Bandpass Fllter Research Articles

A NEW COMPACT MICROSTRIP UWB BANDPASS FILTER WITH TRIPLE-NOTCHED BANDS

A new microstrip ultra-wideband (UWB) bandpass fllter (BPF) with triple-notched bands is presented in this paper. The circuit topology and its corresponding electrical parameters of the initial microstrip UWB BPF are desired by a variation of genetic algorithm (VGA). Then, triple-notched bands inside the UWB passband are implemented by coupling a square ring short stub loaded resonator (SRSSLR) to the main transmission line of the initial microstrip UWB BPF. The triple-notched bands can be easily generated and set at any desired frequencies by varying the designed parameters of SRSSLR. For veriflcation, a microstrip UWB BPF with triple-notched bands respectively centered at frequencies of 4.3GHz, 5.8GHz, and 8.1GHz is designed and fabricated. Simulated and experimental results are in good agreement.

DUAL-BAND FILTER FOR WIMAX AND WLAN WITH IMPROVED UPPER STOP BAND PERFORMANCE

In this paper, a novel and compact dual-band fllter with enhanced upper stop characteristics has been presented. Dual band pass fllter characteristics are achieved by introducing transmission zero (TZ) in pass band of band pass fllter (BPF). The wide band pass fllter (BPF) is implemented by combining low pass fllter characteristics (i.e., stepped impedance resonator) and high pass fllter characteristics (i.e., short stubs). Closed rectangular ring resonator (CRRR) and open loop rectangular ring (OLRR) combination is used to produce two transmission zeros (TZs). One TZ is placed on the pass band of BPF such that resultant fllter characteristic consists of two pass band. However, the second TZ is placed at edge of the pass band in BPF to improve skirt selectivity. The two pass bands are designed to cover two popular wireless bands namely WiMAX (center frequency f1 (3.5GHz) and WLAN (center frequency f2 (5.7GHz)) bands, i.e., 3.35{3.65GHz and 5.5{5.85GHz respectively. Equi-ripple low pass stepped impedance resonator (SIR) fllter response is responsible for improved and spurious free upper stop band (> 20GHz, i.e., > 6f1) and also provides sharp skirt attenuation at upper stop band. The proposed fllter is implemented on an RT/Duroid 5880 (r = 2:2) substrate with thickness of 0.785mm and surface area of 19 £ 12sq ¢ mm. Good agreement between simulated and measured results ensures that the proposed fllter is a suitable candidate for modern dual band communications.

TUNABLE FILTER-ANTENNAS FOR COGNITIVE RADIO APPLICATIONS

In this paper, frequency-tunable microstrip antennas, for cognitive radio applications, are proposed. The approach is based on electrically tuning the antenna's operating frequency by integrating reconflgurable band pass fllters into wideband antenna structures. The design of an open loop resonator (OLR)-based bandstop fllter, and its transformation to a bandpass fllter, are investigated flrst. Then, the incorporation of the bandpass fllter, with a wideband antenna, is detailed. The same methodology is employed to design cognitive radio pattern and polarization diversity tunable fllter-antennas. A good agreement between the simulated and measured results for the difierent fabricated prototypes is attained.

DESIGN OF H-PLANE INDUCTANCE DIAPHRAGM WAVEGUIDE BAND-PASS FILTER FOR MILLIMETER IMAGING FRONTEND

This study presents an equivalent circuit and a design of an H-plane waveguide bandpass fllter (BPF) with chamfer. Traditionally, only thin inductive diaphragm with no chamfers considered in the direct-coupled cavity theory, but this will lead to di-culties in the BPF manufacturing. During manufacturing process the chamfer cannot be avoided, and its equivalent circuit and efiects on frequency shifting are investigated in this paper. A new design method is proposed in order to compensate the efiect of chamfer in the half-wavelength resonator connection between the inductance diaphragm and the waveguide. A modifled empirical formula and corresponding procedure are provided for designing such fllters. The working center frequency and 3dB bandwidths (BW) are simulated considering difierent chamfer radius. The simulated center frequencies are 18GHz, 26GHz, 34GHz and 42GHz, and BWs are 2.265%, 2.5%, 10%, 15% and 20%. Results show that the modifled formula, which conforms better with the simulated results, is superior to the traditional formula. Two H-plane waveguide BPFs are manufactured with center frequency 26GHz with 2.5% BW and 34GHz with 2.265% BW. The results of the modifled formula are in good agreement with measured ones.

