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In this research article, A miniaturized hexagonal split-ring 2.5-dimensional (2.5-D) unit cell is proposed for frequency selective surface (FSS) applications. The 2.5-D FSS provides efficient usage of the available surfaces and optimum increased current paths by connecting its two sides through vias. The size of the FSS unit cell is 0.026 λ 0 × 0.026 λ 0 at the resonance frequency of 1.25 GHz. The proposed FSS has good angle stability due to its small size. The effects of variation of FSS geometry parameters on transmission zero are investigated, namely, the control of bandwidth and roll-off of frequency response by these parameters is studied. An equivalent circuit is obtained for the proposed structure to predict its frequency response, which agrees very well with the results of full-wave simulations. A prototype model of the proposed FSS structure is designed, simulated, fabricated, and tested as proof of concept. [ABSTRACT FROM AUTHOR]

A new design of single‐layered balanced filtering crossover with high selectivity based on square patch resonator is proposed. Originated from the degenerate modes, that is, TM12 and TM21 on square patch resonators, the feasibility of intrinsic common‐mode (CM) suppression and channel isolation is conceived. For demonstration, a first‐order balanced crossover prototype is designed. Afterwards, to enhance selectivity, a square patch resonator is subtly divided into two identical parts and then introduced into the prototype. Hence, a balanced filtering crossover with a fifth‐order Chebyshev response is formed. Furthermore, stubs are deployed between adjacent patch resonators to introduce mixed couplings. Thus, two controllable transmission zeros are obtained, and better out‐of‐band suppression is achieved. Ultimately, the proposed crossover is fabricated and measured. High performance in terms of differential‐mode filtering response, in‐band CM suppression and channel isolation demonstrates the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

This letter presents a six‐channel bandpass filter bank created on substrate integrated waveguide (SIW) with improved bandwidth and frequency selectivity on the lower band. Through SIW square cavities and slant slots, a two‐dimensional multichannel bandpass filter bank with a transmission zero constructed with the SIW orthogonal resonant modes is produced. The substrate integrated square cavity approach is used to achieve the propagation of the two orthogonal‐oriented transverse electric modes, TE102 and TE201, which resonate on the same frequency and bandwidth, depending on the location of the feed ports. The bandwidth could be altered by the coupling matrix synthesis and coupling windows. Better transmission and bandpass responses are produced in each channel when the feed ports and coupling gaps are positioned and appropriately adjusted. However, a pair of slot lines are imprinted along each cavity's designated diagonal to guarantee better isolation while attaining an increased fractional bandwidth. A 3 × 3 array of six bandpass filters with a center frequency of 8.65 GHz has been built, simulated, and measured to establish the suggested technique. Low insertion loss, high return loss, high isolation, an improved fractional bandwidth, and a compact device were the proposal's advantages. [ABSTRACT FROM AUTHOR]

The development of next-generation transceiver system on the terahertz (THz) band demands the integration of key waveguide filters. In this paper, a dual-band filter using TM dual-mode cavities is proposed based on the stackable multilayer MEMS technology to achieve a highly compact design. TM120 and TM210 dual modes in the nearly square cavity have been introduced into the waveguide filter for obtaining the dual-band response. In addition, the non-resonating mode of TM110 in the cavity can be exploited as modal bypass coupling, which can generate two transmission zeros in the vicinity of each passband. Finally, such 220 GHz 3rd-order dual-band waveguide filter with quasi-elliptical response is fabricated through the silicon-based micromachining and nine stacked silicon platelets packaging techniques to achieve the compact thickness of only 2.34 mm. The measurement exhibits that the packaged filter has obtained the 3-dB fractional bandwidths of 4% from 217.5 to 226.5 GHz and 2.9% from 235.5 to 242.5 GHz, low insertion loss of about − 1.2 dB, as well as four obvious transmission zeros in the out-of-band, respectively. The exploitation of the advanced TM multi-mode cavity exemplifies innovation for highly compact THz waveguide filters, which are ideally suitable for multilayer silicon-based micro-processing. [ABSTRACT FROM AUTHOR]

This paper proposes a new type of hybrid eighth‐mode substrate integrated waveguide (EMSIW) and microstrip line (MSL) bandpass filter (BPF) with mixed electric and magnetic coupling. Firstly, two second‐order EMSIW BPFs with mixed coupling and wide stopband performance are investigated. Then, in order to realise high‐order BPF with decent performance, half‐wavelength (λ/2) open‐circuited MSL resonators are employed in the hybrid BPFs design. In the end, two third‐order BPFs and a fourth‐order BPF are developed by combining the EMSIW and MSL resonators together. Extra transmission zeros can be introduced due to the cross couplings in the trisection and quadruplet topologies. For demonstration, the proposed prototypes are designed, fabricated and measured. Reasonable agreements can be achieved between the measurement and simulation. The proposed third‐order BPFs compete against the state of the art, exhibiting the competitive characteristics of the operating bandwidth, physical footprint and upper‐stopband rejection with less order. The proposed fourth‐order BPF features a compact size of 0.34 × 0.34λ0, a low insertion loss of 1 dB, a broad 3‐dB fractional bandwidth of 22.9% and an excellent lower‐stopband suppression. [ABSTRACT FROM AUTHOR]

A novel balanced-to-unbalanced (BTU) Bagley power divider (BPD) with input-reflectionless filtering characteristics is proposed. It features a balanced input port and three single-ended output ports, which is difficult to achieve by means of conventional BTU power dividers. The filtering characteristics are achieved by parallel coupled lines. To further improve the differential-mode filtering selectivity, stepped impedance resonators are applied to introduce two transmission zeros near the passband. The input-reflectionless characteristic in the bandstop region is achieved by loading absorptive branches. For verifying the proposed power divider topology, a prototype of microstrip BTU Bagley power divider operating at 1.0 GHz is designed and fabricated with 3-dB filtering bandwidth of 72%. Furthermore, 10-dB input-reflectionless bandwidth covers the full measurement frequency from 0 to 2.5 GHz. Good agreement between the simulation and measurement validated the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a dual notches ultra-wideband (UWB) bandpass filter (BPF) with high selectivity and wide stopband. It is composed of a multi-mode resonator (MMR) known as a double-T-shaped open stub-loaded MMR, a pair of interdigital coupled lines, and folded split ring resonator. The MMR is designed to place the resulting resonant modes within the UWB passband, then add interdigital coupled lines to achieve strong coupling, resulting in a flat passband. Afterward, multiple complimentary folded split ring resonators (CFSRRs) and folded split ring resonators (FSRRs) are embedded into the designed basic UWB filter to develop dual notches at the desired frequency. The filter is simulated and manufactured using low-cost high-frequency dielectric substrate F4BM. The measurement results agree well with the simulation data. Multiple notches centered on 5.8 and 8 GHz effectively suppress unwanted signals from 5.8 GHz WLAN and 8 GHz satellite systems simultaneously. In addition, two transmission zeros on both sides of the passband are located at 2.7 GHz and 10.76 GHz, respectively, so that the sharp skirt selectivity is improved to 0.857. The measured filter can exhibit high sharp selectivity and wider stopband at the same time. [ABSTRACT FROM AUTHOR]

