Compact Microstrip Bandpass Filter Research Articles

Development of Compact Bandpass Filter Using Symmetrical Metamaterial Structures for GPS, ISM, Wi-MAX, and WLAN Applications

This article describes the development of a compact microstrip bandpass filter (BPF) for multiple wireless communication utilizations. The proposed bandpass filter consists of metamaterial unit cells that are symmetrical in shape. The design process involves the placement of four symmetrical split-ring resonators (SRRs) on the top plane of the BPF. It exhibits improved filter characteristics through the implementation of these SRRs. The filter was modeled and fabricated and its performance was evaluated using a Vector Network Analyzer. The designed bandpass filter shows a 5 GHz bandwidth covering the frequency band spanning from 1 to 5.2 GHz, with a quality factor value of 1.85 across 1.9 GHz, 3.3 across 3.3 GHz and 5.1 across 5.1 GHz. The metamaterial analysis was carried out using ANSYS ELECTRONIC DESKTOP. The proposed filter measures 20 × 18 × 1.6 mm3, which is significantly smaller than current filters. The designed bandpass filter occupies 50% of the space of a conventional filter. The designed bandpass filter exhibits a distributed surface current of 84 A/m, and 94 A/m across the wide- and narrow-band operating frequency. The simulated and measured results indicate that the suggested metamaterial filter is well-suited for multiband wireless applications like GPS (1.57 GHz), WLAN (2.4, 3.6, and 5.2 GHz), Wi-MAX (2.3, 2.5, and 3.5 GHz), and ISM (2.5 GHz).

An improved simplified composite right‐/left‐handed zeroth‐order resonator and its application to design a compact microstrip bandpass filter with enhanced upper stopband

AbstractAn improved simplified composite right‐/left‐handed (SCRLH) zeroth‐order resonator (ISZOR) is introduced, comprising two lateral parallel capacitors and a centred T‐type inductor circuit. Starting from the lumped circuit of the ISZOR, its miniature microstrip layout can be generated with on more than three times full‐wave simulations by virtue of the implicit space mapping technique. Multi‐solutions of the microstrip ISZOR with identical fundamental mode are obtained by sweeping key physical and electrical parameters, uncovering the relationship among physical sizes, resonant modes, unloaded quality factors and circuit elements. A three‐pole microstrip Chebyshev bandpass filter (BPF) with ultra‐wide upper stopband is further designed. By choosing the constituent ISZORs with identical base frequency but different higher resonant frequencies and applying the over‐coupled I/O terminals, wideband spurious response suppression in the upper stopband is achieved. The target BPF centers at 3.1 GHz with a relatively bandwidth of 5%, which is optimised through a customised aggressive space mapping iterative process. The optimal BPF layout dimensions are automatically obtained with just a few time‐consuming full‐wave simulations. A prototype measurement shows the BPF features good bandpass selectivity in a simple and easy‐to‐fabricate structure, with a transversal size reduction of more than 65% compared to a former counterpart and a rejection level better than 15 dB over 40.0 GHz.

Improved SCRLH ZOR‐based compact microstrip bandpass filter with wide upper stopband

AbstractA novel compact microstrip bandpass filter (BPF) based on an improved simplified composite right‐/left‐handed (SCRLH) zeroth‐order resonator (ZOR) is presented in this paper. The improved SCRLH ZOR (ISZOR) can substantially simplify the filter configuration and shrink the filter size as well as ensure a wide upper stopband. A certain orientation of two ISZORs allows a larger gap to produce the specified interstage capacitive coupling, easing the requirement for fabrication precision. Starting from the purely lumped circuit model, the microstrip ISZOR is efficiently generated by utilizing the implicit space mapping technique, with which the microstrip BPF is then constructed and optimized by the Nelder–Mead simplex algorithm. A three‐pole filter with a center frequency of 3.1 GHz and a relative bandwidth of 5% is exemplified to illustrate the design process. The measurement shows that the filter is of good bandpass selectivity, with a transversal size reduction of more than 64% compared to a former counterpart and a rejection level better than 30 dB up to 11.76 GHz (close to 4f0).

