Search

Fiber-reinforced polymers poles were on the increase because they were lightweight, have high strength-to-weight ratios, provide corrosion resistance, can be customized to meet strength and deflection requirements, and have a low life-cycle cost of construction and maintenance. This research presents a comprehensive review of all significant research and existing case studies to review the present knowledge concerning fiber-reinforced polymers poles. The main summary covers 70 works focusing on fiber poles to summarize recent activities on selected relevant topics and highlight possible future implementations. In this context, this study discusses fiber-reinforced polymers poles in six aspects: (i) introduction; (ii) methodology; (iii) Materials properties of FRP poles; (iv) manufacturing techniques of FRP poles; (v) testing of FRP poles (static and dynamic flexure test as cantilever beam); (vi) modeling of FRP poles. Therefore, this critical review will demonstrate an overview of FRP Poles manufacturing techniques (Pultrusion, filament winding, centrifugal process, and hand lay-up) and which Pultrusion technique is the best suited for FRP Poles. Static modeling was the most used of other techniques. [ABSTRACT FROM AUTHOR]

Genus Eucalyptus belongs to the family Myrtaceae and consists of more than 900 species, various hybrids and varieties. The major species that are grown in Kenya are Eucalyptus grandis, E. globulus, E. saligna and E. camaldulensis. Most Eucalyptus species are highly dependent on rainfall and this is challenged by climatic changes owing to global warming making it difficult to effectively match the availability of mature trees and the market demand especially for use as power transmission poles. With the widespread availability of other naturally occurring Eucalyptus species such as E. camaldulensis and E. globulus, it becomes important to determine the genetic diversity and to analyze the phenotypic traits of these species for suitability as power transmission poles in order to counter the overdependence on E. grandis. Phenotypic traits investigated included measuring total tree height and diameter at breast height (DBH), while molecular data were obtained from sequencing MatK, rbcL and TrnL-F genes from selected species and evolutionary analyses such as nucleotide substitution rates, base composition disparity indices, evolutionary divergence, nucleotide diversity indices and phylogeny construction were conducted in MEGA 11. Significant differences in DBH and height among Eucalyptus species were observed when the phenotypic data were subjected to ANOVA. In this study, E. robusta, E. paniculata, E. maculata, E. dunnii, E. camaldulensis and E. citriodora are fit to be used as power transmission poles but they are limited by their short height. However, E. tereticornis and E. glaucina have the desired DBH and height and hence can be used as substitutes for E.grandis. Generally, the molecular phylogeny study has shown that the studied Eucalyptus species are closely related and form various monophyletic clades which can be attributed to the short genetic distances, low substitution rates, low nucleotide bias disparity indices and low diversity scores. Further phylogenetic and gene expression studies involving more Eucalyptus species are needed to better understand Eucalyptus phylogeny, and diversity and identify species with similar genetic make-up to that of E. grandis which has been used extensively for the provision of electricity transmission poles. [ABSTRACT FROM AUTHOR]

Defected Ground Structure (DGS) based on-chip bandstop filter (BSF) design is proposed for millimeter-wave applications. In the proposed structure, a capacitively loaded T-shape resonator is embedded in the original DGS resonator, which forms two high quality (${Q}$ -) factor small loop resonators. Moreover, this structure, in combination with the feedline and series capacitor, independently realizes the position of two transmission poles: one at each side of the parallel resonance without increasing the layout size. The proposed BSF presents a sharp scattering (S-) parameter response due to the appearance of two transmission poles. As a result, the loaded ${Q}$ -factor and negative group delay of the BSF are improved. The prototype of the proposed BSF is fabricated in 0.18- $\mu \text{m}$ Complementary Metal-Oxide-Semiconductor (CMOS) process and measured. The measurement result shows a return loss of 1.78 dB at 53.2 GHz center stopband frequency with the negative group delay of 161 pS. The measurement results also agree well with the electromagnetic simulation results. Without pads, the active area of the prototyped BSF is only 0.024 mm2. [ABSTRACT FROM AUTHOR]

A novel dual-band bandpass filter (BPF) is proposed with independently controllable transmission zeros (TZs) which can realize widely tunable stopband bandwidth (BW). The planar microstrip filter consists of a three-degree L-C ladder lowpass filter loaded with two unsymmetrical shorted stubs which are used to produce different TZs. By tuning the parameters of the two unsymmetrical shorted stubs, the TZs can be independently controlled. Therefore, the BPF has independent controllable center frequencies (CFs), passband bandwidths, and stopband bandwidths between adjacent passbands. All the L-C values in the equivalent circuit of the proposed filter are optimized to fulfill the design specifications. For demonstration, a dual-band BPF is designed. The measured results show good agreement with the simulated ones.