In this paper, a compact, symmetric, simple, and highly selective Ultra Broad Band (UBB) Band Pass Filter (BPF) is constructed on a low-loss Taconic dielectric substrate. The top layer of the BPF is loaded with three headphone-shaped Defected Microstrip Structures (DMSs) and four Open Circuit (OC) stubs whereas the bottom layer is etched with three star-shaped Defected Ground Structures (DGSs). The proposed BPF is designed and simulated using High-Frequency Structure Simulator (HFSS) software at f0. The proposed BPF shows 20 dB return loss and 0.4 dB insertion loss in the 3 dB passband covering 0.52 GHz to 17.1 GHz owing to 16.58 GHz Band Width (BW). Additionally, 10 dB and 25 dB upper stopband rejection is achieved with 1.3 GHz and 1 GHz BW, respectively. Maximum group delay of the simulated filter is about 2.95 ns. The fabricated model transmits from 0.8 GHz to 17.4 GHz which in turn offers a 16.6 GHz BW at 3 dB level. The reflection coefficient of the fabricated filter is about 18 dB, and insertion loss varies from 0 dB to 0.72 dB inside the Transmission Band (TB) with a Fractional Band Width (FBW) of 178.5% and 3.35 ns maximum group delay. Moreover, the occurrence of Transmission Zeroes (TZs) and Reflection Poles (RPs) make the filter highly selective and low loss (flatness). The measured results agree with the simulated outputs with slight deviations due to fabrication tolerances and connector loss. The size of the filter is 0:36μg - 0:36μg. Thus the proposed filter is suitable for mobile phones and satellite communication applications approximately covering L, S, C, X, and Ku frequency bands. [ABSTRACT FROM AUTHOR]

A compact but very simple dual-band bandpass filter (BPF) based on just five pairs of coupled lines is designed in this paper. It can be examined using the even- and odd-mode method because of its symmetry structure. Six transmissions zeros (TZs) can be obtained and calculated by using input impedance analysis. For demonstration, a dual-band narrowband BPF example with center frequencies at 0.94 and 1.12 GHz is fabricated and measured. The 3-dB fractional bandwidths of two passbands are 2% (0.93–0.95 GHz) and 3.4% (1.1–1.14 GHz), whose frequency ratio of upper-band to lower-band is very small. The measurement results agree with the simulation results, confirming the design process. [ABSTRACT FROM AUTHOR]

In recent years, Split-Ring Resonators (SRRs) and Complementary Split-Ring Resonators (CSRRs) have gained significant attention for their unique electromagnetic properties, such as negative permeability and negative permittivity, making them promising candidates for advanced microwave devices. This paper presents the design and analysis of a substrate-integrated waveguide (SIW) filter using CSRR structures for miniaturization. The improved CSRR unit can be easily integrated on the surface of the SIW, making it an ideal candidate for the design of compact SIW filters. In this paper, an improved CSRR-loaded SIW filter is designed and analyzed based on its equivalent lumped parameter model. A filter with a center frequency at 22.6 GHz is designed. Several transmission zeros (TZs) are also realized to improve the skirt selectivity of the filter. The design process involves theoretical analysis and electromagnetic simulations to optimize the dimensions of the CSRR resonators to achieve the desired filter characteristics. The measured and simulated results show good agreement, confirming the effectiveness of the proposed improved CSRR-loaded SIW filter. The successful implementation of the improved CSRR-loaded SIW filter demonstrates its potential for achieving miniaturization and enhanced performance in advanced microwave applications. [ABSTRACT FROM AUTHOR]

A miniaturized microstrip low‐pass filter (LPF) has been designed and fabricated using semicircular‐shaped resonators. The designing procedures as well as the LC equivalent circuit of each step have been reported. Due to the small size of the presented filter, flat group delay in the pass‐band, low insertion loss (IL), and high return loss (RL) in operational frequency. By producing adjusted transmission zeros (TZs), the second to fourth unwanted harmonics were attenuated using the proposed LPF. The machine learning approach has been utilized to adjustment of the filter parameters. The 3 dB cut‐off frequency (Fc), TZs, IL, and RL were predicted using the group method of data handling neural network (GMDHNN). Ninety simulations were performed with different inductor and capacitor values. The collected data were used for neural network training. The GMDHNN can diagnose the efficient inputs, so this feature was applied to determine the efficient L and C elements on TZs, Fc, IL, and RL. Finally, the fabricated filter results are well‐matched with the simulation ones. IL and RL of the suggested filter in operational frequency are −0.09 and −17.26 dB, respectively. The total filter size is only 14.65 mm × 3.5 mm. [ABSTRACT FROM AUTHOR]

In order to meet the increasing demand for adjustable devices in the modern wireless communication system, a compact bandpass filter with active switchable passband is proposed. The filter is based on the half mode substrate integrated waveguide (HMSIW), and uses its cut-off characteristics to form the lower stopband. The resonant characteristics of a quarterwavelength shorted stub generates a transmission zero (TZ) at higher frequency, which forms the upper stopband. The active control of DC power supply determines the biased states of PIN diodes to change the electrical size of the filtering parts. When the diodes are reverse biased, the filter works in C band with the passband of 3.9-5.2 GHz; when the diodes are forward biased, the passband shifts to S band of 2.7-3.6 GHz. The 28.6% relative bandwidth in both frequency bands remains constant. The simple design realizes the active switching between bands, providing a promising idea for active adjustable devices. [ABSTRACT FROM AUTHOR]

