Dual-band Bandpass Fllter Research Articles

DESIGN OF DUAL-BAND BANDPASS FILTERS WITH CONTROLLABLE BANDWIDTHS USING NEW MAPPING FUNCTION

In this paper, a novel design method for a dual-band bandpass fllter (BPF) with arbitrary controllable bandwidths based on a simple frequency mapping function is proposed and its analytical design equations are also derived. The circuit conversion techniques are employed for implementation with distributed transmission line. To validate the proposed dual-band BPF with controllable bandwidths, a low temperature co-flred ceramic (LTCC) transmission line as well as microstrip lines are used, respectively. The two types of design for the dual-band BPF have the same and signiflcantly difierent fractional bandwidths (FBWs), respectively. The flrst type of dual- band BPF with same FBWs are implemented at 2.11{2.17 and 3.45{ 3.55GHz. The second type of dual-band BPF with difierent FBWs are implemented at 3.40{3.60 and 5.15{5.25GHz. The measured and theoretical results show good agreement, signiflcantly validating the proposed frequency mapping function methodology.

COMPACT MULTIBAND TRANSVERSAL BANDPASS FILTERS WITH MULTIPLE TRANSMISSION ZEROES

Novel compact multiband microstrip transversal bandpass fllters (BPF) using short-circuited or open-circuited stub-loaded half- wavelength resonators (SLR) are presented. The dual-band BPF consists of two SLRs and two T-shaped feedlines, and the tri-band BPF can be implemented by a simple reconflguration of adding one resonator above the original circuit of the dual-band BPF. Multiple transmission zeroes are created to improve the selectivity of the fllters. Furthermore, the high degree of design freedom obtained for every passband of dual- or triple-band BPF is achieved by independent resonators and independent signal paths. To verify the proposed concept, two dual-band bandpass fllters (fllter I and II) and one tri- band bandpass fllter (fllter III) are designed and fabricated. Both theoretical and measured results are presented, with good agreements.

NOVEL CLASS OF MICROSTRIP BANDPASS FILTERS WITH IMPROVED UPPER REJECTION BAND

In this paper, we present a novel class of microstrip bandpass fllters with improved upper rejection band. The proposed fllters are composed of two half-wavelength resonators and two short- ended microstrip feed lines for input and output. Using voltage- wave analysis, we examine the resonance and coupling properties at harmonic frequencies. It is found that difierent combinations of the feed line and the resonator with proper selection of the coupling regions can suppress spurious responses. Beneflting from this approach, two single-band and one dual-band bandpass fllters are designed, fabricated and measured. Simulated and measured results indicate that the upper rejection bands of the proposed fllters are increased up to near third- and flfth-order harmonics, respectively. And the rejection level during the stop-bands is more than 20dB.

DESIGN OF DUAL-BAND BANDPASS FILTER WITH WIDE UPPER STOPBAND USING SIR AND GSIR STRUCTURES

In this paper, a new dual-band bandpass (BPF) fllter with multi-spurious suppression is proposed, which is composed of step- impedance resonators (SIR) and grounded-step-impedance resonators (GSIR). It is shown that the resonant frequencies of GSIR can be obtained similar to SIR. Then, by determining the dimensions of SIR to have a specifled resonant frequencies ratio, the dimensions of GSIR can be calculated. It is also shown that the coupling lengths between SIR and GSIR can create several transmissions zeros and can be used to suppress the unwanted higher order resonant frequencies. A third-order fllter is designed and fabricated to operate at two WLAN frequencies of 2.45GHz and 5.8GHz. The measured results show a rejection level of 24dB up to more than 17GHz (7f1). Simulation and measurement results are in good agreement with each other.

COMPACT SPLIT RING SIR BANDPASS FILTERS WITH DUAL AND TRI-BAND

Multi-band microwave fllters are important for multifunc- tional and miniaturization requirement of portable communication equipment. In this paper, tri-section split ring stepped-impedance res- onator is analyzed, and new compact dual-band and tri-band bandpass fllters are proposed by using split ring stepped-impedance resonators, and the designs are demonstrated by measurement. The new dual- band fllters operate at about 2.4 and 5.5GHz which meet IEEE 802.11 application requirements, and the new tri-band fllters operate at about 2.4{2.6, 3.3{3.6 and 5.2{5.6GHz, and fllter sizes are greatly reduced compared with relative reports. The designed fllters have advantages of compact and miniature structures, low passband insertion losses and good frequency selectivity, all these have prospect to be applied in wireless communication systems.

