Band-edge Selectivity Research Articles

Compact quad-channel filtering diplexer using meander hairpin ring resonator aided by grey wolf algorithm

Abstract In this paper, a compact quad-channel filtering diplexer using meander hairpin ring resonators (M-HRR) aided by grey wolf algorithm (GWA) is proposed. To realize a compact size of the multi-channel diplexer, the form of a meander-line structure is applied to the hairpin ring resonator for the miniaturization of the proposed quad-channel diplexer. Then, using the coupling topology of the 0° feeding structure, a transmission zero (TZ) is generated between two resonant frequencies of M-HRR to improve the band-edge selectivity and band-to-band isolation of the diplexer. To address the problematic challenge of the complexity in designing the multi-channel diplexer with a time-consuming optimization manually, an intelligent GWA is utilized to optimize the physical layout of the designed circuit to achieve the desired performance of the diplexer rapidly. Furthermore, different kinds of intelligent algorithms are implemented and compared under identical conditions. Finally, a quad-channel filtering diplexer centering at 3.28/3.75/4.32/4.75 GHz with 3-dB fractional bandwidth (FBW) of 5.4%, 2.9%, 4.9%, and 3.2% respectively is fabricated and measured. The circuit occupies a compact size of 0.22λg × 0.20λg. Good accordance is observed between the simulated and measured frequency responses.

A Compact Modified Elliptical-Shaped Ultra-wideband Filtering Antenna with Improved Band-Edge Selectivity

A compact filtering antenna with higher selectivity near band-edge frequencies for ultra-wideband (UWB) applications is presented and developed in this article. The antenna with filtering characteristics is formulated by integrating a rectangular-impedance resonator-based bandpass filter into the feedline of a modified elliptical-shaped monopole radiator. Initially, a modified elliptical-shaped monopole radiator is designed and numerically simulated to ensure the overall performance over the UWB band. The modified elliptical shape is used as a radiator to increase the electrical length while maintaining minimum physical size. The size of the UWB antenna is merely 0.518λ AL × 0.272 λ AL (where λAL is the guided wavelength at 2.62 GHz). Furthermore, to enhance the performance characteristics of the filtering antenna along with band-edge selectivity, geometrical parameters are optimized using a numerical simulation tool. It exhibits a simulated impedance bandwidth of 112% (3.05–10.81 GHz) with an electrical size of 0.676λ FL × 0.316λ FL (where λFL is the guided wavelength at 3.05 GHz). The experimental results of the fabricated UWB antenna and filtering antenna prototypes agree well with their simulated results.

Novel Compact Lowpass Filter Using Dual-Layer Coupled Resonators

This article presents the synthesis and design of a novel compact lowpass filter (LPF) with low insertion loss and significant near-skirt selectivity. The LPF is designed based on a new structure called dual-layer coupled resonators (DLCRs) implemented with striplines embedded in air cavity, thus characterized with high quality factor and low insertion loss. To enhance band-edge selectivity and stopband attenuation, finite-position transmission zeros (TZs) are introduced with DLCRs to form pseudo-elliptical fitter functions. The equivalent circuit of DLCR is provided first, followed by detailed synthesis preconditions and procedures based on element extraction. With the elucidated synthesis process, TZs can be customized and arbitrarily placed at specified frequencies. The proposed synthesis theories are general and applicable to LPFs with arbitrary order and assigned TZs, thus providing effective guidelines for physical implementation. Besides, with smaller needed capacitances and avoided long-length high-impedance lines in TZ-producing resonant pairs, a more compact footprint is achieved with DLCRs. A 13th-order LPF with three TZs is synthesized and fabricated for navigation satellite applications, of which the good measurement results have validated the proposed theories.

