Stopband Characteristics Research Articles

A New Algorithm for Wire Fault Location Using Time-Domain Reflectometry

In time domain reflectometry (TDR) attenuation and dispersion of the reflected signal limit the reachable accuracy for wire faults location. Because time of flight is evaluated, the wire faults with small impedance changing are difficult to locate. In this paper, a novel method for the TDR-based wire fault detection is presented by transfer function analysis in the time domain. For the determination of the transfer function, a deconvolution should be carried out. Thereby, an inverse problem is to be solved by an adaptive filter approach. Adaptive filters are able to reduce spurious noise of the deconvolution and lead to an acceptable deconvolution estimate. Therefore, a high signal-to-noise-ratio can be reached. The filter's stopband characteristics are optimized by optimization technique to reduce the noise components of the transfer function in the frequency domain. For that a nonlinear fitting procedure is proposed using the Riad-Parruck optimization criterion. The developed method can locate both hard faults (open and short circuits) and soft faults with small impedance changes, and identify the type of wire faults simultaneously in a controlled laboratory environment (without the impedance changes from mechanical vibration, movement, and moisture). The algorithm using adaptive filters and optimization techniques is proposed in this paper for the traditional TDR method, but it is general for most other reflectometry approaches. The estimated wirings are coaxial cables and twisted pair cables, which are used in electrical and power distribution systems.

Dual-Band Superconducting Bandpass Filter Using Quadruple-Mode Resonator

A dual-band high-temperature superconducting (HTS) bandpass filter (BPF) using a quadruple-mode resonator is realized in this paper. The resonator consists of a half-wavelength uniform impedance resonator, an open stub in a symmetrical plane, and two spiral open stubs at the two sides of the symmetrical plane. Distinct characteristics of the quadruple-mode resonator are investigated by using even/odd mode theory, and the design graphs are given to analyze the dual-band filter. A dual-band HTS BPF with central frequencies of 1.8 GHz for GSM applications and 2.4 GHz for wireless local area network applications is designed using the proposed quadruple-mode resonator, which is fabricated by depositing YBCO films on a 0.5-mm-thick MgO substrate. Its size occupies only 13 mm × 17 mm. Measured results demonstrate that an insertion loss within the passbands is less than 0.25 dB. In addition, a transmission zero is achieved in-between two passbands, and two transmission zeros are realized in the upper stopband of the higher passband, which improve the skirt selectivity and stopband characteristics of the filter.

MULTILAYERED LOW PASS MICROSTRIP FILTER USING CSRR

In the present paper a multilayered microstrip low pass filter using complementary split ring resonator is proposed. A design for prominent stop band characteristics with minimized ripples is presented, while maintaining the filter pass-band performance. By properly designing and integrating the complementary split ring resonators with the low pass filter, the proposed structure exhibit superior pass band and stop band characteristics by eliminating unwanted spurious signals. Since the literature is multi-layered, no structure is designed at the ground plane and the problem of distortion of ground plane structure while packaging is resolved. The measured results indicate that the proposed structure achieves significantly improved band characteristics with minimum distortion, when compared with the simulated one.

A Wideband and Compact EBG Structure With a Circular Defected Ground Structure

We propose a new analysis method to determine the bandgap characteristics of an electromagnetic bandgap structure with a defected ground structure (DGS). The proposed method is based on a 1-D segmented transmission line model and a piecewise linear approximation of Zo within a unit cell. Although the previous method is only applicable to rectangular DGSs (RDGSs), the proposed method is applicable to any DGS shapes. As an example, the proposed method is applied to a circular DGS and shows a good agreement with full-wave simulations of the unit cell and measurements of 11 × 11 unit cells. The circular DGS achieves a 15% improvement in the stopband bandwidth over the RDGS with the same perforation area. The proposed method allows us to explore a variety of DGS shapes in the search for better stopband characteristics. It also offers the basis for numerical optimization techniques to be used in synthesizing DGS shapes to meet required stopband characteristics.

Design of Microstrip LPF with Sharp Cut-off Frequency and Wide Stopband

AbstractA novel lowpass filter with wide stopband and sharp skirt characteristics is proposed. To obtain the applicable lowpass filter, several cells of coupled T-shaped resonator, U-shape and dumbbell-shaped resonators are connected in series. The proposed filter has low insertion loss, high return loss in the passband and wide stopband. The transition band is from 3.18 to 3.29 GHz with −3 and −20 dB, respectively. Results of the fabricated filter exhibit a roll-off and relative stopband bandwidth of 217 and 137%, respectively. Measurement and simulation results show good agreement.

