Microstrip Dual-band Bandpass Filter Research Articles

A novel compact microstrip dual-band bandpass filter with independently controlled center frequencies based on dual-mode resonators concept

This letter presents a novel ultra-compact microstrip dual-band bandpass filter (DBBPF) with independently controlled center frequencies, and high Q-factor. The recommended DBBPF is realized by combining two different microstrip dual-mode resonators. One is a short-end stub-loaded resonator used to produce the first passband and the other one is an open-end stub-loaded resonator operating at the second passband which serves as part of the feed lines for the lower passband. To validate the performance of the proposed configuration, a novel compact DBBPF with center passband frequencies of 2.4 and 3.55 GHz is designed, simulated, fabricated and tested. A good agreement has been found between the simulation and measurement results. The designed microstrip DBBPF occupies a small area which is only about 0.19 λg × 0.15 λg. The presented microstrip DBBPF has many advantages in terms of compact size, low insertion loss, good frequency selectivity, easy fabrication, and high selectivity.

Designing a Compact Microstrip Dual-Band Filter with Two T-Shaped Resonators and Suitable Frequency Selectivity

A miniaturized microstrip dual-band bandpass filter (DBPF) with two T-shaped resonators is proposed. The two T-shaped resonators lead to multiple transmission zeros in the stopband and higher filter selectivity. The filter is analyzed using LC and even/odd mode analyses to determine the transmission zeros. The LC equivalent circuit and transfer function are presented. The proposed filter is symmetrical, so the electrical length and impedance values are used for odd/even mode analysis. The designed DBPF is centered at 1.9/5.54[Formula: see text]GHz and is suitable for WLAN applications. The insertion loss of the filter is less than 0.5[Formula: see text]dB and its return loss is more than [Formula: see text][Formula: see text]dB in each band. Five transmission zeros are created with an attenuation greater than [Formula: see text][Formula: see text]dB. The total area of the proposed filter is [Formula: see text][Formula: see text]mm2. To validate the proper performance of the proposed filter, it is fabricated and measured.

Dual-band broadside-coupled based BPF with improved performance

This paper presents a unique structure of a dual-band microstrip bandpass filter (BPF) that works at 1.25 GHz, 1.9 GHz for global positioning systems (GPS) and TV broadcast auxiliary service applications, respectively. The proposed BPF provides compactness, small fractional bandwidth (FBW), small frequency separation, and low IL. The prospective filter is constructed employing broadside-coupling techniques to achieve low insertion loss (IL). The feeding structure is accomplished utilizing a 50 Ω co-planar waveguide (CPW) scheme due to its low loss characteristics. The small 3-dB FBW is accomplished by inserting four transmission zeros (TZs). The size of the overall structure, including I/O transmission lines, is 34.9 × 23.5 mm2. The measured and simulated results fit well with each other and show an IL of 0.77 dB and 0.5 dB, and FBW of 7.6% and 8.4% at 1.25 GHz and 1.9 GHz, respectively.

An Improved Stopband Dual-Band Filter Using Quad-Mode Stub-Loaded Resonators

In this paper, we present a dual-band microstrip bandpass filter (BPF) with an improved stopband, which was constructed by a quad-mode stub-loaded resonator (SLR). Since the SLR is able to produce multiresonance within a single unit, the area saving is significant. The proposed quad-mode SLR was implemented by two stubs allocated at symmetry places, thus the even-/odd-mode can be applied to analysis the resonance. Moreover, to shift the spurious passband, the step impedance structure was applied to shift the harmonic resonance to the higher frequency. Design procedure for high performance dual-band BPF is proposed, and filter examples were designed for wireless local area network (WLAN) of 2.4/5.2 GHz. The measured insertion losses, return losses and fractional bandwidths (FBW) are 1.43 dB, 10 dB, and 14.8% at 2.4 GHz and 1.34 dB, 10 dB, and 12.9% at 5.2 GHz. Moreover, by applying two quarter-wavelength stubs on the input/output ports, the passband selectivity with an isolation of 40 dB can be achieved. The simulation and measurement have a close match, verifying the design concept.

