Showing papers on "Prototype filter published in 2013"
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31 Jan 2013
TL;DR: In this paper, the authors present a survey of algorithms and architectures for image and signal processing based on order statistics and homomorphies, including adaptive nonlinear filters and median filters.
Abstract: 1. Introduction.- 2. Statistical preliminaries.- 3. Image formation.- 4. Median filters.- 5. Digital filters based on order statistics.- 6. Morphological image and signal processing.- 7. Homomorphie filters.- 8. Polynomial filters.- 9. Adaptive nonlinear filters.- 10. Generalizations and new trends.- 11. Algorithms and architectures.
974 citations
TL;DR: A design methodology for synthesis of active N-path bandpass filters is introduced and a 0.1-to-1.2 GHz tunable 6th-order N- path channel-select filter in 65 nm LP CMOS is introduced, achieving a “flat” passband shape and high out-of-band linearity.
Abstract: A design methodology for synthesis of active N-path bandpass filters is introduced. Based on this methodology, a 0.1-to-1.2 GHz tunable 6th-order N-path channel-select filter in 65 nm LP CMOS is introduced. It is based on coupling N-path filters with gyrators, achieving a “flat” passband shape and high out-of-band linearity. A Miller compensation method is utilized to considerably improve the passband shape of the filter. The filter has 2.8 dB NF, +25 dB gain, +26 dBm wideband IIP3 ( MHz), an out-of-band 1 dB blocker compression point B1dB,CP of +7 dBm (Δf = +50 MHz) and 59 dB stopband rejection. The analog and digital part of the filter draw 11.7 mA and 3-36 mA from 1.2 V, respectively. The LO leakage to the input port of the filter is ≤-64 dBm at a clock frequency of 1 GHz. The proposed filter only consists of inverters, switches and capacitors and therefore it is friendly with process scaling.
156 citations
TL;DR: In this article, a dual-band bandpass filter with independently tunable passband center frequencies and bandwidths is proposed, which is realized using a varactor-loaded transmission line dual-mode resonator.
Abstract: This paper presents a novel approach to the design of tunable dual-band bandpass filter (BPF) with independently tunable passband center frequencies and bandwidths. The newly proposed dual-band filter principally comprises two dual-mode single band filters using common input/output lines. Each single BPF is realized using a varactor-loaded transmission-line dual-mode resonator. The proposed filter also offers switchable characteristics to select either of the passbands (either the first or the second passband only). To suppress the harmonics over a broad bandwidth, defected ground structures are used at input/output feeding lines without degrading the passbands characteristics. From the experimental results, it was found that the proposed filter exhibited the first passband center frequency tunable range from 1.48 to 1.8 GHz with a 3-dB fractional bandwidth (FBW) variation from 5.76% to 8.55% and the second passband center frequency tunable range from 2.40 to 2.88 GHz with the 3-dB FBW variation from 8.28% to 12.42%. The measured harmonic results of the proposed filters showed a rejection level of 19 dB, which is up to more than ten times of the highest center frequency of the first passband without degradation of the passbands.
126 citations
TL;DR: In this article, a tunable bandpass filter using cross-shaped multiple mode resonators (MMRs) and N:1 transformer based external quality factor tuning structures is proposed.
Abstract: In this paper, a tunable bandpass filter using cross-shaped multiple mode resonators (MMRs) and N:1 transformer based external quality factor tuning structures is proposed. The use of a cross-shaped MMR simplifies inter-resonators control while two Qe tuning structures are investigated and incorporated with the MMR to implement simultaneous center frequency agility and narrow and wide bandwidth tuning. Compared with traditional tunable filters, the proposed architecture requires less tuning elements and is easier to realize wideband and high-order tunable filters. Two examples (Filter I and II) are presented to validate the design. Both filters use a single MMR and six tuning elements to achieve a third-order wideband tunable filter. Filter I reports 58% center frequency tuning with constant bandwidth and 14%-64.4% fractional bandwidth (FBW) tuning when center frequency locates at 1 GHz. Filter II achieves larger frequency agility and wider FBW tuning of 82.9% and 95%, respectively, for the same bandwidth and center frequency of Filter I.