A Compact Circularly Polarized Crossed Dipole Antenna with Wide Bandwidth using Split Ring Resonator and Parasitic Patches

A new compact broadband circularly polarized (CP) crossed dipole antenna using split ring resonator (SRR) and parasitic patches are presented. The proposed antenna is mainly composed of two orthogonal strip dipoles, two 90∘ phase delay lines, four SRRs, and four parasitic patches. The combination of the orthogonal strip dipoles and the delay lines forms a crossed dipole as the main CP radiator. The well-designed SRR can extend the current path and improve the current distribution of high-frequency without increasing the size of the antenna, thereby reducing the size of the antenna and increasing the axial ratio (AR) bandwidth of the high-frequency. The introduction of parasitic patches can improve the current distribution between the upper and lower cut-off frequency points of the bandwidth, and make up for the defects of the insufficient bandwidth of the crossed dipole and the SRR, thereby realizing broadband CP radiation. To verify the antenna, a physical prototype is fabricated. The measured results show that the impedance bandwidth (IBW) of 69.1% (1.38-2.84 GHz), and a wide AR bandwidth of 57.7% (1.43-2.59 GHz). In addition, the designed antenna achieves a stable gain in the working band and a certain band-edge selectivity. Such a single-fed, simple structure and the wideband CP antenna is an excellent candidate for communication systems such as ISM (2.4 GHz), WiBro (2.3-2.39 GHz)and Inmarsat.

An Ultra-Wideband Integrated Filtering Antenna with Improved Band-Edge Selectivity Using Multimode Resonator

In this paper, a novel design of ultra-wideband (UWB) filtering antenna integrated with the multimode resonator (MMR) bandpass filter is proposed, aiming to enhance band-edge selectivity. At the beginning, a MMR bandpass filter is modified and studied. Based on the classic MMR filter, the proposed filter folds the microstrip transmission line to reduce its size while retaining the original filtering performance. Moreover, an open stub and short stub are added to the proposed filter to obtain a transmission of zero. Then, the folded filter with stubs and a UWB bow-tie antenna are integrated together to form a filtering antenna. The open stub and short stub in the MMR structure enhance the antenna’s upper and lower band-edge selectivity, respectively. Series of parameters are studied to analyze their influences on the frequency selection range and band-edge characteristics. Compared with the original UWB dipole antenna, such an integrated approach brings many benefits. Firstly, the UWB filter not only broadens the bandwidth of the device, but also improves band-edge selectivity, which can eliminate the unwanted passband near the operating frequencies. Secondly, the integrated system reduces the size and cost of the devices, which is very important in the miniaturization of wireless systems. In this research, the reflection coefficient (S11) of integrated filtering antenna is lower than −10 dB between 2.92 and 11.51 GHz, and it has a fractional bandwidth of 119%. The measured shape factor is 1.027 (very close to 1), which proves that this design has a better band-edge selectivity. Simultaneously, good radiation characteristics are also attained, with a maximum realized gain of 6 dBi. Theoretical simulation results are similar to the experimental results. The measurement results of the manufactured device effectively validate that its performances have reached the simulation design requirements.

Advanced Synthesis and Precise Design of Inline Fully Canonical Filters With High Selectivity

This article presents an advanced synthesis and novel designs of inline fully canonical filters with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> cascaded extracted pole (EP) sections, providing higher band-edge selectivity and suppressing interference from adjacent bands. The conventional fully canonical prototype is reconfigured to significantly facilitate filter design and fabrication. Moreover, to synthesize realizable circuits, a general node scaling method based on admittance matrix is implemented. All associated elements, especially the junction susceptances, can be scaled directly without the aid of inverters, avoiding intricate equivalent circuit transforms. Furthermore, the importance of precise control over the junction susceptances in filter design is discussed for the first time. Accurate junction susceptance enables the exact mapping from synthesized circuits to physical structures, preventing brute-force optimization. In particular, a new and compact EP structure in coaxial technique is proposed with flexibly tuned loading phase and accurately regulated junction susceptance. The good measurement results of a coaxial EP filter with four reflection zeros (RZs) and four transmission zeros (TZs) validate the effectiveness of the proposed theories. Also, this is the first reported coaxial fully canonical filter with only build-in capacitive couplings to avoid passive intermodulation (PIM).