Compact Balanced Dual-Band BPFs Based on Short and Open Stub Loaded Resonators With Wide Common-Mode Suppression

Two balanced microstrip dual-band bandpass filters (BPFs) based on short stub loaded resonator (SSLR) and open stub loaded resonator (OSLR) are presented in this brief, respectively. The center frequencies of the two differential-mode (DM) passbands can be controlled quasi-independently by adjusting the lengths of resonators. Moreover, a stepped impedance microstrip line etched with an interdigital coupling line is utilized to introduce a coupling between the two resonators, which generates two extra controlled transmission zeros (TZs) to obtain better selectivities. Furthermore, balanced microstrip/ slotline (MS) transition structures are employed as feed networks, which can suppress common-mode (CM) inherently while the DM responses are not affected, thereby the design procedure can be simplified significantly. In order to demonstrate the theoretical design, two balanced dual-band BPFs were designed and fabricated. The simulated responses are compared with the measured ones and a good agreement is obtained.

Compact Ultra-Wide Upper Stopband Microstrip Dual-Band BPF Using Tapered and Octagonal Loop Resonators

AbstractIn this paper, a microstrip dual-band bandpass filter (DBBPF) based on an octagonal loop resonator (OLR), tapered resonators and open bended stubs (OBSs) is designed and analysed. The proposed structure produces two passbands with the centre frequencies of 3.65 and 5.67 GHz. The marked advantages of the proposed filter are as follows: Two centre frequencies can be individually tuned. The bandwidth of the upper passband can also be controlled. Furthermore, the DBBPF benefits from an ultra-wide upper stopband from 5.9 up to 21 GHz with an attenuation level of higher than 20 dB and a small size of 0.21 λg × 0.26 λg, where λgis the guided wavelength at 3.65 GHz. The designed filter is horizontally and vertically symmetrical leading to a reciprocal S matrix. Other remarkable specifications of the proposed filter are the insertion loss < 0.62 dB, the return loss > 20.2 dB and sharp response. To provide an analytical description, the LC equivalent circuits of initial and main resonators are presented. Acceptable similarity between simulated and measured results verifies the design process.

High-Performance Ultra-Compact Dual-Band Bandpass Filter for Global System for Mobile Communication-850/Global System for Mobile Communication-1900 Applications

This work presents a novel microstrip dual-band bandpass filter (BPF) using meandros spirals and patch cells, which is proposed for the first time by this work. It occupies a very compact size of 0.0017 λg2. The proposed filter is designed to operate at Fo1=0.85 GHz and Fo2=1.85 GHz for GSM-850/GSM-1900 applications. In addition to the small size, it has several advantages in terms of wide fractional bandwidths (FBW), low insertion losses and high return losses at both channels. The simulated insertion losses at the lower and upper passbands are 0.05 dB and 0.1 dB, respectively. Another advantage of the proposed BPF of this work is the attenuated harmonics, where it is able to suppress 1st, 2nd, 3rd and 4th harmonics (4.11 Fo1) with -20 dB maximum harmonic level.

A balanced dual‐band bandpass filter with a wide stopband and controllable differential‐mode frequencies and fractional bandwidths

In this article, a balanced microstrip dual-band bandpass filter (BPF) is designed. The proposed filter is achieved by employing a microstrip U-shape half-wavelength resonator, a folded stub-loaded resonator and balanced microstrip/slotline transition structures. The center frequencies and the fractional bandwidths of the two differential-mode (DM) passbands can be controlled independently by changing the physical lengths of the two resonators and the gaps between each resonator, respectively. The balanced microstrip/slotline transition structures can achieve a wideband common-mode (CM) suppression. Meanwhile, the DM passbands are independent from the CM responses, which significantly simplify the design procedure. In addition, a wide DM stopband is also realized. In order to validate the design strategies, a balanced dual-band BPF centered at 2.57 and 3.41 GHz was fabricated and a good agreement between the simulated and measured results is observed.