100 citations
TL;DR: This paper proposes a method to dramatically reduce the number of unknowns of the optimization problem through approximation of the constraints, so that the optimal solution of the approximated optimization problem can be obtained with acceptable computational complexity.
Abstract: Recently, filter bank multicarrier (FBMC) modulations have attracted increasing attention. The filter banks of FBMC are derived from a prototype filter that determines the system performance, such as stopband attenuation, intersymbol interference (ISI) and interchannel interference (ICI). In this paper, we formulate a problem of direct optimization of the filter impulse-response coefficients for the FBMC systems to minimize the stopband energy and constrain the ISI/ICI. Unfortunately, this filter optimization problem is nonconvex and highly nonlinear. Nevertheless, observing that all the functions in the optimization problem are twice-differentiable, we propose using the $\alpha$ -based Branch and Bound ( $\alpha$ BB) algorithm to obtain the optimal solution. However, the convergence time of the algorithm is unacceptable because the number of unknowns (i.e., the filter coefficients) in the optimization problem is too large. The main contribution of this paper is that we propose a method to dramatically reduce the number of unknowns of the optimization problem through approximation of the constraints, so that the optimal solution of the approximated optimization problem can be obtained with acceptable computational complexity. Numerical results show that, the proposed approximation is reasonable, and the optimized filters obtained with the proposed method achieve significantly lower stopband energy than those with the frequency sampling and windowing based techniques.
95 citations
TL;DR: In this paper, a microstrip lowpass filter is proposed to achieve an ultra wide stopband with 12th harmonic suppression and extremely sharp skirt characteristics, and the operating mechanism of the filter is investigated based on proposed equivalent-circuit model, and an overall good agreement between measured and simulated results is observed.
Abstract: A novel microstrip lowpass filter is proposed to achieve an ultra wide stopband with 12th harmonic suppression and extremely sharp skirt characteristics. The transition band is from 1.26 to 1.37 GHz with -3 and -20 dB, respectively. The operating mechanism of the filter is investigated based on proposed equivalent-circuit model, and the role of each section in creating null points is theoretically discussed. An overall good agreement between measured and simulated results is observed.
84 citations
TL;DR: In this article, a dual-band bandpass filter with controllable frequencies and bandwidths as well as a high out-of-band rejection level is presented, which utilizes a stub-loaded quad-mode resonator.
Abstract: This letter presents a novel dual-band bandpass filter with controllable frequencies and bandwidths as well as a high out-of-band rejection level. The proposed filter utilizes a novel stub-loaded quad-mode resonator. Every two modes, which can be flexibly controlled, are utilized to form a passband with controllable frequency and bandwidth. Source-load coupling and hook-shape feed lines are introduced and high selectivity is achieved. An experimental filter is implemented and the experimental results are presented for validation.
83 citations
26 May 2013
TL;DR: A novel scaling method for efficient stochastic logic implementations of inner products and digital filters by incorporating the filter coefficients into the probability of the selection signals of the multiplexors, which can achieve better signal scaling with lower cost than the one derived from a traditional structure.
Abstract: Stochastic computing has recently gained attention due to its fault-tolerance property. In stochastic computing, numbers are represented by probabilities of sequences. This paper addresses implementation of inner products and digital filters using stochastic logic. Straightforward implementations of stochastic inner products and digital filters lead to significantly large output error. To overcome this, this paper proposes a novel scaling method for efficient stochastic logic implementations of inner products and digital filters. By incorporating the filter coefficients into the probability of the selection signals of the multiplexors, the proposed weighted summation circuit can achieve better signal scaling with lower cost than the one derived from a traditional structure. This paper also presents how to vary the seeds in stochastic filters in order to reduce the correlation. Implementing IIR filters using stochastic logic limits possible pole locations. To overcome this, a new stochastic IIR filter structure is presented that includes a binary multiplier and stochastic-to-binary and binary-to-stochastic converters. Our experimental results show that the proposed architecture for the inner-product unit can lead to more than 12 times reduction in the error-to-power ratio. The stochastic FIR filters can perform the desired filtering function, but their accuracy degrades with the increase of filter order. The direct-form stochastic IIR filters may fail for large filter orders, but their performance can be improved by using cascade-form filter architecture.