Fiber-reinforced polymers poles were on the increase because they were lightweight, have high strength-to-weight ratios, provide corrosion resistance, can be customized to meet strength and deflection requirements, and have a low life-cycle cost of construction and maintenance. This research presents a comprehensive review of all significant research and existing case studies to review the present knowledge concerning fiber-reinforced polymers poles. The main summary covers 70 works focusing on fiber poles to summarize recent activities on selected relevant topics and highlight possible future implementations. In this context, this study discusses fiber-reinforced polymers poles in six aspects: (i) introduction; (ii) methodology; (iii) Materials properties of FRP poles; (iv) manufacturing techniques of FRP poles; (v) testing of FRP poles (static and dynamic flexure test as cantilever beam); (vi) modeling of FRP poles. Therefore, this critical review will demonstrate an overview of FRP Poles manufacturing techniques (Pultrusion, filament winding, centrifugal process, and hand lay-up) and which Pultrusion technique is the best suited for FRP Poles. Static modeling was the most used of other techniques.

Genus Eucalyptus belongs to the family Myrtaceae and consists of more than 900 species, various hybrids and varieties. The major species that are grown in Kenya are Eucalyptus grandis, E. globulus, E. saligna and E. camaldulensis. Most Eucalyptus species are highly dependent on rainfall and this is challenged by climatic changes owing to global warming making it difficult to effectively match the availability of mature trees and the market demand especially for use as power transmission poles. With the widespread availability of other naturally occurring Eucalyptus species such as E. camaldulensis and E. globulus, it becomes important to determine the genetic diversity and to analyze the phenotypic traits of these species for suitability as power transmission poles in order to counter the overdependence on E. grandis. Phenotypic traits investigated included measuring total tree height and diameter at breast height (DBH), while molecular data were obtained from sequencing MatK, rbcL and TrnL-F genes from selected species and evolutionary analyses such as nucleotide substitution rates, base composition disparity indices, evolutionary divergence, nucleotide diversity indices and phylogeny construction were conducted in MEGA 11. Significant differences in DBH and height among Eucalyptus species were observed when the phenotypic data were subjected to ANOVA. In this study, E. robusta, E. paniculata, E. maculata, E. dunnii, E. camaldulensis and E. citriodora are fit to be used as power transmission poles but they are limited by their short height. However, E. tereticornis and E. glaucina have the desired DBH and height and hence can be used as substitutes for E.grandis. Generally, the molecular phylogeny study has shown that the studied Eucalyptus species are closely related and form various monophyletic clades which can be attributed to the short genetic distances, low substitution rates, low nucleotide bias disparity indices and low diversity scores. Further phylogenetic and gene expression studies involving more Eucalyptus species are needed to better understand Eucalyptus phylogeny, and diversity and identify species with similar genetic make-up to that of E. grandis which has been used extensively for the provision of electricity transmission poles.

A fifth-order bandpass filter (BPF) with super high selectivity using three pairs of coupled lines and two open stubs is proposed. Twelve transmission zeros (TZs) from 0 to 2f_0 (f_0 denotes center frequency of the passband) and five transmission poles (TPs) in the passband can be obtained to realize good out-of-band suppression and sharp roll-off skirts. For demonstration, a simple BPF prototype centered at 2.04 GHz is designed, fabricated with measured 3-dB fractional bandwidth of 18% and very high transition band roll-off rates of over 567 dB/GHz. Good agreement between the simulations and measurements validates the design method.

In this paper, a simple high‐selectivity wideband bandpass filter based on a novel π‐shaped coupled‐line structure is introduced. The presented filter realizes wide bandwidth, excellent passband selectivity and good stopband suppression by using two coupled lines with diagonal open‐circuited ports and three coupled lines with cascaded ports. The design theoretical analysis and the complete equation derivation are provided in detail. Furthermore, a prototype with 3‐dB fractional bandwidth of 50.9% is simulated, fabricated, and measured. The simulated and measured results have a good consistency, which verifies the analytical design principle. [ABSTRACT FROM AUTHOR]

