Bandpass Fllter Research Articles

A COMPACT DUAL-BAND BAND-PASS FILTER WITH WIDE STOP-BAND USING TWO RESONATORS COMBINED BY VIA-HOLE

A compact dual-band band-pass fllter is proposed in this paper. The central frequencies of the passbands are around 2.46GHz and 5.86GHz. There are two resonators located at the top side layer and the bottom side (the CPW) layer, respectively. Dual-resonance operation usually needs two resonators on the same layer to generate two passbands simultaneously. However, in this paper the size can be reduced e-ciently by connecting resonators at two layers through via-holes to implement dual-band performance. Furthermore, the stop- band for this novel fllter with T slot-line, L-line and rectangular micro- strips can be extended to 30GHz. To verify the feasibility of the design above, a dual-band band-pass fllter has been implemented on a Rogers RT5880 substrate (thickness is 0.508mm). This fllter with passbands operated at 2.46GHz and 5.86GHz can flnely meet the IEEE 802.11n wireless local area network (WLAN) bands requirements.

MINIATURIZED WIDEBAND BANDPASS FILTER UTILIZING SQUARE RING RESONATOR AND LOADED OPEN-STUB

In this paper, a miniaturized wideband bandpass fllter utilizing a square ring resonator and loaded open-stubs is proposed. One pair of bent open-stubs characterized as perturbations is installed outside the diagonal corners of the ring, and another pair of loaded open-stubs is added inside the ring resonator. By stretching the perturbation stubs more than half-wavelength of the ring, three pairs of degenerated modes in a ring are split for wideband operation. The flrst two split modes form the dominant passband. Meanwhile, the loading efiect introduced by the loaded open-stubs could move the third split mode into the dominant passband. At the same time, an additional transmission zero is generated by the loaded open- stub, which improves the skirt selectivity. Due to the applying of the perturbation stubs as long as more than half-wavelength, this kind of wideband microstrip ring resonator fllter occupies a smaller size than those conventional ones that based on ring resonator. To verify the mechanism above, a wideband bandpass fllter centered at 3.5GHz is designed, implemented, and fabricated. Measured results of experimental circuit show good agreement with simulated responses.

DESIGN OF RECONFIGURABLE MINIATURIZED UWB-BPF WITH TUNED NOTCHED BAND

A new miniaturized ultra-wideband bandpass fllter with embedded reconflgurable multiband frequency notch function was designed and implemented by embedding all the passive components into a printed circuit board with a high dielectric constant. The proposed fllter consists of compact 2U-shaped DGS resonators shunt connected to parallel coupled lines to achieved frequency notch. To tune the notched band, suitable capacitor elements within the inner/outer U-DGS and RF PIN diode within the outer U-DGS are integrated. A curve fltting formula is derived to show the efiect of the capacitor value on the center frequency of the notched band, which is decreased by 56.7%. These capacitors improved the quality factor and have the efiect of reducing the fllter size by 72% as compared to other fllters. The RF PIN diode in the outer U-DGS acts as a switch to exhibit a band notch covering the bandwidth of the WLAN for IEEE 802.11a/h at 5.5GHz and RFID ISO 18000 series pars 5 in microwave (MW) which is set at 5.8GHz, 6.1GHz and 6.8GHz, and the other bands. RF PIN diodes control the notched band and raises it from 5.25GHz to 6.85GHz (27%) or remove the band notched according to its positions. In order to validate the feasibility of the proposed structure, UWB BPF with center frequency of 6.85GHz is designed, fabricated, and measured. The fllter has passband from 3.2GHz to 10.7GHz and notched band designed to generate stop band from 5.25 to 6.85GHz, and the two transmission zeros are observable at 2GHz and 12.5GHz, respectively by measurement. This paper shows the

A SIMPLE FILTERING-ANTENNA WITH COMPACT SIZE FOR WLAN APPLICATION

This paper presents a simple microstrip flltering-antenna with compact size for WLAN application. The T-shape resonator through an inset coupling structure can be treated as the admittance inverter and the equivalent circuit of the flltering-antenna is exactly the same as the bandpass fllter prototype. With a little extra circuit area, the proposed flltering-antenna has almost twice wider bandwidth, good skirt selectivity and high suppression in the stopband compared to the conventional microstrip antenna.

