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A bandpass filter based on hybrid spoof surface plasmon polaritons (SSPPs) and half-mode substrate integrated waveguide (HMSIW) is proposed. The filter consists of a traditional HMSIW structure and an E-type slot array etched on the top metal layer of the HMSIW to support SSPP modes. The passband of the filter can be adjusted by changing the dispersion characteristics, which can be realized by tuning the parameters of the unit cell. The simulation results show that the proposed structure has great filter characteristics within a passband from 3.05 to 3.65GHz with high return loss (> 15 dB), low insertion loss ( 40 dB).

A 60 GHz third-order on-chip bandpass filter (BPF) based on half-mode substrate integrated waveguide (HMSIW) cavity is synthesized using GaAs pHEMT technology. Two coupling slots are etched to divide the HMSIW cavity into three resonators, and then a third-order Chebyshev BPF is designed with predicted transmission zero, return loss and bandwidth through the synthesis method. The theoretical and extracted external quality factor and coupling coefficients are used to determine the dimensions of the BPF. For demonstration, a BPF sample with a bandwidth of 29.2% is fabricated, and its simulations and measurements are in good agreement.

A miniaturized broadband on-chip bandpass filter (BPF) is presented based on shunt dual-layer meander-line resonators and several metal-insulator-metal (MIM) capacitors. To understand the operational mechanism of the proposed BPF structure, it is analyzed using a simplified LC equivalent circuit model for further investigation of the transmission zeros (TZs) distributions. To validate the proposed idea, the BPF with three TZs is implemented in a commercial 0.13- $\mu \text{m}$ SiGe (Bi)-CMOS process. The measured results show that the BPF has a center frequency at 18 GHz with a very broad bandwidth of 66.7%, and the minimum insertion loss within the passband is 2.9 dB. The chip, excluding the GSG pads, is about 0.318 mm $\times0.392$ mm.

A new dual‐band bandpass filter (BPF) using two very simple coupled microstrip rings is proposed in this paper. The two identical 3λg/2 microstrip rings are coupled each other with λg/2 coupled length, resulting in the generation of dual frequency bands with multiple transmission zeros (TZs). Theoretical deduction is presented to verify the proposed structure. The center frequencies and bandwidths of the two passbands can be tuned by controlling the impedance parameters of the microstrip rings. For demonstration, a prototype example of this dual‐band BPF is fabricated and characterized. The measured results show that it has high selectivity and great return losses of passbands with multiple TZs at the stopband.

A spoof surface plasmon polariton (SSPP) half-mode substrate integrated waveguide (SIW) is proposed by GaAs processing technique. Due to the strong field confinement of the SSPP propagation, as compared to the traditional solutions, the proposed solution shows better suppression to the self-generated coupling signal, which can be used to reduce the occupied areas of integrated circuits. Compared with existing SSPP-SIW structures, the proposed one is developed from GaAs techniques for the first time with the advantage of reduced size. And the proposed idea has the advantages of lower coupling due to the strong confinement of the SSPPs. To verify the proposed idea, such structure is designed, fabricated, and measured showing SSPP propagation and better coupling-suppression features.

In this paper, a Hewlett-Packard (HP) memristor model with a new window function and its versatile characteristics are presented. SPICE behaviors of the linear and nonlinear memristor model are studied through PSpice simulation. High flexibility is demonstrated for emulating the behaviors of the practical HP memristors. Furthermore, the characteristics of the composite SPICE behaviors are both investigated when two memristors are connected in series and in parallel. The polarity of each memristor is also taken into consideration. The relationships among flux, charge, voltage, current, and memristance of the double memristor circuits are simulated and analyzed.