76 citations
TL;DR: In this article, a broadband post-loaded electric coupling structure in single-layered substrate integrated waveguide with enhanced coupling is proposed and investigated, which can achieve the maximum electric coupling coefficient of more than 0.11.
Abstract: A broadband post-loaded electric coupling structure in single-layered substrate integrated waveguide with enhanced coupling is proposed and investigated. The proposed structure can achieve the maximum electric coupling coefficient of more than 0.11. The effects of dimensional parameters on the electric coupling are studied by simulation. The proposed structure is verified by designing two bandpass filters, namely, a wideband fourth-order quasi-elliptic filter and a narrowband fourth-order quasi-elliptic filter. The measured results show that the designs are capable of providing the 12% bandwidth for the wideband fourth-order quasi-elliptic filter and the 3% bandwidth for the narrowband fourth-order quasi-elliptic filter at 5.8-GHz WiMax bands.
75 citations
TL;DR: In this article, a new approach to design differential-mode (DM) bandpass filters is proposed and implemented based on the substrate integrated waveguide (SIW) technology, by properly constructing the topologies of SIW resonant cavities, the balanced section of the proposed filter achieves an attractive capacity in simultaneously realizing the desired DM transmission and expected common-mode suppression in a certain band.
Abstract: A new approach to design differential-mode (DM) bandpass filters is proposed and implemented based on the substrate integrated waveguide (SIW) technology. By properly constructing the topologies of SIW resonant cavities, the balanced section of the proposed filter achieves an attractive capacity in simultaneously realizing the desired DM transmission and expected common-mode (CM) suppression in a certain band. In design, the specified DM frequency response is achieved with an equivalent two-port circuit model. To illustrate the possibilities of the new approach, a fourth-order Ku-band prototype is designed and fabricated on a single-layer substrate. Measured results agree well with the predicted counterparts.
74 citations
TL;DR: In this article, a 60 GHz on-chip multimode bandpass filter (BPF) is implemented using a sandwich capacitor, which shows functions of multimode perturbation and stopband control in the BPF design.
Abstract: A 60-GHz on-chip multimode bandpass filter (BPF) is implemented using a sandwich capacitor. The proposed loaded sandwich capacitor shows functions of multimode perturbation and stopband control in the BPF design. An additional magnetic coupling path from the source to the load is introduced to generate two extra zeros. Thus the quasi-elliptical filter response is achieved. The proposed filter implemented with a commercial SiGe BiCMOS process demonstrates a low insertion loss of 4 dB and compact size of only 0.16 mm2.
TL;DR: A new type of a passive filter, called hybrid LC filter, is proposed, based on design guidelines for the passive LC filters, and simulation and test results of the proposed filter in time and frequency domains are shown.
Abstract: This paper provides design guidelines for the passive LC filters Based on these guidelines, a method to design a new type of a passive filter, called hybrid LC filter, is proposed A filter design example accompanies the considerations; simulation and test results of the proposed filter in time and frequency domains are shown
TL;DR: Differential (balanced) microstrip bandpass filters (BPFs) implemented by combining open split ring resonators (OSRRs) and open complementary split ring Resonators (OCSRRs) are proposed in this paper.
Abstract: Differential (balanced) microstrip bandpass filters (BPFs) implemented by combining open split ring resonators (OSRRs) and open complementary split ring resonators (OCSRRs) are proposed. The OSRRs are series connected in both strips of the differential line, whereas the OCSRRs are paired face-to-face and connected between both line strips in a symmetric configuration. For the differential mode, the OCSRRs are virtually connected to ground and the structure can be modeled, to a first-order approximation, by a cascade of series resonators (OSRRs) alternating with shunt resonators (OCSRRs), i.e., the canonical circuit model of a BPF. These filters have the ability to suppress the common mode by properly adjusting the metallic area surrounding the OCSRRs. An order-3 balanced Chebyshev BPF is designed and fabricated to illustrate the possibilities of the approach. The filter does not require vias (contrary to previous single-ended microstrip BPFs based on OSRRs and OCSRRs), filter dimensions are small, and the common mode is efficiently suppressed with more than 20 dB rejection within the differential filter pass band.
TL;DR: The design results included in the paper clearly show the improvement of the proposed PSO technique over earlier reported results.