An impedance transformer (IT) with wideband and high selectivity is presented in this paper. Three transmission poles were obtained within the passband and provides a wide passband response. Moreover, there are two transmission zeros (TZs) close to the passband that were achieved by a shunt parallel coupled line and provide high selectivity. For validation of proposed circuit, the ITs were designed at a center frequency (f0) of 3.5 GHz using an impedance‐transforming ratio (r) of 5 and 10. For r = 5, |S21| and |S11| are 0.36 dB and 28 dB at f0, respectively. Within the passband, |S21| and |S11| are better than 0.65 dB and 18 dB, respectively. The TZs at 2.65 GHz (0.76f0) and 1.22f0, close to the passband, were measured with attenuation better than 37 dB. The out‐of‐band attenuations are higher than 20 dB from DC to 2.77 GHz of the lower stopband and from 4.16 GHz to 9.73 GHz of the higher stopband. For r = 10, |S21| = −1.4 dB and |S11| = −23 dB were measured at f0. An 18 dB return loss was obtained from 3.415 GHz to 3.694 GHz (FBW = 7.96%). [ABSTRACT FROM AUTHOR]

A compact dual-band bandpass filter (BPF) based on parallel coupled lines and shorted stubs has been presented in this Letter. The transmission and reflection coefficients of the proposed dual-band BPF are straightforwardly derived via the input impedances using odd- and even-mode analysis methods. Four transmission poles in the two passbands and nine deep transmission zeros (TZs) in the stopband can be realised. The centre frequencies and bandwidths of the two passbands can be tuned by controlling the impedance parameters of the coupled lines and shorted stubs. For demonstration, a prototype example of this dual-band BPF with a small size is experimentally characterised. The measured results show that it has high-frequency selectivity with multiple TZs at the stopband. [ABSTRACT FROM AUTHOR]

A high selectivity bandpass filter with multiple transmission poles (TPs) and transmission zeros (TZs) has been presented. By employing three pairs of parallel-coupled lines and two shorted stubs, sharp roll-off skirts and high stopband rejections can be achieved with five TPs and ten TZs. Theoretical analysis is explained and simulated results are illustrated on this high-performance filter. Finally, a bandpass filter example with center frequency of 2.15 GHz and 3-dB fractional bandwidth of 19% is designed, fabricated, and measured. It is shown that the measured transition band roll-off rates are better than 425 dB/GHz. Good agreement between the simulations and measurements validates the design method. [ABSTRACT FROM AUTHOR]

A fifth-order bandpass filter (BPF) with super high selectivity using three pairs of coupled lines and two open stubs is proposed. Twelve transmission zeros (TZs) from 0 to 2f0 (f0 denotes center frequency of the passband) and five transmission poles (TPs) in the passband can be obtained to realize good out-of-band suppression and sharp roll-off skirts. For demonstration, a simple BPF prototype centered at 2.04 GHz is designed, fabricated with measured 3-dB fractional bandwidth of 18% and very high transition band roll-off rates of over 567 dB/GHz. Good agreement between the simulations and measurements validates the design method. [ABSTRACT FROM AUTHOR]

Treated wooden utility poles, from trees such as eucalypts, are the most commonly used for telephone and electricity transmission lines in Uganda. In the last decade, however, frequent failure of wooden poles in service has been reported, likely due to the preservative chemical, wood used or the treatment process. The objective of this study was to assess the creosote preservative penetration and retention in eucalypt wood. A total of 126 Eucalyptus grandis poles i.e. 42 poles for each size category, with an average moisture content of below fibre saturation point (28%) were treated in different charges depending on their size. In length, poles used were 9, 11 and 14m. Every charge consisted of poles within the same size category. The Full Cell pressure method was used to treat the different charges with creosote preservative. For all the charges the same treatment schedule was maintained. Creosote penetration was highest in 14m poles (20.5mm) and lowest in 9m poles (18.4mm), Creosote retention was also highest in 14m poles (193kgm-3), but lowest in 11m poles (162kgm-3). Irrespective of differences in level of penetration and retention among the various pole sizes, all the poles acquired more than the required standard minimum level of penetration and retention i.e. 15mm and 115kgm-3 respectively. However, for all the pole sizes, creosote penetration was less than the sapwood depth. The current treatment schedule seems better suited for the larger poles of 14m than the 9 and 11m. For better treatment, it is recommended that smaller poles i.e. 9m and 11m should be treated for a longer period than 14m poles since they tend to have lager sapwood. The minimum basis of 15mm penetration should be increased to at least cover the entire pole sapwood depth.

