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In this paper, a low profile, dual-band dual-polarized patch antenna is proposed for antenna-filter function with a relatively low profile of 0.032 wavelength. A simple symmetric open/short-circuited stub (O/SCS) is proposed to excite a square radiating patch, and an additional resonant mode is generated except for the patch-mode. At the lower band, the proposed antenna works as a dual-polarized patch antenna. At the upper band, transmission characteristic is obtained between the two ports, and the antenna structure can be used as a bandpass filter. A $1\times 2$ array is also designed to validate its application potential in MIMO system. The two antennas can operate as radiators with high port isolation levels at the lower band. Meanwhile, at the upper band, the two antenna elements can act as one bandpass filter as the good transmission characteristic. In addition, a $2\times 2$ array is also developed meet dual-function demands in dual-polarized MIMO systems. The low profile, simple structures and excellent performances indicate that the proposed antenna can be a good candidate in future wireless communication applications with shared functions.

This paper presents a fluidically loaded microstrip patch antenna on a multi-layered substrate with frequency and polarization reconfigurability in the 2400 MHz band. A square patch loaded at all the corners with short circuited $\lambda _{g}/4$ long stubs is utilized. An arrangement of fluidic channels fabricated by moulding Polydimethylsiloxane (PDMS) with 3D printed mould is incorporated beneath each stub. By injecting or withdrawing distilled water into the channels, variable loads are realized. It exhibits frequency tunable linearly polarized (LP) mode with symmetric loading or circularly polarized (CP) mode with asymmetric loading. The sense of CP can be switched by swapping the loading configuration along the diagonals of the patch. The equivalent circuit for the antenna is presented. A prototype is fabricated and measured. In LP mode, frequency tuning of 7.85% is achieved. The minimum realized gain is 5.67 dBi with cross-polarization (X-pol) isolation $\geq20$ dB. In the CP modes, the overlapping bandwidth for ${\mid }\text{S}_{11}{\mid } \leq -10$ dB and axial ratio $\leq3$ dB (ARBW) is $\geq16$ MHz for both LHCP/RHCP modes. Frequency tuning of 141 MHz (5.76%) is measured in the RHCP mode. The minimum realized gain is 4.86 dBic and total efficiency is >60%.

This paper introduces a novel transparent proximity-coupled-fed patch antenna with enhanced impedance bandwidth and good filtering response. The proposed antenna consists of a ground plane, a specific feeding structure and a slotted patch. All the conducting surfaces are realized with metal meshes printed on glass substrates. Optical transparency of the antenna depends on the mesh density. The feed line of a traditional proximity-coupled-fed patch antenna is terminated with a driven stub etched with a half-wavelength U-shaped slot. This modification introduces an additional resonant mode but also a radiating null. By further etching a pair of quarter-wavelength open slots on the radiating patch, another resonant mode accompanied with an extra radiation null is generated. Finally, three resonant modes within the operating band along with two radiation nulls near the two edges of the passband are achieved. The proposed antenna is implemented to demonstrate an impedance bandwidth of 7.6% from 3.41 to 3.68 GHz and a maximum gain of 4.6 dBi.

Waveguide structures effectively controlling and guiding terahertz (THz) waves can achieve interesting resonance effects when combined with resonators. At present, achieving high quality factor (Q-factor) resonance in THz resonator-coupled waveguide structure is still a critical consideration to expand its practical application. Here, a high Q-factor Fano resonance based on a metal-dielectric-metal (MDM) waveguide consisting of a stub resonator and a metal wall with an aperture in the center is investigated theoretically and numerically in the THz region. The results show that the sharp and asymmetric Fano resonance peak is induced by the destructive interference between the stub resonator and metal wall which act as a Fabry-Pérot cavity. Q-factor is obviously improved about 60 times (3.72 to ~225) by introducing the metal wall into the stub-coupled MDM waveguide. Moreover, Fano resonance can be effectively tuned by varying different structure parameters. Owing to the high sensitivity of Fano resonance peak to dielectric surroundings, a large-range refractive index (RI) sensor based on the proposed structure with a high sensitivity of 96480 nm/RIU is obtained. The figure of merit (FOM) of 195 is greatly improved compared to other THz Fano-based RI sensors. These results provide possibilities for subwavelength MDM waveguide structure to apply for THz bio/chemical sensing, bandpass filters, and on-chip highly integrated plasmonic device.