Absorbing radiation is a major challenge from the initial period and much research has still in progress in the area of absorbing radiation coming from space. In the absorber materials and structure field, it is hardly noticed that having uniform absorbance has many applications. To utilize these applications thick film structures have been investigated in this study. Here in this work, the proposed three-layer structure gives almost similar absorption over the full spectral range. The proposed structure is demonstrating above 98.09% absorption over the entire spectrum which is observed. Where the maximum absorption is 98.36% for a wavelength range of 2800 nm and the minimum absorption is 98.09% for a 200 nm wavelength range. In this paper, we proposed the structure is performing almost 98.09% absorption with ± 0.27% of variation with wavelength. Thick film structures are easy to fabricate and fewer materials require in that; which leads to low-cost devices. The devices that can be designed using this structure have applications in optical sensors, bio-sensors, and other devices used for nuclear reactors, satellites, and spacecraft-like technology due to zero transmission of radiation. [ABSTRACT FROM AUTHOR]

In this work, a highly directional ultra-wideband (UWB) microstrip patch antenna as a single-element is suggested. The proposed antenna’s gain is enhanced with a novel dual-band frequency selective surface (FSS) placed beneath it. The FSS design has a hexagonal structure with meander line inductances and a capacitance-like structure connecting all of the corners to the middle. There is no metallic layer on the other side of the substrate, which shows transmission zeros at 4.95 GHz and 12.7 GHz, and a modified U-shaped monopole antenna is developed. First, the performance characteristics of the antenna and FSS are analyzed from the simulation results, and they are validated experimentally after fabrication, followed by measurement. The compact configuration comprises an antenna loaded with the proposed FSS results S11 less than -10 dB from 3.15 GHz to 22.65 GHz, covering the UWB band together with the X, Ku-band with a bandwidth of 19.5 GHz (151.16% FBW). The antenna’s overall physical dimensions would be 38.8 mm×38.8 mm×25.2 mm (0.407λo×0.407λo×0.265λo), with λo denoting the lowest frequency’s free-space wavelength. The FSS loading results in a 9.9 dBi maximum gain at 10 GHz. The antenna’s small size increases bandwidth, and its high peak gain makes it ideal for use in real-time applications. [ABSTRACT FROM AUTHOR]

In order to meet the requirements for the suppression of mirror frequencies in the 5G RF front end, this paper proposes a novel miniaturized image rejection bandpass filter by loading SteppedImpedance Resonators (SIR). By analyzing the relationship between the impedance ratio of a halfwavelength SIR and its electrical length, we have designed an improved second-order bandpass filter, which reduces the size by 34.3% compared to traditional five-order hairpin filters. In order to further enhance the performance of the filter, the use of a radial stub, as opposed to the traditional rectangular open stub, allows for the generation of a wider band transmission zero, which can be analyzed using lumped equivalent circuits. This integration improves the stopband rejection of the filter. The results show that the passband range is 5.35 GHz–6.64 GHz; the rejection in the stopband range 8.10 GHz– 11.98 GHz is over 45 dB; and the size is only 0.385λg × 0.295λg. [ABSTRACT FROM AUTHOR]

This article presents a simple method to introduce multiple Transmission Zeros in the stopbands of a triple passband Chebyshev filter and also suppress the spurious bands below a satisfactory level, so that it can be treated as a Quasi-Elliptic filter. A pair of Stub Loaded Step Impedance Resonators (SLSIRs) is used to produce the Chebyshev filter with central passbands at 2.5, 5.5, and 9 GHz. An asymmetric Non-Resonating T (NRT) structure is implemented on each of the SLSIRs to achieve the improved skirt selectivity. Each non-resonating structure produces three Transmission Zeros (in total six). In addition to the satisfactory stopband performances, the Quasi-Elliptic triple band filter produces insertion losses of |0.4|, |0.6|, and |0.7| dB at three centre frequencies, respectively. Simulation of the proposed filter is done using HFSS13 software, and to validate the simulation, a prototype is fabricated on an Arlon AD250 (Dielectric Constant 2.5, height 0.76 mm) substrate. [ABSTRACT FROM AUTHOR]

Interconnects have become a major obstacle in chip scaling. Spoof surface plasmon polariton (SSPP) modes have gained attention for their ability to manipulate light beyond diffraction limits at a given frequency, leading to SSPP interconnects. This article investigates the transmission characteristics of SSPP interconnect pairs placed side by side in the terahertz frequency range with comprehensive performance analysis. The proposed SSPP waveguide pair exhibits a maximum transmission coefficient of around −0.05 dB in the −3 dB band in the terahertz frequency range. Due to field confinement near the metal–dielectric interface, energy remains confined for the designed SSPP interconnect pair system. The proposed SSPP structure shows several bands in the terahertz frequency range, whereas conventional interconnects shows almost zero transmission at such frequencies. Additionally, the effect of geometric parameters on transmission coefficients (S 21 ) and coupling coefficients (S 41 ) has been investigated. Moreover, it has been shown that the bandwidth, as well as the upper cutoff frequency, can be tuned by varying the geometric parameters such as groove height, groove width and groove density. Since global interconnects undergo bending in actual circuits during distant data transmission on chips, geometric mismatches may occur between adjacent pairs of SSPP interconnects. Hence, it has also been examined how bending and mismatches affect transmission and coupling coefficients. Several SSPP schemes have been simulated, among which the best performance is obtained with 2 μ m mismatch in groove height. For this optimized design, two corrugated metal interconnects are considered with groove heights of 20 μ m and 22 μ m, respectively, a groove width of 3 μ m, a period of 20 μ m, and the number of grooves at 50. For this particular configuration, an ultra-wide passband is found having a bandwidth of almost 400 GHz, with a signal reflection of below −12 dB and little insertion loss of ∼−1.43 dB. [ABSTRACT FROM AUTHOR]

