Microstrip Dual-mode Filter Research Articles

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.

Transmission Line Tunable Resonators With Intersecting Resonance Regions

A new property of tunable lumped-distributed circuits, namely, the intersection effect of resonant regions of two resonators with variable capacitors, is observed. As is known, the resonant regions of widely used resonators with varactors are separated by frequency intervals from each other. The construction of the proposed resonators is based on the resonance equations. One resonator is a loop hairpin stepped-impedance resonator with one capacitor. In this resonator, a controlled regime of dual-mode oscillations is realized, when the even and odd modes of the oscillations can change places. For this a one variable capacitor is used only. Another resonator is a symmetrical stepped-impedance resonator with two capacitors at the ends. Its resonance regions for several oscillations with frequencies ${f} _{0}$ , ${f} _{1}$ , ${f} _{2}$ intersect each other. This effect allows tuning in a very wide frequency range with simultaneous use of these oscillations. The results of the measurements and simulation for the reconfigurable microstrip dual-mode filter with one capacitor are presented.

Varactor-Tuned Dual-Mode Bandpass Filter With Nonuniform <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math> </inline-formula> Distribution

This letter demonstrates an electronically reconfigurable microstrip dual-mode filter with nonuniform Q lossy technique. Varactors are used for continuous tuning of the bandwidth and center frequency. By deploying nonuniform Q distribution on the dual-mode open-loop filter, passband flatness is improved by loading resistors on the even–odd symmetrical plane of resonators. Coupling matrix is used to describe the tunable lossy filter. Design of this type of four-pole tunable lossy filter is presented and validated experimentally.

Improving the Pass-Band Return Loss in Liquid Crystal Dual-Mode Bandpass Filters by Microstrip Patch Reshaping.

In this paper, the design and experimental characterization of a tunable microstrip bandpass filter based on liquid crystal technology are presented. A reshaped microstrip dual-mode filter structure has been used in order to improve the device performance. Specifically, the aim is to increase the pass-band return loss of the filter by narrowing the filter bandwidth. Simulations confirm the improvement of using this new structure, achieving a pass-band return loss increase of 1.5 dB at least. Because of the anisotropic properties of LC molecules, a filter central frequency shift from 4.688 GHz to 5.045 GHz, which means a relative tuning range of 7.3%, is measured when an external AC voltage from 0 Vrms to 15 Vrms is applied to the device.

Wideband Dual-Mode Microstrip Filter Using Short-Ended Resonator With Centrally Loaded Inductive Stub

In this paper, a new class of wideband filters utilizing a novel dual-mode resonator is presented. For the first time, the resonator realized by loading an inductive short-circuited stub at the center of the short-ended resonator is proposed. The inductive stub is tuned to control the filter bandwidth by splitting two degenerate modes. For wideband application, source-load coupling, which is introduced to compensate the insufficient I/O coupling strength in a parallel-coupled microstrip line, not only improves the property within the passband, but also produces transmission zero to enhance passband selectivity. In addition, the method of extraction of the source-load coupling coefficient is proposed, and through equivalent circuit topology analysis, three types of dual-mode wideband filters, by utilizing the proposed basic resonant unit and connecting two or three short-circuited points, are designed and fabricated with good performance.

Miniaturized transmit dual-mode HTS patch filter with stripline structure

A miniaturized dual-mode high-temperature superconducting (HTS) patch filter is described that has a stripline structure. A conventional microstrip dual-mode HTS patch filter, which has much weaker current concentration at the resonator edge, is usually used to improve the power handling capability of a filter. However, it is difficult to design a miniaturized microstrip filter because a microstrip dual-mode filter designed with a short distance between the resonators is limited in filter response by cross-coupling between nonadjacent modes. The proposed filter overcomes this problem because a stripline filter can be made smaller than a microstrip filter due to the weaker cross-coupling between resonators in the stripline filter. A four-pole dual-mode patch stripline filter with a 5.0GHz center frequency and a 100MHz bandwidth was designed using an electromagnetic simulator based on the moment method. Two Al2O3 substrates were used, each with a thickness of 0.5mm and a relative dielectric constant of 9.9. The filter was approximately 65% smaller than a microstrip filter. This indicates that a dual-mode HTS patch filter with a stripline structure can be miniaturized and have high-power handling capability.