The multilayered parallel-plate structure (MPPS) is a typical structure in microwave engineering. In numerical simulation, MPPS is usually modeled by an infinitely large planarly layered medium (PLM) to simplify the computation. For a realistic microwave circuit, however, the substrate is always finite in spatial extent, i.e., it is a finite-sized MPPS (FS-MPPS). To address this issue, a novel surface integral equation (SIE) formulation is proposed for the efficient simulation of FS-MPPS. In this article, the surface equivalence principle is first revisited. For the exterior and interior problems, different Green’s functions are utilized. In particular, the common homogeneous-medium Green’s function is used for the exterior homogeneous region, whereas the layered-medium Green’s function (LMGF) is applied for the interior multilayered structure. In this manner, FS-MPPS is no longer directly approximated by the infinite PLM model, but instead, it is modeled accurately by SIE whose integration kernel is derived from PLM. Finally, a PMCHWT SIE is established for the electromagnetic analysis of FS-MPPS. Due to the finite nature of the inner problem, the setting of PLM and LMGF is not unique. This nonuniqueness is studied in theory and verified by numerical simulation. It is revealed that such a nonuniqueness of the setting of the inner problem does not change the uniqueness of the final solution. To validate the proposed approach, a multidomain FS-MPPS and an FS-MPPS with embedded dielectric structures are investigated. Compared with the conventional brute-force SIE methods for FS-MPPS, where all the interfaces of the layered structure should be discretized and assigned with degrees of freedom (DOFs), the proposed method is more succinct and efficient.

We numerically demonstrate a tunable dual-band terahertz metamaterial absorber (MA) with near-unity absorption using single-layer square graphene ring structure with T-shaped graphene strips. By periodically loading four T-shaped graphene strips to the square graphene ring periodic array without additionally increasing the size of MA device, the pre-existing resonant frequency will have a red shift and simultaneously a new resonance will be generated at higher frequency for achieving a dual-band MA. The two absorption peaks can be tuned to the resonant frequencies of interest by varying the parameters of the square graphene ring and T-shaped graphene strips. The operating frequency of the absorption spectrum can be also manipulated by adjusting the chemical potential of graphene, without changing their geometric parameters. Additionally, numerical results show that the proposed MA possesses polarization-independent and incident-angle-insensitive properties. To further extend the proposed structure’s application with more absorption peaks, a tri-band MA is investigated through adding four more T-shaped graphene strips based on the dual-band absorber configuration. Therefore, our research work will be a good candidate for the design of various graphene-based tunable multi-band absorbers at different frequency regions with potential applications in optoelectronic devices and systems.

© 1989-2012 IEEE. Ultra-wideband spoof surface plasmon polaritons (SSPPs) based on compact balanced coplanar stripline (CPS) waveguides are proposed. Compared with the conventional CPS-based terahertz (THz) SSPP unit cell, the proposed one has achieved a size reduction of 55.2% under the condition of the same asymptotic frequency. The propagation and attenuation characteristics of the proposed SSPP waveguide can be easily manipulated by adjusting the geometry dimensions of the SSPP unit cell. It indicates that the cut-off frequency of the SSPP waveguide has its tunable flexibility thereby facilitating the filter design. To further validate the proposed idea, a similar topology in microwave regime is designed and measured, where the microwave feeding can be easily realized by embedding a balun structure from unbalanced microstrip line to balanced CPS. The measurement of the microwave filter prototype illustrates ultra-wideband bandpass filtering characteristics with return losses of over 10 dB and average insertion losses of 3.2 dB in the passband of 1.9-14 GHz. The presented work may have significant potentials to develop the miniaturization of various planar plasmonic devices and integrated circuits in microwave and THz regimes.

Spoof surface plasmon polaritons (SSPPs) are developed in a rectangular waveguide (RWG) to realize a controllable band-pass propagation feature for millimeter-wave applications. The proposed SSPP structure consisting of a single row of corrugated metallic blocks, is embedded inside the closed structure of an RWG. The dispersion property of the RWG-based SSPP (RWG-SSPP) has tunable lower and upper cut-off frequencies, and a band-pass filter with flexible bandwidth has been designed using an RWG-SSPP structure. The proposed band-pass filter is based on an RWG-SSPP with an all-metal structure, which is of great potential for millimeter-wave applications due to small losses.