THIRD-ORDER DUAL-BAND BANDPASS FILTER WITH CONTROLLABLE BANDWIDTHS USING SHORT STUB-LOADED RESONATORS

A compact microstrip-line dual-band bandpass fllter using a short stub-loaded resonator is presented. The resonator is formed by loading one short stub in shunt to a simple uniform impedance line. A key merit of the fllter conflguration is that the center frequency and bandwidth of the flrst passband can be conveniently controlled by properly adjusting the lengths of the short stubs and the coupling between the short stubs, whereas those of the second passband are flxed. To illustrate the concept, a third-order dual-band fllter is designed, fabricated and measured. Simulated and measured results are found to be in good agreement with each other.

HIGH-ORDER DUAL-BAND BANDPASS FILTER WITH INDEPENDENTLY CONTROLLABLE FREQUENCIES AND BANDWIDTHS

A multi-stub-loaded resonator is presented in this paper. The resonators can be conveniently applied to design high-order dual-band bandpass fllters (BPFs). Base on the analysis of the resonator, the flrst two even-mode resonant frequencies are controlled independently by the lengths of the loaded stubs. Two high-order dual-band BPFs using the flrst two even-mode resonant frequencies of the multi-stub-loaded resonators are proposed. The bandwidth of each passband can be adjusted independently by the coupling strength of the adjacent resonators. This paper deals with the analysis and design of the proposed high-order dual-band BPFs as well as the experimental validations of the predicted dual-band performance.

DUAL-BAND BANDPASS FILTER WITH CONTROLLABLE CHARACTERISTICS USING STUB-LOADED RESONATORS

A compact microstrip-line dual-band bandpass fllter with controllable characteristics is presented using a stub-loaded resonator. The resonator is formed by loading one open circuit terminated stub in shunt to a simple uniform impedance line. The passband frequencies of the dual-band fllter can be conveniently controlled by tuning the lengths of stub-loaded resonators. The bandwidth of the flrst passband can be controlled by tuning the parameters of center stub-loaded resonator, and the bandwidth of the second passband is determined by the coupling between the sideward stub-loaded resonators. To illustrate the concept, a second-order dual-band fllter is designed, fabricated and measured. Simulated and measured results are found in good agreement with each other.

MINIATURIZED DUAL-MODE RESONATORS WITH MINKOWSKI-ISLAND-BASED FRACTAL PATCH FOR WLAN DUAL-BAND SYSTEMS

The miniaturized dual-mode dual-band band-pass fllters (BPF) using Minkowski-island-based (MIB) fractal patch resonators are proposed in this paper. The BPF is mainly formed by a square patch resonator in which a MIB fractal conflguration with 2nd order iteration is embedded in the patch. By perturbation and inter- digital coupling, the wide-band and dual-band responses are obtained respectively. For miniaturized wide-band design, at 2.41GHz central frequency it has good measured characteristics including the wide bandwidth of 2.26{2.56GHz (3-dB fractional bandwidth of 12.4%), low insertion loss of 0.72dB, high rejection level (i52:5/i44:9dB), and a patch size reduction with 60.6%. For compact dual-band design, the proposed fllter covers the required bandwidths for WLAN bands (2.20{2.96GHz and 4.74{5.85GHz). The patch size reduction of 78.1% is obtained. Two transmission zeros are placed between the two pass- bands and resulted in good isolation.

VERY MINIATURE DUAL-BAND AND DUAL-MODE BANDPASS FILTER DESIGNS ON AN INTEGRATED PASSIVE DEVICE CHIP

This work presents extremely compact dual-mode and dual-band bandpass fllter designs based on dual-resonance composite resonators developed by using integrated passive device (IPD) technology on a glass substrate. A dual-mode bandpass fllter is also devised using a symmetric composite resonator with a perturbation element of grounding inductor to determine the fllter bandwidth. Additionally, a feedback capacitive coupling path on the proposed dual-mode fllter is implemented to produce three transmission-zero frequencies in the stopband. Furthermore, the proposed dual-band bandpass fllter is designed in a high-density wiring transformer conflguration with magnetic and electric mixed coupling. In addition to individually determining the fractional bandwidth of dual passbands, the magnetic and electric mixed coupling provides multiple transmission zeros to enhance the isolation between the two passbands and greatly improve the stopband rejection.

