Tri-band Filter Research Articles

Inter-digital coupled dual-mode patch resonator with crossed-island configuration for tri-band filter design

The miniaturized dual-mode tri-band band-pass filters BPF using crossed-island patch resonator is proposed in this article. The BPF is mainly formed by a square patch resonator in which a crossed-island configuration is embedded in the patch. The patch size reduction with 74.4% is achieved. By the perturbation and the alternative inter-digital coupling, the tri-band responses are obtained. The proposed filter covers the required bandwidths for WLAN band 2.26-3.11 GHz and 5.02-6.0 GHz and X-band 7.58-8.41 GHz applications. Five transmission zeros are placed between three pass-bands and resulted in a good isolation. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:457-463, 2014.

Compact tri-band bandpass filter based on quarter-wavelength resonators

In this work, a planar microstrip tri-band filter based on quarter-wavelength resonators is presented, which allows independent control of the positions of all three passbands. Furthermore, the topology of the filter provides five transmission zeros and thus results in a highly selective response in all passbands. A synthesis procedure of the filter is presented and used to design a tri-band filter which operates at WLAN frequencies of 2.4/3.5/5.2 GHz. The designed filter outperforms all other state-of-the-art tri-band filters in terms of compact size, high selectivity and transmission, and return-loss characteristics.

Tri-band Microstrip Bandpass Filter Using Dual-Mode Stepped-Impedance Resonator

This letter presents a compact dual-mode tri-band bandpass filter by using a short-circuited stub-loaded stepped-impedance resonator (SIR) and a short-circuited stub-loaded uniform impedance resonator. Also, a hairpin SIR geometry is introduced to miniature the size of this filter while maintaining excellent performance. The use of a short-circuited stub at the central point of the hairpin SIR can generate two resonant modes in two passbands. Its equivalent circuit structure is analyzed by using the even-odd mode theory. For demonstration purposes, a tri-band filter for the applications of the Global Positioning System at 1.57 GHz, Worldwide Interoperability for Microwave Access at 3.5 GHz, and wireless local area networks at 5.2 GHz is designed, fabricated, and measured.

Tri-band Microstrip Bandpass Filter Using Dual-Mode Stepped-Impedance Resonator

This letter presents a compact dual-mode tri-band bandpass filter by using a short-circuited stub-loaded stepped-impedance resonator (SIR) and a short-circuited stub-loaded uniform impedance resonator. Also, a hairpin SIR geometry is introduced to miniature the size of this filter while maintaining excellent performance. The use of a short-circuited stub at the central point of the hairpin SIR can generate two resonant modes in two passbands. Its equivalent circuit structure is analyzed by using the even-odd mode theory. For demonstration purposes, a tri-band filter for the applications of the Global Positioning System at 1.57 GHz, Worldwide Interoperability for Microwave Access at 3.5 GHz, and wireless local area networks at 5.2 GHz is designed, fabricated, and measured.

Design and Analysis of a Tri-Band Dual-Mode Chip Filter for 60-, 77-, and 100-GHz Applications

A tri-band dual-mode chip filter, which is fabricated with a commercial monolithic microwave integrated circuit technology and suitable for millimeter-wave applications, is presented in this paper. This filter is constructed by using stacked ring resonators with individual perturbation and feeding capacitors, thus fractional bandwidths and center frequencies of three passbands can be flexibly controlled. An equivalent model of the tri-band filter that considers coupling effects between the stacked ring resonators is adopted, and then a new set of design equations that can determine element values of dual-mode ring filters realized with different length ratios of upper parts over lower parts of the ring resonators are derived and proposed to design the filters with desired characteristics. Theoretical and experimental results reveal that dual-mode ring filters realized with different length ratios can change the positions of transmission zeros while keeping their widths of passbands equal, provide different characteristics of roll-off rates, and stopband suppressions. By following proposed design guidelines, the layout pattern of the tri-band dual-mode filter can be determined quickly. To verify the proposed design concept, an experimental prototype, locating three passbands at 60, 77, and 100 GHz, respectively, was fabricated on GaAs substrate. The size of the filter is about 0.46 × 0.91 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the measured insertion losses in the three passbands are less than 2.4, 2.7, and 3.5 dB over the frequency bands of interest, and their associated return losses are greater than 18, 17, and 8 dB, respectively.

A novel tri-band filter realization via band-splitting technique

This letter presents a novel microstrip tri-band filter in which a shunt-stub bandpass filter and a dual-band bandstop filter are integrated into a single structure of short length. The two stopbands of the bandstop filter are allocated within the wideband passband of the bandpass filter, resulting in a filter having three passbands. Good return loss is obtained using an optimization routine. This technique has high flexibility on setting the bandwidths and center frequencies of passbands. A prototype filter is designed and fabricated. Good agreements between simulation and measurement in respect of low insertion loss and high isolation are demonstrated.