The recent rise of active materials offers new opportunities for dynamically tunable metamaterial devices. However, metamaterial devices with a dynamically switchable function are in high demand. Inspired by previous studies, a dynamically switchable and tunable bifunctional THz (THz) metamaterial absorber based on vanadium dioxide ( V O 2 ) and graphene is proposed and investigated in this paper. Using the phase transition properties of V O 2 , the switchable performance between broadband near-perfect absorption and multiband near-perfect absorption can be achieved. When V O 2 is in the metallic state, the designed metamaterial absorber acts as a broadband near-perfect absorber with more than 90% absorption in the frequency range from 2.6 THz to 7.5 THz. Alternatively, the designed metamaterial absorber with the same geometry can be transformed into a tunable multiband absorber when V O 2 is converted to the insulated state. The performance of the absorber is analyzed by the multiple interference theory (MIT), which is in good agreement with the numerical simulation results. Due to the high symmetry of the structure, the presented absorber exhibits excellent polarization insensitivity and wide incident-angle stability, which opens a direction to design a new type of multifunctional metamaterial devices in the THz regime.

The problem of reducing the number of elements in a broadband linear array with multiple simultaneous crossover frequency-invariant (FI) patterns is considered. Different from the single FI pattern array case, every element channel in the multiple FI pattern array is divided and followed by multiple finite-impulse-response (FIR) filters, and each of the multiple FIR filters has a set of coefficients. In this situation, a collective filter coefficient vector and its energy bound are introduced for each element, and then the problem of reducing the number of elements is transformed as minimizing the number of active collective filter coefficient vectors. In addition, the radiation characteristics including beam pointing direction, mainlobe FI property, sidelobe level, and space-frequency notching requirement for each of the multiple patterns can be formulated as multiple convex constraints. The whole synthesis method is implemented by performing an iterative second-order cone programming (SOCP). This method can be considered as a significant extension of the original SOCP for synthesizing broadband sparse array with single FI pattern. Numerical synthesis results show that the proposed method by synthesizing multiple discretized crossover FI patterns can save more elements than the original iterative SOCP by using a single continuously scannable FI pattern for covering the same space range. Moreover, even for multiple FI-patterns case with complicated space-frequency notching, the proposed method is still effective in the reduction of the number of elements.

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 2f0 (f0: 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.

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.

The index of relative importance (IRI), niche breadth, and niche overlap (Q基于2016年5月至2017年2月在乐清湾进行的4个航次渔业资源调查数据,计算乐清湾主要游泳动物的相对重要性指数(IRI)、生态位宽度及生态位重叠值(

In this paper, some new spoof surface plasmon polariton (SSPP) waveguides are presented, including the fish-bone structure with enhancement of the field confinement, coplanar stripline-based SSPP waveguide, broadband high-mode SSPP waveguide, and differential-fed SSPP waveguide. The dispersion features and frequency response of these presented SSPP structures are demonstrated and analyzed providing guidance to facilitate further similar designs. Some of these proposed ideas are not only validated in terahertz regime, but also proved by designing, fabricating, and measuring the prototypes in microwave. Through these developments, the frontier of researches on SSPPs has been pushed forward.

This paper proposes a simple polarization reconfigurable annular ring slot antenna (ARSA). By introducing an appropriate inductance at a particular location across the annular ring slot, the circular polarization (CP) property can be attained. Two PIN diodes are incorporated to simultaneously provide the required inductance and switch between linear polarization (LP), right-handed CP (RHCP), and left-handed CP (LHCP). This simplified design employs the packaging parasitic inductance, and hence eliminates the necessity of additional CP perturbation structures. All three polarizations exhibit good impedance matching. Excellent CP performance has been obtained for both CP polarizations.

A compact coplanar waveguide (CPW)-fed ultra-wideband (UWB) monopole antenna using embedded E-shaped structure with wireless local area network (WLAN) band-rejection is presented. The introduction of this E-shaped structure working as the radiator can enhance the impedance bandwidth of the UWB antenna without increasing the overall size. For preventing the interference from WLAN system, a pair of L-shaped stubs are connected to the ground of UWB antenna to create the rejected band. The center frequency of this rejected band is about 5.5 GHz with the rejection range of 5.2~5.8 GHz. Good agreement can be observed between the simulated and measured results.