A basic plasmonic system, consisting of a stub metal-insulator-metal (MIM) waveguide coupled with a ring resonator, is presented to realize Fano resonance and electromagnetically induced transparency-like (EIT-like) effect, which are numerically calculated by the finite element method (FEM). Meanwhile, the formation mechanism of Fano resonance is analyzed according to numerical simulations. Besides, the coupled mode theory (CMT) and the standing wave theory are used for explaining the Fano and EIT-like resonances phenomenon. Based on this system, an inner ring cavity is connected to the ring resonator by a slot and another ring cavity is later introduced under the stub resonator in order to constitute a new coupled plasmonic resonator system, providing quadruple Fano resonances and double EIT-like responses finally. In addition, the Fano and EIT-like resonances can be independently tuned by adjusting the structural parameters, which makes the design of highly integrated photonic circuits more flexible. The main contribution of this paper is that the proposed structure has a relatively good sensitivity of 1600 nm/RIU and an ultra-high FOM value of $1.2\times 10^{6}$ as a refractive index nanosensor. Moreover, it can serve as an all-optical switch with a high on/off extinction ratio of about 43 dB. Additionally, its maximum group delay time and group index are about 1.49 ps and 221, indicating that the proposed system has a pretty good slow light effect. Therefore, the proposed structures are believed to have significant applications in high-performance nanosensors, switches, slow light devices and nonlinear areas in highly integrated plasmonic devices.

High-order quasi-reflectionless bandpass filters with improved passband flatness and good impedance matching both in-band and out-of-band are proposed in this work. The proposed design consists of conventional coupled-lines bandpass sections loaded with the presented absorptive stubs at the input and output. Analysis shows that the absorptive stub is equivalent to a 2-pole bandstop filter. Compared to the prior art, the higher-order nature of the presented absorptive stub enables a flatter passband and better out-of-band rejection. The overall filter stopband attenuation can be readily improved by increasing the number of coupled-lines sections without altering the passband responses. Furthermore, cross-coupling between the two absorptive stubs can be used to improve the out-of-band rejection by introducing two transmission zeros without affecting the absorption characteristics. The proposed design concepts are experimentally validated by the design and fabrication of a set of 2.4-GHz 1-, 2-, and 3-pole microstrip quasi-reflectionless bandpass filters. Measured frequency responses of these filters closely match those of the simulation.

A dual-wideband bandpass filter is proposed and analyzed, which is based on loaded open-/short-circuited stubs. The dual-band filter consists of a second-order bandpass filter and a third-order bandpass filter, which can be designed separately. The bandwidth of two passbands can be adjusted by tuning the impedance and the length of the stubs. A dual-band bandpass filter prototype operating at 2.4/5.2 GHz is designed for demonstration. It shows a low insertion loss of 0.3 dB and wide bandwidth of 51.9% at 2.4 GHz and 23.3% at 5.2 GHz. The filter structure is simple without narrow coupling gap between resonators, which is easy for fabrication.

In this paper, a wideband 3 dB hybrid 180° rat-race coupler is introduced in the printed ridge gap waveguide technology. It has simultaneous wide matching and isolation bandwidth with low output amplitude imbalance. It operates in the millimeter wave band from 25.8 to 34.2 GHz (27.96%) with 15 dB return loss and isolation, and ±0.5 dB output amplitude imbalance. The proposed design employing an open stub at the middle of the $3 \lambda /4$ branch line and quarter wavelength lines at all the ports of the coupler. The objective of the added open stub is to separate the output ports amplitudes around the -3 dB level by certain values depending on the required amplitude imbalance. The analytical derivation for the role of the added open stub is presented along with a parametric study on its effect on amplitude imbalance, matching, and isolation. This results in having two intersection points for the output ports instead of one of the conventional coupler and hence the amplitude imbalance bandwidth increases. The objective of the added quarter wavelength lines is to improve the matching and isolation bandwidths. First, the conventional rat-race coupler is presented and a bandwidth of 14.25% at 30 GHz is achieved. After that the rat-race with the added quarter wavelength lines is presented to illustrate the objective of the added quarter wavelength lines and a bandwidth of 19.44% is achieved. Finally, the rat-race with the quarter wavelength lines and the added stub is presented and a prototype is fabricated and measured. The s-parameters measurements are in a good agreement with the simulated ones.