In this paper, a wideband absorptive filtering power divider (AFPD) which features the characteristics of high selectivity and flat output distributions is proposed. It is composed of one unequal width three-coupled line (TCL), two coupled lines (CLs), two stepped open-circuited stubs, two kinds of isolation resistors, and two types of absorptive branches. The design equations of the proposed AFPD are derived using an even-odd decomposition method, and parametric investigations are also performed. It is found that the passband bandwidth can be adjusted by the stepped open-circuited stub which generates two transmission zeros (TZs). By combining the TCL with the CLs, the passband bandwidth is effectively enlarged. In addition, two isolated resistors are utilized for achieving good isolation and output-port matching performance. Without affecting the passband responses, the input port absorptive feature within the whole frequency band can be obtained by loading the absorptive branches both on the input and output ports. For validation, an example operating at the center frequency of 2 GHz was modeled and tested. Results exhibit that the passband FBW reaches 72% under 1 dB criterion, which illustrates flat output port distributions. In addition, for 10 dB return loss, the input and output impedance matching bandwidths are 250% and 78%, respectively. The features of good filtering responses are demonstrated by realizing the rectangle coefficient of 1.24 and the out-of-band suppression of more than 20 dB. [ABSTRACT FROM AUTHOR]

W-band filters play a crucial role in modern millimeter-wave communication and radar systems, finding applications in 5G/6G networks, automotive radar, and passive imaging. With the growing demand for higher data rates and efficient wireless communication, W-band filter development has gained significant attention in recent years. Various design techniques and fabrication technologies have been explored for improved performance and integration possibilities. This paper presents a planar substrate-integrated waveguide (SIW) dual-mode cavity filter as a solution to the challenges faced by previous designs in terms of integration, size, and cost. The dual-mode cavity coupling principle and design parameters are analyzed to optimize the filter's performance. A W-band 4th-order dual-mode filter prototype is designed and fabricated on a 0.127-mm-thick RO5880 substrate, and a finline waveguide-to-microstrip transition structure is employed for compatibility with the test instrument. Simulation and experimental results demonstrate that the proposed filter exhibits low insertion loss, good in-band standing wave performance, and improved out-of-band suppression. Moreover, a visible high-frequency out-of-band transmission zero is implemented to enhance the steep roll-off characteristics in the high-frequency out-of-band region. [ABSTRACT FROM AUTHOR]

This study presents a novel compact design of the Gysel topology and a filtering power divider (FPD) that utilizes a coupling structure. The proposed design replaces the traditional four-quarter wavelength transmission lines of the Gysel power divider with transmission lines and lumped components, resulting in a significantly reduced circuit size. Furthermore, the introduction of this coupling structure ensures the integration of the filtering and power division functions. Two transmission zeros are created near the passband to enhance the frequency selectivity of the responses. Theoretical analysis is carried out, and closed-form equations are derived based on the even–odd-mode method. To validate the theory, a three-port equal Gysel FPD operating at 2 GHz was designed and fabricated. The simulated and measured results demonstrate that this FPD has good power splitting and filtering capability with the size of 0.15 λ g × 0.25 λ g ( λ g is the medium wavelength of the central frequency), which is a significant reduction compared to the existing Gysel FPDs. The simulated and measured results are presented to verify the theoretical derivation, demonstrating good features, such as a return loss greater than 15 dB, isolation greater than 15 dB, and an insertion loss of about 4.02 dB (3 + 1.02 dB) in the passband. [ABSTRACT FROM AUTHOR]

In this study, we present a novel dual-polarized patch antenna that exhibits high isolation and two in-band transmission zeros (TZs). The design consists of a suspended metal patch, two feeding probes connected to an internal neutralization line (I-NL), and a T-shaped decoupling network (T-DN). The I-NL is responsible for generating the first TZ, and its decoupling principles are explained through an equivalent circuit model. Rigorous design formulas are also derived to aid in the construction of the feeding structure. The T-DN realizes the second TZ, resulting in further improvement of the decoupling bandwidth. Simulation and experimental results show that the proposed antenna has a wide operating bandwidth (2.5–2.7 GHz), high port isolation (>30 dB), and excellent efficiency (>85%). [ABSTRACT FROM AUTHOR]

This article presents a miniaturized C-band triplexer fabricated with high-temperature superconducting (HTS) microstrip lines and to be applied to quantum computers. The triplexer consists of three bandpass filters and branch lines. In the design of the bandpass filters, folded step impedance resonators (SIRs) are firstly used to achieve good stopband performances by harmonic suppression. Secondly, cross-coupling structures are also utilized to further improve the passband edge steepness of the bandpass filters. Finally, the parasitic transmission zeros originating from the assembling box sizes are employed to achieve a deeper out-of-band rejection. Three bandpass filters are designed and connected to the common input port of the triplexer. After that, the triplexer is coarsely optimized by advanced design system (ADS) for time-saving and is finely optimized by Sonnet for better accuracy. The optimized layout of the triplexer is fabricated on a 2-inch diameter and 0.5 mm thickness MgO wafer; here, the MgO wafer is double-sided coated with HTS YBa2Cu3O7 (YBCO) thin films. The measured passband bandwidths (return loss greater than 12 dB) of the triplexer are 6.420-6.680 GHz, 6.780-7.030 GHz, and 7.110-7.380 GHz, respectively, which satisfy the required design specifications. [ABSTRACT FROM AUTHOR]

In this paper, a novel switchable bandpass filter is proposed. By switching p-i-n diodes on/off, the proposed filter can be switched between the single-band bandpass filter and the dual-band bandpass filter. The filter is mainly composed of eight pairs of series LC resonators, which generate passbands and transmission zeros. Considering the requirement of miniaturization and low cost, the filter is realized by interdigital capacitors and microstrip section inductors. The layout is designed by 3D simulation software HFSS, and the active part is designed by ADS software. The proposed filter has a compact structure, and its size is only 22.20 mm × 25.66 m m. For a demonstration, a switchable bandpass filter has been designed, fabricated, and measured. The simulated and measured results have a good agreement. [ABSTRACT FROM AUTHOR]