In this paper, a compact circularly polarized co-designed filtering annular slot antenna (ASA) is proposed. The antenna comprises a distributed capacitor-loaded annular slot radiator to produce circular polarization (CP) radiation, which is seamlessly integrated with a microstripline bandpass filter (BPF) to enhance out-of-CP-band suppression. Two tightly coupled arc branches protruding into the annular slot are used to provide the required perturbation capacitance. The filter is designed by employing three concentric arc-shaped coupled microstripline resonators. The ground plane is shared by the annular slot radiator and the filter to reduce size occupation. It is found that the proposed antenna can not only yield high frequency selectivity, but also obtain widened CP bandwidth under the assistance of the filtering circuit. An antenna prototype has been fabricated and measured, showing that the antenna achieves a 10 dB return loss impedance bandwidth of around 13.7%, enclosing a 3 dB axial ratio (AR) bandwidth of more than 10.6%. Details of design considerations and experimental results are presented and discussed.

Double dipoles on a single-layer substrate are utilized to construct a triple-mode printed quasi-Yagi antenna for the multi-band and broadband antenna applications. A stub-loaded dipole generating two resonant modes (i.e., lower dual-mode dipole) is allocated on the underside of a simple dipole (i.e., upper single-mode dipole) introducing the third resonant mode. Using these three resonant modes, three compact printed quasi-Yagi antennas, i.e., tri-band, dual-band, and broadband printed quasi-Yagi antennas, are designed with the same antenna prototype but different parameter values. Seen from the measured results, all of these three antennas have good unidirectional radiations, high radiation efficiencies, and low cross-polarization levels at the operating frequencies within the impedance bandwidths.

A tunable dual-band bandstop filter (BSF) in the far-infrared region is proposed based on a graphene surface plasmon. The BSF consists of a graphene waveguide and two graphene-ribbon resonators on the SiO2/Si substrate, supporting waveguide mode and edge mode, respectively. The influence of graphene structure parameters on transmission spectra is numerically investigated, which shows that the resonant properties are sensitive to the lengths of the graphene-ribbon resonators, and each stopband of dual-band BSF can be individually designed and tuned without affecting the other stopband. Moreover, the center frequencies of the two stopbands can be actively tuned independently by respective chemical potential of graphene-ribbon resonators. The proposed filter structure is promising to be utilized in future photonic integrated circuit applications as an ultracompact dual-band BSF.

A dual-layer patch antenna using multiple parasitic patches for the bandwidth enhancement is presented. Two additional resonances can be obtained with the help of the parasitic patches of the antenna. Consequently, a wide impedance bandwidth of 17% ( $\vert \text{S}_{\mathbf {11}}\vert dB) can be achieved. Then, without the increase of the antenna array footprint, the combinations of two decoupling techniques (i.e., metalized via walls and short-circuited stepped-impedance structures as the neutralized networks) are adopted for mutual coupling reduction when the antenna element is extended to $2\times1$ , $2\times2$ , and even $4\times4$ array applications. To validate the design idea, a $2\times2$ antenna array is fabricated and tested, whose measured isolations between any two feeding ports are better than 28 dB within the frequency range of 3–4 GHz. The measured peak gain fluctuates from 12.6 to 13.6 dBi within the 10-dB impedance band of 3.35–3.95 GHz, and the cross-polarization levels in both the E- and H-planes are lower than −38 dB at the boresight direction.

© 2013 IEEE. A compact triplexer based on E-stub-loaded composite right-/left-handed (ESL-CRLH) resonators with quasi-lumped impedance matching network is presented in this paper. The equivalent circuit model of the ESL-CRLH resonator is presented first and its left-/right-handed capacitance/inductance elements are fully derived. Then, a quasi-lumped impedance matching circuit is designed to connect the three ESL-CRLH resonator based filter channels for the triplexer construction. Finally, the designed triplexer obtains high isolations among the ports and low in-band insertion losses of the three filter channels centered at 1.86, 2.41, and 3.25 GHz, of which a miniaturized layout has been realized. Good agreement between the simulated and measured results can be observed to validate the design idea.