An eight element, compact Ultra Wideband- Multiple Input Multiple Output (UWB-MIMO) antenna capable of providing high data rates for future Fifth Generation (5G) terminal equipments along with the provision of necessary bandwidth for Third Generation (3G) and Fourth Generation (4G) communications that accomplishes band rejection from 4.85 to 6.35 GHz by deploying a Inductor Capacitor (LC) stub on the ground plane is presented. The incorporated stub also provides flexibility to reject any selected band as well as bandwidth control. The orthogonal placement of the printed monopoles permits polarization diversity and provides high isolation. In the proposed eight element UWB-MIMO/diversity antenna, monopole pair 3-4 are 1800 mirrored transform of monopole pair 1-2 which lie on the opposite corners of a planar 50 × 50 mm2 substrate. Four additional monopoles are then placed perpendicularly to the same board leading to a total size of 50 × 50 × 25 mm3 only. The simulated results are validated by comparing the measurements of a fabricated prototype. It was concluded that the design meets the target specifications over the entire bandwidth of 2 to 12 GHz with a reflection coefficient better than -10 dB (except the rejected band), isolation more than 17 dB, low envelope correlation, low gain variation, stable radiation pattern, and strong rejection of the signals in the Wireless Local Area Network (WLAN) band. Overall, compact and reduced complexity of the proposed eight element architecture, strengthens its practical viability for the diversity applications in future 5G terminal equipments amongst other MIMO antennas designs present in the literature.

This paper discusses the study of antenna development for partial discharge measurement, which has been conducted in the Laboratory of Voltage and High Current, School of Electrical Engineering and Informatics, Bandung Institute of Technology. This paper was created to find out the most effective shape of antenna as a partial discharge detection sensor. In the design of the antenna, there are simulation antenna, print the antenna on the PCB, and experiments using VNA-Vector Network Analyzer. In the simulation of the antenna, the application used is Ansoft HFSS. In the design, there are substrates, antenna patches, and ground with thickness and materials that are adjusted to the needs of each antenna. After simulating the antenna on Ansoft, then the antenna is printed on the PCB, for further experiments using VNA. The results of simulations as well as from experiments are compared. In antenna design, there are antenna parameters that need to be considered, including bandwidth, voltage standing wave ratio (VSWR), and return loss. From the antenna experiments that have been done in the laboratory, the most effective antenna is obtained as a sensor. It is found that the bowtie antenna with modifications at the end, the dipole antenna with the stub, and the Hilbert 3rd order fractal antenna, are the best antenna of all antennas.

The problem of increased stopband and reduced dimensions of dual-mode T-shaped resonator is solved. Stepped-impedance transmission line segments (SILS) with the required arrangement of resonant frequencies are synthesized for this. Two ends of the SILS are open-circuited. To the middle of the synthesized SILS an open-circuited stub is connected. The method of parametric synthesis of SILS was used, which provides the required arrangement of resonant frequencies at the minimum value of the parameter $\boldsymbol{m}=\boldsymbol{Z}_{\boldsymbol{0\max}}/\boldsymbol{Z}_{\boldsymbol{0\min}}$ . As result, the new dual-mode T-shaped filter with increased stopband and reduced dimensions is obtained. A new effect is observed in the synthesized filter. It contains both dual-mode and simple oscillations, which alternate with each other. The measurement data and EM simulation of an experimental microstrip filter are presented.

The problem of improving dual-band filter functionality based on dual-mode resonator is solved. Stepped-impedance transmission line segments (SILS) with the required arrangement of resonant frequencies are synthesized to solve this problem. These SILS have the minimum value of parameter m = Z 0 max/Z 0 min, which is defined as the optimal criterion. The method of parametric synthesis was used for optimization. Two ends of the SILS are short-circuited. A short-circuited stub of short length is connected to the middle of the synthesized SILS. As result, a new dual-mode dual-band filter with enhanced functionality is obtained. This filter allows us to change the relative position of two passbands over a wide range. This filter can also significantly increase the operating frequencies. The data of measurements of the microstrip filter prototype are presented.