This paper presents a novel fourth-order bandpass filter with high selectivity and out-of- band suppression based on equivalent magnetic side wall cavities (MSWCs). By loading a via hole into an MSWC to produce a zero mode as a non-resonating node and using the dual MSWC modes TEM001 and TE100 as resonant modes, a modified doublet with two poles and two transmission zeros (TZs) can be formed. Three types of frequency response, either quasi-elliptic or asymmetric, can be obtained and designed exibly. The TZs can be located on both sides of the passband or both on just one side. The mechanisms for generating the TZs are analyzed, and the adjustment of the TZ positions is discussed. The proposed four-pole quasi-elliptic filter with four TZs is a cascade of two such doublets with two different types of asymmetric response. It has been fabricated and measured to validate the design. Comparison is made with some previous work on substrate integrated waveguide filters. The developed filter is free from radiation and relatively compact among high order filters with multiple adjustable TZs based on cascaded cavities of the substrate integrated waveguide type. [ABSTRACT FROM AUTHOR]

A balanced bandpass filter (BPF) with a wide differential mode (DM) bandwidth and steep DM passband selectivity and high common-mode (CM) block based on slotline stub-loaded resonators (SSLRs) is designed in this brief. The proposed SSLR, which is composed of a half-wavelength slotline resonator and a shorted slot stub loaded at the symmetrical plane, is applied to achieve a broad DM passband with a center frequency at 5.1 GHz and a 3 dB bandwidth of 92%. Meanwhile, two transmission zeros (TZs) are introduced to realize a steep DM passband selectivity. The center frequency and bandwidth of the DM passband can be adjusted by changing the dimensions of SSLRs and the gaps between them. Meanwhile, one narrow notched band with a 3 dB bandwidth of 4.9% is realized by employing one coupled quarter-wavelength short-circuited stub at the input ports. In addition, the DM stopband with a rejection level of 10 dB can be extended to 20 GHz. The designed balanced broadband filter is stimulated by a U-shaped microstrip line to slotline transition structure, which can realize wideband a CM block with a high suppression level without influencing the DM one, and this can reduce the design complexity. In order to prove the idea, a balanced broadband filter is designed and measured. The predicted results of S parameters are compared with the measured ones, and a good agreement is achieved. [ABSTRACT FROM AUTHOR]

In this paper, a new approach for designing a planar high frequency selectivity filtering coupler based on a circular patch resonator is proposed. In order to explain the operating principle, the resonant property of the circular patch resonator has been investigated firstly. Two circular patch resonators connected by two microstrip lines are used in this design. A filtering coupler is achieved by adjusting the feeder position and the length and width of the microstrip line used to connect the two resonators. Without additional circuits, the desired 0° and 180° phase differences are realized by the inherent in-phase and out-of-phase characteristics of E-fields at the TM11 mode. To improve the passband selectivity, transmission zeros are created by introducing a coupling between the source and load through the coupling slots etched on the ground. Finally, a prototype of the filtering coupler centered at 2.12 GHz is designed, implemented, and tested, while the measured results coincide well with simulated ones, verifying the proposed design concept. [ABSTRACT FROM AUTHOR]

In this paper, we study meandered topologies of a dual-mode loop resonator for microwave multiplexer applications. Compact channel filter structures that characterize controllable transmission zeros locating simultaneously at the lower stopband or upper stopband are, for the first time, investigated for such a kind of resonators and based on this, a microstrip triplexer is proposed. The studied triplexer uses one of the filter structures to realize the middle channel, and the rest structure to realize the upper and lower channels. The center frequencies of the three channels are 1.8 GHz, 2.0 GHz and 2.2 GHz, and the 3-dB fractional bandwidths are 3.6%, 3.6% and 4.1%, respectively. The developed triplexer features high channel-isolations of over 40 dB as a result of the controllable transmission zeros of the channel filters. [ABSTRACT FROM AUTHOR]

This paper presents a high‐power and sharp‐skirt‐selectivity bandpass filter with flexible transmission zero (TZ) and bandwidth. The proposed filter consists of three cascaded dual‐mode resonant cavities and a bandstop resonant structure. The dual‐mode resonant cavity is composed of a substrate‐integrated waveguide structure and a mushroom metal structure, which can implement a controllable bandwidth and generate a TZ for sharp skirt selectivity. Meanwhile, the middle dual‐mode resonant cavity is an oversized waveguide structure to improve power capacity. Moreover, the integrated bandstop resonant structure is used to generate another flexible TZ. The effect of different dimensional mushroom metal structures and bandstop resonant structures are also analyzed in detail. Finally, the proposed structure is fabricated and tested. Simulation results show that the proposed filter has an insertion loss of −1 dB at the passband 8.9–10.7 GHz with two TZs on both sides of the passband. Additionally, the proposed filter can obtain an 11 MW power capacity. Compared with the traditional filters, the proposed filter possesses high‐power and sharp skirt selectivity characteristics, and its position of TZ and bandwidth can be properly adjusted. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a novel, compact, and highly selective metamaterial inspired filter with low insertion loss, lowpass, and triple‐band bandpass characteristics. The presence of five transmission zeros and seven poles facilitates highly selective filtering performance. The improved impedance matching and transmission characteristics have been achieved by embedding complementary split ring resonator as defected ground structure. The filter circuit area excluding 50 Ω feed lines is merely 0.17λg × 0.05λg at 3‐dB cut‐off frequency of lowpass passband (1.11 GHz). The 3‐dB fractional bandwidths of the three bandpass regions are 39.50% (1.3–1.94 GHz), 21.20% (3.12–3.86 GHz), and 21.06% (4.04–4.99 GHz) at the center frequencies of 1.62, 3.49, and 4.51 GHz, respectively. Intended filter also offers a wide stopband extending from 2.15 to 2.96 GHz at close to 20 dB attenuation level. Further, position of transmission zeros and 3‐dB passband bandwidths can be adjusted by carefully choosing structural design parameters. The metamaterial effect of the proposed filter has been demonstrated by plotting refractive index followed by validating the performance with the help of experimental measurements. No filter shows lowpass characteristic along with three bandpass performances as found by the authors exploring literature, which presents the novelty of the proposed work. [ABSTRACT FROM AUTHOR]

