result of optimization, the LPF FR steepness increased from 20.0 to 22.9 dB/GHz and the suppression band widen from 1.9 to 3.8 GHz at the level of –60 dB. The optimized FR has a steepness higher than the FR LPF based on lumped elements equal to 21.5 dB/GHz. 3 Experimental results. Photos and experimental FRs of the 3D stub and LPF with 3D stubs are given. 3D stub experimental and calculated values of the rejection frequency, the rejection level and the relative error of the calculated values are 6.41 and 5.72 GHz, −51.5 and −49.4 dB, 11% and 4%, respectively. The experimental LPF FR is in a good agreement with calculated one. 4 Results discussion. The presence of the third size in the microstrip elements provides not only a significant increase in their efficiency, but also additional design possibilities. Since the value of the parasitic inductance, which determines the rejection frequency, depends on the 3D stub hole depth, this parameter, as well as the contact pads sizes are optimization parameters to the FR steepness and suppression bandwidth. Conclusion. The use of 3D stubs as quasi-lumped capacitances allows to optimize the LPF FR by choosing the stubs hole depth and the stub contact pad sizes. As a result of LPF optimization, the FR steepness increased and the suppression band widen. The steepness of the optimized FR is higher than the FR LPF based on lumped elements.

Dual split resonator lowpass filter with ultra‐wide stopband and sharp roll‐off rate

A novel microstrip lowpass filter design using rectangular split-ring resonators with dual splits are designed, analysed, and fabricated with exceptional performance such as ultra-wide stopband and sharp roll-off rate along with its compactness. The symmetrical suppressing cells are also employed to reject higher-order harmonics from the stopband without affecting selectivity. The expression for transmission zero of dual split resonator-1 is extracted from the equivalent circuit analysis and observed the significance of coupling. A sharp roll-off performance of 224 dB/GHz and relative stopband width of 161% are achieved with a cut-off frequency of 2.9 GHz.

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.

New design of an adjustable compact microstrip lowpass filter using Z‐shaped resonators with low VSWR

AbstractIn this article, an adjustable microstrip lowpass filter(LPF) with the cut‐off frequency (fc) at 1.59 GHz is designed and fabricated. The proposed structure is composed of a Z‐shaped resonator as basic resonator and a combination of modified T‐shaped and Z‐shaped resonators as suppressor units. To describe a theoretical design, the L‐C equivalent circuit of the basic resonator and also its transfer function are calculated precisely; then, the location of the first transmission zero (TZ) is accurately computed. Generating a deep TZ near the cutoff frequency leads to a high roll‐off rate of 195 dB/GH. The LPF also benefits from an extremely wide stopband from 1.72 to 23.67 GHz (15 fc). In passband region, the insertion loss and return loss of the LPF are 0.62 and 22.9 dB, respectively. The experimental results also show that maximum variation of group delay is only 0.53 ns regarding a negligible figure. The electrical size of the LPF is 0.187 × 0.083 (where λg is the guided wavelength at 1.59 GHz). Finally, the proposed LPF achieves a high figure of merit of 57 860 deemed a great accomplishment.

Design and analysis of a modified rectangular-shaped lowpass filter based on LC equivalent circuit

In this paper, a new compact microstrip lowpass filter (LPF) with a sharp roll off and wide stopband is presented. The structure is composed of a defected rectangular-shaped resonator and a rectangular shape resonator as a suppressing cell. All resonators and their additional components are analyzed based on their LC equivalent circuits, and the role of each section and its equivalent circuit are described. The LPF with 3 dB cutoff frequency at 1.44 GHz has advantages such as low insertion loss and high return loss. Based on the measurement results, the proposed LPF has a sharp transition band that is 0.22 GHz from −3 to −20 dB. On the other hand, the measured value of the group delay in the whole passband is only 47 ns, which is one of the essential advantages of this filter. The designed LPF has been simulated, fabricated and, measured. There is a proper agreement between simulation and measured results.

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 hairpin DGS resonator for application to microstrip lowpass filters

Abstract A hairpin shaped DGS, consisting of two tilted slots with a separation angle, is studied as a unit cell in this contribution. It is further served as a microwave resonator for microstrip lowpass filter applications. Two prototype filters that respectively cascade the same unit cells and the scaled cells with a different scale ratio are analyzed. For demonstration purposes, the two prototype filters are optimally developed, fabricated and examined both from numerical simulations and from experimental validations. Results show the cascaded scaled type demonstrator features a high stopband suppression level within a wide frequency band.

Compact wide stopband microstrip lowpass filter using polygon patches and meandered lines

In this paper, a low pass filter based on T-Shaped resonator is presented. The T-Shaped resonator consists of meandered lines and rectangular patches. Also, the LC model and transfer function of the proposed resonator is presented. For suppression of spurious harmonics, a bandstop structure consists of hexangular patches and open stubs has been utilized. Finally, the wide stopband microstrip lowpass filter with cutoff frequency 2.72 GHz has been simulated, fabricated and measured. The LPF has good characteristics such as wide stopband and insertion loss lower than 0.18 dB in the passband region. The rejection level is less than -20 dB from 2.98 up to 21.3 GHz. The filter size is 10.5 mm×12.7 mm, or 0.131 λ<sub>g</sub>× 0.158 λ<sub>g</sub>, where λ<sub>g</sub> is the guided wavelength. The measured and simulated results of the filter is in good agreement with each other, which show the merits of low insertion loss and wide stopband.

Comparison of Microstrip Low-Pass Filter Characteristics for various Dielectricconstants

The technique which is introduced here is the comparisonof microstrip low pass filter response for different dielectric materials.Performance of microstrip low pass filter can be judged by using Insertion loss and return loss curve through simulation software. The application of this microwave filter is for L-band purpose

Compact microstrip lowpass filter with high harmonics suppression using defected structures

A compact microstrip lowpass filter with sharp selectivity and wide stopband designed on the basis of dual-plane, is presented. Initially, a basic one pole defected ground structure (DGS) filter is modified so as to achieve sharp selectivity as well as compact size. The modified DGS reduces the circuit size of the filter by 68.8%. To suppress the higher order harmonics, mirrored symmetrical uniform impedance stubs are designed in the top surface of the substrate, thereby wide stopband up to 20 GHz is achieved. The stopband suppression level of the filter is improved by incorporating a spurline resonator which acts as a defected microstrip structure (DMS) in the top microstrip line. The designed filter has 3 dB cutoff frequency of 2.11 GHz with high relative stopband bandwidth of 159.2% within the rejection level of 18 dB. The wide passband frequency range of the proposed filter covers the GSM, GPS, Wi-Fi communications and various L-band applications such as aircraft surveillance etc.

A Novel Simple Miniaturization Technique for Microstrip Couplers

This paper analyzes the new compact design of couplers based on the use of microstrip lowpass filters. The proposed design achieves significant reduction in coupler size while obtaining the same characteristics as of the conventional coupler. Prototype of the coupler with the central frequency of 1 GHz was produced on the substrate with dielectric permittivity of 4.4. The experimental results showed good agreement with numerical simulations. The size of the rat-race coupler was reduced by 83.7%.