Compact Microstrip Lowpass Filter Research Articles

Design and fabrication of a compact microstrip low-pass filter with ultra-wide stopband and sharp roll-off-rate

Microstrip low-pass filters (LPFs) with good performance are used in most telecommunication systems. In this study, a modified T-shaped hairpin resonator is used to design LPF, and suppression cells are used to improve the performance of the filter in the stopband up to 22 GHz. The proposed LPF had a -3 dB cut-off frequency of 1.89 GHz. The proposed LPF is designed, fabricated and measured. The simulated and measured results for the proposed LPF are in good agreement with each other. Attenuation in the stopband is 34 dB, which is an extremely large number. Roll-off-rate (ROF or ζ) parameter is sharp and equal to 96.3 dB/GHz. The group delay in the passband is almost constant and in the range of 0.3-0.42 ns. In the following, an SMV-1247-079LF SMD varactor diode is used to adjust the proposed LPF. The tuning range for the proposed LPF is 0.46-3.2 GHz..

Compact microstrip low pass filter with flat group-delay using triangle-shaped resonators

In this paper, a compact microstrip lowpass filter (LPF) using triangle-shaped resonators is presented. The designed LPF includes three symmetric triangle-shaped resonators to provide a suitable passband and sharp response. A suppressing unit composed of several suppressing cells is designed to obtain a wide rejection band and low insertion loss in the passband. The fabricated LPF has been measured and indicts that it has −3 dB cut off frequency at 5.15 GHz. The rejection band has been expended from 5.51 GHz to 43.2 GHz with maximally flat return loss in this region nearby to 0 dB. Also, simulation and experimental results show that the proposed filter has a very flat group delay in the passband, which is the minimum value in comparison with the published works since 2017.

Compact low‐pass filter with ultra‐wide stopband using analysed triangular‐shaped resonator

A compact microstrip low-pass filter (LPF) with ultra-wide stopband using the analysed triangular-shaped resonator is presented. To achieve LC equivalent circuit of the triangular-shaped resonator, the structure of a rectangular-shaped resonator is adopted. To investigate the behaviour of the proposed triangular-shaped resonator, transfer function of the main triangular resonator is calculated. The designed LPF has −3 dB cut-off frequency of 1.52 GHz with the stopband bandwidth around 12fc and total circuit size of 0.062λg × 0.104λg . The proposed LPF has the figure of merit of 46,718, which shows its good performance. The proposed filter is designed, simulated and fabricated. It is observed that the measurement results are well matched with simulation results.

Compact microstrip lowpass filter with ultra‐wide stopband based on dual‐plane structure

A microstrip lowpass filter (LPF) with ultra-wide stopband suppression and compact size based on dual-plane structure is presented. The LPF is composed of high-impedance resonators loaded by folded patches on the topside plane, combined with hybrid slot and step-impedance resonators on the ground plane. Multiple transmission zeros are created in the stopband region by different resonators. Thus, an ultra-wide stopband with 11th-harmonic suppression is achieved. A demonstration filter with 3 dB cutoff frequency ( f c ) at 2.45 GHz has been designed, fabricated and measured. Results show that the relative stopband bandwidth is 163.8% with attenuation level of 20 dB. The insertion loss is lower than 0.3 dB and the return loss is better than 17 dB in the passband. The size of the LPF is only 8.90 mm × 8.93 mm, which corresponds to 0.115 λ g × 0.116 λ g ( λ g is the guided wavelength at f c ).

Compact low‐pass filters with deep and ultra‐wide stopband using tri‐ and quad‐mode resonators

On the basis open stub-loaded tri- and quad-mode resonators, two compact microstrip low-pass filters (LPFs) with deep and ultra-wide stopband are presented. Modal characteristics of the tri- and quad-mode resonators are analysed by even–odd-mode method. Multimode resonator can be modelled as multiple LC resonant circuits and the lumped-element equivalent circuit models of the proposed LPFs are presented. The tri- and quad-mode resonators have strong slow-wave and bandstop effects, which can achieve ultra-wide and deep stopband and size reduction in the design of LPFs. For the proposed low-pass filter using tri-mode resonators, the 3 dB cutoff frequency is 2.5 GHz and the stopband with 40 dB suppression is from 4.5 to 17.7 GHz. The low-pass filter based on quad-mode resonators has a 3 dB cutoff frequency of 2.2 GHz and the stopband with 30 dB suppression is from 4.1 to 18 GHz.

