Compact Microstrip Lowpass Filter 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.

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.

Design and Fabrication of Compact Microstrip Low-pass Filter with Thin Film Technique for Wideband Applications

This paper introduces a compact microstrip low-pass filter (LPF) with a very sharp rejection. The proposed LPF is designed to be used for electronic warfare in defense industry. It has 62 dB/GHz attenuation rate, 10 GHz of stopband width and 48.6 dB of stopband attenuation. Moreover, it also has a wide passband and has a high cut-off frequency (f_c) of 6 GHz. The designed filter has been fabricated using alumina (Al2O3) substrate and titanium-gold (Ti-Au) coating on top of that with thin film technique in a clean room. The experimental measurements of the proposed LPF show great agreement with the simulation results, which validates that the presented filter is convenient to be used for applications up to C-band in electronic warfare systems.

A compact simple microstrip lowpass filter based on elliptical analyzed resonator

Abstract In this article, a compact microstrip lowpass filter (LPF) using elliptical shaped resonators with ultra-wide stopband is rendered. In this respect, LC equal structures of the elliptical shaped resonators are calculated based on the formula of circumference. In addition, to calculate transmission zeros of the presented elliptical shaped resonator, the LC equal structure and its output to input ratio are employed. The proposed LPF has a −3 dB cut-off frequency at 1.50 GHz and the stopband bandwidth of the designed filter is about 13fc, which refers to its ultra-wide stopband. The occupied circuit size of the presented filter is 0.151λ g × 0.044λ g (λ g is the guided wavelength at 1.50 GHz). The designed filter is fabricated on RT/Duroid 5880 substrate. The results of the fabricated and designed filter have clearly demonstrated that not only has the proposed LPF shown a suitable agreement between measured and simulated S-parameters, but also an appropriate stopband bandwidth.

Investigations on Three-Pole Microstrip Low-Pass Filters Incorporated with DGS and Fractals for Selectivity Improvement

In this paper, an investigation on compact microstrip low-pass filters (MLPFs) with extremely perfect low-pass characteristics and improved out-band suppression has been carried out for the improvement of the selectivity parameter ([Formula: see text]). For this purpose, two different defected ground structures (DGSs) based on Moore fractals and Meander line have been designed and experimentally validated. The proposed third-order low-pass filter (LPF) configurations are designed and simulated using the High-Frequency Structure Simulator (HFSS). To validate the simulation models, the prototypes of the suggested low-pass filters are fabricated using Teflon (TM) substrate having a relative permittivity of 2.65 and a loss tangent of 0.001, and measured using the Vector Network Analyzer. The simulation and measurement results are in good agreement. The proposed filters occupy a compact size of [Formula: see text]. The selectivity parameter values for the proposed Moore fractals- and Meander line-modeled DGS-based LPFs are 425[Formula: see text]dB/GHz and 850[Formula: see text]dB/GHz, respectively. The proposed microstrip low-pass filters offer a significant improvement in the selectivity parameter, offering a maximum value of 850[Formula: see text]dB/GHz. The proposed filters exhibit a very high figure of merit (FOM), reporting 71,335 for Moore fractals-based LPF and 118,354 for the Meander line-based LPF. These proposed filters are suitable for advanced mobile phone services, [Formula: see text]-band radar, Global Positioning System, mobile, paging services, Wi-Fi, Bluetooth and wireless LAN.

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.

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.

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.

Design of compact microstrip low pass filter using triangular and rectangular shaped resonator with ultra-wide stopband and sharp roll-off

In this paper a new microstrip lowpass filter (LPF) is designed and fabricated with sharp roll-off and ultra-wide stop-band. To obtain these features, triangular and T-shaped resonators are utilized. The main resonator is created by two triangular and rectangular shaped structures. LC equivalent circuit and transfer function of the main resonator is extracted to compute transmission zeros of the main resonator. The proposed LPF has a 3 dB cut-off frequency of 1.663 GHz. The occupied size of the designed filter is 209.33 mm2 (17.3 mm × 12.1 mm). The ultra-wide stopband is achieved from 1.81 to 29.4 GHz with better than 20 dB attenuation. The achieved figure-of-merit of the proposed LPF is 33,813, which shows good specifications of the filter.

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.

Design and fabrication of microstrip lowpass filter using asymmetric hairpin resonator

In this letter, a compact microstrip lowpass filter (LPF) is designed using serial connecting of two modified asymmetric hairpin resonators. The proposed design is consists of four open-circuited stubs that are used to suppress spurious harmonics in the stopband. The proposed filter has wide-stop band with attenuation level better than −28 dB from 2.16 up to 26.1 GHz and sharp roll-off. The proposed LPF has −3 dB cutoff frequency equal to 2.11 GHz, wide stopband width around 12th harmonic suppression and insertion loss less than 0.1 dB at about 85% of the passband. The excellent agreement is observed between the simulated results and measured values of the fabricated LPF.

High performance LPF with negligible group delay using circular resonator and transfer function analysis

AbstractUsing circular and rectangular resonators, a new design of a compact microstrip lowpass filter (LPF) with negligible losses is proposed and fabricated. The proposed LPF has a 3 dB cut‐off frequency at 1.375 GHz with an adjusting range of 14.5%; moreover, the suggested configuration leads to a competitive roll‐off rate of 189 dB/ GHz and a negligible group delay of 0.47 ns. Attenuator cells have capability to produce numerous transmission zeros (TZs) at high frequencies; consequently, an ultra‐wide stopband (14 fc) with high suppression level (25 dB) is successfully obtained. Furthermore, the LPF has a small size of 0.067λg × 0.134λg (λg is the guided wavelength at 1.375 GHz). The transfer function is also calculated to adjust the location of the main TZs and the cut‐off frequency. Finally, an acceptable similarity between the simulated results and the tested ones verifies the simulation results.

