Four-pole Filter Research Articles

Substrate Integrated Folded Waveguide (SIFW) Partial H-Plane Filter with Quarter Wavelength Resonators

In this paper, the design and experiment of a novel substrate integrated folded waveguide (SIFW) partial H-plane bandpass filter, consisting of quarter wavelength resonators, is presented. In the proposed filter, two adjacent quarter wavelength resonators are coupled by connecting an admittance inverter and an impedance inverter alternately. Here, the admittance inverter and impedance inverter are realized by H-plane slot of open-ended evanescent waveguide and H-plane septa of short-ended evanescent waveguide, respectively. In order to validate the new proposed topology, a four-pole narrowband bandpass filter is designed and fabricated using standard printed circuit board process. The tapered line is used as transition between SIFW and microstrip-line for easy integration and measurement. The measured results are in good agreement with simulated results.

Design of waveguide bandpass filter based on nonresonating ‘T’ junctions

A design method for waveguide bandpass filters based on nonresonating ‘T’ junctions is presented. The wideband characteristics of the nonresonating waveguide ‘T’ junction are fully considered in the design method. As a design example, a four-pole waveguide bandpass filter with about 6% fractional bandwidth has been designed and fabricated. The measured results agree well with the calculated results and it shows good in-band equal ripple performance and sharp rejection performance.

New Coupling Scheme for Microstrip Bandpass Filters With Quarter-Wavelength Resonators

A new coupling scheme for microstrip bandpass filters with quarter-wavelength (lambda/4) stepped-impedance resonators is proposed. In the proposed coupling scheme, two adjacent lambda/4 stepped-impedance resonators are coupled by directly connecting an admittance inverter between them. By properly designing the connecting position, one may adjust the coupling coefficient between two resonators so that narrow to broad bandwidth filters may easily be fabricated without coupling gaps. Here, the admittance inverter is realized by a lambda/4 stepped-impedance line. Based on the proposed coupling scheme and the conventional magnetic coupling structure, the filters with narrow or wide bandwidth may be designed and implemented. In addition, folded lines are adopted to make the filter size compact. In this study, a two-pole filter with a 3-dB bandwidth of 5.1% and two four-pole filters with 3-dB bandwidths of 33% and 51% are successfully fabricated. Good agreement between measured and simulated results is observed.

Elliptic-type bandpass filter and bandstop notch filter inspired by metamaterial NRI-TL topology

Compact and highly selective filters can be implemented by loading a transmission line with series printed capacitors and shunt resonant λ/4 stubs resembling the familiar printed negative-refractive-index transmission-line topology. Simulation and experimental results of a microstrip two-stage bandpass filter and a bandstop notch filter are presented. The four-pole bandpass filter exhibits an elliptic-type response with 3% fractional bandwidth. The microstrip bandstop notch filter exhibits a 50 dB deep stopband and a notch Q of 50. Both filters were designed at an operating frequency of 2.0 GHz.

Wideband Cross Coupled Filter Using Split-Ring Resonator Defected Ground Structure

A wideband cross coupled bandpass filter making use of square split-ring resonator (SRR) defected ground structure (DGS) and parallel microstrip feed line is presented in this paper. The coupling between a pair of SRR DGS is much larger than that of the conventional SRR, which is fully investigated and applied to the design of wideband cross coupled filter. By extracting the coupling coefficient of various coupling structures and external quality factors of various feed structures, a SRR DGS four-pole filter with center frequency of 2.2 GHz and bandwidth of 20% is designed and fabricated.

Low-Cost Dielectric-Resonator Filters With Improved Spurious Performance

A dielectric-resonator filter configuration implemented as a single piece of a high-K ceramic substrate is presented in this paper. The proposed filter configuration considerably reduces the cost of the assembly and the integration associated with conventional dielectric-resonator filters. A two- and four-pole filter of this type operating in the TEH01 fundamental mode have been developed, manufactured, and tested. Theoretical designs of the filters are confirmed and supported by measurement results. The wideband spurious performances of the filters are investigated and the improvement of the spurious response is demonstrated theoretically and experimentally for both two- and four-pole filters. Furthermore, a novel triplet structure based on the proposed concept is presented, which provides a new approach to implement nonadjacent couplings for the realizations of asymmetric filtering characteristics. The proposed dielectric-resonator filter configurations can be potentially used to implement dual-mode dielectric-resonator filters. The concept is very attractive for use in low-cost high-Q mass production of wireless filter applications.