Novel filtering and diplexing linear tapered slot antenna with high-selectivity

In this article, a novel filtering and diplexing antenna using a linear tapered slot antenna (LTSA) are demonstrated. To begin, a highly-selective, second order bandpass filter is designed using generalized Chebyshev filter synthesis technique. Filtering and diplexing antennas are realized by co-designing the filter along with a wideband LTSA. The proposed filtering antenna exhibits 3.21% fractional bandwidth (FBW) over (4.29–4.43) GHz, high band-edge selectivity performance with 6 dBi flat in-band realized gain and stable end-fire radiation patterns with a low cross-polarization level of less than -30 dB. Further, a diplexing antenna with good bandpass filtering characteristics is also implemented. The design shows FBW of 3.32% (3.55–3.67) GHz and 3% (4.91–5.06) GHz and flat-radiation gain of 5.2 dBi and 5 dBi with sharp roll-off in Tx (lower) and Rx (upper) passbands, respectively. It also demonstrates good out-of-band suppression level of more than 20 dB, end-fire radiation patterns with cross-polarization lower than -27 dB and back-lobes lower than -14 dB for both the passbands. In order to validate their functionality, both the designs are fabricated and the experimental results correlate well with the simulated results.

Design and analysis of UWB antenna with quintuple band-notched and wide-band rejection characteristics

AbstractIn this study, a compact ultra-wideband (UWB) antenna with quintuple band-notched and wide-band rejection characteristics is studied. The proposed antenna mainly consists of a rectangular radiating patch, a microstrip feeding line, and a modified rectangular ground plane. The quintuple band-notched functions with narrow stop bands are achieved at WiMAX (3.3–3.7 GHz), WLAN (5.15–5.35 GHz and 5.725–5.825 GHz), C-band IEEE INSAT/super-extended (6.7–7.1 GHz) by using three modified inverted U-shaped slots and two symmetrical rectangular slots on the radiating path. Each stop band formed in the UWB antenna can be adjusted independently, and deep reflection zeros are formed between the adjacent stop bands. The formation of reflection zeros improves the band-edge selectivity of the stop band, and the notch characteristics are more prominent. To further study the wide stop band (C-band and X-band) with good selectivity characteristics, a pair of L-shaped open slot is added to the edges of two rectangular slots. Additionally, a pair of modified Rho-shaped resonators is located near the feeding line to realize band-notched characteristic at ITU service bands (8.025–8.4 GHz), thus a quintuple band-notched UWB antenna is achieved. The shape factor (ratio of the −3 dB bandwidth to the −10 dB bandwidth) of the wide stop band is 0.56, which indicates that the antenna has excellent band-edge selectivity. To verify the performance of the proposed design, both the time-domain and the frequency-domain characteristics of the antenna have been studied and analyzed. The simulated and measured results verify the design as a good candidate for various portable UWB applications.

A High Selectivity and High Efficiency Filtering Antenna With Controllable Radiation Nulls Based on Stacked Patches

A high selectivity and high efficiency filtering antenna is presented in this communication. A double-layer filtering patch antenna is first proposed, which can generate a radiation null due to the mixed electric and magnetic coupling between the two patches. By changing the length of the slot line on the patch, the position of the radiation null can be flexibly set at the lower band edge or upper band edge. Based on this mechanism, a three-layer patch antenna with two radiation nulls is designed. Two radiation nulls are introduced on both sides of the passband, consequently, a quasi-elliptic bandpass response can be obtained. Moreover, the proposed antenna features high efficiency since no extra filtering circuit is utilized. A prototype antenna operating at 1 GHz is designed, fabricated, and measured for validity verification. The measured results agree well with the simulated one, showing that the prototype antenna has a fractional impedance bandwidth of 16% (0.91–1.07 GHz), a flat passband gain response with peak value of 8.83 dBi, a high efficiency about −0.41 dB in the passband. The band-edge selectivity is highly improved by the radiation nulls near the passband edge.