BALANCED SINGLE- AND DUAL-BAND BPFS USING RING RESONATORS

This paper presents new balanced single- and dual-band bandpass fllters (BPFs), both of which are constructed using two ring resonators. For each BPF, open-circuited stubs are added to one of the two resonators so that the transmitted common-mode (CM) signals can be attenuated, and source-load coupling is established so that two transmission zeros are generated near the edges of each desired difierential-mode (DM) passband to sharpen the passband selectivity. The measurement agrees well with the simulation. For the single-band BPF, the measured minimum DM insertion loss is 1.4dB in the DM passband, in which the CM suppression is larger than 41.6dB. For the dual-band BPF, the minimum DM insertion losses are 1 and 1.35dB in the flrst and second passbands, respectively, in which the CM rejections are larger than 29 and 22dB.

PLANAR MULTIBAND BANDPASS FILTER WITH MULTIMODE STEPPED-IMPEDANCE RESONATORS

Planar multiband bandpass fllters are implemented based on the versatile multimode stepped-impedance resonators (SIRs). The resonant spectrum of a SIR can be calculated as functions of the length ratios for various impedance ratios of the high- and low-impedance sections. Thus, by properly selecting the geometric parameters and designing the input/output coupling structure, the SIRs are feasible to realize multiband multimode fllters. Using a single SIR, a dual- mode dual-band, a dual-mode triple-band or a hybrid dual-/triple- mode dual-band bandpass fllter can be realized. Emphasis is also placed on designing specifled ratios of center frequencies and fractional bandwidths of the passbands. To extend the design ∞exibility, extra shunt open stubs are used to adjust the ratio of the passband frequencies. In addition, sharpness of the transition bands is improved by designing the input/output stages. Simulation results are validated by the measured responses of experimental circuits.

MINIATURIZED DUAL-MODE RESONATORS WITH IMPROVED DOUBLE SQUARE LOOP AND INTER-DIGITAL COUPLE FOR WLAN DUAL-BANDS

A novel dual-mode double square loop resonator (DMD- SLR) for dual-band band-pass fllter (BPF) is presented in this paper. The simple meander loop in DMDSLR is studied to improve the perfor- mance of the conventional DMDSLR. Signiflcant size reductions over 33% are achieved. In addition, the designed meander-loop DMDSLR fllter shows lower insertion loss (2.24 and 2.28dB), higher rejection level (28/56dB and 53/36dB), wider bandwidth (about 8.5% and 28%) at the 2.47 and 5.47GHz bands, respectively. Two transmission zeros are placed between the two pass-bands and result in a good isolation.

COMPACT DUAL-BAND BANDPASS FILTER USING FOLDED SIR WITH TWO STUBS FOR WLAN

A novel compact dual-band bandpass fllter using tri- section stepped impedance resonators (SIRs) is presented for Wireless Local Area Network (WLAN). SIRs and one stub between parallel couple line are employed to realize two satisfactory passbands. Meanwhile, one transmission zero is generated between the two passbands to achieve a high out-of-band rejection. Simulated results show that two central frequencies are located at desired 2.4 and 5.2GHz with 3dB fractional bandwidths of 6.3% and 3.4% respectively. The measured results are in good agreement with the simulated ones.

COMPACT DUAL-BAND BANDPASS FILTER USING IMPROVED SPLIT RING RESONATORS BASED ON STEPPED IMPEDANCE RESONATOR

In this letter, a compact planer dual-band bandpass fllter (BPF) using novel split-ring resonators (SRRs) is proposed. Compared with conventional SRRs, the stepped impedance split ring resonator (SIR-SRR) has better performance on miniaturization. To verify good characteristics of the novel structure, a new resonator-embedded cross- coupled fllter, constructed by a pair of new resonators, is designed. This new fllter has good characteristics of compact size and high selectivity. The improved SRR unit cell has a size of 0:108‚g£0:108‚g (where ‚g is the guided wavelength) at central frequency (2.25GHz) of upper passband. Simulated results show that two central frequencies of the fllter locate at 1.90 and 2.25GHz with 3-dB fractional bandwidths of 1.0% and 7.7%, respectively. The lower passband band is generated by inner resonator with a via hole to gound plane, while the upper passband is created by outer resonator. Moreover, a good out-band performance is shown in this letter. Its stop-bands are extended 0{ 1.85GHz at lower band and 2.4{5.8GHz at upper band with a rejection level of about 20-dB. The measured and simulated results are well complied with each other.