Abstract: In this paper, a new particle swarm optimization (PSO) based method is proposed for the design of a two-channel linear phase quadrature mirror filter (QMF) bank in frequency domain. The origional particle swarm optimization technique is modified by introducing the concept of Scout Bee from Artificial Bee Colony (ABC) technique for designing a low pass prototype filter having ideal filter characteristics in the passband and stopband regions, and its magnitude response at quadrature frequency is 0.707. The design problem is formulated as a linear combination of passband error and residual stop band energy of the low pass filter, and the square error of the overall transfer function of the QMF bank at the quadrature frequency π/2, in the transition band. The design results included in the paper clearly show the improvement of the proposed PSO technique over earlier reported results.
TL;DR: In this paper, a novel high performance ultra-wideband (UWB) bandpass filter that satisfies FCC UWB specifications is presented, which is based on a composite right/left handed (CRLH) structure consisting of an asymmetric unitcell with a short circuited inductive stub that exhibits stopband rejection level greater than 25 dB at both the lower and upper band edges while maintaining an insertion-loss of less than 0.5 dB across its passband.
Abstract: This paper presents a novel high performance ultra-wideband (UWB) bandpass filter that satisfies FCC UWB specifications. The filter is based on a composite right/left handed (CRLH) structure consisting of an asymmetric unit-cell with a short circuited inductive stub that exhibits stopband rejection level greater than 25 dB at both the lower and upper band edges while maintaining an insertion-loss of less than 0.5 dB across its passband. In addition, a simple and effective technique is proposed to create and control sharp rejection notch-bands within the filter's passband in order to provide interference immunity from undesired radio signals, such as wireless local area networks (WLAN) that co-exist within the UWB spectrum. The proposed technique was verified practically to validate the design methodology. The experimental results of the prototype circuit are presented and compared with the simulation results. The dimensions of the proposed filter are 0.37λ × 0.10λ (i.e., 16.4 × 4.8 mm2). The filter's characteristics and compact size make it suitable for UWB systems.
TL;DR: In this article, a fluidic-based approach for designing tunable coupled resonator bandpass filters is presented, which employs broadside coupled split ring resonators (SRR) with one of their open loop resonators constructed from liquid metal.
Abstract: A fluidic-based approach for designing tunable coupled resonator bandpass filters is presented. These filters employ broadside coupled split ring resonators (BC-SRR) with one of their open loop resonators constructed from liquid metal. The tuning mechanism is based on dynamically moving the liquid metal to reshape the resonator. To demonstrate the concept, a second order Butterworth filter with continuous tuning range from 650 to 870 MHz is designed and experimentally verified by utilizing PTFE tubing filled with liquid metal and Teflon solution. Due to an inductive external coupling mechanism and 180° rotated resonators, the filter exhibits a near constant 5% fractional bandwidth throughout its tuning range with > 10 dB return and <; 3 dB insertion loss. The filter is realized over a 1.27 mm thick Rogers 6010.2LM substrate and has an approximate footprint of 20 × 40 mm2.
28 Mar 2013
TL;DR: This work solves the noise issue of [6] while achieving the same out-of-band linearity and adding 25dB of voltage gain to relax the noise requirement of the subsequent stages.
Abstract: Radio receivers should be robust to large out-of-band blockers with small degradation in their sensitivity. N-path mixers can be used as mixer-first receivers [1] with good linearity and RF filtering [2]. However, 1/f noise calls for large active device sizes for IF circuits and high power consumption. The 1/f noise issue can be relaxed by having RF gain. However, to avoid desensitization by large out-of-band blockers, a bandpass filter (BPF) with sharp cut-off frequency is required in front of the RF amplifiers. gm-C BPFs suffer from tight tradeoffs among DR, power consumption, Q and fc. Also, on-chip Q-enhanced LC BPFs [3] are not suitable due to low DR, large area and non-tunability. Therefore, bulky and non-tunable SAW filters are used. N-path BPFs offer high Q while their center frequency is tuned by the clock frequency [2]. Compared to gm-C filters, this technique decouples the required Q from the DR. The 4-path filter in [4] has only 2nd-order filtering and limited rejection. The order and rejection of N-path BPFs can be increased by cascading [5], but this renders a “round” passband shape. The 4th-order 4-path BPF in [6] has a “flat” passband shape and high rejection but a high NF. This work solves the noise issue of [6] while achieving the same out-of-band linearity and adding 25dB of voltage gain to relax the noise requirement of the subsequent stages.