In this research article, the design and fabrication of a miniaturized flexible rectifier at 24 GHz for wireless power transfer to wearables is presented. The proposed circuit consists of a shunt topology rectifier including a single stub impedance matching network. Conventional PCB fabrication technique is used for the prototyping of the proposed flexible rectifier. It has a total footprint of 5.29 cm2. The proposed rectifier exhibits a good trade-off between compactness and RF-to-DC conversion efficiency. The implementation on a very thin substrate (130 µm) makes it durable for wearables applications. Experimental results of the proposed rectifier show an output DC voltage of 2.0 V across an optimal load resistance of 250 Ω and measured RF-DC conversion efficiency of 23% for an input power of 17 dBm at 24 GHz.

This paper presents a 3D-printed hemispherical lens integrated with flower-shaped stub antenna for liquid-mixture characterization. The proposed lens antenna is designed, fabricated, and integrated with the ultra-wideband planar antenna. A high impact polystyrene (HIPs) is selected to design the 3D-printed lens antenna by using the fused deposition modelling (FDM) technique, due to low loss 3D-printed material. The optimum the dimensions of the lens antenna are obtained by using the 3D EM Simulation CST Studio, which is used to investigate the performance of the antenna, e.g., gain, radiation pattern and reflection coefficient. To discriminate the liquid content in ethanol-water mixture, the level of the transmission coefficient (S21) is detected. The proposed sensor system offers various preferable features, e.g., non-destructive method and non-contact measurement. Five samples, e.g., 60%, 65%, 70%, 75%, and 80% ethanol in the ethanol-water mixtures, are measured and performed to generate the extraction model. The proposed sensor also offers other advantages, e.g., real-time monitoring and no life-cycle limitation.

Two-port multi-input multi-output (MIMO) antenna for a 5G application is presented in this paper. The presented made of 2 monopole elements with an overall size of 11 x 4.5 mm2. To reduce the effect of one antenna element to another element, an optimized study has been considered. To reduce isolation between the ports of the designed MIMO, a stub has been put into the ground plane. The presented MIMO for 5G wireless application has been carried out using HFSS software. The S 11 value of deigned MIMO antenna obtained at 26 GHz resonance frequency and bandwidth of 4.3 GHz (from 24.0 GHz to 28.3 GHz) and isolation is below -27 dB. The MIMO performance of the presented MIMO antenna gives good results such as impedance bandwidth, radiation pattern, isolation, and gain. The presented MIMO antenna shows a high-quality applicant for 5G mm-wave application.

This paper proposes a compact, Fork Shaped stub to enhance the isolation between 2×2 MIMO antenna in Ultra- Wide Band. The overall size of the antenna is 28×20×1.6mm3. The proposed antenna was designed with Multiple-input -multiple-output (MIMO) and operated at a frequency of 5.1GHz for Wireless Communication. This MIMO having two antenna elements placed side by side to each other. A Fork shaped stub is placed in between two antenna elements to reduce mutual coupling. This Stub reduces the electromagnetic interferences in between MIMO elements and enhances the isolation. The proposed antenna was designed with Characteristic mode analysis for a better understanding of physical insight of structure. The dominant mode of the proposed antenna can find out easily with Characteristic Mode Analysis without applying the feed and excitation. The proposed antenna maintain good isolation more than 22dB entire UWB spectrum and Envelop correlation coefficient is (ECC)

A co-planar waveguide (CPW) fed stub loaded slot antenna is designed and is stretched to ten elements multiple input and multiple output (MIMO) for mm wave 5G communication system in this paper. It covers a wide band (22.9-28.8 GHz) of Millimeter wave (mm wave) and the stub loading technique is used to achieve desirable 5G frequency spectrum (24.2-27 GHz) with proper impedance matching. The fractional bandwidth is almost 22.8%. The |S 11 | and isolation characteristics of the proposed MIMO antenna are below -20 dB which indicates good impedance matching with significantly low mutual coupling between the adjacent elements. The diversity performances such as envelope correlation coefficient (ECC) is below 0.0004 and Channel capacity Loss (CCL) is below 0.1 bps/Hz over the entire bandwidth. The system is developed using ten elements antenna and the overall layout area is 1.37 λ X 6.88 λ. The compactness of the MIMO system and antenna characteristics imply that the proposed design can be a promising structure for future 5G mm wave communication system.