Synthesis and design of an LPF with wide-stop band and high rejection level

In this paper, a compact microstrip lowpass filter (LPF) is designed, analyzed, simulated, and tested. The proposed design that consists of a basic part in the central section of the structure and two parts of suppression of harmonics that are inserted in the first and last sections of the basic part, have wide-stop band, high suppression factor (−38 dB attenuation level from 2.4 GHz up to 27.4 GHz), low normalized size and sharp roll-off. The proposed LPF has a −3 dB cut-off frequency of 2.4 GHz, a wide stopband bandwidth around 11th harmonic suppression and an insertion loss less than 0.1 dB at passband. This filter has been fabricated and tested and good agreement is observed between the simulated and measured results.

Compact microstrip lowpass filter with ultrasharp response using a square-loaded modified T-shaped resonator

A miniaturized lowpass filter (LPF) with ultrasharp response, good figure of merit (FOM), and simple structure is proposed. The designed structure is fabricated and measured with a 2.9 GHz cut-off frequency. The proposed LPF consists of high impedance lines that are loaded by three similar resonators and two uniform suppressing cells. The filter size is only 0.08~$\times $~0.23~$\lambda $g, which indicates small circuit size. The proposed design exhibits good features, such as an ultrasharp roll-off rate of about 1609 dB/GHz and a good FOM of 162,820. The insertion loss of the proposed LPF is less than 0.14 dB in the passband. With these excellent obtained specifications and flat group delay, this structure can be used in wireless antennae.

Compact microstrip low pass filter design using U‐shaped folded high‐impedance line

AbstractA microstrip low pass filter using a U‐shaped folded high impedance line is designed. Comparison with conventional filter has shown almost ripple free pass band and better stop band characteristics in the filter with folded line. Effective optimization of filter dimensions led to smoother and spurious free responses, which are desirable in the radio frequency and microwave systems. Size of overall filter is reduced by 7.5% and 9.02% for third order and fifth order filters, respectively. Both simulated and measured responses of fifth order filter are presented and found in agreement.

Miniaturized microstrip lowpass filter using cylindrical-shaped resonators for integrated applications

A novel compact microstrip lowpass filter is presented in this paper. The structure uses stepped impedance and radial patches and it has the − 3 dB cut-off frequency at 4.39 GHz. The proposed lowpass filter has a wide rejection band from 6 to 30 GHz with rejection level more than − 20 dB. It has also other advantages such as: low insertion-loss < 0.1 dB and high return-loss more than 22 dB in 80% of the passband. The circuit size of the presented filter is about 90 mm2. Such important advantages make the proposed lowpass filter applicable to be integrated in many high frequency circuits such as power amplifiers, oscillators, couplers and power dividers. It also can block the unwanted video transmitter interference nearby 4 GHz such as implementing between transmitter and antenna. The lowpass filter has simulated and fabricated and a good agreement was seen between the simulation and fabrication results.

Compact microstrip lowpass filter using meandered unequal T-shaped resonator with ultra-wide rejection band

In this paper, a compact lowpass filter (LPF) with ultra-wide rejection band has been presented. In fact, a novel meandered semi-hairpin resonator has been used and the stopband characteristics have been improved by using a combinatorial suppressing unit. The suppressing unit contains a combination between T-shaped and semi-circular patches, which are loaded symmetrically to the designed resonator. For the proposed LPF, the-3 dB cut-off frequency has been adjusted to 2.2 GHz. After simulations, the proposed LPF has been fabricated and tested. The experimental results validated that the rejection bandwidth is expanded from 2.471 GHz to 28.62 GHz with corresponding attenuation level of −20 dB. The transition band is only 0.271 GHz from 2.2 GHz to 2.471 GHz with corresponding attenuation levels of −3 dB to −20 dB, respectively. In addition, the measured maximum insertion loss and return loss in the passband, from DC to 2.04 GHz (93% of the passband region) are 0.2 dB and 17 dB, respectively.

Compact Microstrip Lowpass Filter with Low Insertion Loss for UWB Medical Applications

A microstrip lowpass filter based on transmission line elements for UWB medical applications is proposed in this paper. The filter is constructed of two symmetric shunt open‐circuited stubs and three series unit elements. The filter is designed to exhibit an elliptic function response with equal ripple in the passband and the rejection band. A prototype is successfully designed, fabricated, and measured, where a good agreement is attained. The filter shows a high filtering selectivity and an ultra‐wide stopband up to 20 GHz with an attenuation level of more than 20‐dB. The filter is compact and has a low insertion loss and an ultra‐wideband (UWB) rejection which makes it attractive for many technologies such as UWB medical applications.

Study of compact microstrip lowpass filter with improved performance using defected ground structure

A compact lowpass filter (LPF) with wide stopband which uses four non-uniform cascaded defected ground structure (DGS) units along with a 50 Ω microstrip line is reported in this article. Each DGS unit, which consists of a combination of three isosceles U-shaped DGSs is analyzed in terms of an equivalent RLC circuit model. Every DGS of the DGS unit along with microstrip line provides one attenuation pole. It is found through performance comparison of the proposed U-shaped DGS with dumbbell- and fork-shaped DGSs that the proposed U-shaped DGS is compact and provides higher quality factor. Further, the modeling of the proposed LPF is carried out using equivalent RLC circuit model. The results obtained through numerical and circuit simulations are compared. The proposed LPF has size of 14.44 mm × 3.4 mm, 3-dB cut-off frequency of 14.2 GHz, and greater than 40 dB and 22 dB stopband rejection up to 21.8 GHz and 30 GHz respectively. The proposed LPF is fabricated and experimentally tested. The experimental results are nearly in agreement with corresponding numerical/circuit simulation results.