Analysis of signals propagating in a phononic crystal PZT layer deposited on a silicon substrate

The design of a stop-band filter constituted by a periodically patterned lead zirconate titanate (PZT) layer, polarized along its thickness, deposited on a silicon substrate and sandwiched between interdigitated electrodes for emission/reception of guided elastic waves, is investigated. The filter characteristics are theoretically evaluated by using finite element simulations: dispersion curves of a patterned PZT layer with a specific pattern geometry deposited on a silicon substrate present an absolute stop band. The whole structure is modeled with realistic conditions, including appropriate interdigitated electrodes to propagate a guided mode in the piezoelectric layer. A robust method for signal analysis based on the Gabor transform is applied to treat transmitted signals; extract attenuation, group delays, and wave number variations versus frequency; and identify stop-band filter characteristics.

Conditions for Lth-band filters of order 2N as cascades of identical linear-phase FIR spectral factors of order N

This paper presents formulas for the number of optimization parameters (degrees of freedom) when designing Type I linear-phase finite-length impulse response (FIR) Lth-band filters of order 2N as cascades of identical linear-phase FIR spectral factors of order N. We deal with two types of degrees of freedom referred to as (i) the total degrees of freedom DT, and (ii) the remaining degrees of freedom DR. Due to the symmetries or antisymmetries in the impulse responses of the spectral factors, DT roughly equals N/2. Some of these parameters are specifically needed to meet the Lth-band conditions because, in an Lth-band filter, every Lth coefficient is zero and the center tap equals 1/L. The remaining DR parameters can then be used to improve the stopband characteristics of the overall Lth-band filter. We derive general formulas for DR with given pairs of L and N. It is shown that for a fixed L, the choices of N, in a close neighborhood, may even decrease DR despite increasing the arithmetic complexity, order, and the delay.

Guest Editorial: Advanced Techniques for Efficient Electronic System Design

This special section in Circuits, Systems, and Signal Processing on Electronic System Design (CSSP) contains five papers which present highly interesting state of the art methodologies and circuits relating to different important aspects of electronic system design including the multi-standard communication, digital watermarking, memory integrity detection and protection in embedded systems, information security in systems on chips (SoC), and elliptic curve cryptography (ECC). Channelization is an essential computation-intensive function for multi-standard communication. The paper entitled “A Low-Complexity Uniform and Non-uniform Digital Filter Bank Based on an Improved Coefficient Decimation Method for MultiStandard Communication Channelizers” by Ambede et al. provides an efficient lowcomplexity solution for this important function. In this paper, the authors present a novel filter bank (FB) design technique based on the combination of the conventional coefficient decimation method (CDM) and the recently proposed modified coefficient decimation method. It is shown that the proposed FB has superior stop band and transition band characteristics, and involves significantly lower complexity compared with the conventional CDM-based progressive decimation filter bank (PDFB). The proposed approach provides uniform as well as non-uniform subbands to be used

High Isolation Microstrip Diplexer with Enhanced Stopband Characteristics for GSM and WLAN Application

ABSTRACTIn this article, a high‐isolation microstrip diplexer with enhanced stopband characteristics is presented for GSM and Wireless Local Area Network (WLAN) application. The proposed diplexer consists of two compact bandpass filters (BPFs) using short‐circuit centered stepped impedance resonators (SCSIRs), operated at 1.8 and 2.45 GHz, respectively. Due to the intrinsic characteristics of the SCSIRs, multiple transmission zeros can be generated for high selectivity and wide upper‐stopband. By locating the transmission zero of one channel at the passband of the other channel, and utilizing good impedance matching between two BPFs, high output isolation can be achieved. A microstrip diplexer prototype is designed and fabricated. The upper‐stopband of two channels in experiment is extended up to 10.2 GHz with an insertion loss larger than 28 dB. Meanwhile, the measured isolation greater than 48 dB in GSM passband and more than 52 dB in WLAN passband is achieved between two channels. A satisfactory agreement between the simulated and measured results validates the proposed configuration. The size without the 50‐Ω feed lines is only in which is the guided wavelength at 1.8 GHz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2990–2993, 2013

Granular metamaterials for vibration mitigation

Acoustic metamaterials that allow low-frequency band gaps are interesting for many practical engineering applications, where vibration control and sound insulation are necessary. In most prior studies, the mechanical response of these structures has been described using linear continuum approximations. In this work, we experimentally and theoretically address the formation of low-frequency band gaps in locally resonant granular crystals, where the dynamics of the system is governed by discrete equations. We investigate the quasi-linear behavior of such structures. The analysis shows that a stopband can be introduced at about one octave lower frequency than in materials without local resonances. Broadband and multi-frequency stopband characteristics can also be achieved by strategically tailoring the non-uniform local resonance parameters.