HTS Quasi-Elliptic Filter Using Capacitive-Loaded Cross-Shape Resonators With Low Sensitivity to Substrate Thickness

The design and implementation of a four-pole quasi-elliptic filter for X-band radar applications using high-temperature superconductors is presented. The resonators used consist of cross-shape ring resonators with additional interdigital capacitive loads that allow miniaturization with reduction of sensitivity to substrate thickness. The experimental and simulated results are shown together with the power dependence of the filter

Aperiodic artificial substrates for multipole bandpass filters

Though periodic structures have been the focus of intense research for the past decade, in practice, a truly periodic structure is rarely the proper topology to give a desired or specified transfer function. Traditionally, filtering in periodic substrates was shown by creating defects in an otherwise periodic lattice. However, this approach limits the transfer function of the resulting filter. The use of perturbations in the periodicity in order to create multipole filters with arbitrary transfer functions that are not available inside simple periodic substrates is demonstrated. A methodology is presented to design the aperiodic substrates. Measured and simulated four-pole filter responses are shown for both all-dielectric substrates with high-dielectric-constant titania inclusions and metallodielectric substrates with metallic inclusions inside low-temperature cofired ceramics (LTCC). The measured all-dielectric substrate demonstrates a filter at 21.6 GHz with an insertion loss of 1.69 dB and a narrow bandwidth of only 0.89%, indicating quality factors >1000. Filters with specified Chebyshev transfer functions inside LTCC metallodielectric substrates show consistency within <0.5% at 10.89 GHz due to the mature fabrication process.

Study of 2-bit Antenna–Filter–Antenna Elements for Reconfigurable Millimeter-Wave Lens Arrays

This paper presents a new reconfigurable antenna-filter-antenna (AFA) element based on slot antennas and switchable resonators. This reconfigurable AFA can operate in four modes of operation as a three- or four-pole filter, and yields a 2-bit variable phase delay. As a result, the multimode AFA can be used as the building block of 2-bit adaptive lens arrays. This paper details design, modeling, and miniaturization of the reconfigurable AFA, and demonstrates its performance through preconfigured prototypes. The proposed AFA has a loss of 1.4-1.6 dB measured at 32 GHz in both three- and four-pole filter modes, and exhibits a frequency response that is almost insensitive to the angle of incidence. Several proof-of-concept fixed lens arrays have been also fabricated for output beams scanned to 0deg, 15deg, 30deg, 45deg, and 60deg in the E- and H-plane. The measurement results show that the output beam can be scanned to plusmn60deg in both principle planes, with a worst case sidelobe level of less than -11 dB and a scan loss that hardly exceeds the theoretical limit

Novel Dual-Mode Bandpass Filters Using Hexagonal Loop Resonators

Novel dual-mode hexagonal loop resonators with the patch and notch perturbation are proposed in this paper. The field patterns of the degenerate modes and their mode splitting characteristics are investigated. The applications of the dual-mode hexagonal loop resonator as bandpass filters are presented. It is shown that different responses can be realized using only a single dual-mode resonator by changing the position of the perturbation. A coupling and routing scheme is presented to model the operations of these filters. Two- and four-pole filters of this type are demonstrated for the first time. All the theoretical analysis and design procedures have been verified by experimental results

Symmetric dual-mode filter based on substrate integrated waveguide (SIW)

A planar four-pole dual-mode filter with symmetric transmission response based on substrate integrated waveguide (SIW) is proposed. The filter centered at 10 GHz, consisting of two TE102–TE201 dual-mode SIW cavities, is implemented in a single layer substrate by PCB process. A linear microstrip taper is used to implement the transition between 50 Ω microstrip and SIW. The measured results are in agreement with simulated results.

DIELECTRIC RESONATORS LOADED BY FERROELECTRIC VARACTORS FOR TUNABLE Ka BAND FILTER

ABSTRACT Novel design of microwave four-pole band-pass filter based on the tunable waveguide dielectric resonators with the embedded planar (Ba,Sr)TiO3 film ferroelectric varactors is presented. The following operational parameters were obtained after the experomental test in Ka-band: the bandwidth at 1 dB level is about 350 MHz (1.2%), the range of tuning is 570 MHz (1.9%) and insertion losses are no more than 5.0 dB.

Design flexibility of an open-loop resonator filter using similarity transformation of coupling matrix

In this letter, the design flexibility of an elliptic-response open-loop resonator filter is achieved through similarity transformation of the coupling matrix. To verify the proposed method, a compact four-pole elliptic-response bandpass filter is designed using the conventional structure with open-loop resonators. Designed filter has the resonators with very narrow spacing for the required coupling coefficient and it is impossible to implement a filter with wider fractional bandwidth. Two possible configurations to overcome this problem are presented through similarity transformation of the coupling matrix. From this design flexibility, a filter with wider fractional bandwidth is designed with realizable design parameters.

Applications of Layer-by-Layer Polymer Stereolithography for Three-Dimensional High-Frequency Components

A laser-based layer-by-layer additive process, stereolithography, is used to create truly three-dimensional (3-D) structures for high-frequency applications. High aspect-ratio complicated 3-D structures embedded inside of a layer-by-layer package are created by this process. Previously, Q's greater than 3000 and tolerances of /spl sim/0.19% have been achieved for embedded resonators. In this paper, more applications are demonstrated. Particular examples include the integration of a nonplanar monopole antenna coupled to a high-Q embedded cavity with only 0.26% shift in resonant frequency (19.37 GHz) and a slight 0.06% reduction in bandwidth compared to simulation. Stacked cavities and coupling sections within a substrate are also demonstrated to create vertically integrated filters. For 2% bandwidth two-pole filters, insertion losses as small as 0.27 dB are measured. Furthermore, a vertically integrated 1.2% four-pole filter is demonstrated with acceptable performance without tuning after fabrication. These applications illustrate that the laser-based stereolithography process is suitable for the integration of high-frequency and high-Q 3-D structures within a package.