Abstract High-selectivity single-ended and balanced bandpass filters (BPFs) using dual-mode ring resonators and coupled lines loaded with multiple stubs are proposed in this paper. With the help of the loaded short-circuited and open-circuited stubs, six deep transmission zeros (TZs) from 0 to 2 f 0 (f 0 : center frequency of the passband) can be realized in both of single-ended and balanced BPFs to improve the stopband suppressions. The functions of the loaded short/open stubs and calculated analysis of TZs' positions have been presented. For further demonstration, two examples of single-ended BPF and balanced BPF with high common-mode suppression are designed and fabricated, whose center frequencies are both at 2.1 GHz. Their measured 3-dB fractional bandwidths are 23.7% and 24.7% (differential-mode), respectively. The simulated results and measurements of these two filters are in good agreement. [ABSTRACT FROM AUTHOR]

A brief review of current research on uplift or pull-out capacity of plate anchors buried in various types of soils is presented. The definitions of shallow and deep foundations are examined with reference to direct embedded transmission poles. Classical uplift capacity models for plate anchors are discussed. Both cohesion-less (sand) and cohesive (clay) soils are considered. Procedures for computing approximate uplift capacity of transmission poles with base shoes and practical challenges are discussed. Numerical applications involving wood and steel poles embedded in soft clay and loose sand are provided. Results indicate that simplified approaches appear to agree well with classical theory for both the wood and steel poles, though the difference is more noticeablein soft clay. [ABSTRACT FROM AUTHOR]

Current guidelines for determining direct embedment depths for tangent transmission poles are evaluated. Embedment depths from approaches based on pole stability as well as lateral resistance are compared. Numerical embedment calculations are performed in three different types of soils - moist sand, submerged sand and saturated cls*y - using two specific computer programs, for moderate ground line reactions. Based on the results, nominal adjustment factors for industry typical embedment depths are proposed for the three soil types. Suggestions for future extensions of the approach are made. [ABSTRACT FROM AUTHOR]

Treated wooden utility poles, from trees such as eucalypts, are the most commonly used for telephone and electricity transmission lines in Uganda. In the last decade, however, frequent failure of wooden poles in service has been reported, likely due to the preservative chemical, wood used or the treatment process. The objective of this study was to assess the creosote preservative penetration and retention in eucalypt wood. A total of 126 Eucalyptus grandis poles i.e. 42 poles for each size category, with an average moisture content of below fibre saturation point (28%) were treated in different charges depending on their size. In length, poles used were 9, 11 and 14m. Every charge consisted of poles within the same size category. The Full Cell pressure method was used to treat the different charges with creosote preservative. For all the charges the same treatment schedule was maintained. Creosote penetration was highest in 14m poles (20,5mm) and lowest in 9m poles (18,4mm), Creosote retention was also highest in 14m poles (193kg.m-3), but lowest in 11m poles (162kg.m-3). Irrespective of differences in level of penetration and retention among the various pole sizes, all the poles acquired more than the required standard minimum level of penetration and retention i.e. 15mm and 115kg.m-3 respectively. However, for all the pole sizes, creosote penetration was less than the sapwood depth. The current treatment schedule seems better suited for the larger poles of 14m than the 9 and 11m. For better treatment, it is recommended that smaller poles i.e. 9m and 11m should be treated for a longer period than 14m poles since they tend to have lager sapwood. The minimum basis of 15mm penetration should be increased to at least cover the entire pole sapwood depth. [ABSTRACT FROM AUTHOR]

A novel dual‐band bandpass filter (BPF) based on a single triple‐mode ring resonator is proposed. The proposed BPF could provide three transmission poles for each passband to improve operating bandwidth. Meanwhile, seven transmission zeros are achieved at the stopband to improve the selectivity. The proposed dual‐band BPF was designed, fabricated and tested. The measured results are in good agreement with the simulated values.

A novel reflectionless triple‐band bandpass filter (RTBPF) with compact structure and high controllability is proposed by combing the reused multi‐mode resonator (MMR) with a coupled‐line based absorptive network. The MMR is coupled to feeding lines to share its even‐mode resonating points as transmission poles (TPs) in bandpass branch and transmission zeros (TZs) in bandstop branch. By employing the coupled‐line based absorptive network, additional TZs and TPs are obtained in bandstop branch. Since these resonances in bandpass branch and the absorptive network are controlled independently, the bandwidth and centre frequency of the RTBPF can be tuned flexibly. The implemented RTBPF demonstrates a minimum insertion loss of 1.68 dB@2.4 GHz, 1.65 dB@3.2 GHz, 1.5 dB@4.3 GHz, three absorption peaks of − 6, −7 and −8 dB from dc up to 6 GHz. The overall circuit size is 0.22 λg2. [ABSTRACT FROM AUTHOR]