Compact dual-mode microstrip bandpass filter based on slotted square patch resonator

PurposeThe purpose of this paper is to present the design of a compact microstrip bandpass filter (BPF) in dual-mode configuration loaded with cross-loop and square ring slots on a square patch resonator for C-band applications.Design/methodology/approachIn the proposed design, the dual-mode response for the filter is realized with two transmission zeros (TZs) by the insertion of a perturbation element at the diagonal corner of the square patch resonator with orthogonal feed lines. Such TZs at the edges of the passband result in better selectivity for the proposed BPF. Moreover, the cross-loop and square ring slots are etched on a square patch resonator to obtain a miniaturized BPF.FindingsThe proposed dual-mode microstrip filter fabricated in RT/duroid 6010 substrate using PCB technology has a measured minimum insertion loss of 1.8 dB and return loss better than 24.5 dB with a fractional bandwidth (FBW) of 6.9%. A compact size of 7.35 × 7.35 mm2 is achieved for the slotted patch resonator-based dual-mode BPF at the center frequency of 4.76 GHz. As compared with the conventional square patch resonator, a size reduction of 61% is achieved with the proposed slotted design. The feasibility of the filter design is confirmed by the good agreement between the measured and simulated responses. The performance of the proposed filter structure is compared with other dual-mode filter works.Originality/valueIn the proposed work, a compact dual-mode BPF is reported with slotted structures. The conventional square patch resonator is deployed with cross-loop and square ring slots to design a dual-mode filter with a square perturbation element at its diagonal corner. The proposed filter exhibits compact size and favorable performance compared to other dual-mode filter works reported in literature. The aforementioned design of the dual-mode BPF at 4.76 GHz is suitable for applications in the lower part of the C-band.

Design of compact microstrip bandpass filter with two switchable operating passbands

A new bandpass filter (BPF) with two switchable operating passbands has been proposed. The BPF topology is formed by switchable resonators and stepped-impedance resonators. The two operating bands can be switched on and off independently. For verification, a switchable BPF with a third-order Chebyshev bandpass response was designed and fabricated using microstrip technology. The developed BPF was measured to verify the predicted and simulated results. A close agreement was observed between them. The proposed switchable BPF has good in-band and out-of-band performances. Besides, the attenuation is > 30 dB as the passband is switched off.

Compact microstrip bandpass filters using triple‐mode resonator with lumped elements

AbstractCompact microstrip bandpass filters using triple‐mode resonator are investigated in this paper. At the center frequency of 2.45 GHz, a half‐wavelength microstrip open‐circuited resonator is loaded with a chip capacitor and a chip inductor to realize the triple‐mode resonator. By adjusting the resonator's parameters, the first three resonant mode frequencies could be tuned for bandpass filters with various fractional bandwidths. Three bandpass filters with different measured bandwidths (13.8%, 55.5%, 98.6%) are designed, fabricated, and tested to validate the design concept.

Compact microstrip bandpass filter with sharp roll-off and broad stopband using modified 0° feed structure

A compact microstrip bandpass filter (BPF) with sharp roll-off skirt and broad stopband, consisting of the proposed modified 0° feed structure and the shorted stub-loaded tri-section stepped impedance resonator (SSLTSIR), is presented. The first two high-order parasitic resonant frequencies of the conventional 0° feed structure can be suppressed when a pair of open-circuited SIRs is loaded on its upper transmission path. Thus, the proposed modified 0° feed structure with broad stopband response is realized. Moreover, the theoretical analysis and numerical investigations are carried out. Furthermore, by embedding the SSLTSIR into the proposed modified 0° feed structure, a BPF with sharp roll-off skirt and broad upper stopband is achieved. A demonstrated BPF is fabricated and measured, and its measured results agree well with the simulated ones.

Generalised Chebyshev function bandpass filters in box‐like topologies based on the properties of dual‐mode loop microstrip resonator

A new class of compact microstrip bandpass filters in doublet topology based on a dual-mode loop microstrip resonator with controllable locations of input/output feeding lines is presented and researched. Filters with up to five poles are proposed and researched. Diagonal cross-coupling path in box-like topology can be introduced to produce a finite transmission zero (TZ) with controllable position. Some design examples are provided to illustrate the performances of the proposed two-, three-, four- and five-pole filters with controllable TZs. A three-pole and a five-pole filters were fabricated and measured. Good agreement is achieved between the simulated and the measured results.

Design and Fabrication of an Ultra-Wide Stopband Compact Bandpass Filter

In this brief, we present a novel ultra-wide stopband compact microstrip bandpass filter (BPF) with low insertion loss and compact size. The proposed filter is designed based on two five-stage stepped impedance resonators (SIRs) which are capacitively coupled to each other’s. The five-stage SIRs can be used to have miniaturized size as well as suppression of harmonics. In this BPF, by increasing stages of SIRs, multiple transmission zeros are generated. Therefore, a compact BPF with a ultra-wide stopband could be achieved. The bandpass region of the proposed filter is extended from 3.58 GHz up to 10.31 GHz with insertion loss lower than 0.42 dB. The rejection level is better than −26 dB from 11.25 GHz up to 30 GHz and better than −17.5 dB up to 100 GHz. The center frequency of the proposed BPF is located at 6.95 GHz with −3 dB fractional bandwidth (FBW) of 97%. The dimension of the fabricated filter is $0.128\,\,{\lambda }_{\textbf {g}}{\times }{0.378}\,\,{\lambda }_{\textbf {g}}$ . The simulation results are verified by fabrication and measurement up to 30 GHz that there is a good agreement between them.