NOVEL COMPACT DUAL-BAND BANDPASS MICROSTRIP FILTER

In this paper, a novel microstrip structure is developed to realize a dual-band bandpass fllter. The proposed bandpass structure uses a microstrip resonator with two independently controlled resonance frequencies producing two frequency bands of interest controlled by adjusting the dimensions of the resonator. Parametric analysis is performed on the structure to determine the optimum dimensions to obtain the desired frequency response and is explained in the paper. The dual-band bandpass fllter developed in this paper exhibits dual operating frequencies at 1390MHz and 2520MHz with 9.85% and 9.92% fractional bandwidths respectively. We achieved a compact second-order dual-band bandpass fllter with controllable resonance frequencies and low insertion losses in the passband with high selectivity. The measured results are in good agreement with simulated results. Additionally, it can be easily fabricated and can be used in applications where miniaturization and compatibility with microstrip technology are of primary concern.

NEW DUAL-BAND BANDPASS FILTER WITH COMPACT SIR STRUCTURE

New dual-band bandpass fllters with compact coupling and sizes reduction are proposed by using split ring stepped-impedance resonators and two paths coupling. In the new design, split ring SIR and defected ground structure are applied not only to reduce fllter size but also to improve the fllter performances. The presented fllters have advantages of compact and novel structures, miniaturization and dual- band with nicer performances such as high selectivity, low passband insertion losses and so on, and these performances are demonstrated by measurement. The new design may be quite useful in wireless communication systems.

DESIGN OF A DUAL-MODE DUAL-BAND FILTER USING STEPPED IMPEDANCE RESONATORS

A microstrip dual-mode dual-band bandpass fllter using stepped impedance resonators (SIRs) is designed for dual-band wireless local area networks (WLANs) applications at 2.4/5.2GHz. By appropriately selecting the impedance ratio (Rz) and length ratio (fi) of the SIRs, the harmonic frequencies can be tuned for generating the dual-bandpass response. Based on SIRs, a dual-mode dual-band bandpass fllter is designed with one transmission zero. To improve the selectivity, another three transmission zeros in stopbands are created by introducing two stubs in input/output (I/O) lines. Two experimental fllters are fabricated. Both simulated and measured results are presented.

TRANSMISSION ZERO DESIGN GRAPH FOR DUAL-MODE DUAL-BAND FILTER WITH PERIODIC STEPPED-IMPEDANCE RING RESONATOR

Compact dual-mode dual-band bandpass fllters are realized with a single periodic stepped-impedance ring resonator. Neither extra resonator nor substrate layer is required for implementing the second passband. Based on the transmission line theory, a transmission zero design graph consisting of the transmission zeros together with the resonant frequencies of the resonator is developed against the space separation angle between the input and output ports. Based on this graph, when the line-to-ring feed structure is implemented, the space angle can be determined for the dual-mode dual-band design with designated zeros near the two passbands. It is believed that this is the flrst design graph for designating the transmission poles and zeros of a dual-mode ring resonator fllter before the excitation structure is realized. Three dual-mode dual-band bandpass fllters are carried out for demonstration. All circuits occupy only 60% of the area of the conventional ring resonator bandpass fllter

DESIGN OF DUAL-BAND BANDPASS FILTERS USING A DUAL FEEDING STRUCTURE AND EMBEDDED UNIFORM IMPEDANCE RESONATORS

In this paper, a simple method and structure to design a dual-band bandpass fllter (BPF) by using a dual feeding structure and embedded uniform impedance resonator (UIR) is presented. In this structure, two passbands can be designed individually and several transmission zeros can be created to improve the band selectivity and stopband performance. The flrst passband is determined by the dual feeding structure and the second passband is determined by the UIR. Moreover, by using the inter coupling in the UIR, the performance of the second passband can be easily tuned without degrading the flrst passband. In order to verify the design concept, two fllter