A novel dual-band microstrip bandstop filter with multiple poles using open/shorted coupled lines is proposed in this paper. Nine transmission poles near the two stopbands can be easily realized by conventional coupled lines and transmission lines. The two center frequencies of the dual-band bandstop filter can be adjusted flexibly by only changing the even/odd-mode of the coupled lines. The planar microstrip dual-band bandstop filter ( $\varepsilon r = 2.65$ and $h = 0.5$ mm) with nine transmission poles is designed and fabricated. High selectivity and good in-band performances can be achieved in the proposed filter. [ABSTRACT FROM PUBLISHER]

A novel tri‐band bandpass filter (BPF) using a stepped‐impedance square ring loaded resonator (SISRLR) is presented. The proposed resonator consists of a square ring with two open stubs and two short stubs. By tuning the impedance ratios of the SISRLR, the passbands can be adjusted and three pairs of transmission poles are produced for tri‐band design. On the basis of the resonator, a miniaturised tri‐band BPF operating at 1.7 GHz (mobile communication), 3.5 GHz (worldwide interoperability for microwave access application), and 5.8 GHz (WLAN application) has been designed and fabricated. Measured results demonstrate good agreement with simulations. [ABSTRACT FROM AUTHOR]

On the basis of a single multimode resonator (MMR), a miniaturised microstrip sext‐band bandpass filter (BPF) with high band‐to‐band isolations has been presented. The proposed MMR is an stepped impedance resonator (SIR) with one short‐circuited stub loaded in the middle and two identical open‐circuited stubs located at two sides. Transmission poles (TPs) and transmission zeros (TZs) can be excited when the electrical lengths of two open stubs increase. The TZs introduced by open stubs separate the TPs into multiple groups; therefore, the design of a sext‐band BPF becomes available. Moreover, two input/output tapped branches and radical stub‐loaded short‐circuited lines are treated as perturbation structures in order to increase design freedoms for improving filter performance. Good agreement between simulated and measured results validates the design method. [ABSTRACT FROM AUTHOR]

A novel dual‐band bandpass filter (BPF) based on a single triple‐mode ring resonator is proposed. The proposed BPF could provide three transmission poles for each passband to improve operating bandwidth. Meanwhile, seven transmission zeros are achieved at the stopband to improve the selectivity. The proposed dual‐band BPF was designed, fabricated and tested. The measured results are in good agreement with the simulated values. [ABSTRACT FROM AUTHOR]

A novel ultra-wideband (UWB) bandpass filter (BPF) is proposed and implemented by using a four-mode resonator, which has four resonant frequencies within the passband of the filter. By enhancing the coupling between the resonator and the input/output feed lines, an UWB BPF with six transmission poles is realized, although only one resonator is utilized. To alleviate the requirement on fabrication precision, aperture-enhanced coupled lines are introduced to replace the parallel-coupled lines in the filter. The fabricated filter exhibits good performances and the measured results show good agreement with the simulated results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 696–699, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23184 [ABSTRACT FROM AUTHOR]

An impedance transformer (IT) with a ultra-high impedance transforming ratio (UHITR) is presented in this letter. The UHITR is obtained by controlling coupling coefficients of cascaded open-circuited coupled lines. Two transmission poles have appeared in the passband for an under-matched region. For the validation, the IT with impedance transforming ratio of 10 was designed at a center frequency (f0) of 2.6 GHz. From the experiment, insertion and return losses at f0 were determined as 0.55 dB and 21.47 dB, respectively. Within the operating band from 2.515 to 2.73 GHz, the insertion and return losses were better than 0.8 dB and 18 dB, respectively. The out-of-band suppression characteristics are higher than 20 dB from dc to 1.92 GHz and better than 18 dB from 3.28 to 7.2 GHz. [ABSTRACT FROM PUBLISHER]

A compact and high frequency selectivity two‐stage microstrip bandpass filter is designed and experimentally demonstrated. Such a kind of filter is composed of two pairs of twist‐modified asymmetric split‐ring resonators (SRRs) to achieve three transmission poles within the passband and four transmission zeros at low and high rejection bands. Sharply out‐of‐band reductions contributing to the high frequency selectivity are obtained by properly detuning the gaps among the SRRs. The measured results show that the proposed filter with dimensions of 0.088 × 0.088λ2 has a 3 dB passband of 15.2% centred at 1.98 GHz. This filter can be flexibly integrated in miniaturised radio‐frequency/microwave circuits. [ABSTRACT FROM AUTHOR]