Design of a wide-stopband bandpass filter using stepped impedance resonators

In this paper, a compact bandpass filter (BPF) with improved stopband characteristics using stepped impedance resonators (SIRs) is proposed. The filter consists of two quarter-wavelength SIRs with radial stubs and a PI-network of capacitance, which is used to suppress the upper frequency spurious signals. An odd- and even-mode analysis is adopted considering the structure’s symmetry. A new BPF centered at 1.57 GHz has been designed and fabricated to verify the validity of the proposed method. Measured results are in good agreement with the electromagnetic simulation. The frequency selectivity was enhanced via introducing two finite transmission zeros (TZs) near the passband, located at 1.21 GHz with 43.5 dB rejection and 3.10 GHz with 62.3 dB rejection, respectively. The spurious frequencies of the upper stopband are suppressed better than 20 dB from 2.07 to 16.25 GHz. And the circuit only occupies 0.09 λg × 0.09 λg.

Design of compact bandpass filter with enhanced stopband characteristics

In this paper, a compact third-order bandpass filter with enhanced stopband characteristics is proposed. The filter consists of three stepped impedance resonators, where one is embedded into the other two resonators for compact size. Multiple transmission zeros (TZs) can be realized near the passband by introducing frequency-dependent coupling between the nonadjacent resonators for enhanced frequency selectivity. Besides, defected ground structure is employed to suppress the harmonics over a broad bandwidth. A new filter centered at 1.51 GHz has been analyzed, simulated, and fabricated to verify the validity of the proposed method. The measured results show that there are three finite TZs near the passband, which are located at 1.1 GHz with 62.1 dB rejection, 1.76 GHz with 34.2 dB rejection, and 2.48 GHz with 37.2 dB rejection, respectively. And, the spurious frequencies of the upper stopband are suppressed below 20 dB from 1.7 to 25 GHz.

Design of ultra‐wideband bandstop filter using defected ground structure

A simple wideband bandstop filter which yields equal ripples in the stopband is described. The filter comprises only two resonators and a connecting transmission line. Ultra-wide stopband characteristic is achieved by realising three transmission zeros near the passband edges. Stopband rejection depth and bandwidth can be controlled by impedances of the configuration. The defected ground structure is chosen to realise the high impedance line. To validate the proposed topology, a compact microstrip bandstop filter centred at 1.5 GHz with a measured 20 dB rejection bandwidth of about 139% is fabricated.

Compact tunable bandpass filter with wide tuning range and enhanced stopband characteristics

A compact tunable bandpass filter (BPF) with wide tuning range and enhanced stopband characteristics based on low-temperature co-fired ceramic technique is proposed. The wide tuning range is realised by properly introducing an axial coupling structure. Three transmission zeros are obtained near the passband for enhanced frequency selectivity by introducing mixed electric/magnetic (E/M) coupling between the source/load and the taped inductor. Back-to-back varactor diodes are adopted to improve linearity characteristics. A tunable BPF with a 120% tuning range from 370 to 850 MHz has been designed and fabricated to verify the proposed design concept. The measured results are in good agreement with the electromagnetic simulation. The circuit occupies only 4.0 × 3.0 × 1.6 mm3.

A Compact Ultra-Wideband Monopole Antenna with Dual Bandstop Characteristics

A compact and simple ultra-wideband microstrip-fed planar antenna with double bandstop characteristic is presented. The antenna consists of a rectangular monopole and two W-shaped slots inserted into the radiating patch and the truncated ground plane. By using a W-shaped slot defected ground structure (DGS) in the feedline, a stopband of 800 MHz (from 5.1 to 5.9 GHz) for band rejection of wireless local area network (WLAN) is achieved. To obtain the other stopband (from 3.7-4.4 GHz), a same shaped slot is etched into the monopole. Moreover, the two stopbands can be controlled by adjusting the length of the slot respectively. The simulation results show that the designed antenna, with a compact size of 38.5 mm×42.5 mm, has an impedance bandwidth of 2.811 GHz for voltage standing wave ratio (VSWR) less than 2, besides two frequency stopbands of 3.74.4 GHz and 5.15.9 GHz. Moreover, the main features including omnidirectional H-plane radiation patterns and the appropriate impedance characteristic are achieved by beveling the radiating patch and the microstrip-fed line of the proposed antenna.