A compact dual‐band bandpass filter (BPF) with high selectivity based on 3D printable groove gap waveguide (GGW) for millimeter application is proposed by the authors. Two stacked dual‐mode GGW resonant cavities including TE102 and TE201 are used to realise a compact structure. The dual‐band bandpass response of the GGW BPF is developed from a split‐type coupling topology which produced two transmission zeros (TZs) between the two passbands. In addition, two TZs are generated outside the two passbands after introducing a source‐load coupling, which achieves a higher frequency selectivity. For verification, a prototype is designed, fabricated and measured. The measured results agree well with the simulated ones, which validates the proposal. [ABSTRACT FROM AUTHOR]

A design method for highly‐selective bandpass filters based on novel dual‐mode fan‐shaped patch resonator (FSPR) is presented in this article. Different from traditional dual‐mode patch filters, two higher‐order modes TM020 and TM110 are utilised to generate a passband, and the two resonant frequencies can be controlled well by its radius and angle. A dual‐mode filter with two transmission zeros (TZs) is implemented by using one FSPR, and locations of TZs can be controlled well. To further improve the selectivity of FSPR filters, four‐pole filters based on two identical dual‐mode FSPRs with co‐directional and reverse‐directional cascade are simulated, fabricated and measured. Furthermore, three‐ and four‐pole filters based on dual‐mode FSPR and single‐mode uniform impedance resonators are proposed, which are also simulated, fabricated, and measured. The later proposed filters not only achieve high selectivity and wide stopband, but also have simple structure and small size. [ABSTRACT FROM AUTHOR]

Summary: This article proposes a generalized PI observer with approximate disturbance decoupling (ADD‐GPIO) for detecting incipient actuator faults of a system subject to periodic input disturbances. Robustness to disturbances and sensitivity to faults is achieved through dynamic configuration of the disturbance transmission zeros and pole‐optimization respectively. By incorporating the v$$ v $$‐gap metric with H−$$ {H}_{-} $$ index, a novel interpretable fault sensitivity optimization objective function is proposed. It is the first time in the fault detection observer design that the difference between the transfer function matrices (TFMs) relating fault detection residual to the disturbances and faults is quantified by the proposed v$$ v $$‐gap metric, which allows a more differentiated treatment of the disturbance and fault signals for better fault detection. Then, the optimal design of the ADD‐GPIO is modeled as a mixed‐integer optimization problem and the Lagrangian relaxation is adopted to find the near‐optimal parameters of the ADD‐GPIO at less computation costs in real application. Finally, both simulation and lab experiments of a two‐wheeled self‐balancing robot are carried out to validate the improved performance of the proposed method. [ABSTRACT FROM AUTHOR]

The dynamics of a quadruple tank system (QTS) represent an extensive class of multivariate nonlinear uncertain systems found in the industry. It has been established that changes in split fractions affect the transmission zero location, thereby altering the operating conditions between the minimum and non-minimum phase regions. The latter is difficult to control as more fluid flows into the two upper tanks than into the two bottom tanks, resulting in competing effects between the initial and final system responses. This attribute, alongside nonlinearity, uncertainties, constraints, and a multivariate nature, can degrade closed-loop system performance, leading to instability. In this study, we addressed the aforementioned challenges by designing controllers for the regulation of the water flow in the two bottom tanks of the QTS. For comparative analysis, three controller algorithms—a nonlinear model predictive controller (NMPC), NMPC augmented with an extended Kalman filter (i.e., NMPC-EKF) and linear model predictive controller (LMPC)—were considered in the analysis and design of the control mechanism for the quadruple water level system in a non-minimum phase condition via the Matrix Laboratory (MATLAB) simulation package environment. The simulated and real-time results in the closed loop were analyzed, and the controller performances were considered based on faster setpoint responses, less oscillation, settling time, overshoot, and smaller integral absolute error (IAE) and integral square error (ISE) under various operational conditions. The study showed that the NMPC, when augmented with an EKF, is effective for the control of a QTS in the non-minimum phase and could be designed for more complex, nonlinear, and multivariable dynamics systems, even in the presence of constraints. [ABSTRACT FROM AUTHOR]

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N-order bandpass filter (BPF) with parallel resonators and cross and mixed couplings can have (N + 1) transmission zeros (TZ) located on the complex plane s = σ + jω. TZs at real frequencies (jω axis) are also called attenuation poles (AP). The authors propose an alternative possibility of AP forming in filters using resonators with special properties, which significantly increases the AP number from (N + 1) to (3N + 1). Increasing the AP number with fewer resonators allows us to increase the selectivity and rejection level and reduce BPF insertion losses. The special properties of resonators are that their input admittance Y has one or two poles (ωp1, ωp2) located next to the resonance frequency ω0. This leads to the appearance of AP in a BPF. We propose and analyze three resonators with special properties. They are formed by a cascade connection of a quarter-wave resonator and lumped L and C. The input of the resonators is located on the side of the lumped elements. It was found that the Q-factors of lumped elements do not affect the filter losses in the passband. The reduction of QL and QC leads only to the decrease of the AP "depth." For the first time, 7 APs were implemented in the experimental second-order microstrip BPF. [ABSTRACT FROM AUTHOR]

In this article, two dual-band microstrip bandpass filters (BPFs) with high selectivity and independently controllable passbands are designed based on three parallel-coupled lines (TPCLs). The first BPF proposed in this paper is achieved by employing a pair of folded F-type resonators (FFRs) and conventional TPCL structure. By adjusting the above parameters of each FFR, the center frequencies of the two passbands can be controlled easily. In the meantime, TPCL can enhance the coupling between the source and load, and introduce multiple transmission zeros (TZs), which can conduce to a higher selectivity. To obtain superior selectivity, the second BPF is designed based on a novel TPCL. The novel TPCL is based on the traditional one, which further enhances selectivity since transmission paths are doubled. In order to achieve miniaturization and enhance coupling, FFRs are folded. In addition, four transmission zeros (TZs) are generated to improve the selectivity of the two passbands. The measured results of the fabricated BPFs centered at 2.45/3.5 GHz agree well with the simulated ones, which validates the proposed design method. [ABSTRACT FROM AUTHOR]