UWB BANDPASS FILTER WITH HYBRID STRUCTURE AND TWO TRANSMISSION ZEROS IN THE NOTCHED BAND

An ultra-wideband (UWB) bandpass fllter (BPF) with hybrid coplanar waveguide (CPW)/microstrip structure is introduced in this paper. Then a pair of lowpass fllters is integrated on the CPW feed lines to achieve a good out-of-band rejection. At last, a notched band with two transmission zeros is realized at 5.8GHz by using a symmetric E-shaped slot-line and etching slots on microstrip resonator. Two transmission zeros are realized in the desired notched band, and out-of band rejection is more than 32dB. In order to prove the validity, the proposed fllter is fabricated and measured, and the measured results are in good agreement with simulated ones.

DESIGN OF FILTERING MICROSTRIP ANTENNA USING FILTER SYNTHESIS APPROACH

Design, simulation, and measurement of a compact flltering microstrip antenna is presented. A feed line, two hairpin resonators, and a rectangular patch are integrated to form the flltering antenna. The elements together function as a third order bandpass fllter with Chebyshev equal ripple response of 0.043dB at midband frequency of 2.0GHz. The rectangular patch acts not only as a radiating element, but also as the last resonator of the bandpass fllter. The proposed flltering antenna exhibits good out-of- band gain suppression, ∞at in-band gain response, good selectivity at the band edges, and well-shaped radiation pattern.

NOVEL BAND-NOTCHED UWB BANDPASS FILTER USING MICROSTRIP/SLOTLINE RING RESONATORS

A novel ultra-wideband (UWB) bandpass fllter (BPF) with notched band based on microstrip/slotline ring resonators is presented in this paper. The UWB BPF is fabricated with two microstrip ring resonators on the top copper layer and a slotline ring resonator on the bottom ground layer. Thus, an ultra-wide passband can be achieved owing to the coupling efiects and microstrip/slotline transitions of these three ring resonators. Then, a notched band which is created at 8.0GHz for satellite communication system is designed based on loaded short-circuited stubs. Both the simulated and measured results show that this compact UWB BPF has good performances of wide passband and notched band.

COMPACT MICROSTRIP UWB BANDPASS FILTER WITH TWO BAND-NOTCHES FOR UWB APPLICATIONS

A new microstrip ultra-wideband (UWB) bandpass fllter (BPF) with dual sharply rejected notched bands based on E-shaped resonator is proposed in this paper. The basic UWB BPF is designed using two microstrip interdigital coupled lines and one rectangular patch multiple-mode resonator (MMR). Then, to achieve dual band-notched performance, the proposed dual-mode E-shaped resonator is investigated and coupled to the rectangular patch multiple-mode resonator of the basic UWB BPF. To validate the design theory, a microstrip UWB BPF with two notch-bands centered at the frequencies of 5.8GHz and 8.0GHz, respectively, is designed and fabricated. Both simulation and experimental results are provided with good agreement.

A NOVEL POWER DIVIDER INTEGRATED WITH ONE BANDPASS FILTER

A novel compact wideband inphase multilayer power divider based on slotline-to-microstrip coupling structure is presented in this paper. To improve the isolation between output ports, this power divider breaks the conventional half-wavelength slotline conflguration and introduces a lumped resistor. A wideband bandpass fllter integrated with the power divider is designed to allow the power divider to reject the undesired signals located in adjacent frequency channels. This fllter consists of two E- shape units. In order to improve its performance at low frequency band, a lumped capacitor is bridged between the two E-shape units. As an example, a wideband power divider combining with a bandpass fllter is designed and fabricated. The experimental results show that the proposed power divider has a low insertion loss, high isolation, good return losses at all ports, good amplitude and phase balance, as well as ∞at group delay over the wide frequency band from 3.5GHz to 10GHz. In addition, the width of upper stopband reaches up to 3.8GHz (12.9GHz{16.7GHz) corresponding to attenuation more than 20dB.

COMPACT MICROSTRIP UWB BANDPASS FILTER WITH TRIPLE-NOTCHED BANDS AND WIDE UPPER STOPBAND

A novel compact ultra-wideband (UWB) bandpass fllter (BPF) with triple sharply notched bands and wide upper stopband is proposed. The basic UWB BPF is composed of two microstrip interdigital coupled lines and one multiple-mode resonator (MMR). Then, to achieve triple band-notched performance, the proposed triple-mode stepped impedance resonator (TMSIR) is studied and coupled to the interdigital coupled lines of the basic UWB BPF. To validate the design theory, a microstrip UWB BPF with three notched bands respectively centered at 5.2GHz, 5.8GHz, and 6.8GHz is designed and fabricated. Both simulated and experimental results are provided with good agreement.