Compact, flexible and highly selective wideband complementary FSS with high angular stability

AbstractThis article presents a novel miniaturized (0.105λ0 × 0.105λ0) flexible complementary frequency selective surfaces (CFSS) structure with sharp band edge selectivity and very high angular stability. To explore two diverse applications as a passband and stopband filter, a novel complementary convoluted square loop (CCSL) type structure has been designed and investigated on ultrathin dielectric material of thickness 0.0023λ0. The second-order wide controllable passband with fractional bandwidth of 19.23% (−3 dB) and remarkably wide stopband of 64.7% (−10 dB) and 54.8% (−20 dB) respectively have been achieved by using a cascaded resonating structure which is composed of asymmetrical meandered CCSL array, arranged on two ultrathin dielectric layers with air foam separation. This particular format would lead to sharp band edge selectivity with steep roll-off (72.43 dB/GHz) and an excellent passband selectivity factor (0.731). An equivalent lumped LC circuit in conjunction with the transmission line model has also been adopted to comprehend the physical mechanism of the proposed single layer and double layer structures. Further, better passband and stopband angular stability at an oblique incident angle of 45° and the bending characteristics have also been investigated thoroughly for the proposed flexible CFSS to check their employability in different conformal structures with WiMAX passband and WLAN stopband application.

Self-consistent analysis of photonic-crystal surface-emitting lasers under continuous-wave operation.

We develop a self-consistent theoretical model for simulating the lasing characteristics of photonic-crystal surface-emitting lasers (PCSELs) under continuous-wave (CW) operation that takes into account thermal effects caused by current injection. Our model enables us to analyze the lasing characteristics of PCSELs under CW operation by solving self-consistently the changes in the in-plane optical gain and refractive index distribution, which is associated with heat generation and temperature rise, and the change in the oscillation modes. We reveal that the lasing band-edge selectivity and beam quality of the PCSELs are affected by the spatial distribution of the band-edge frequency of the photonic crystal formed by the refractive index distribution, which depends on the temperature distribution in the resonator. Furthermore, we show that single-mode lasing with narrow beam divergence can be realized even at high current injection under CW operation by introducing a photonic-crystal structure with an artificially formed lattice constant distribution, which compensates such band-edge frequency distribution.

Evaluating the impact of catalyst selection and semiconductor band edge on the photoelectrochemical production of H2O2 via a real-time in situ probe

Abstract Generating H2O2 through the use of photoelectrochemical cells (PECs) is attractive for integrating renewable energies into the production of this environmentally-friendly chemical oxidant. Here, we fabricate a PEC for producing H2O2, establish an effective analytical platform for studying this device, and determine optimal catalysts to use. Specifically, we use scanning electrochemical microscopy (SECM) as an analytical technique to measure H2O2 production in-situ from a PEC and study a variety of electrocatalysts and photocatalysts. The effects of materials properties such as photoanode band edge and H2O2 electrocatalyst selectivity are probed here to determine ideal catalytic properties for an optimal H2O2 PEC. This work successfully incorporated SECM as an H2O2 detection method into a 2-electrode PEC, and it also demonstrates the potential to streamline the discovery of new materials for implementation into a high efficiency H2O2 PEC.

A novel differential filtering patch antenna with high selectivity

A novel differential filtering antenna with high selectivity is proposed. The antenna is mainly composed of three different-size patches, a slot, a pair of differential feeding lines, and a line resonator. An air gap is adopted to improve the impedance bandwidth and the filtering performance. The line resonator helps to generate high common-mode (CM) rejection. Owing to the parasitic concave and convex patches, the filtering performance and the bandwidth of the antenna are enhanced. The parasitic concave patch affects the lower band-edge selectivity while the parasitic convex patch influences the upper band-edge selectivity. In addition, the frequencies of two radiation nulls can be controlled independently to achieve two high sharp roll-off rates by adjusting the lengths of the parasitic patches. Considerable impedance matching bandwidth is achieved through an aperture coupling. Finally, a prototype of the differential filtering antenna is fabricated and tested. The measured results are in good agreement with the simulated results, showing an impedance bandwidth of 9.9% and an average realized gain of 7.5 dBi. Besides, two filter zero transmissions located at 3.40 and 3.84 GHz produced two radiation nulls.