TL;DR: This paper demonstrates a design of a frequency-agile bandstop-to-bandpass switchable filter that is composed of tunable substrate-integrated cavity resonators and can be switched to have either a bandstop or bandpass response.
Abstract: In this paper, we show a new bandstop filter circuit topology. Unlike conventional bandstop filter circuit topologies, the new circuit topology has inter-resonator coupling structures. The presence of these inter-resonator coupling structures enables convenient switching from a bandstop to a bandpass filter. Using the new bandstop filter topology, this paper demonstrates a design of a frequency-agile bandstop-to-bandpass switchable filter. The filter is composed of tunable substrate-integrated cavity resonators and can be switched to have either a bandstop or bandpass response. Switching is achieved by turning on and off switches placed within the filter structure. A prototype of the proposed design is fabricated and the concept is verified experimentally.
TL;DR: In this article, a third-order tunable diplexer and a third order tunable dual-band bandpass filter with flexible tuning capabilities and high selectivity are proposed.
Abstract: In this paper, a third-order tunable diplexer and a third-order tunable dual-band bandpass filter with flexible tuning capabilities and high selectivity are proposed. Both the diplexer and dual-band filter consist of two passbands that share a common resonator for size reduction. By adding tuning elements in the middle and ends of the common resonator, the resonant frequencies of the even and odd modes can be independently tuned, thus offering flexible tuning for multi-band operations. Also, by adding extra resonators next to the common resonator, high-order tunable multi-band filters can be obtained with higher stopband suppression. The 1.3-2.4-GHz tunable diplexer shows that the two channels can be either independently tuned or simultaneously tuned as desired. The two channels cover a fractional tuning range of 34% and 18.6%, respectively, while keeping high stopband suppressions, higher isolation, and good input impedance matching. Similarly, the 1.1-2.45-GHz tunable dual-band filter shows independent and simultaneous tuning capability operating with good impedance matching and high stopband suppression.
TL;DR: In this paper, split ring resonators (SRRs) were applied to the design of compact bandpass filters for terahertz surface waves on single-wire waveguides, the so-called planar Goubau lines (PGLs).
Abstract: This paper is focused on the application of split ring resonators (SRRs) to the design of compact bandpass filters for terahertz surface waves on single-wire waveguides, the so-called planar Goubau lines (PGLs). Through equivalent circuit models, electromagnetic simulations, and experiments, it is shown that, while a pair of SRRs coupled to a PGL inhibits the propagation of surface waves along the line, introducing a capacitive gap to the PGL switches the bandstop behavior to a bandpass behavior. In order to highlight the potential application of the proposed structure to the design of practical higher order terahertz bandpass filters, two types of compact bandpass filters are designed and fabricated: 1) third-order periodic bandpass filters based on SRR/gap-loaded PGL and 2) coupled-resonator bandpass filters. It is shown that, while the frequency response of the both filter types can be controlled by altering the physical dimensions of the structure, a wider bandwidth can be achieved from the coupled-resonator filters. The design concept and simulation results are validated through experiments.
TL;DR: In this article, a superconducting ultra-wideband (UWB) bandpass filter (BPF) with sharp rejection skirts and miniaturized size using multiple-mode resonator (MMR) is presented.
Abstract: This letter presents a superconducting ultra-wideband (UWB) bandpass filter (BPF) with sharp rejection skirts and miniaturized size using multiple-mode resonator (MMR). The MMR is formed by loading a stepped-impedance open-end stub in shunt to a modified stepped-impedance resonator (SIR). The modified SIR generates three resonant modes within the 3.1-10.6 GHz UWB band, whereas the stepped-impedance open-end stub creates two transmission zeros and two additional resonant modes improving the bandedge steepness. Interdigital coupled-lines are used for the external couplings to enhance the coupling strength. A superconducting UWB BPF is realized with a compact size of 20 mm × 11 mm. The measured results without any tuning show good performance. The insertion loss at the center frequency is 0.58 dB, the return loss is greater than 10.6 dB, and the group delay variation is less than 1.76 ns. Furthermore, the experimental results of the filter are in good agreement with the simulated ones.