This paper examines the feasibility of cloaking an obstacle using Plate-type Acoustic Metamaterials (PAMs). We present two distinct strategies to cloak this obstacle, using either the near-zero-density regime of a periodic arrangement of plates or the acoustic doping phenomenon to achieve simultaneous zero-phase propagation and impedance matching. The strong limitations induced by viscothermal and viscoelastic losses that cannot be avoided in such a system are studied. A hiding zone is reported analytically, numerically, and experimentally. In contrast to cloaking, where zero-phase propagation must be accompanied by total transmission and zero reflection, the hiding configuration requires that the scattering properties of the hiding device must not be affected by the presence of the obstacle embedded in it. Contrary to cloaking, the hiding phenomenon is achievable even with a realistic PAM possessing unavoidable losses. [ABSTRACT FROM AUTHOR]

In this paper, we propose the application of a new geometric procedure in order to calculate a set of transmission zeros of a propagation environment. Since the transmission zeros play a crucial role in modern communication systems, there is a need to apply the efficient solutions characterized by a maximum speed operation. It turns out that the classical method based on the Smith–McMillan factorization is time-consuming, so its contribution to the detection of transmission zeros could be unsatisfactory. Therefore, in order to fill the gap, we present a new algorithm strictly dedicated to the multivariable telecommunications systems described by the transfer-function approach. Consequently, a set of new achievements resulted, particularly in terms of computational efforts. Indeed, the proposed procedure allows us to overcome obstacles derived from technological limitations. The representative simulation examples confirm the great potential of this new method. Finally, it has been pointed out that the newly introduced geometric-originated approach has significantly reduced the computational burden. Indeed, for the randomly selected matrix of the 5×5 dimension describing the sensor-related propagation environment, two representative scenarios were performed in order to manifest the crucial properties. In the first scenario, the sets of multiple transmission zeros were analyzed, ultimately leading to intriguing results. The Smith–McMillan solution took three times longer to discover the mentioned sets. On the other hand, the second instance brought us the same result. Naturally, the discussed difference has increased as a function of the number of matrix elements. For the square matrices involving 100 components, we have observed the respective differences, both over QI=100 and QII=60. It should be emphasized that the finding derived from the Smith–McMillan factorization corresponds to the geometric-related approach in the context of some mechanisms. This is particularly visible when appointing the greatest common divisors.

A compact microstrip multifunctional reconfigurable filtering power divider (FPD) is proposed based on varactor‐loaded three‐parallel‐coupled line section (TLCS) in this letter. Continuously tunable third‐order filtering power division response with two transmission zeros (TZs) including centre frequency (CF), bandwidth (BW) and power division ration (PDR) is successfully attained by varying the external and internal coupling through loading varactors into a three‐parallel‐coupled line topology. For validation, a prototype is implemented. The results indicate that the CF can be tuned from 0.46 to 0.8 GHz, a tunable 3‐dB BW of 80 to 190 MHz is exhibited with better than 17‐dB return loss and higher than 15‐dB in‐band isolation. In addition to the CF and BW tunability, the power division ratio (PDR) for the presented FPD can also be adjusted from 1:1 to 1:5. Additionally, a compact size is realized with only 0.12λg × 0.16λg. [ABSTRACT FROM AUTHOR]

A novel stripline diplexer design using frequency‐dependent couplings (FDC) to achieve multiple transmission zeros is developed in this paper. The transmission zeros generated by FDCs are flexible and controllable; on the basis of the existing cross‐coupled, more transmission zeros are introduced to improve the frequency selection characteristics. Based on this characteristic, the authors synthesized and designed a 2.6‐GHz diplexer, its transmitting channel filter is five orders with three transmission zeros, and the receiving channel filter is four orders with three transmission zeros. The authors fabricated and measured it, in narrowband, the tested results, synthesis responses and simulation results are well matched with each other, which will provide more flexibility in the design of diplexers for wireless communication system. [ABSTRACT FROM AUTHOR]

In this paper, a third-order, high selectivity Substrate Integrated Waveguide (SIW) bandpass filter (BPF) loaded with Circular Complementary Split-Ring Resonator (CCSRR) is proposed for C band applications. The SIW cavity BPF comprises two stepped resonators ( R 1 and R 3 ) and one CSRR ( R 2 ) engraved on the top metal plate. Initially, the cavity loaded with stepped resonators ( R 1 and R 3 ) alone does not make a good selectivity on the lower out of band. Hence, the CCSRR is introduced between the stepped resonators ( R 1 and R 3 ) to improve the filter's selectivity and enhance the filter's bandwidth. The introduction of CCSRR enhances the selectivity on the lower out-of-band at 5.5 GHz, and the extra pole increases the bandwidth. The metamaterial behavior of CCSRR is validated by permittivity extraction. The 3 dB bandwidth of the third-order SIW filter is 840 MHz with a center frequency of 6.18 GHz. The designed filter uses RTDuroid 5880 substrate of ϵ r = 2.2 with a size of 28.4 × 28.4 × 0.51 mm3. The proposed filter measurement and simulated results agree with each other. [ABSTRACT FROM AUTHOR]

This paper presents a low profile cylindrical cavity quadruple-mode dual-band bandpass filter. Five short-circuited metal pillars are loaded in a cylindrical cavity to change the electric field distributions of the original resonant modes. The changed TM 010 mode and TM 110+ mode form the first passband, and the changed TM 110- mode and TM 210+ mode form the second passband. The center frequencies of the two passbands are 3.05 GHz and 3.59 GHz, with relative bandwidths of 1.72% and 2.5%, respectively. The first passband can be adjusted independently, and the stopband range of the proposed bandpass filter is relatively wide. By using the degenerate modes, two transmission zeros are introduced to improve the selectivity of the proposed bandpass filter. The use of TM mn 0 mode effectively reduces the height of the cavity. The fabricated cavity bandpass filter is measured, and the measured results are accordance with the simulated ones. [ABSTRACT FROM AUTHOR]

The article presents a novel circular substrate-integrated waveguide (SIW) bandpass filter (BPF) with controllable bandwidth. The proposed BPF was configured using two microstrip feed lines, semi-circular SIW cavities, capacitive slots, and inductive vias. The circular cavity was divided into two halves, and the two copies were cascaded. The resulting bisected and cascaded structures were then connected back-to-back. Finally, by introducing two inductive vias to the circular center cavity, a transmission zero was generated. In order to examine the design concept, a coupling matrix was generated. To demonstrate the theory, a third-order BPF was realized, fabricated, and experimentally validated. The BPF prototype features a wide passband of 8.7%, a low insertion loss of 1.1 dB, and a stopband of 1.5 f 0 with a rejection level better than 20 dB, which makes it a potential candidate for microwave sensing and communication industries. [ABSTRACT FROM AUTHOR]