A novel high-selectivity bandpass filter (BPF) with multiple transmission poles (TPs) and transmission zeros (TZs) using six pairs of quarter-wavelength coupled lines has been presented. By employing two pairs of side-coupled lines and four pairs of open/shorted coupled lines, high roll-off skirt characteristic, and good stopband rejection can be achieved with five TPs and six TZs. Theoretical analysis is explained and simulated results are illustrated for this high-performance filter. Finally, a BPF example with a centre frequency of 1.9 GHz and a 3 dB fractional bandwidth of 9% is designed, fabricated, and measured. It is shown that the measured lower and upper stopband rejections are better than 38 and 16 dB, respectively. Good agreement between the simulations and measurements validates the design method.

A compact fifth-order wideband bandpass filter (BPF) using simple coupled lines with sharp rolloff skirts is proposed in this letter. Five transmission poles within the passband and eight deep transmission zeros from 0 to $2\!f_{0}$ ( $f_{0}$ denotes the center frequency of the passband) can be realized through input impedance calculations. For demonstration, a wideband BPF prototype centered at 2.05 GHz with high-stopband rejection is designed and fabricated, whose measured 3-dB fractional bandwidth is of 60% (1.44–2.66 GHz). Good agreement between the simulations and measurements validates the design idea.

A half-mode substrate integrated waveguide (HMSIW) combined with spoof surface plasmon polariton (SSPP) structure is proposed to realize bandpass filter (BPF) characteristic and miniaturization, which is termed as the half-mode substrate integrated plasmonic waveguide (HMSIPW). Compared with the conventional HMSIW structure having identical cutoff frequency, this new design of HMSIPW not only supports SSPP modes, but also realizes a transversal size reduction of 19.4% and longitudinal reduction of more than 60%. Then, a diplexer based on two back-to-back placed HMSIPW BPFs is designed, and it has only one row of metallized via holes to further reduce the transversal size. The experimental prototypes of the filters and diplexer have been manufactured, and the measurement results agree well with simulation ones. Due to the size miniaturization and simple structure, the proposed designs will have many potentials in the integrated devices and circuits for wireless communication systems.

We numerically demonstrate a switchable metamaterial absorber with two states (i.e., ultra-broadband and narrowband) in the terahertz region. Such switchable functionalities are accomplished by using a simple absorption system consisting of a hybrid metamaterial with vanadium dioxide ( V O 2 ) and graphene. Theoretical calculations show that when V O 2 is in the metal state, the absorption system without a graphene ring can act as a broadband absorber. For the broadband absorber, the absorption bandwidth of 5.05 THz (i.e., 93%) can be obtained under the condition of over 90% absorption rate, covering a frequency range of 2.91–7.96 THz. Meanwhile, the absorber exhibits tunable characteristics, whose absorption rate can be continuously adjusted from 1% to 99% by controlling the conductivity of V O 2 from 2 × 1 0 2 to 2 × 1 0 5 S / m . It is polarization-insensitive with a large angle tolerance in both transverse electric and transverse magnetic waves. Multiple interference theory is used to analyze the mechanism of the broadband absorber, and the theoretical results are in good agreement with simulations. When the V O 2 is changed to the insulator state, the absorber system with a graphene ring can be switched to a narrowband absorber. This work will have great potential applications in the terahertz regime, such as tunable broadband absorbers, dynamic sensing, cloaking, and photodetectors.

A higher order approach for the accurate simulation of a thin dielectric sheet is proposed in this paper. Due to the small thickness of thin dielectric sheet, an equivalent surface integral equatio...