In this Letter, a three‐dimensional (3D) frequency selective surface (FSS) is proposed, exhibiting a dual‐bandpass response with high selectivity and small band ratio. The unit cell of the presented 3D FSS consists of a pair of gridded double square loops (GDSLs) and a waveguide structure. Multiple transmission zeros and transmission poles are obtained from the electromagnetic coupling between the GDSLs. The electromagnetic coupling is enhanced by the waveguide structure, resulting in a dual‐passband behaviour with high selectivity. Double square loops are designed to locate close to obtain a small band ratio. The measured results of the implemented FSS agree well with the simulated ones, which show that the proposed design can achieve the desired response to variations of incident angle from 0° to 60° for both TE and TM polarisations. [ABSTRACT FROM AUTHOR]

Quadruple-mode coupled-ring resonator is used to design quasi-elliptic function bandpass filters (BPFs) with a relatively wide bandwidth. The resonator consists of a pair of coupled rings with two open stubs symmetrically tapped to the inner ring. The stubs are used to move a transmission zero near the center frequency to lower transition band. It is believed that it is the first ring resonator BPF based on the coupled-ring to create four transmission poles and four transmission zeros. Two filters with relative bandwidths of 10% and 15% are fabricated and measured. Good agreement between simulation and measurement is obtained. [ABSTRACT FROM PUBLISHER]

A compact bandpass filter is proposed for lower-band ultra-wideband applications. It entails the design concept of a stub-tapped half-wavelength line resonator which provides three transmission poles in the passband and two transmission zeros at the high and low rejection bands. The two stubs are replaced by a single dual-band stub and the parallel coupled-line structures are meandered, leading to a compact size of 0.26lambdag by 0.32lambda g [ABSTRACT FROM PUBLISHER]

A novel microstrip-line ultra-wideband (UWB) bandpass filter is proposed and implemented using a multiple-mode resonator (MMR), aiming at transmitting the signals in the whole UWB passband of 3.1-10.6GHz. In the design, the first three resonant frequencies of this MMR are properly adjusted to be placed quasiequally within the UWB. Then, the parallel-coupled lines at the two sides are longitudinally stretched so as to raise the frequency-dispersive coupling degree with the coupling peak near the center of the UWB. After optimization of this filter, a good UWB bandpass behavior with five transmission poles is theoretically realized and experimentally confirmed. Within the whole UWB passband, the return loss is found higher than 10dB, and the group delay variation is less than 0.23ns. [ABSTRACT FROM PUBLISHER]

This letter presents the design of six-resonator multiple-coupled microstrip filter. A low-pass prototype of six-resonator multiple-coupled filter is developed first based on the conventional Chebyshev filter. The characteristics of attenuation poles located on both sides of the frequency response are described. According to the low-pass prototype, the design of a six-resonator multiple-coupled microstrip hairpin filter at 6 GHz is completed with the aid of EM simulation. The experimental results are demonstrated and discussed. [ABSTRACT FROM PUBLISHER]

A compact microstrip bandpass filter is developed using a half-wavelength (λ/2) transmission line resonator with a pair of tap-connected open-ended stubs. Such paired stubs with total length of about λ/2 constructs an equivalent line resonator. Together with two separated λ/4 line resonators, the three transmission poles can be achieved inside the passband. Meanwhile, two stub lengths are adjusted slightly longer and shorter than λ/4 to realize the two transmission zeros at both low and high rejection bands. Further, the long tapped-stub is kept wider than its short counterpart to improve the low rejection behavior. A filter sample is designed and fabricated to provide an experimental verification on the proposed filter. [ABSTRACT FROM PUBLISHER]

A dual‐wideband bandstop filter with high selectivity using transversal signal‐interaction concept is proposed. Five transmission poles in the passband between the two stopbands can be achieved due to the superposition of signals for the two transmission paths. A planar dual‐wideband bandstop filter prototype for WLAN bands with 10 dB fractional bandwidths of 76.2% and 26.9% has been designed and fabricated. [ABSTRACT FROM AUTHOR]

A compact dual‐wideband bandpass filter using an asymmetrical resonator is presented. The proposed resonator consists of three uniform microstrip lines of different lengths, and provides not only three transmission poles but also two transmission zeros for each passband. Thus, the bandpass filter has wide bandwidths and sharp cutoff responses. Theory as well as experimential results are given to validate this design concept. [ABSTRACT FROM AUTHOR]