13 May 2013
TL;DR: A detailed survey of hybrid active power filters considering converter topologies, supply system and passive filter type is presented in this paper, where the control strategies are discussed in detail and a broad perspective on the status of HAPF technology to researchers and application engineers dealing with power quality is provided.
Abstract: Hybrid active power filter (HAPF) consisting of passive filter and active filter in various configurations to each other has now become preferred technology for harmonic compensation in two wire, three wire and four wire ac power networks with nonlinear loads. This paper presents a detailed survey of hybrid active power filters considering converter topologies, supply system and passive filter type. In addition, the control strategies are discussed in detail. The main aim of this paper is to provide a broad perspective on the status of HAPF technology to researchers and application engineers dealing with power quality. More than eighty research papers are reviewed and classified into categories and subcategories.
TL;DR: In this article, a circuit for differential wideband bandpass filter (BPF) is presented, which works as a bandpass and bandstop filter under differential and common-mode excitation, respectively.
Abstract: A circuit for differential wideband bandpass filter (BPF) is presented. The circuit works as a bandpass and bandstop filter under differential- and common-mode excitation, respectively. Under differential-mode, two transmission zeros are generated by the short-ended parallel-coupled stubs and supply a very sharp differential passband. The circuit parameters are analyzed and given to show the circuit characteristics. Finally, the circuit is implemented using microstrip technology and a differential wideband BPF is designed, simulated and measured. Simulated and measured results are well agreed.
TL;DR: In this article, a unified synthesis method for the bandpass filters based on the alternative J/K inverters and λ/4 microstrip line resonators is proposed, which is applied to design two classes of even-order Chebyshev band-pass filters with fourth and sixth order on microstrip-line topology, which operate at 2.4 GHz with the fractional bandwidths of 10% and 15%.
Abstract: This paper proposes a unified synthesis method for the bandpass filters based on the alternative J/K inverters and λ/4 microstrip line resonators. Firstly, an even-order Chebyshev bandpass filter prototype with equal terminations is transformed to two dual networks based on hybrid J/K inverters and λ/4 resonators. In this work, two adjacent λ/4 resonators are coupled with each other through a semi-lumped via-hole as the K inverter; the tailored method is employed and effectively demonstrated to extract the J/K inverters' values and their respective associated effective lengths. As its application examples, the proposed synthesis method is applied to design two classes of even-order Chebyshev bandpass filters with fourth and sixth order on microstrip-line topology, which operate at 2.4 GHz with the fractional bandwidths of 10% and 15%, respectively. Finally, both classes of filters are fabricated and measured. Simulated and measured results provide a good verification for the theoretical counterparts.
TL;DR: In this article, a waveguide 3rd order bandpass filter was designed and fabricated using SU8 photoresist technology, and tested and presented, with a 53.7 GHz 3-dB bandwidth at a central frequency of 671 GHz.
Abstract: A WR-1.5 band (500-750 GHz) waveguide 3rd order bandpass filter has been designed, fabricated, using SU8 photoresist technology, tested and presented. The filter is composed of three silver-coated SU8 layers, each of the same nominal thickness of 191 μm. This filter structure is based on three offset resonators. This novel structure is ideally suitable for the layered SU8 micromachining process. The filter exhibits a 53.7 GHz 3-dB bandwidth at a central frequency of 671 GHz. The median passband insertion loss is measured to be 0.65 dB and the return loss is better than 11 dB over the whole passband.
TL;DR: In this article, the authors demonstrate the use of absorptive bandstop filters that give anomalously deep notches for a given quality factor, which is used in a fabricated design example to isolate a sensitive wideband LNA from interference in 45-nm SOI complementary metaloxide-semiconductor.