Design of Compact Wide Stopband Microstrip Low-pass Filter using T-shaped Resonator

In this letter, a compact microstrip low-pass filter (LPF) using T-shaped resonator with wide stopband is presented. The proposed LPF has capability to remove the eighth harmonic and a low insertion loss of 0.12 dB. The bandstop structure using stepped impendence resonator and two open-circuit stubs are used to design a wide stopband with attenuation level better than −20 dB from 3.08 up to 22 GHz. The proposed filter with −3-dB cutoff frequency of 2.68 GHz has been designed, fabricated, and measured. The operating of the LPF is investigated based on equivalent circuit model. Simulation results are verified by measurement results and excellent agreement between them is observed.

Ultra-Wide Stopband Low-Pass Filter Using Multiple Transmission Zeros

A compact microstrip low-pass filter (LPF) with an ultra-wide stopband and its design procedure are proposed in this paper. Using three-stepped impedance stubs(SISs), multiple transmission zeros are introduced in the stopband and can be freely controlled by tuning the impedance ratio of the SISs. Without using the defected ground structures to expand the stopband, three additional open-circuited stubs are used to suppress more spurious passbands of the LPF. To illustrate the concept, an experimental stopband LPF with cut-off frequency ( $ f_{c})$ at 0.9 GHz is designed, simulated, fabricated, and measured. A metallic box with absorbent material is used to load the lowpass filter with wide stopband. The measured results are found in good agreement with the simulated results, and indicated good performance: broad stopband ( $>17.6f_{c})$ with attenuation higher than 22.4 dB, low-passband insertion loss (<0.5 dB), and compact size.

Design of a sharp response microstrip lowpass filter using taper loaded and radial stub resonators

This paper proposes a compact microstrip lowpass filter with a wide stopband and a very sharp roll-off. This structure consists of two dual taper-loaded resonators that are connected to the radial stubs. The resonators are described using an LC model, and its Z- and S-parameters are extracted as a function of the LC component. In the proposed filter, cut-off frequency is placed at 1.76 GHz, roll-off rate is higher than 142 dB/GHz, insertion loss is less than 0.42 dB from DC to 1.5 GHz, and rejection is greater than -24 dB from 1.88 to 15.2 GHz. The proposed filter is designed, fabricated, and measured, and the measured values are in good agreement with the EM-simulated results.

Compact Microstrip Low-pass Filter with Wide Stop-band Using P-Shaped Resonator

This paper, a compact lowpass filter (LPF) with an Elliptic function response using P-shaped resonators is presented. The LPF with simple structure results in the low insertion loss less than 0.1 dB and high return loss better than 20 dB, in the passband. The proposed filter with a -3 dB cutoff frequency of 2.61 GHz is fabricated and measured. The measured results show that the proposed LPF has significant advantages such as a wide stopband from 2.9 GHz to 17.3 GHz with the suppression level better than -20 dB, and it has an acceptable sharp frequency response in the transition band. The measurement results are in good agreement with the simulation results.

Design of a compact microstrip lowpass filter with sharp roll‐off using combined T‐shaped and L‐shaped resonators

A novel compact microstrip lowpass filter with high performance is designed and analysed based on transfer function. The main resonator consists of L-shaped and T-shaped patches. The L-shaped resonator is used to increase the width of the stopband. The presented filter has −3 dB cut-off frequency at 2 GHz. It also has a wide stopband about 17.82 GHz with the suppression level of −21 dB. The transition band is ∼168 MHz from −3 to −40 dB. The locations of transmission zeros are calculated by transfer function. The presented lowpass filter has other advantages, such as high return loss more than 20 dB and low insertion loss <0.15 dB in the passband. The size of the filter is only 0.087 × 0.170 λg2, where λg is the guided wavelength at the cut-off frequency. The proposed lowpass filter has the figure of merit of 50,285, which shows its strong efficiency. The lowpass filter is simulated and fabricated and there is a good agreement between the simulation and measurement results.