This paper introduces a compact configuration of bandpass filter using multi-mode resonator (MMR) structure with high selectivity and wide upper stopband for ultra-wideband (UWB) applications. Modified open ended stub loaded resonators are attached to a uniform impedance resonator (UIR) for constituting the MMR unit. The MMR structure is excited through inter-digital coupled lines placed at the input and output side of the bandpass filter. The proposed bandpass filter is designed and implemented in high frequency structure simulator software and attains an ultra-wide passband of 7.43 GHz (2.94 GHz-10.37 GHz). Besides, the bandpass filter exhibits satisfactory attenuation level (

A compact and circularly polarized CPW-fed antenna for ISM, Biomedical and satellite applications is presented. The L-shaped stub in the ground is used to improve the impedance matching and perturb the current which is responsible for circular polarization(CP). The |S11| in dB of the antenna varies from 5.35 GHz to 8.88 GHz. The 3dB Axial Ratio of antenna varies from 7.83 GHz to 8.77 GHz. The antenna is analyzed for wearable applications on a three-layer skin phantom model and the SAR value obtained is 0.38 W/Kg, which is below the maximum permissible level.

In this research article we have proposed parametric study of a compact antenna with UWB applications. The antenna consists of a nonagon (9 side polygon) shape patch with a rectangular ground plane on one side, a radiating patch on the other side made of the FR4 substate (ϵ r =4.4) and a microstrip patch line that feeds the radiating patch, also a square slot has been etched into the radiating patch and an inverted T filter has been stubbed to the radiating patch to reduce the interference from the existing IEEE WiMAX band from 3.3GHz to 3.8GHz. The size of the antenna is only 20x28x1.6mm3 in dimensions. The proposed antenna is simulated on the HFSS software and the results obtained indicated that the antenna can be used for the UWB applications till 6.85GHz. In this region this antenna will have low losses below -10dB and suitable gain for the applications stated.

This paper presents a new method to design quasi-elliptic bandpass filters (BPFs). A short-circuited coupled-line stub (SCCLS) is proposed to serve as a resonator of a BPF and also generate a pair of symmetrical transmission zeros (TZs) at the stopband frequencies. An equivalent circuit model of the SCCLS is derived to facilitate the design procedure. To demonstrate an example, a 3rd-order quasi-elliptic BPF is designed and fabricated. The implemented quasi-elliptic BPF is based on a coupled-resonator filer design, except a connected coupling mechanism is introduced to incorporate the SCCLS into a BPF. The measured results agree well with the simulations thus successfully verify the design concept.

This report proposes a millimeter-wave broadband reflectionless bandpass filter which is integrated by a bandpass filter and a bandstop filter. The bandpass filter is constructed by cascaded coupling lines, and the bandstop filter is constructed by a coupling line and a stub line. By adopting the hybrid broadside coupling structure of a coplanar waveguide and a microstrip, the broadband characteristics of the filter can be realized. At the same time, broadband reflection wave absorption is introduced in the auxiliary channel by two cascaded bandstop filters. The reflectionless bandpass filter centers at 47GHz with a fractional bandwidth of 62%, insertion loss of 1.04dB, and out-of-band suppression of more than 17dB. The return loss of the reflectionless bandpass filter is better than 10dB from 22.88GHZ to 68.52GHz, meanwhile, high frequency selectivity is also realized.

Self-interference cancellation (SIC) is critical for In-Band Full-Duplexing (IBFD) systems, which facilitate doubling of the spectrum efficiency [1] . Propagation-level SIC methods are especially attractive as they ease the required dynamic range of the receiver (Rx) hardware. While the multi-antenna solutions increase the form factor of transmitter (Tx) – Rx system, the single antenna configurations typically employ expensive and bulky circulators. Polarization-based isolation has been previously shown for a two-antenna system by employing an active-component loaded stub-resonator [2] . However, the design requires multiple-layers of thick substrate to provide both the matching and directivity to the antennas. In addition, the reflections from the stub resonator interfere with the Tx antenna patterns and the distortions produced by the active component propagate through the Rx chain, degrading its sensitivity.