© 1963-2012 IEEE. A virtual active element pattern (AEP) expansion method is presented in which each AEP in an unequally spaced array is considered to be the pattern radiated by a subarray of some equally spaced virtual elements. With the help of this method, the pattern of an unequally spaced array including mutual coupling can be efficiently evaluated by fast Fourier transform (FFT). By incorporating this idea into the iterative Fourier transform procedure, we develop a novel iterative synthesis method, which can apply the iterative FFT to efficiently synthesize unequally spaced arrays including mutual coupling. Different excitation constraints, such as phase-only control and amplitude-phase optimization with a prescribed dynamic range ratio, can be easily added into the proposed synthesis procedure. A set of synthesis examples for different antenna arrays with pencil and shaped beam patterns are provided to validate the effectiveness and advantages of the proposed method.

On the basis open stub-loaded tri- and quad-mode resonators, two compact microstrip low-pass filters (LPFs) with deep and ultra-wide stopband are presented. Modal characteristics of the tri- and quad-mode resonators are analysed by even–odd-mode method. Multimode resonator can be modelled as multiple LC resonant circuits and the lumped-element equivalent circuit models of the proposed LPFs are presented. The tri- and quad-mode resonators have strong slow-wave and bandstop effects, which can achieve ultra-wide and deep stopband and size reduction in the design of LPFs. For the proposed low-pass filter using tri-mode resonators, the 3 dB cutoff frequency is 2.5 GHz and the stopband with 40 dB suppression is from 4.5 to 17.7 GHz. The low-pass filter based on quad-mode resonators has a 3 dB cutoff frequency of 2.2 GHz and the stopband with 30 dB suppression is from 4.1 to 18 GHz.

© 2002-2011 IEEE. A novel method called alternating convex optimization is presented to synthesize unequally spaced linear arrays with minimum element spacing constraint. In this method, the problem of synthesizing an unequally spaced array is formulated as a sequence of alternating convex optimization problems, and the excitation vector and auxiliary weighting vector are alternately chosen as the optimization variables. The minimum spacing constraint for considering the physical element antenna size can be easily imposed in this alternating optimization process. Two examples for synthesizing unequally spaced linear arrays with focused and shaped patterns are provided to validate the effectiveness and advantages of the proposed method.

A novel short- and open-stub loaded spiral resonator (SOSL-SR) is presented and analysed by the odd- and even-mode method to obtain three controllable resonant modes. Therefore, a triple-mode bandpass filter (BPF) has been designed with good frequency selectivity based on the proposed SOSL-SR. Then, by dividing these three resonant modes into two passbands or stopbands, a dual-band BPF and a dual-band bandstop filter using the proposed SOSL-SR have been demonstrated. Because of the spiral structure, the sizes of these three designed microstrip filters are reduced significantly. Good agreement between simulated and measured results validates the design concept.

A novel but very simple bandpass filter using just three pairs of coupled lines with multiple transmission zeros (TZs) and transmission poles is proposed in this letter. The filter structure can be seen as the two one-wavelength ring resonators coupled each other with $\lambda _{g}/4$ coupled length and sandwiched between the $3\lambda _{g}/4$ input and output feedlines. Good out-of-band suppression and sharp roll-off skirts can be realized by multiple fixed and tunable TZs without complicated coupling scheme. For further demonstration, a filter example with center frequency at $f_{0}= 2.1$ GHz is implemented with generation of eight TZs at the frequency range from 0 to $2f_{0}$ for theoretically calculated certification. Good agreement between simulation and measured results validates the design method.

A compact seventh-order wideband bandpass filter (BPF) with sharp roll-off skirts using coupled lines and open stubs (OSs)/shorted stubs (SSs) is proposed. Seven transmission poles in the passband and four deep transmission zeros from 0 to 2f 0 (f 0 denotes centre frequency of the passband) can be realised with the help of half-wavelength OSs and quarter-wavelength SSs. For demonstration, a wideband BPF prototype is designed, fabricated with a measured 3-dB fractional bandwidth of 78% (1.22–2.77 GHz) and transition band roll-off rates of over 175 dB/GHz. Good agreement between the simulations and measurements validates the design method.