A NOVEL APPROACH TO DESIGN OF MICROSTRIP UWB BANDPASS FILTER USING MODIFIED GENETIC ALGORITHM

A novel approach to design microstrip ultra-wideband (UWB) bandpass fllter (BPF) using modifled genetic algorithm (MGA) is proposed in this paper. To achieve high e-ciency and accuracy, conventional GA is modifled. By improving the fltness evaluation, selection, crossover, and mutation, the two possible drawbacks of conventional GA, i.e., slow rate of convergence and local-best solution, are overcome. The modifled genetic algorithm is then applied to simultaneously search for the appropriate circuit topology and the corresponding electrical parameters with UWB characteristic. To demonstrate the efiectiveness of the novel approach, a new microstrip UWB BPF is designed and fabricated. Measurement results agree well with the design index and full-wave EM simulated results.

DESIGN OF A COMPACT AND HIGH SELECTIVITY TRI-BAND BANDPASS FILTER USING ASYMMETRIC STEPPED-IMPEDANCE RESONATORS (SIRS)

In this article, a compact tri-band microstrip bandpass fllter (BPF) using asymmetric stepped-impedance resonators (SIRs) is proposed. Only one set of asymmetric SIRs are used in designing this fllter to achieve triple passband response with high selectivity and band-to-band isolation level. By properly selecting the impedance and electrical length ratios of the asymmetric SIRs, the tri-band BPF is designed. By using a cross-coupled conflguration and 0 - feed structure, high selectivity frequency responses with six transmission zeros are achieved. The three bands of the proposed tri-band fllter are located at 1.57/3.9/7GHz, respectively, and the circuit size is much smaller in comparison with previous works using the same substrate. Measured results are in good agreement with electromagnetic (EM) simulation.

COMPACT TRI-BAND BANDPASS FILTER FOR WLAN AND WIMAX USING TRI-SECTION STEPPED-IMPEDANCE RESONATORS

In this paper, a compact tri-band microstrip bandpass fllter (BPF) using tri-section stepped- impedance resonators (TSSIRs) with open stub line and zero-degree feed line is presented. Three tunable passbands are achieved by changing the ratio of impedance. By adding the open stub line, the frequency responses of tri-band at 2.4GHz/3.5GHz/5.2GHz can be obtained precisely. With a proper length of the cone-shaped zero-degree feed structure, we can obtain transmission zeros in stopbands and better return loss in passbands. The proposed tri-band BPF has high selectivity and is simple in fabrication.

COMPACT MICROSTRIP BANDPASS FILTER IMPROVED BY DMS AND RING RESONATOR

In this paper, complementary split ring resonators (CSRRs) as band-stop elements are used in combination with coupled microstrip lines as high and low pass elements to design and fabricate very compact bandpass fllter (BPF) having controllable characteristics. The proposed fllter provides several advantages such as compactness (occupying area less than 0:1‚g £ 0:1‚g in which ‚g is calculated at center frequency of pass band), sharp rejection, suitable insertion loss (IL 3-dB bandwidth of roughly 2GHz from 0.7GHz to 2.7GHz, i.e., more than 115% FBW), good return loss (RL less than i8:5dB in all of the bandwidth) and low cost. Defected Microstrip and Ring Resonator Structures have been used for eliminating the created spurious pass band in upper frequencies. The simulation results have been done with full-wave softwares, i.e., CST MWS and ANSYS HFSS by time and frequency domain solvers, respectively. Also, the equivalent lossless lumped circuit of total structure has been obtained and simulated by ADS software. These simulated results show good agreements with experimental ones.

NOVEL COMPACT TRI-BAND BANDPASS FILTER USING MULTI-STUB-LOADED RESONATOR

In this paper, a compact tri-band bandpass fllter (BPF) using multi-stub-loaded resonator with controllable frequencies is presented. The multi-stub-loaded resonator consists of a main transmission line, two open stubs and a short stub. Characterized by using even- and odd-mode analysis, it is found that the resonator consists three modes, and the modes can be controlled individually, which enables convenient designs of tri-band BPFs. To demonstrate the proposed idea, a tri-band BPF with operating frequencies of 2.45, 3.8 and 5.15GHz is implemented. Five transmission zeros are generated near the passband edges, resulting in high skirt selectivity. The total size of the fllter is 0.19‚g £0:13‚g, featuring compact size. The comparisons of the measured and simulated results are presented to validate the theoretical predications.