A Silicon Micromachined Four-Pole Linear Phase Filter

A 27-GHz four-pole linear phase filter constructed of micromachined cavities in silicon is presented. The structure of the filter consists of four side-by-side horizontally oriented cavities, which are coupled in turn by evanescent waveguide sections with three direct-couplings and one cross-coupling between the first and fourth cavity resonators. The cavities are reduced-height waveguide resonators and are fed by microstrip lines through slot apertures. A time-domain tuning technique is employed to improve the efficiency of the design synthesis. The measured results are presented and compared to those predicted by a finite-element-method model. The simulated filter response has a bandwidth of 2.2% centered at 27.480 GHz with an insertion loss of 1.4 dB at that frequency. The measured performance indicates a 1.9% bandwidth centered at 27.604 GHz with a deembedded insertion loss of 1.6 dB at that frequency and a measured unloaded Q of 1465.

Theory and Experiment of Dual-Mode Microstrip Triangular Patch Resonators and Filters

In this paper, we report on the results of an investigation into dual-mode operation of microstrip triangular patch resonators and their applications for designing dual-mode bandpass filters. It has been found theoretically that the dual modes can result from the rotation and superposition of a fundamental mode. The characteristics of the dual modes and their mode splitting are described. The applications of this new type of dual-mode microstrip patch resonator in the design of microwave planar filter are presented. A circuit model for operation of this type of filter is proposed. Two- and four-pole filters of this type are demonstrated for the first time. Both theoretical and experimental results are presented.

Millimeter-Wave Tune-All Bandpass Filters

Distributed microelectromechanical varactors on a coplanar waveguide have been used to design a two- and four-pole bandpass tune-all filters. The two-pole initial bandwidth is 6.4% at 44.05 GHz with a mid-band insertion loss of 3.2 dB and with matching better than 15 dB. The four-pole initial bandwidth is 6.1% at 43.25 GHz with a mid-band insertion loss of 6.5 dB and with matching better than 10 dB. The use of microelectromechanical system bridges allows a continuous tuning for both center frequency and bandwidth. The varactors biasing network has been designed so that the center frequency and bandwidth can be tuned separately. The two-pole filter center frequency can be changed from 44.05 to 41.55 GHz (5.6% tuning range), while the bandwidth can be independently changed from 2.8 to 2.05 GHz. The four-pole filter center frequency can be changed from 43.25 to 40.95 GHz (5.3% tuning range) and the bandwidth can be changed from 2.65 to 1.9 GHz.

Miniaturized Superconducting Filter Realized by Using Dual-Mode and Stepped Resonators

In this paper, the design principles of a new miniaturized superconducting planar filter configuration is presented. The configuration is based on the combined use of dual-mode cross-slotted patch resonators and stepped resonators. Four-pole filters exhibiting a quasi-elliptical response and with operating frequencies in K-, L-, and C-bands have been designed as a test vehicle of the new configuration. The analyzed topology exhibits a high degree of miniaturization, requiring less than 50% of the area occupied by filters based on dual-mode or hairpin resonators. The physical origin of the transmission zeros is discussed, deriving equivalent-circuit descriptions that are capable of reproducing the measured frequency response. In order to confirm the validity of the introduced design principles, experimental performances on an exemplary L-band filter, realized using a YBCO film deposited on an MgO substrate and exhibiting a 3% fractional bandwidth, are presented. The measured frequency response obtained at T = 77 K agrees well with the simulations, presenting an insertion loss of 0.1 dB and a power handling of 34 dBm.

14 GHz Tunable Filters Base on Ferroelectric Films

Two new types of microwave four-pole tunable waveguide filters containing planar (Ba,Sr)TiO3 film ferroelectric capacitors are presented. The frequency tuning of the filters is due to the variation of ferroelectric capacitance with applied dc voltage. The parameters of the Ku-band filters are the following: 1 dB bandwidth is ∼0.9%, the range of tuning is 350 MHz and 260 MHz, insertion losses are not more than 4.7 dB and 3 dB respectively.

Compact microstrip resonators for 900 MHz frequency band

A technique to reduce the size of planar resonators is investigated using a transmission line model and a finite-difference time-domain (FDTD) method. New miniaturized square microstrip resonators are proposed for 900 MHz band. The resonators offer low impedance sections leading to a better handling of power. The feasibility of compact filters using the proposed resonators is demonstrated. The input/output coupling lines of a two-pole filter have been positioned in a way that produces a filter response with transmission zeros on the both sides of the pass-band. Sharper skirts and higher out-of-band rejection are obtained for four-pole filters with cross-coupled resonators.