In this paper, a tunable bandstop filter (BSF) based on quarter-wavelength stepped-impedance resonators is proposed. The center frequency of the BSF is continuously tunable by changing the voltage of the varactor diodes that loaded at the end of resonators. The experimental result shows it has the in-band suppression level of larger than 30 dB and out-of-band insertion loss of smaller than 1.3 dB. Six similar tunable BSFs with different sizes are designed and controlled by the programmable SP6T switch to obtain wider frequency tunable range of 1-6-GHz.

Feasibility study of low profile multilayer patch antennas using stacked BSTO-YIG thin film heterostructure has been investigated. This stacked heterostructure is comprised of an electrical-field-tunable ferroelectric BSTO with two embedded platinum electrodes, a ferromagnetic YIG thin film on a GGG substrate, and a relatively rigid Si substrate. The heterostructure dielectric parameters were analyzed. The calculated results demonstrate that a BSTO-YIG can be only tuned over a relatively narrow bandwidth.

Two quarter-wavelength three-line coupled structures (TLCSs) are employed in the design of filtering power divider (FPD) to achieve a wide fractional bandwidth and good out-of-band rejection. The center frequency of the FPD passband can be adjusted flexibly by changing the length of the TLCS while the fractional bandwidth will remain unchanged. The frequency selectivity and passband bandwidth of the FPD can be easily controlled with the variations of the TLCS width and gap, respectively. Furthermore, the proposed FPD topology can be extended to design a four-way FPD through adding two conventional Wilkinson power dividers. This four-way FPD is fabricated with the center frequencies of 2.42 GHz and 3-dB fractional bandwidths of over 100%. The simulated and measured results are compared with good agreement.

A fifth-order bandpass filter (BPF) using three pairs of coupled lines and two shorted stepped-impedance stubs is proposed in this paper. Five transmission poles (TPs) within the passband and six deep transmission zeros (TZs) from 0 to 2f 0 (f 0 :passband center frequency) can be realized through input admittance calculation. For demonstration, a sharp roll-off BPF prototype centered at 2 GHz with good in-band characteristics (insertion losses and return losses) and high stopband rejections is designed, whose 3-dB fractional bandwidth is of 34%.

Two-dimensional materials (2DMs) such as graphene and black phosphorus (BP) have aroused considerable attentions in the past few years. Engineering and enhancing their light-matter interaction is possible due to their support for localized surface plasmon resonances in the infrared regime. In this paper, we have proposed an infrared broadband absorber consisting of multilayer graphene-BP nanoparticles sandwiched between dielectric layers. Benefiting from the properties of graphene and BP, the absorber exhibits both perfect broadband responses and strong anisotropy beyond individual graphene and BP layers. The absorber is tunable with the variation of geometric parameters as well as the doping levels of graphene and BP. The physical insight is revealed by electric field distributions. Furthermore, the angular robustness for incident wave is investigated. The proposed anisotropic omnidirectional broadband absorber may have promising potential applications in various biosensing, communication and imaging systems.

A graphene-based dual-band bandstop filter (DB-BSF) is presented in the infrared band. The filter is made up with a graphene waveguide and two graphene-ribbon resonators on the Al2O3/Si substrate, which supports waveguide mode and edge mode, respectively. The center frequency of each stopband can be independently adjusted by applying different bias electric fields upon graphene ribbons. The proposed configuration is significant in novel optical communication systems as a critical component.

An electronically reconfigurable notch filter for cognitive radios application is presented. By loading the stub-loaded resonator along the transmission line, two notched bands are created. Central frequency tuning of one notched band is realized by using the silicon varactor diodes, while the other notched band remains almost unchanged during tuning. Bias Ts and the resistors having high resistance value are adopted to function as DC paths for the varactors. A tuning range of 1.92–2.92 GHz for the one notched band with average insertion loss 2.4 dB across the passband (0.1–5 GHz) is achieved, and the other notched band is used to suppress the WiMAX signal (3.3– 3.8 GHz). The highest rejection level of the tunable notched band is 21.5 dB, while the static notched band shows rejection of more than 30 dB at 3.66 GHz.