Design of Compact Dual-Mode Microstrip Filters

This paper presents a novel filter design technique for the compact microstrip dual-mode filters. An equivalent circuit for the single dual-mode filter section is derived to show that a single unit behaves as a pair of coupled synchronously tuned single-mode resonators. The equivalent circuit was linked to the inverter-coupled bandpass prototype network to allow higher order filters to be realized. A complete design example (from design to realization) of a fourth-order Chebyshev bandpass filter is presented. It is shown that the dual-mode resonator may be employed to design cross-coupled filters with finite frequency zeros. Two filters are designed using optimized coupling matrix method, fabricated and tested. Experimental and simulation results are presented to validate the argument. Finally, it is shown that more compactness may be achieved with narrowband filters by employing folded resonators.

Design of Miniaturized Microstrip Dual-Mode Filter With Source-Load Coupling

A miniaturized microstrip dual-mode filter with different responses is developed in this letter. A coupling and routing scheme is presented to model the operations of this filter. The new filter reduces the occupied area up to 33% compared with the conventional one at 1.89 GHz. Meanwhile, the proposed circuit enables the second harmonic response to be effectively suppressed. A demonstrator filter is designed and validated with good agreement between the full-wave electromagnetic simulations and measurements.

Application of inductive source-load coupling in microstrip dual-mode filter design

The technique to utilise inductive source-load coupling to improve the performance of microstrip dual-mode filters is explored intensively. The functions of the inductive coupling on the filter's performance, including its potential to generate controllable transmission zeros to create a quasi-elliptic response, is investigated in detail. A demonstration filter has been designed, fabricated and tested to show the validity of the proposed design concept.

Compact Narrow Band Non-Degenerate Dual-Mode Microstrip Filter with Etched Square Lattices

A compact narrowband non-degenerate dual-mode microstrip filter with square shape cuts is presented. The structure is developed by loading the conventional non-degenerate dual-mode resonator by open circuit stubs at two opposite corners. The filter bandwidth is controlled by only decreasing the higher cutoff frequency of the conventional type. With Square shape cuts, return loss is improved. A 20% fractional bandwidth filter is designed and implemented on FR4 material with 4.4 dielectric constant and 1.6 mm thickness at center frequency of 1.5 GHz with passband of 1.3 GHz to 1.6 GHz. Analysis has been achieved using the IE3D simulator. Experimental results do agree with simulations.

Dual-mode filter design based on uniform or stepped impedance resonator

This article presents a design of compact microstrip dual-mode filter. The design uses dual-mode resonators developed from a uniform or stepped impedance resonator with a load tapped at the middle of the resonator. Four different types of loads can be employed to excite an additional even mode. This kind of dual-mode resonator is applicable in filter design. To validate the new approach, several bandpass filters are designed, fabricated and measured. Measurements have verified the effectiveness of the method.

Dual-mode microstrip filters with adjustable transmission zeros

A new type of dual-mode microstrip square-loop resonator that produces asymmetrical frequency responses is proposed. The coupling between degenerate modes of the proposed dual-mode resonator is discussed depending on the perturbation size. The effect of non-orthogonal input/output feed lines located along a straight line on the frequency response is investigated using full-wave electromagnetic simulations. Two second-order bandpass filters using this type of dual-mode microstrip resonator are designed, fabricated and measured to demonstrate the dual-mode microstrip filters exhibiting transmission zero (TZ) shifting property. The one of the second-order filters produces a filter characteristic with two TZs in the upper stopband, whereas the other one has two TZs in the lower and upper stopbands. The shifting property of one of the TZs from one side of the passband to the other side is realised by only changing the perturbation size. The fourth-order filters of this type are also investigated. Both simulated and measured results are presented.