Multiband bandpass filter is a key component in multistandard wireless communication system. This paper proposes a novel tri‐band bandpass filter (TB‐BPF) which consists of two mesh‐type multimode resonators (MT‐MMR) and two stub‐loaded U‐type feedlines. The MT‐MMR is formed by parallel connecting two open‐end stubs and one mesh‐type structure. Such specific configuration is featured by four inherent transmission zeros. The in‐depth analysis on the generation mechanism of the transmission zeros is made, and then a fast hybrid approach is developed for design procedure. Some explicit design equations are presented for fast determining initial values of some key parameters, and then further optimized by using a constraint condition, which effectively accelerate design process. For verification, an example of the TB‐BPF was designed fabricated and measured. Its center frequencies are at 3.16, 4.27, and 5.70 GHz, respectively. Six transmission zeros are generated for sharp frequency selectivity, and are at 1.46, 3.58, 3.86, 4.73, 5.51, and 7.18 GHz, respectively. Its size is about 0.59 × 0.19 λg2. [ABSTRACT FROM AUTHOR]

A miniaturized ultra‐wideband (UWB) bandpass filter (BPF) based on broadside coupled technology with multiple passband notches is reported. The basic geometry of BPF has microstrip lines on the top plane coupled to the modified short‐circuited coplanar waveguide in the bottom plane. This broadside alignment leads to the development of a UWB response with good frequency characteristics due to the presence of two transmission zeros at lower/upper passband edges. Later, multiple circular resonators and one complimentary folded split ring resonator are embedded into the basic architecture to develop triple passband notches at our frequencies of interest. Eventually, a prototype is fabricated and tested to validate the simulated data. The proposed BPF occupies a minimal physical area of 14 × 11.4 mm2. [ABSTRACT FROM AUTHOR]

This article presents a novel microstrip line topology implementation of an ultra-wideband (UWB) bandpass filter. The proposed topology is a shortcircuited stepped-impedance ring resonator with an open-circuit stub and a short-circuit stub loaded at the central vertical position of the low impedance of this resonator, respectively. Within the UWB spectrum, five modes are allocated under weak coupling, and to increase filter selectivity, two transmission zeros are added. It is possible to extend the upper stopband and provide sufficient external coupling by utilizing interdigitalcoupled lines. To demonstrate the design theory, a prototype is designed and manufactured on a 0.8 mm thick substrate of the affordable F4B-2, and its performance is verified. Measurements show a 3-dB bandwidth span from 2.8 to 9.5 GHz, insertion loss of 0.36 dB, and return loss better than 13 dB. [ABSTRACT FROM AUTHOR]

Designing microwave filters with high selectivity and sharp roll-off between the stop and pass bands can be challenging due to the complex nature of the R.F. signals and the requirements for achieving high performance in a limited physical space. To achieve a high selectivity and sharp roll-off rate, this paper presents a compact filter with a triple passband response. The two different passbands at 1.57 GHz and 3.5 GHz are achieved using a step impedance resonator (SIR) with metallic slots perturbation added to the lower corner of the high impedance section of the SIRs, which helps to enhance the filter's selectivity and size reduction greatly. The embedded L-shaped structure originates a third passband at 4.23 GHz, resulting in a triband response with eight transmission zeros below and above the passbands at 1.22/1.42/1.98/3.18/3.82/3.98/4.38/4.53 GHz, respectively. The prototype has low signal attenuation of <1.2 dB and high signal reflection of >25 dB for the three passbands. The fractional bandwidths achieved are 2.54%, 4.2%, and 1.65% at 1.57/3.57/4.23 GHz, respectively, with rejection levels in the stopband greater than 15 dB. Lastly, the structure is fabricated on RO-4350B PCB and observed good matching between experimental and measured results. This demonstrates that the prototype can be successfully implemented in real-world applications such as GPS, WiMAX, and Satellite systems. The area occupied by the filter on a substrate or in a circuit is 0.31 λg × 0.24 λg, where λg is the guided wavelength of the material calculated at the lowest frequency. [ABSTRACT FROM AUTHOR]

Ultrathin and broadband metamaterial absorber with loaded four lumped resistors is proposed and analyzed. The reported design is based on increasing the absorptivity by reducing the reflection and transmission coefficients simultaneously. Therefore, continuous metallic ground is used to achieve zero transmission while the reflection is reduced by matching the impedance of the proposed metamaterial absorber with the impedance of free space (Z = Z0 or μr = εr). Additionally, electric and magnetic resonances are achieved simultaneously with perfect absorptivity. The finite element method is used to simulate and analyze the reported absorber. The suggested absorber shows higher absorption than 90% over large frequency range (14.35–29.18 GHz) for both transverse electric and transverse magnetic polarizations. Further, the proposed design has high absorption through incident angle variation from 0° to 50°. Therefore, the reported perfect metamaterial absorber has good potential applications in communications, stealth and imaging fields. [ABSTRACT FROM AUTHOR]

An ultra-wideband common-mode (CM) filter for a gigahertz (GHz) data rate signal is proposed in this paper. The proposed filter was designed only on the printed circuit board (PCB) ground plane; no additional components wererequired. We took advantage of producing second-order transmission zero by an asymmetrical magnified coupled DGS to extend the suppression bandwidth. Full-wave simulations and equivalent circuit models of the DGS resonator were established to predict the suppression performance. The measured differential-mode insertion loss (Sdd21) from direct current (DC) to 12.35 GHz was obtained within the −3 dB definitionin the frequency domain. The CM noise was suppressed by more than10 dB in the frequency range from 2.9 GHz to 16.2 GHz. The fractional bandwidth (FBW) reached 139.3%. The proposed filter blocked 62.3% of the CM noise magnitude in the time domain measurement. In addition, the eye diagram measurement proved that good transmission quality was maintained. The proposed filter can be widely implemented to reduce electromagnetic interference (EMI) in radio frequency (RF) andWi-Fi (wireless fidelitystandard) 5 and 6E wireless communication applications. [ABSTRACT FROM AUTHOR]