Selectivity and in-band impedance enhancement of a compact slot antenna with defected ground structures

AbstractIn this study, a new ultra-wideband (UWB) band-edge selectivity antenna with a modified radiation slot using defected ground structure (DGS) is presented to obtain bandpass filtering reflection coefficient and gain performance. The well-designed DGS is designed on backside metallic of the substrate and can be seen as a low-pass filter that provides a good roll-off at a higher frequency. By connecting the DGS and the stepped slot and making them merge with each other, good cut-off property in the upper passband and better in-band impedance characteristics are obtained. Measured results show that the proposed design not only shows good band-edge selectivity in reflection coefficient and gain performance but also has a good impedance matching of −13.5 dB reflection coefficients and a good radiation efficiency of 90% in the operating frequencies. The measured bandwidth defined with the reflection coefficient less than −10 dB is from 3.1–11.2 GHz. Furthermore, the size of the filtering UWB antenna is 22 mm × 12 mm, which is smaller than many individual UWB antennas and UWB filters.

Compact slot antenna with enhanced band‐edge selectivity and switchable band‐notched functions for UWB applications

In this study, a new reconfigurable stepped slot antenna with enhanced band-edge selectivity of the UWB passband and switchable band-notched characteristic is presented. Good out-of-band rejection and sharp cut-off at band-edge are achieved by the use of defected ground structure (DGS) and a parasitic slot near the stepped slot. The well-designed DGS not only produces transmission zero to obtain good cut-off property in upper sideband but also provides better impedance matching of in-band. The frequency range of the proposed antenna is from 3.1 to 11.1 GHz (114%) with the reflection coefficient < − 10 dB. The shape factor is 1.05, which indicates that the proposed design has an excellent selectivity. To obtain the notched band, two passive strip lines near the feeding line are designed. Furthermore, the reconfigurable function with four states can be easily realised by the control of two diodes between the passive strip line and the ground. The structures of the notched band and bias circuit are relatively simple and independent of antenna radiation structure. The performance of the antenna is presented and compared with other competitive antennas. The proposed design has many significant advantages in dimension, good out-of-band characteristics, and controllable states for different UWB applications.

Design of reconfigurable filtering ultra-wideband antenna with switchable band-notched functions

AbstractA compact reconfigurable filtering ultra-wideband (UWB) antenna with switchable band-notched functions is proposed. The basic structure of the proposed design is a filtering slot antenna with good band-edge selectivity using stepped impedance resonator feeding line. The reconfigurability is achieved by using two microstrip lines paralleling to the feeding line and two PIN diodes. The reconfigurable structure and bias circuit of the antenna are relatively simple and are not connected to the radiation structure, so they have little negative influence on the radiation characteristics of the antenna. Total four states could be achieved by using two PIN diodes to short the microstrip lines and ground. To verify the performance of the final design, multiple measured and simulated results in frequency and time domain are studied and analyzed. The measured results agreed very well with simulation. Compared with the traditional UWB antenna, the proposed antenna has advantages in size, filtering function in-band and out-of-band, and tunable states for multiple UWB applications.

SIW cavity‐backed dual‐band antenna with good stopband characteristics

A dual-band antenna with good stopband characteristics is proposed. Different from conventional antennas, two transverse slots are etched on a substrate integrated waveguide (SIW) cavity. Two half modes are excited to achieve a dual-band operation and two non-radiating modes, a TE110 mode and an even TE120 mode, are induced to generate radiation nulls. With the aid of the two radiation nulls, the stopband characteristics of the proposed design including non-radiating gain and band-edge selectivity are significantly improved. A fabricated prototype is measured. The measured centred frequency of two passbands is at 3.28 and 3.77 GHz, respectively. The maximum gain is about 5.2 dBi in the passbands while the minimum gain is only −18.9 dBi in the stopband. The measured efficiency is 86% in the lower passband and 75% in the upper passband but it sharply decreases to lower than 5% between 3.36–3.7 GHz.