Miniature Dual-Mode Microstrip Filters

In order to reduce the size of dual-mode microstrip filters by keeping excellent performance, novel filter geometry is proposed. The novel filter includes a dual-mode resonator based on a meander structure. The effect of input/output feed lines located along a straight line on filter response is investigated for the dual-mode filter. The coupling between degenerate modes of the proposed dual-mode microstrip resonator is discussed depending on the perturbation size. The two dual-mode microstrip bandpass filters with real axis and imaginary axis transmission zeros (TZs) are designed, fabricated, and measured to document the validity of the description of the positive and negative coupling coefficient

Miniaturized dual-mode triangular patch filter with inverted V-shaped slot

In this paper, an isosceles triangular patch resonator with an inverted V-shaped slot pattern is fabricated to realize a miniaturized microstrip dual-mode filter. The proposed structure possesses the elliptic characteristic and has the advantage of size and loss reduction. After analyzing the results, the relationships between the filter characteristics and the geometrical parameters of the inverted V-shaped slot are derived. The dual-mode filter exhibits a fractional bandwidth of 14.5% centered at 1.93 GHz with the lowest insertion loss of 1.4 dB. It is shown that a size reduction of 37% is achieved compared with a conventional dual-mode triangular filter. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1969–1974, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21824

Compact dual-mode microstrip resonator for 900 MHz bandpass filter applications

A novel dual-mode microstrip filter operating at 900 MHz is proposed using degenerate modes of a microstrip-loop resonator. The resonator structure that is formed of meandered microstrip-line elements has a smaller size than the other dual-mode microstrip resonators in the literature. The dual-mode filter is verified by both simulation and measurement. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 376–377, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20828

Microstrip dual-mode filters with miniaturized size and broadened stopband using meander-shaped stepped-impedance ring resonator

An improved class of microstrip dual-mode bandpass filter is proposed using the meander-shaped stepped-impedance ring resonator (SIRR). This meander SIRR, together with a uniform impedance ring resonator (UIRR), is at first studied to demonstrate its attractive features of harmonic-resonance suppression and overall-size miniaturization. A pair of squared notches is then etched out on the corners along either of diagonal lines of this symmetrical SIRR that is capacitively driven by the two perpendicular feed lines. Two SIRR-based dual-mode filters are therefore designed, simulated and fabricated. The overall size of this filter finds to be reduced by about 50% in area. The 1st harmonic passband of this filter is raised to 5.30GHz that exceeds the three times of its fundamental passband at 1.52GHz as verified by experiment.

Reduced-size dual-mode slotted patch resonator for low-loss and narrowband bandpass filter applications

A compact, low-loss and narrowband dual-mode microstrip filter is proposed using degenerate modes of a microstrip patch resonator loaded with two narrow slots. The resonator structure is fed by inset lines connected directly to the centre of adjacent edges of a microstrip patch with two notches. The dual-mode filter is verified by both simulation and measurement.

A novel dual-mode bandpass filter with wide stopband using the properties of microstrip open-loop resonator

A novel dual-mode microstrip square loop resonator is proposed using the slow-wave and dispersion features of the microstrip slow-wave open-loop resonator. It is shown that the designed and fabricated dual-mode microstrip filter has a wide stopband including the first spurious resonance frequency. Also, it has a size reduction of about 50% at the same center frequency, as compared with the dual-mode bandpass filters such as microstrip patch, cross-slotted patch, square loop, and ring resonator filter.

A joint field/circuit model of line-to-ring coupling structures and its application to the design of microstrip dual-mode filters and ring resonator circuits

A joint field/circuit model is proposed in this paper to characterize a class of line-to-ring coupling structures for design and optimization of microstrip dual-mode filters and ring resonator circuits. The generic model is derived from field theory and presented in terms of circuit elements by applying a newly developed numerical deembedding technique called "short-open calibration" in a deterministic method-of-moments scheme. It provides a new design strategy for characterizing and optimizing electrical performance of the line-to-ring coupling structures. Such three-port topologies are explicitly formulated by using an equivalent network having circuit elements calculated by the proposed joint field/circuit model. Three microstrip tightly coupling geometries and their related ring resonators are studied with the extracted J-inverter susceptance parameters. Experiments are performed to validate the joint model and also show coupling characteristics of the three types of line-to-ring circuit for the design of ring resonators and dual-mode filters. With this new technique, an optimized microstrip dual-mode filter is successfully designed and the prediction agrees well with our measurements.

Design of dual-mode ring resonators with transmission zeros

A set of design equations is presented for the implementation of dual-mode ring filters with transmission zeros. These expressions also give insight into the design limitations in practical situations. The simulated and measured results of a 1.4 GHz microstrip dual-mode ring filter are shown.