Abstract: A new approach for protecting sensitive receivers through large attenuation and its realization on-chip is presented for the first time. This paper demonstrates the use of absorptive bandstop filters that gives anomalously deep notches for a given quality factor. This approach is used in a fabricated design example to isolate a sensitive wideband LNA from interference in 45-nm SOI complementary metaloxide-semiconductor (CMOS). For reconfigurable RF front-ends, a frequency-agile design is newly developed with Q tunable resonators because an absorptive bandstop filter must balance both intrinsic Q of the resonators and the resonant frequency of the filter. Therefore, the design requires variable resistors, variable capacitors, and intimate coupling of inductors of disparate values. The layout of overlapping inductors on closely spaced metal layers is required for proper absorptive properties. The size of one filter presented in this paper is 310 by 340 μm, making it the smallest absorptive bandstop filter demonstrated so far. Despite using small-size, on-chip low-Q resonators in the bandstop filter design, an attenuation level from 31 to 63 dB and a frequency tuning range from 2.9 to 4.3 GHz are achieved with potential to suppress potential interference or an image frequency signal.
TL;DR: In this article, a novel resonator with modified interdigital fingers and vertical meander line is proposed for the design of a narrow-band filter with a wide stopband, which has a high first spurious frequency.
Abstract: In this paper, a novel resonator with modified interdigital fingers and vertical meander line is proposed. This resonator has a high first spurious frequency and is suitable for the design of a narrow-band filter with a wide stopband. A compact narrow-band six-pole high-temperature superconducting filter at the ultrahigh-frequency band is successfully designed and fabricated with this resonator. The measured out-of-band rejection is better than 75 dB up to 2600 MHz, which is as high as 5.2 times of the fundamental frequency.
TL;DR: In this article, a miniaturized tri-band bandpass filter (BPF) using a multimode stepped-impedance resonator (SIR) with a 0 ° tapped-feed structure is presented.
Abstract: In this letter, a miniaturized tri-band bandpass filter (BPF) using a multimode stepped-impedance resonator (SIR) with a 0 ° tapped-feed structure is presented. The odd- and even-mode fundamental resonant frequencies and the first high-order resonant frequencies of the SIR are utilized to generate dual-mode dual-band response and the tapped side-coupled feed-lines construct an additional passband avoiding occupying extra size. Owing to the 0 ° tapped-feed structure and the intrinsic characteristics of the SIR, multiple transmission zeros are created to improve the selectivity of the filter. The bands of the designed tri-band BPF are located at 1.57 GHz (GPS application), 3.5 GHz (WiMAX application) and 5.8 GHz (WLAN application). Good agreement between the simulated and the measured results is observed.
TL;DR: In this paper, a multilayer substrate integrated waveguide (SIW) filter with an improved stopband using mixed coupled modified trisections (MCMTs) is presented.
Abstract: A novel multilayer substrate integrated waveguide (SIW) filter with an improved stopband using mixed coupled modified trisections (MCMTs) is presented. The proposed filter is composed of two cascade MCMTs embedded in LTCC substrate. Four transmission zeros (TZs) can be generated with only three resonators, where two TZs near the passband are utilised to achieve sharper skirt selectivity, and another two TZs for the upper wide stopand. A 10 GHz experimental filter has been designed, fabricated and measured to validate the proposed method.
TL;DR: In this paper, a multiband bandpass microwave photonic filter (MPF) whose passband number and position can be selected is theoretically analyzed and experimentally demonstrated, which is based on a wideband optical source (WBOS) and a two-order high-birefringence fiber loop mirror (HB-FLM), which serves as slicing filter.
Abstract: A multiband bandpass microwave photonic filter (MPF) whose passband number and position can be selected is theoretically analyzed and experimentally demonstrated. The proposed MPF is based on a wide-band optical source (WBOS) and a two-order high-birefringence fiber loop mirror (HB-FLM), which serves as a slicing filter. Two segments of high-birefringence fiber (HBF) with the lengths of 3 m and 6 m are used in the HB-FLM, and three typical spectral periods or their combinations can be independently achieved by simply adjusting the polarization controllers (PCs) in the HB-FLM. Subsequently, the light source is sliced with uniform or mixing wavelength spacing. A coil of single-mode fiber (SMF) is then used to act as a dispersive medium to introduce time delay between taps. Thus, a single or multiband bandpass response is obtained at the output of a high-speed photodetector (PD). In addition, the passband centered at dc frequency is removed due to the use of phase modulation. All of the radio frequency (RF) characteristics of the proposed MPF show good agreement with the theoretical prediction. It has the merits of good flexibility, high spectrum efficiency, and great potential of extension.