In brief

PAGE 1259 Researchers in China have proposed an unconventional dual-band antenna with two transverse slots etched onto a substrate integrated waveguide (SIW) cavity. The design exhibits good stopband characteristics including significantly improved non-radiating gain and band-edge selectivity. Experimental results verify the effectiveness of the antenna and promote its use in wireless communication applications. PAGE 1302 i-vector based speech recognition frameworks require effective channel compensation methods for enlarging class differences while reducing class variations. Using a discriminatively learned network (DLN) a team of Chinese researchers used both speaker classification and supervising verification signals for identification. The DLN performs better than linear discriminant analysis (LDA) methods. Electric field distributions at different frequencies. PAGE 1298 A large collaboration of researchers from the USA and Qatar report the enhancement of electrical characteristics in thin film transistors (TFTs) by stacking layers with alternating precursor solution concentrations. The mobility of the fabricated alternating-layer TFT was higher than those with only single concentrations. Future work will study the underlying reason for this effect. Similar DNN parameter architecture. PAGE 1292 A novel analytical model of polarimetric dispersion (PD) based on frequency-domain range pulse compression has been analysed and proposed by researchers in China. The simulation results indicate that spaceborne P-band ultra-wideband synthetic aperture radar systems are heavily influenced by PD effects from ionospheric Faraday rotation. Field effect mobility of TFTs at different concentrations. PAGE 1260 A simple internal antenna combining a planar inverted F antenna and a loop antenna to achieve wideband ultra-high frequency operation for digital television applications has been presented by researchers in Korea. The antenna is implementable within T models with sufficiently wide bandwidth and high peak gain to provide good performance. Polarimetric distortion coefficient function with bandwidth. 3D structure of proposed loop antenna.

Integrated design of filtering antenna with high selectivity and improved performance for L-band applications

An integrated design of compact filtering antenna having high selectivity and suppressed unwanted harmonics is proposed in this paper. The proposed filtering antenna is obtained by integrating a modified elliptic-shaped monopole antenna with a modified interdigital bandpass filter (IBPF). At first, a modified elliptic-shaped monopole antenna is designed and investigated through numerical simulation and experimentally. Further, the modified IBPF reported in the literature is integrated with the proposed monopole antenna to achieve good passband selectivity and suppressed unwanted harmonics for the proposed filtering antenna. The proposed filtering antenna is analysed through numerical simulation software. The simulated −10 dB reflection coefficient bandwidth of the proposed filtering antenna covers the frequency range 1.01–1.96 GHz with improved band-edge selectivity and unwanted harmonic suppression up to 8 GHz (= 5.4 f0, where f0 is the centre frequency of passband). It has nearly stable omnidirectional radiation patterns over the whole frequency band. The proposed filtering antenna was fabricated and experimentally tested. The experimental results are nearly in agreement with corresponding numerical simulation results. The proposed filtering antenna can be a suitable candidate for various L-band wireless communication applications.

A new compact ultra-wideband filtering antenna with improved performance

ABSTRACTA new compact ultra-wideband (UWB) filtering antenna having good band-edge selectivity and suppressed unwanted harmonics is proposed in this paper. The proposed UWB filtering antenna is obtained by integrating modified elliptic-shaped UWB antenna with super-compact UWB bandpass filter (BPF). Initially, a UWB antenna is designed and investigated through numerical simulation and experimentally. Further, the geometrical parameters of BPF are optimized using numerical simulation software for its integration with the proposed UWB antenna to improve the passband selectivity and unwanted harmonic suppression capability of the proposed UWB filtering antenna. The proposed UWB filtering antenna has simulated −10 dB impedance bandwidth of 7.65 GHz (3.07–10.72 GHz) and unwanted harmonic suppression up to 30 GHz. It has nearly stable omnidirectional radiation patterns over whole UWB frequency band. The proposed filtering antenna was fabricated and experimentally tested. The experimental results for the filtering antenna are nearly in agreement with corresponding simulation results.