A Novel Design of Compact Dual-Band Bandpass Filter for Wireless Communication Systems

In this paper, design, fabrication, and measurement of a new microstrip dual-band bandpass filter with compact size and high selectivity characteristics for modern wireless communication systems is presented. The filter structure is composed of folded non-uniform meander resonators along with defected ground structure patterns. The proposed filter with a total size of 14.43 × 9.04 mm2 is designed to exhibit two passbands centered at 2.18 GHz and 5.12 GHz with fractional bandwidths of 16.2% and 6.48%, respectively. The measured insertion losses are about 1.13 dB and 2.65 dB at the lower and upper passband, respectively. The simulation and experimental measurement results are basically in good agreement which validate the proposed approach.

Dual band Stepped Impedance Interdigital Microstrip Filter for LTE Bands

In this paper, a dual band microstrip bandpass filter has been proposed utilizing three edge coupled resonators, interdigital stubs and DGS technique. To enhance the coupling degree, two interdigital coupled feed lines are employed in this filter. The suppressing cell consists of stepped impedance ladder type resonators, which provides a wide stopband. The proposed suppressing cell has clear advantages like low insertion loss in the passband and suitable roll off. The frequency response of the filter looks like a standard dual band band-pass filter. The filter exhibits a dual passband with resonant frequencies at 2.2GHz and 3.45GHz covers LTE1 and LTE22 bands.

Dual band Stepped Impedance Interdigital Microstrip Filter for LTE Bands

In this paper, a dual band microstrip bandpass filter has been proposed utilizing three edge coupled resonators, interdigital stubs and DGS technique. To enhance the coupling degree, two interdigital coupled feed lines are employed in this filter. The suppressing cell consists of stepped impedance ladder type resonators, which provides a wide stopband. The proposed suppressing cell has clear advantages like low insertion loss in the passband and suitable roll off. The frequency response of the filter looks like a standard dual band band-pass filter. The filter exhibits a dual passband with resonant frequencies at 2.2GHz and 3.45GHz covers LTE1 and LTE22 bands.

Miniaturized microstrip dual-band bandpass filter with wide upper stop-band bandwidth

A novel microstrip dual-band bandpass filter (BPF) with bended microstrip lines, rectangular resonators and stepped impedance resonator (SIR) is designed, analyzed and fabricated. This circuit provides two pass-bands with the center frequencies of 3.6 and 5.7 GHz. Moreover, the LC equivalent circuits of the basic and main resonators are meticulously computed so as to present an analytical description. The surface current distributions of the proposed filter are shown to verify the performance of the filter and provide physical insight. The measured data of the proposed filter indicate that the insertion losses are better than 0.53 and 0.67 dB and the return losses are 25 and 24.7 dB in the first and second bands, respectively. One of the most outstanding features of the proposed filter is that the upper band can be tuned between 5.7 and 8.4 GHz without any increment in the circuit size. The compact size, wide upper stop-band bandwidth, low insertion loss, sharp transition bands, and high attenuation level in the stop-bands are the other marked positive points of the designed filter. Finally, a suitable agreement between the simulated and measured S-parameters can be observed.

A compact and high performance dual-band bandpass filter based on unbalanced composite right/left-handed transmission lines for WLANs applications

In this paper, a novel compact microstrip dual-band (DB) bandpass filter with high selectivity for wireless local area networks applications is proposed. The design procedure is based on unbalanced composite right/left-handed (UCRLH) transmission lines (TLs). The DB features can be achieved by unbalancing the CRLH transmission line. The necessary conditions to obtain a discontinuous transition between the left- and right-handed bands, intended to provide UCRLLH TL, are investigated. The application of this technique to design of compact DB filters is illustrated. The structure of the proposed DB filter is implemented by a series interdigital capacitor located between two microstrip lines that shorted to the ground plane by vias. The vias with microstrip lines acting as a shunt connected inductor while the series capacitor is realized by interdigital capacitor. The design procedure based on a simple equivalent circuit is also introduced. The proposed filter has advantages such as compact size, easy fabrication, high selectivity, low insertion loss, high return loss and, design flexibility. To validate the proposed technique, the proposed DB filter has been fabricated and tested. Good agreement has been found between simulation and measurement results. The total size of the proposed UCRLH DB filter is 0.17 λg × 0.048 λg, where λg is the guided wavelength of the lower pass-band. The size of the proposed DB filter is more compact in comparison with known similar filters.