Integrated Dual-Band BPF and Single-Band BSF for Tri-Band Filter Design

This paper presents a tri-band bandpass filter in which a dual-band bandpass filter (BPF) and a single-band bandstop filter (BSF) are integrated into a single circuit of short length. The dual-band BPF contains several two-section stepped-impedance stubs which are mounted onto a main transmission line. The BSFs are constructed using capacitor-loaded shunt stubs which are connected by transmission lines. After circuit embedding, one wide passband of the dual-band BPF is converted into two passbands by the stopband of the BSF, resulting in a total of three passbands. A prototype tri-band filter is designed according to prescribed specifications: the required passbands are 1–1.4, 1.8–2.0 and 2.42–2.66 GHz with return loss above 10 dB, while the expected isolations between bands are above 40 dB. Optimization method is adopted for extracting the circuit parameters. The simulated and measured results are compared, and good features such as low insertion loss and high isolation are demonstrated.

Design of Tri-Band Filter Based on Stub Loaded Resonator and DGS Resonator

A tri-band bandpass filter using stub loaded resonator (SLR) and defected ground structure (DGS) resonator is proposed in this letter. The DGS resonator on the lower plane constructs the first pass-band, and the SLR on the upper plane forms the second and third pass-bands, in which a DGS loop is properly used to provide the coupling between the SLRs. The three pass-bands are combined together with a common T-shaped feed line, and a reasonable tuning method is adopted to tune the three pass-bands with smooth responses. A compact tri-band filter with three pass-bands centered at 2.45, 3.5, and 5.25 GHz is designed and fabricated. The measurement results agree well with the full-wave electromagnetic designed responses.

Design of tri‐band microstrip bandpass filter using folded tri‐section stepped‐impedance resonator

AbstractA tri‐band microstrip bandpass filter using folded tri‐section stepped‐impedance resonators is designed, analyzed, and fabricated in this article.Furthermore, the filter's coupling structure analysis and equivalent circuit model are discussed theoretically, and the design methodology of tri‐band filter is explained. Simulated and measured results verify that the central frequencies of the three passbands are located at about 1.6, 2.3, and 4.3 GHz, respectively. Besides, the circuit size of the proposed filter occupies only 26 × 26 mm2 (≈ 0.22λg × 0.22λg). © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:895–898, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25063

A novel tri‐band filter using stub‐loaded open loop ring resonators

AbstractIn this article, a novel type of compact tri‐band filter using stub‐loaded open‐loop ring resonators (OLRRs) is presented.With the open stub loaded, the resonant frequency of the OLRR can be tuned by the tapped location and length of the loaded stub, which makes the OLRR more compact. Making use of the microstrip open‐ended feed line, proper external couplings are provided to each passband by magnetic coupling. A tri‐band filter centered at 2.0 GHz, 3.2 GHz, and 4.3 GHz is designed, fabricated and measured. Predicted results are verified by the experiments. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 523–526, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24971

Design of Compact Tri-Band Bandpass Filter using λ/4 and Stub-Loaded Resonators

This paper presents a novel approach for designing triband bandpass filters with independently controlled center frequencies and bandwidths. λ/4 and short stub loaded resonators are employed to obtain tri-band responses. λ/4 resonators are designed to operate at the third passband, and stub-loaded resonators are designed to operate at the first and second passbands. The bandwidth of each passband can be tuned independently by adjusting the coupling gaps or lengths. A tri-band filter was designed and simulated to verify the presented concept, the filter achieved insertion losses of 1.4, 1.8 and 1.8 dB at 2.4, 3.5, 5.5 GHz, respectively.

Design of Tri-Band Filters With Improved Band Allocation

A new design method for tri-band filters with improved band allocation is proposed. The design concept treats different band allocations with different methodologies. For the bands assigned to adjacent frequency regions, transmission zeros are introduced to split one of the single bands into two. For the bands that are assigned separately, different harmonic modes of stepped-impedance resonators are used to realize different passbands. Two design examples with different responses and band allocations are given, and were verified by experiments, as well as full-wave simulation results.

A Novel Crossed Resonator and Its Applications to Bandpass Filters

A novel open and short stubs loaded crossed resonator and its applications to cross-coupling filter and tri-band bandpass filters are presented in this paper. Based on the lossless transmission line model analysis, it is found that the first three resonance frequencies of the crossed resonator can be conveniently controlled. Benefiting from this feature, the resonator can be utilized to design not only a cascaded triplet (CT) filter, but also a tri-band bandpass filter. The tri-band filter offers two tunable passbands and one fixed passband. The first and third passband frequencies can be tuned effectively by changing the lengths of the stubs. To demonstrate these applications, a CT filter and two tri-band bandpass filters using a crossed resonator are implemented. The experiments verify the theoretical predictions and simulations.

Tri-band bandpass filter using stub loaded resonators

A tri-band bandpass filter using short and open stubs loaded resonators is presented. The first and the third passband frequencies of the tri-band filter can be flexibly controlled by tuning the lengths of the stubs, whereas the second passband frequency is fixed. A tri-band filter has been implemented with four transmission zeros, the filter has good tri-passband performance at 1.57, 2.4, 3.5 GHz measured results agree well with simulated ones.

Compact Dual-band and Tri-band Filters with Loaded Open-loop Resonators

A novel design method of dual-band and tri-band band-pass filters is proposed in this paper. A compact loaded open-loop resonator(LOLR) structure is introduced. The resonant frequency response of the resonator is described in detail. A dual-band filter and a tri-band filter are designed with the LOLRs. 0° feed structures are applied to improve the selectivity of the proposed filters. The measurements of the filters are in good agreement with the simulated results.