Microstrip Bandpass Filter with Wide Stopband and High Out-of-Band Rejection

This paper presents a compact microstrip bandpass filter exhibiting a wide stopband, high selectivity and easily tunable passband. The filter comprises of asymmetric resonator structures, which are interconnected by an inter-digital capacitor to enable the realization of a wide bandwidth with high rejection level. High selectivity and easily tunable passband are obtained by optimizing the parameters of the interdigital capacitor. The filter has high out-of-band rejection 30 dB, less than 0.6 dB of insertion-loss, up to 5.5 GHz spurii free and more than 15 dB of return-loss. Full-wave electromagnetic simulator ADSTM based on Method of Moment technology is used to analyze and optimize the prototype bandpass filter. The proposed technique was verified practically to validate the design methodology. The experimental results of the prototype circuit are presented and a good agreement was obtained comparing with the simulation results. The dimensions of the proposed filter are 32×24 mm2. The filter’s characteristics and compact size make it suitable for wireless communication systems.

DESIGN OF COMPACT BANDPASS QUASI-ELLIPTIC MICROSTRIP FILTERS

This paper considers an algorithm for development of the sixth order compact microstrip bandpass filters with quasi-elliptic characteristics. The proposed technique is applied for synthesis of two filters for the L- and X-band. The recursive computational approach is employed to obtain the coupling matrix with simple topological implementation. Next, the full-wave transmission line analysis based on spectral-domain method of moments is applied for calculation of coupled microstrip resonator eigen frequencies. This approach is then used to compute magnitude and sign of the coupling coefficient for basic coupled resonator configurations. Finally, two quasi-elliptic filter topologies are synthesized and structure optimization in Ansys HFSS is performed. As a result, prototypes of the developed microstrip filters are manufactured and measured.

Tuning the Resonance Frequency and Miniaturization of a Novel Microstrip Bandpass Filter

In this paper, a compact microstrip bandpass filter is designed using two open loop resonators. In order to obtain a tunable bandpass response with low insertion loss, two stubs are loaded inside them. The design process is based on obtaining the input admittance. Then, using the input admittance, a method is presented to control the resonance frequency and miniaturization simultaneously. The obtained insertion loss and the return loss at the resonance frequency are 0.1 dB and 19.7 dB respectively. To verify the design method, the proposed filter is fabricated and measured. The measured results are in good agreement with the simulated results.

Tuning the Resonance Frequency and Miniaturization of a Novel Microstrip Bandpass Filter

In this paper, a compact microstrip bandpass filter is designed using two open loop resonators. In order to obtain a tunable bandpass response with low insertion loss, two stubs are loaded inside them. The design process is based on obtaining the input admittance. Then, using the input admittance, a method is presented to control the resonance frequency and miniaturization simultaneously. The obtained insertion loss and the return loss at the resonance frequency are 0.1 dB and 19.7 dB respectively. To verify the design method, the proposed filter is fabricated and measured. The measured results are in good agreement with the simulated results.

Compact microstrip bandpass filter using dual closed-loop stepped impedance resonator

AbstractA dual closed-loop stepped impedance resonator (DCLSIR) is investigated and used in designing a compact microstrip bandpass filter (BPF). The proposed DCLSIR is symmetrical; as a result, the symmetric characteristics of the resonator have been used. The design equations are derived and used to support the circuit design. The center frequency, position of transmission zeros, and fractional bandwidth (FBW) are easily tuned by changing the physical dimensions of the resonator. Three transmission zeros are generated to improve the performance in the upper stopband. A DCLSIR prototype BPF is fabricated with a center frequency of 9.3 GHz, and evaluated to validate the design concept. The measured FBW is 9.25%, the insertion loss is 1.58 dB, and the return loss is over 17 dB. The measurement results agree well with the simulation results.