A NOVEL DUAL-BAND PASSBAND FILTER WITH CONTROLLABLE CENTER FREQUENCIES AND BANDWIDTHS

A high-order dual-band bandpass fllter using novel combined stub-loaded resonators (CSLRs) is presented in this paper. The key merits of the fllter conflguration are that the center frequency and also the bandwidth of each passband can be controlled conveniently. Moreover, it can build the high-order dual-band bandpass fllters using the proposed resonators because of the su-cient coupling through the four symmetric stubs. A flfth-order dual-band bandpass fllter designed at 2.5/3.5GHz was built and tested. The measurement and simulation results agree very well, demonstrating the validity of the method.

A SUBSTRATE INTEGRATED WAVEGUIDE BANDPASS FILTER USING NOVEL DEFECTED GROUND STRUCTURE SHAPE

In this paper, a X-band wideband bandpass fllter based on a novel substrate integrated waveguide-to-defected ground structure (SIW-DGS) cell is presented. In the cell, the DGS is etched on the top plane of the SIW with high accuracy, so that the performance of the fllter can be kept as good as possible. Finally, the fllter, consisting of three cascaded cells, is designed and measured to meet compact size, low insertion loss, good return loss as well as smooth group delay. There is good agreement between the measurement and simulation results.

A NOVEL SYNTHESIS PROCEDURE FOR ULTRA WIDEBAND (UWB) BANDPASS FILTERS

In this paper, a novel synthesis procedure is presented to achieve optimum solution for UWB fllter parameters. It is found that the narrowband approximation is not valid for any arbitrary powered rational type flltering function. For wider bandwidths, the frequency dependent terms have signiflcant efiects on the frequency response. Hence, extracted flltering function cannot be mapped to generalize Chebyshev polynomials. This paper will provide an exact synthesis procedure for step impedance resonators (SIR's) type UWB bandpass fllters. To validate the synthesis procedure prototypes are designed and fabricated. Simulated and measured results show good agreement with proposed theory.

DESIGN OF DEFECTED GROUND BAND PASS FILTERS USING STEPPED IMPEDANCE RESONATORS

In this paper, band-pass fllters based on the microstrip conflguration and utilizing coupled defected ground structures are presented. The 50› microstrip line has a gap discontinuity in the middle and characterized by stepped impedance resonators on either half. The four fractal geometries tested for defected ground are the flrst and second iterations of the modifled Moore curve, the closed staircase curve and a dual concentric closed staircase curve. The fllters have a compact size and planar geometry. The modifled Moore flrst iteration has a measured pass band from 2.27GHz to 11.86GHz, whereas the second iteration has a measured pass band from 1.85GHz to 6.71GHz. The measured pass band of the closed staircase fllter is from 2.38GHz to 7.21GHz. The dual-concentric closed-staircase DGS fllter ofiers a dual-band response with the measured pass band being from 2.41GHz to 5.01GHz and from 5.81GHz to 8.35GHz. All the fllters can have applications in the UWB region. A parametric study showing the efiect of the various controlling parameters is also presented.

AN APPROACH FOR MULTI-BAND BANDPASS FILTER DESIGN BASED ON ASYMMETRIC HALF-WAVELENGTH RESONATORS

This paper presents that the extra passband with two transmission zeros can be obtained by adding shunt open stubs to the asymmetric half-wavelength resonators structure. By using this method, a fourth or even higher passband with good selectivity and compact size can be obtained. Dual-band, tri-band and quad-band bandpass fllters are demonstrated by using this method. The measured bandwidth is 80/180MHz for the dual-band, 60/180/180MHz for the tri-band and 130/360/170/70MHz for the quad-band fllter, respectively. The measured insertion loss for the dual-band, tri-band and quad-band fllter is less than 2.7dB, 2.5dB and 2.9dB at the center frequency. All the simulated results and the measured results agree well.

A COMPACT DUAL-MODE RESONATOR WITH SQUARE LOOPS AND ITS BANDPASS FILTER APPLICATIONS

In order to realize bandpass fllter with Chebyshev and elliptic function responses using a single resonator only, a dual-mode square resonant structure is proposed. Four small square loops are added into a large loop. One of small loops is deflned a perturbation element, other small ones are references. By changing the thickness of the perturbation element with respect to that of a reference element, the resonator can produce a capacitive or inductive coupling between two degenerate modes. The capacitive coupling can acquire an elliptic function characteristic since it can create the transmission zeros on both the lower and upper sides of the pass band, while the inductive coupling cancels them which exhibit a Chebyshev characteristic. Therefore, both Chebyshev and elliptic function responses can be obtained for the fllter. The proposed device is with a wider stopband and more compact in size. Experiment results have been verifled this design.