Dual‐band bandpass filter using loop resonator with independently‐tunable passband

A dual-band microstrip bandpass filter using the rectangular loop resonator (RLR) is proposed. A microstrip open stub is implemented to perturb modes of the RLR, and the two modes form the low-frequency passband. The stepped impendence microstrip lines are adopted to excite the RLR and the lines also work as the resonant stubs, i.e. one is 3/4-wavelength resonance stub and another is full-wavelength resonance stub. As a result, the second passband is introduced. Furthermore, each passband can be tuned independently through the corresponding resonant paths (parameters), which are discussed in detail. Without the connection stub between stepped impendence microstrip lines and RLR, this dual-band bandpass filter will degenerate to a dual-mode single-band bandpass filter and the corresponding results are also obtained and demonstrated. The measured results agree with the simulated results well.

High-frequency microstrip dual-band bandpass filter fabricated using FR-4 glass epoxy material

In this paper, design, fabrication and measurement of a novel microstrip dual-band bandpass filter (BPF) structure with a compact size using FR-4 glass epoxy material is presented. The filter structure is composed of folded non-uniform meander resonators. The proposed filter with a total size of 0.24λg × 0.16λg is designed to exhibit two passbands centred at 2.68 GHz and 5.64 GHz with fractional bandwidths of 25.38% and 10.4%, respectively. The simulation and experimental measurement results are basically in good agreement which validate the proposed approach.

High‐selectivity dual‐mode dual‐band microstrip bandpass filter with multi‐transmission zeros

A dual-mode dual-band microstrip bandpass filter using the hybrid structure resonator derived from microstrip patch is proposed. Microstrip rectangular rings are used to excite the TE200 mode and TE002 mode of microstrip patch resonator, forming the high-frequency passband while it also works as a resonator which provides the low-frequency passband. The designed filter has 11 transmission zeros, resulting in good selectivity and good out-band rejection, extending the stopband, with a size of 0.45λ g × 0.41λ g. The measured results are in a good agreement with simulated results.

Design of ultra compact dual-band bandpass filter using L-shaped resonator

A compact dual-band microstrip bandpass filter (BPF) is presented for application at the frequencies 2.4 and 5.84 GHz. The proposed main resonator consists of two L-shaped resonators. To improve the upper-stopband of the proposed filter, modified U-Shaped resonators are accepted. The operation mechanism of the filter is investigated based on proffered equivalent-circuit model and transformation function. The sketched dual-band BPF attends the insertion loss less than 0.1 and 0.4 dB Also the return loss is 26 and 28 dB at 2.4 and 5.84, respectively. This proffered filter structure is proper for Bluetooth and wireless local area networks and other wireless communication systems. An overall good agreement between measured and simulated results is observed.

Microstrip dual-band bandpass filter with independently tunable passbands using varactor-tuned stub loaded resonators

In this paper, a dualband bandpass filter with independently tunable passband is proposed. Two half-wavelength resonators with shunt stub have been placed side by side, fed with a common input-output microstrip line to achieve the individual tunability without affecting other passband. For tuning resonance frequency, varactor diodes are used at the ends of the half wavelength resonators and also at the end of the shunt stubs. Proper shunt stub length and width are derived numerically in such a way that only one control voltage is required in each passband. Measured results show that lower passband can be tuned in a frequency range from 1.78 to 1.96GHz, whereas the upper passband varies from 2.27 to 2.39GHz individually. H shaped DGS is integrated below the input-output feed lines to suppress higher order harmonics up to 21GHz with more than 19dB attenuation.

Erratum: A microstrip dual-band bandpass filter using feed line with SIR [IEICE Electronics Express Vol. 14 (2017) No. 4 pp. 20170022

Erratum: A microstrip dual-band bandpass filter using feed line with SIR [IEICE Electronics Express Vol. 14 (2017) No. 4 pp. 20170022

A microstrip dual-band bandpass filter using feed line with SIR

A microstrip dual-band bandpass filter using feed line with SIR