Theoretical Based Design of Ultra-Wideband Filter with Dual Band-Notch

In this paper, a compact ultra-wideband microstrip band-pass filter with single/dual-notched bands is proposed. The filter is theoretically designed based on a multiple-mode resonator which consists of a short circuit stub loaded-ring resonator. A multi stepped impedance resonator is also applied to reject unwanted in-band frequencies and extend the upper-stopband. The proposed filter is analyzed by utilizing graphs according to odd- and even-mode method. The resonant modes are allocated between 3.1 GHz to 10.6 GHz and transmission zeros are adjusted at upper stopband to create a sharp roll-off and suppress the spurious harmonics, as well as a compact physical size. Full-wave simulations are performed for three types of filters, with and without notch-bands, to verify theoretical results. The measurement results demonstrate that not only − 3 dB fractional bandwidth is more than 120% and but also at least − 20 dB suppression can be achieved at upper-stopband.

Compact Stepped Impedance Resonator Bandpass Filter with Tunable Transmission Zeros

This paper proposes a compact microstrip bandpass filter (BPF) with tunable transmission zeros, narrow bandwidth and low insertion loss. A λ/4 stepped impedance resonator (SIR) with two additional via holes has been adopted to obtain a compact size and a pair of transmission zero (TZ). Furthermore, three techniques have been developed to create a pair of controllable transmission zeros on both side of each passband. The TZ can be controlled by adjusting either magnetic or electric coupling. The measured return losses and insertion loss is larger than 18 dB and 2.2 dB respectively. The overall size of the proposed design filter is 5.3mm x 5.5mm without considering the feeding lines.

A compact trisection microstrip bandpass filter with frequency-dependent cross-coupling

ABSTRACTA compact microstrip bandpass filter using stub loaded ring resonators and double-loop ring resonators in an embedded triplet configuration with frequency-dependent cross-coupling is proposed in this article. The embedded triplet configuration is realized by putting the loops of the double-loop ring resonator into the circles of the stub loaded ring resonators. The frequency-dependent cross-coupling has been introduced to the filter by a manner of separate electric- and magnetic-coupling path. Three transmission zeros are obtained to enhance the frequency selectivity and stopband performance. Among them, two are achieved by the frequency-dependent cross-coupling, the other one is created by the harmonic effect of the transmission lines. The filter is designed for 2.4 GHz Wireless Local Area Networks application with 20.8% fractional bandwidth. The measured results show reasonable agreement with the simulated ones.

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.

Design of Compact Bandpass Filters based on Fractal Defected Ground Structure (DGS) Resonators

Modified Minkowski fractal geometry has been found to be attractive for microwave circuit designers because of its high space-filling property. This property will lead to the design of compact circuits; meeting the requirements of the modern communications systems to be with small size. In this paper, the design of a compact microstrip BandPass Filters (BPF) has been proposed based on the modified Minkowski fractal (DGS) resonators. The proposed BPF structure is composed of two coupled resonators etched as fractal DGS structures. Results reveal that as the iteration level of fractal based DGS becomes higher, more compact filter structure will result in. Furthermore, the presented DGS structures with fractalshaped resonators can be adopted to design compact planar BPFs with reasonable performances. The performance curves offered by the resulting filters are characterized by the low loss across the passband and high rejection levels outside it with steep roll-off in both edges of passband. Measured results of a fabricated prototype of a 2nd iteration fractal DGS BPF have shown reasonable agreement with those predicted by simulation. Measured results of a 2nd iteration fractal DGS BPF have shown satisfactory agreement as compared with simulation results. There is a slight shift of the lower edge of the passband response of the transmission characteristics, while the upper edge is s very close. The results have shown that the filter has reasonable performance characteristics with considerable reduction of higher harmonics. The compact size of the proposed filter together with the realized high selectivity will make it suitable for a broad range of the recently available wireless communication services.

A Design and Analysis of Compact Microstrip Bandpass filter with Integrated LNA for 0.8 to 2.7 GHz

This paper represents the design and analysis of the Microstrip wideband integrated low noise amplifier Bandpass filter for the frequency range of 0.8 GHz to 2.7 GHz. This frequency range is chosen for the design as most of the wireless applications work in this frequency range. The paper uses the compact design structure for designing the wideband filter from ref [5]. The filter has good performance in pass band as well as in stopband of the filter. The filter has the compact size and higher selectivity of 0.923 and the input return loss below 10 dB and the output return loss less than 10 dB for the whole frequency range. The integrated low noise amplifier is from the analog devices ADL5544 which has the gain of 15 dB at 0.8GHz and the gain roll of 2 dB in the whole frequency band of the filter. The filter hardware is fabricated and tested with the network analyzer from Rohde & Schwarz model no ZVH8 which can measure from 100 KHz to 8 GHz. The simulated and the measured results are in good agreement with each other.