A DUAL-BAND BANDPASS FILTER WITH A TUNABLE PASSBAND

In this paper, a novel dual-band bandpass fllter with a tunable passband is proposed. Based on two quarter-wavelength resonators and one half-wavelength resonator, dual-band character is designed by introducing two independent coupling paths. The fllter structure is designed and can be divided into two parts. The Transmission Zeros (TZs) are derived through simulation. By varying the reverse bias voltage applied to the varactor diodes which are connected to the resonators, the flrst passband can be independently tuned. The second passband can be easily controlled by the width of the half-resonator. Finally, simulation results show a flrst tunable passband with a constant fractional-bandwidth of 3:9 § 0:3%, a center frequency of 1.472{1.886GHz, and the second passband almost remains constant with a fractional-bandwidth 2.4% at frequency range 2.24GHz. The measurement of the fabricated example shows good agreement with the simulation.

A NOVEL SYNTHESIS TECHNIQUE FOR MICROWAVE BANDPASS FILTERS WITH FREQUENCY-DEPENDENT COUPLINGS

This paper presents a novel synthesis technique for microwave bandpass fllters with frequency-dependent couplings. The proposed method is based on the systematic extraction of a dispersive coupling coe-cient using an optimization technique based on the zeros and poles of scattering parameters representing two coupled resonators. The application of this method of synthesis is illustrated using two examples involving four and flve-pole generalized Chebyshev fllters implemented in substrate-integrated waveguide (SIW) technology. As a dispersive inverter, a parallel shorted stub with an additional septum was used. The septum lends greater ∞exibility to the dimensional synthesis, in that it increases the allowable range of the coupling coe-cients. The measured and simulated results are in excellent agreement, which conflrms the validity of the proposed approach.

NOVEL DESIGN OF A COMPACT TRIPLE-BAND BANDPASS FILTER USING SHORT STUB-LOADED SIRS AND EMBEDDED SIRS STRUCTURE

A novel compact planar triple-band bandpass fllter using two sets of short stub-loaded stepped impedance resonators (SSLSIRs) and a pair of embedded stepped impedance resonators (ESIRs) has been proposed. The SSLSIRs can adjust the bandwidths of the corresponding passbands over a wide range, and the ESIRs employing non 0 - -feed coupled structure with mixed electric and magnetic coupling can obtain an extra transmission zero. The embedded resonators structure can further miniaturize the dimensions of the whole triple-band fllter. The operating frequencies of the SSLSIRs and ESIRs are designed for the applications of the WLAN (2.45/5.2GHz) and WiMAX (3.5GHz) systems, respectively. The simulated and measured results are both presented and show good agreement.

CO-DESIGN OF A COMPACT DUAL-BAND FILTER-ANTENNA FOR WLAN APPLICATION

A co-designed compact dual-band fllter-antenna suitable to be embedded inside a wireless access point (AP) in the 2.45/5.2- GHz wireless local area network (WLAN) bands is presented. The proposed fllter-antenna comprises a loop-loaded dual-band monopole radiator and a microstrip dual-band pseudo-interdigital bandpass fllter. The monopole consists of a uniform width monopole, two identical capacitively loaded magnetic resonators and a top loaded loop. The two magnetic resonators are loaded at the center of the monopole for dual-band operation and the rectangular loop loaded at the top is involved for miniaturization. Instead of using the traditional 50› interfaces, the impedance between the fllter and antenna is optimized to improve the performance. The fllter-antenna and the system circuit board of an AP share the same substrate and ground plane. In this case, the design can fully integrate the circuit board of the AP into an internal fllter-antenna solution. The proposed fllter-antenna provides good selectivity and rejection in out of band regions and omni-directional radiation patterns within the two desired bands. The measured results show good agreement with the simulated ones.