A compact microstrip low-pass filter with ultra wide stopband using compact microstrip resonant cells

In this paper, a novel compact microstrip low-pass filter (LPF) with ultra wide stop band and sharp roll off, is proposed. In the proposed structure, a high impedance transmission line is loaded by compact microstrip resonant cells, which results in ultra wide stopband. The −3 dB cut-off frequency of filter is 1.5 GHz and the maximum insertion loss is &lt;0.1 dB in the passband. The proposed LPF presents extremely wide stopband from 1.68 to 44 GHz, with more than the −20 dB attenuation level, which suppresses the 2nd to 29th harmonics with high rejection levels. The size of the proposed LPF is only 0.1 λg × 0.19 λg, which shows excellent size reduction. There is a good agreement between the simulated and measured results.

A harmonic-suppressed high-efficiency class-F power amplifier with Elliptic-Function low-pass filter

In this paper, a novel method is developed in order to design a harmonic control circuit block using a compact microstrip low-pass filter (LPF) for a P-HEMT class-F PA. The design procedure is performed using Harmonic-Balance analysis. The key benefit is a novel compact defected Elliptic-Function resonator to design a LPF, which has a wide rejection band. The advantages of the presented method are the attenuation of nth harmonics in AM-AM distortion, high power added-efficiency (PAE) and more linearity in comparison with a conventional class-F PA. The experiment is carried out at 1.8GHz and shows a maximum PAE about 77% with 40dBm output power.

Compact microstrip lowpass filter with wide stopband and very‐sharp roll‐off

A novel microstrip lowpass filter (LPF) with good specifications such as wide stopband and sharp roll-off is reported. The filter structure consists of split ring resonator loaded by folded polygene patches. The proposed filter with −3 dB cut-off frequency at 1.57 GHz has been designed, fabricated and measured. The LPF has a wide stopband from 1.67 to 14 GHz with a rejection level greater than −20 dB, sharp roll-off rate equal to 170 dB/GHz and low insertion loss lower than 0.13 dB in 94% of the passband. Finally, a high figure of merit of 51,178 is obtained.

Compact microstrip lowpass filter with ultra-sharp roll-off and ultra-wide stopband using stepped impedance Hairpin resonator

A novel microstrip lowpass filter (LPF) with very sharp roll-off, compact size and ultra-wide stopband is presented in this paper. The structure consists of modified stepped impedance Hairpin resonator and a circular patch as a suppressor. The proposed LPF has the cut-off frequency of 1.07GHz. The simulation results indicated that the transition-band of the proposed LPF is 0.09GHz from −3 to −20dB. Maximum insertion-loss at about 80% of the passband is 0.1dB. The proposed LPF has been designed, fabricated and measured. From the measurements, good agreements with the simulated results are obtained. Also, an ultra-wide stopband was achieved. Proposed LPF has an ultra high figure-of-merit (FOM) of 151,523, which shows its strong efficiency.

High performance LPF Structure with sharp roll‐off and low VSWR

A symmetrical compact microstrip lowpass filter (LPF) with ultra-wide rejection band and low voltage standing wave ratio (VSWR) using a novel structure of stepped impedance and butterfly-shaped resonators is presented and fabricated. The LPF has a 3 dB cut-off frequency at 1.513 GHz. The series structure of the butterfly-shaped resonators result in a high roll-off rate of 187.8 dB/GHz. By generating multiple transmission zeros, a wide stopband (with 35 dB rejection degree) is achieved. To reach a small circuit, the bended transmission line is properly utilised. Moreover, 171% relative stopband bandwidth and dimensions of 0.087λ g × 0.157λ g (λ g is the guided wavelength at 1.513 GHz) are other specifications of this LPF. In addition, an acceptable match is obtained between the simulated and measured responses. In the end, the LPF achieves a high figure-of-merit of 82288.