A COMPACT TRIPLE-MODE BANDPASS HMSIW FILTER

A simple method for designing a triple-mode bandpass fllter is presented in this paper. Triple-mode is achieved by using half-mode substrate integrated waveguide (HMSIW) cavity. Three perturbation metal vias were introduced for shifting resonant modes. The resonant frequencies of these modes can be adjusted by the location and the diameter of perturbation vias properly. In order to improve the out-of-band rejection, the CPW-to-SIW transition was added. A triple-mode HMSIW fllter with the center frequency of 13GHz was designed and fabricated. The measured fractional bandwidth is 35% with a transmission zero located at 20.4GHz. Good agreement is observed between simulation and measurement.

DESIGN OF A MINIATURIZED DUAL-BAND BANDPASS FILTER WITH HIGH SELECTIVITY

In this paper, a miniaturized dual-band bandpass fllter with high selectivity and band-to- band isolation is presented. The fllter consists of two quarter-wavelength stepped impedance resonators (SIRs) which share a common grounded via-hole and two symmetrical half-wavelength SIRs which are embedded into the inner space to reduce the size of the fllter. Two independent mixed coupling paths which are created by the coupling between these SIRs introduce two difierent passbands. Five transmission zeros (TZs) are generated near the two passbands to achieve high frequency selectivity and band-to-band isolation. To validate the design theory, a dual-band fllter operating at 2.45 and 5.2GHz was designed and fabricated. The size of the proposed fllter only occupies 0:095‚g £ 0:109‚g and the measured 3dB fractional bandwidth (FBW) of the flrst and second passbands is 11.5% and 7.4% respectively. The measured results are in good agreement with the simulated results.

A FOLDED SIR CROSS COUPLED WLAN DUAL-BAND FILTER

A compact cross-coupled dual-band bandpass fllter based on folded Stepped Impedance Resonators (SIRs) with four controllable transmission zeros is proposed in this paper. A pair of stepped impedance tapped lines is utilized to improve the dual band impedance matching, which reduces the insertion loss of the fllter; meanwhile the tapped lines are also coupled with non-adjacent resonators to produce transmission zeros to improve skirt characteristics. At the end of this paper, the simulated and measured results are compared with each other, and good agreement is achieved.

PLANAR BANDPASS FILTER WITH 100-DB SUPPRESSION UP TO TENFOLD PASSBAND FREQUENCY

This paper proposes a miniature microwave bandpass fllter. It comprises quasi-lumped suspended substrate stripline resonators of a new type. Their common substrate consists of two contiguous dielectric layers. Every resonator in the fllter has three parallel strip conductors. Two of them are placed on the outer substrate surfaces and the rest is placed inside the substrate. The fllter of the sixth order was designed with the use of special optimization rules that are universal for all resonator fllters. The substrate of the fabricated fllter was made of RT/Duroid 5880 (r = 2:2, tan- = 0:002) with thickness of 0.127mm. It has dimensions of 12mm £ 45:5mm. The measured passband has a center frequency of 1.01GHz, 3-dB fractional bandwidth of 11%, and minimum insertion loss of 1.4dB. The 100-dB upper stopband extends up to 10.5GHz.

BAND-NOTCHED ULTRA-WIDEBAND BANDPASS FILTER USING DUAL-MODE RESONATOR LOADED SLOTLINE

In this article, a novel band-notched ultra-wideband (UWB) bandpass fllter based on hybrid microstrip/slotline structure is proposed. A quad-mode stubs-loaded slotline resonator is fed by two orthogonal microstrip lines and ultra-wideband bandpass characteristic is excited. A stub-loaded dual- mode microstrip resonator is externally loaded to the quad-mode slotline resonator, and a notched band with sharp roll-ofi characteristic is achieved. The circuit model for the dual-mode microstrip resonator loaded slotline is given and analyzed. The proposed fllter is designed and fabricated. Simulated and measured return losses are i12dB/i18dB and i18dB/i10dB in lower and higher passband. The return loss in the notched band is greater than 15dB.