A NOVEL WIDEBAND BANDPASS FILTER USING TRIPLE-MODE SLOTLINE RING RESONATOR

A novel wideband bandpass fllter on a triple-mode slotline ring resonator is proposed in this letter. By attaching two stubs with difierent lengths and/or widths to the symmetric plane of a slotline ring resonator, the frequencies of flrst three resonant modes can be rearranged towards quasi-equal separation. By feeding this slotline resonator using the microstrip feed lines at positions with an angle of 90 - to the symmetrical plane, these three resonant modes can be simultaneously raised up, aiming to form up a wide passband. Meanwhile, a wide upper-stopband can be realized by setting the lengths of two stubs unequally. After the principle of an initial wideband fllter is described, a prototype of compact fllter with internally-loaded stubs is designed with fractional bandwidth of 66% at center frequency of 3.0GHz. Measured results well validate the predicted ones.

NOVEL CAPACITIVE GAP-COUPLED BANDPASS FILTER USING NON-UNIFORM ARBITRARY IMAGE IMPEDANCE

This paper introduces a new design technique for a capacitive gap-coupled bandpass fllter (BPF) using non-uniform arbitrary image impedances. Based on the proposed BPF equivalent circuit model, the fllter's design equations are derived, and they are validated from comparisons of the calculated and simulated results. For this theoretical veriflcation, the BPF using non-uniform arbitrary image impedances is designed using the speciflcations of: center frequency (fc) = 5:8GHz, fractional bandwidth (FBW) = 3:5%, and fllter stage (N) = 3. The calculated and simulated results of the designed fllter show good agreement. The BPF using the proposed design method could provide an advantage that one can arbitrarily determine two difierent image impedances, which ultimately afiects the BPF's coupling gaps and line widths. This could result in suitable fllter dimensions, i.e., gaps and line width, for a conventional low resolution photolithography fabrication although a low or high dielectric constant substrate is used for the design.

DESIGN OF LATTICE FORM OPTICAL DELAY LINE STRUCTURE FOR MICROWAVE BAND PASS FILTER APPLICATIONS

The design of a multi-channel (M = 5) lattice form band pass optical delay line fllter is reported. The fllter synthesis is based on the division of total transfer function into unit blocks and the circuit parameters are obtained by constrained least square method. This band pass fllter has better performance compared with the results obtained in the conventional design techniques. For a fllter of order 35, a stop band attenuation greater than 50dB is achieved. Further, the band pass fllter is introduced in a optical flber link and simulated in Optisystem software, to verify its characteristics.

COMPACT DUAL-MODE FILTER USING MEANDER SHORTED STUB LOADED RESONATORS

To reduce the size and improve the performance, a 4th- order miniaturized dual-mode microstrip bandpass fllter (BPF) is developed. A meander shorted stub loaded resonator is used, and much compact size is obtained. Theoretical model is set up, and the odd and even modes of the BPF are analyzed based on a symmetrical structure. Full wave simulation validates the design method. To verify the design, a fabricated BPF sample has been tested. Experiment result demonstrates that the designed BPF has wider stopband and better selectivity. Its fractional bandwidth and a center frequency are available.

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.

SUSPENDED SUBSTRATE STRIPLINE BANDPASS FILTERS WITH SOURCE-LOAD COUPLING STRUCTURE USING LUMPED AND FULL-WAVE MIXED APPROACH

This paper presents the design of two suspended substrate stripline (SSS) bandpass fllters (BPFs), both with a source-load coupling structure embedded to create a transmission zero (TZ) near each side of the passband edges. For the flrst BPF, the physical circuit layout is proposed flrst and followed by the establishment of an equivalent LC circuit. The optimization of element values of the LC circuit using a circuit-level simulator leads to quick adjustment of the structural parameters of the physical circuit layout with the aid of a full-wave simulator. For the second BPF, the ingenious equivalent LC circuit modifled from that of the flrst one is proposed for bandwidth enhancement, which is achieved by exciting two extra loaded resonances in the passband. With the element values of the LC circuit optimized, proper reshaping the physical circuit layout from that of the flrst BPF is easily accomplished. The presented lumped and full-wave mixed approach is very e-cient in that the circuit- level simulator is used to the largest extent and the time-consuming full-wave simulator is employed only at the later stage of the design. Experiments are conducted to verify the design of the two SSS BPFs and agreements are observed between the measured and simulated data.