Design of terahertz band-stop filter based on a metallic resonator on high-resistivity silicon wafer

In this paper, we present a terahertz (THz) band-stop filter realized by fabricating a metallic T-shaped resonator pattern on the high-resistivity silicon wafer. The filter exhibits two typical band-stop response characteristics depending on the incident direction of electric field with respect to the T-shaped resonator. When the long and the short arms of the T-shaped resonator were electrically polarized by changing the incident THz wave transmission directions, the corresponding central frequencies of the band-stop filter were found to be 0.436 THz at −42dB and 0.610 THz at −28 dB, respectively. Using three-dimensional (3D) finite-integral time-domain simulations, the band-stop filter was designed, which can operate in the wavelength between 0.2 and 0.8 THz. Experimental verification was also performed using a free space THz time-domain spectroscopy system. The band-stop response characteristics are in good agreement with the simulation results. The interesting THz band-stop filtering properties suggest a promising application in the modern THz communication systems, THz time-domain spectroscopic imaging and THz continuous wave imaging.

A Wide-Stopband Bandpass Filter Using < λ /16 Capacitive-Coupled Short-Circuited Resonators in Wide-Gap Coplanar Waveguide Structure

A compact bandpass filter (BPF) using a very short capacitively coupled resonator exhibits wide-stopband characteristics. It is based on two <λ/16 short-circuited resonators built on a coplanar waveguide (CPW) having unusually wide gap. The filter's input/output ports are connected to the resonator through microstrip-to-CPW broadside-coupled transition structure. The proposed filter is simple and compact without employing any additional structural elements that are often used in conventional approaches. It is found that the stopband characteristic can be significantly extended only by properly setting the coupling capacitance of the broadside coupling structure, the length of the resonator, and the CPW gap. A second-order BPF with a center frequency (f0) of 2.45 GHz and a 3-dB bandwidth of 10.6% is fabricated on a liquid crystal polymer substrate, demonstrating dramatically extended stopband suppression of 30 dB up to 9.8f0. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1752–1755, 2013

Design of coplanar-waveguide-based elliptic filter using T-shaped defected ground structure

In this paper T-shaped Defected Ground Structure (DGS) has been proposed in the ground plane of the conventional coplanar-waveguide (CPW) structure. The T-shaped DGS has wider gap capacitance than the conventional dumbbell-shaped DGS, and provides a wide stop band and slow-wave characteristics. Thus, utilizing the above properties array of two T-shaped DGS structures has been introduced to obtain an elliptic low-pass filter (LPF). This proposed LPF is suitable for transferring low frequency signal up to 2.5 GHz satisfactorily. It provides sharp transition between pass- and stop-band with good sharpness factor, but almost 1.2 dB insertion loss in the pass-band. Therefore, the insertion loss in the pass-band is reduced with the help of compensated Hi–Lo coplanar waveguide (CPW) transmission line.

결함 접지 구조를 이용한 주파수 스캐닝 방식의 마이크로파 태그 시스템

In this paper, a microwave tag system of a frequency-scanning type is proposed with multi-resonators using defected ground structures. While a conventional chip-based RFID stores time-sequential codes, the proposed type achieves pure passive tags by using multi-resonant bits over a frequency range. Moreover, the resonators of the spiral defected ground structures implemented on the back side of transmission lines have advantages of the excellent bandstop characteristics as well as the bit-error avoidance by the re-radiation on normal resonators. The proposed microwave tag is designed with UWB antennas at 3~7 GHz. From the experimental results in an anechoic chamber, it has been verified of the excellent recognitions for various 5-bits identification codes.

Compact thin ground plane UWB antenna with dual band stop characteristics

AbstractA compact coplanar waveguide (CPW)‐fed convex hexagonal‐shaped ultrawide band (UWB) antenna, with L‐shaped thin ground plane for lower frequency band stop function and tapered rectangular vertical slot in radiating patch for upper frequency band stop is presented. The proposed antenna of dimension 40 × 22 × 1.6 mm3 provides good impedance matching over dual operational UWB resonating at 5.4 and 9.6 GHz with fractional bandwidth 69.54 and 33.83%, respectively. The lower frequency stop band in the vicinity of 2.4 GHz and higher frequency stop band in the vicinity of 7 GHz has bandwidth of 3.17 and 1.8 GHz, respectively, to avoid the interference of PCS, GSM 800/1900, ISM, WLAN, and X‐band satellite uplink (7.25–7.75 GHz) and downlink (7.9–8.4 GHz) communication system. The E‐plane radiation pattern observed is bidirectional in nature due to CPW feed and that of the H‐plane pattern is omnidirectional. The resonating lower and higher UWB achieves the peak gain 2.16 and 6.5 dBi, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1045–1049, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27470