High-Selectivity Low-Pass Filters With Ultrawide Stopband Based on Defected Ground Structures

Compact microstrip low-pass filters (LPFs) with ultrawide stopband based on a defected ground structure (DGS) and their design procedures are presented in this paper. A key merit of the filter configuration is that the selectivity of the LPFs can be conveniently controlled, whereas the bandwidth is fixed. The LPFs are realized using open-circuited uniform impedance stubs and stepped-impedance stubs (SISs). The position of the transmission zeros can be freely controlled by tuning the impedance ratio of the SISs. To expand the stopband, the dumbbell DGS is used to suppress the spurious passbands of the LPFs. Two demonstration filters with a cutoff frequency at 1 GHz have been designed, fabricated, and measured. The measured results indicate good performance: broad stopband ( $>15 f_{c}$ or $20~f_{c}$ ), low passband insertion loss (<0.3 dB), compact size, and sharp skirt characteristic.

Tunable microstrip lowpass filter with compact size and ultra‐wide stopband

A compact varactor-tuned microstrip lowpass filter (LPF) with a large cutoff frequency tuning range and an ultra-wide stopband is presented. By employing a pair of parallel coupled-lines and a low-impedance stub loaded with a varactor diode, the introduced filter can successfully realise the tunable cutoff frequency function. Besides, both radial patch resonators and stepped-impedance resonators are introduced to achieve an ultra-wide stopband in all the states in this design. A varactor-tuned microstrip LPF is designed, fabricated and measured. The measured results show that the proposed LPF provides not only a large cutoff frequency tuning range of 91.3% from 0.85 to 2.28 GHz, but also an ultra-wide stopband which extends to 20 GHz.

Compact microstrip lowpass filter with very sharp roll-off and ultra-high figure-of-merit for wireless applications

This study presents a novel lowpass filter (LPF) with very sharp roll-off and ultra-high figure-of-merit (FOM). The −3 dB cutoff frequency of the proposed LPF is set nearby 1.39 GHz to eliminate the higher frequencies for wireless applications in communication systems. The measurement results indicated that the transition band of the proposed LPF is 0.04 GHz from −3 dB to −20 dB and 0.06 GHz from −3 dB to −40 dB, which shows a very sharp roll-off. Also, an ultra-wide stopband from 1.39 GHz to 20.2 GHz and low insertion loss and high return loss in the passband region are achieved. The proposed LPF has an ultra-high FOM which is probably the highest FOM ever reached in related works until 2014, thus showing its strong sufficiency. The proposed LPF is fabricated and tested, and there is a good agreement between the simulation and measured results.

Design of compact microstrip low-pass filter with analytical sharpness of transition band

A novel microstrip low-pass filter (LPF) using radial patched resonator and modified T-shaped resonators is designed to achieve ultra-wide stop-band. Also, the designed LPF has successfully addressed the problems of compactness and insertion loss, simultaneously. LC equivalent circuit of the proposed filter is calculated and equation for the sharpness in transition band is obtained based on LC equivalent circuit and transfer function. The proposed filter not only exhibits a very wide stop-band of 168%, but also is able to suppress the 11th-harmonic response in conjunction with a small size of 0.147 × 0.052λg, where λg is the guided wavelength at 1.47 GHz. It is shown that the simulated results are highly consistent with the measured data.

Design of Compact Composite Microstrip Low Pass Filter Using MEMS Technology

This paper presents the design technique of a compact composite microstrip filter operating at ultra high frequency (UHF) band and its fabrication using micro-electro mechanical system MEMS technology. The fringing compensation method is applied into the design of the microstrip line transformation from lumped element. The filter lumped circuits and microstrip line circuit were designed and simulated using Advanced Design Software (ADS) and fabricated on silicon substrates to obtain the best filter characteristic based on S-parameter. The measured and simulated results have achieved a good agreement within the frequency of interest. This shows that the fringing compensation method of transforming lumped element into microstrip line is able to solve the conventional design of complexity size of circuit of composite low pass filter (LPF) into microstrip line. The proposed filter design can replace the conventional filters in wireless communication as they offer better performance at lower cost in the RF microwave communication applications.