In this paper simple and novel broadband microstrip branch line coupler (BLC) for L-band microwave applications is presented. The novel design of double box BLC with open ended stub at center frequency of 1.5 GHz is discussed. Using proposed method of open ended stub bandwidth around 42% of design frequency is obtained. The proposed broadband coupler is implemented using FR-4 microstrip substrate. The measured results have shown good agreement with simulated response. The proposed broadband double box BLC can be used for various L-band microwave applications.

This contribution, nominates and investigates a compact two element micro-strip fed 8-shaped self-affine fractal inspired Ultra-wideband (UWB) Multiple-Input-Multiple-Output (MIMO) antenna. The configuration exploits a 2nd order 8-shaped self-affine structure miniaturization of the overall size of each monopole element and provides wideband attributes to the antenna. The antenna exhibits an impedance bandwidth ranging from 2.6 GHz to 12 GHz, covering the entire UWB spectrum. The two element wideband MIMO antenna is realized within a compact layout of 32.3 mm×36.2 mm=1169.3 mm2. The isolation among the pair of planar monopoles with 2nd order Koch fractal boundary is found to be > −20 dB throughout the UWB spectrum even with a marginal inter-element spacing of 9.55 mm. The wideband isolation enhancement is also attained as a result of an extended ground stub with Koch fractal boundary. Moreover, the envelope correlation coefficient (ECC) of the UWB MIMO antenna is calculated to be < 0.01. The concurrence admits the diverse simulation results verify that the proposed arrangement can be a worthy competitor for handy UWB as well as UWB MIMO systems.

We present the design and simulation results of a highly-miniaturized and efficient flat-top plasmonic band-pass filter based on a MIM waveguide. In addition to that, it is revealed that by adjusting the length of stub segment, the desired spectral response can be easily realized.

An ultra-wide band (UWB) antenna having a notch band is proposed in this article. The antenna structure comprises of a pentagonal radiator loaded with dual stub. The bottom is utilized to enhance the bandwidth while the upper stub is utilized to achieve notch band. The antenna with compact size of 15 × 20 × 0.254 mm3 operates over 3.1 – 14.7 GHz along with a notch band of 3.8 – 4.7 GHz providing more than 2.3 dBi gain, while it decreases up to -4 dBi in notched band region. Moreover, the wide bandwidth, compact size, simple geometrical structure, high gain and efficiency makes the proposed work a potential candidate for physically small devices.

A design of self-diplexing cylindrical dielectric resonator antenna (DRA) is presented in this paper. The DRA is based on ceramic material. The $\text{HEM}_{11\delta}$ and $\text{TM}_{02\delta}$ modes of the cylindrical DRA are excited by differential feeding and a metal probe respectively. A stub is adopted to suppress spurious modes of HEM and improve the isolation of the two input ports. The results show that, within two frequency bands 2.73-3.05 GHz and 6.19-6.52 GHz, the proposed antenna achieves good impedance matching ( $\vert S_{11}\vert ), and isolation (>26 dB). The proposed self-diplexing DRA could be appllied in modern wireless communication.

This paper presents a kind of Ku-band filtering power divider(FPD) design with thin-film integrated passive device(IPD) technology and improved isolation structure. The Thin-Film IPD technology can well meet the greater requirements of processing accuracy and circuit layout in higher frequency band. Fourth-order quasi-elliptic filter is employed to realize good passband selectivity and out-of-band rejection. A compound structure including a GaAs-based resistor and an inductive stub is adopted to achieve good in-band isolation and matching. Phase difference can be changed by selecting different feeding point. Finally, two FPDs operating at 16 GHz are designed and adjusted.

In this paper, an enhanced 5G millimeter-wave (mmW) wideband monopole antenna is shown. The proposed design antenna covers broadband of 5G frequencies (upper band) extends from 20 to more than 40 GHz. The antenna design consists of a monopole radiator with multiple stubs backed by a partial ground plane. The antenna is realized by Appling photolithographic procedure. The antenna has stable radiation characteristics through the operating band. A Maximum realized gain of 5.1 dBi is achieved at 28 GHz. The proposed antenna shows very good agreement between both the simulated and the practical results.

With the signal speeds doubling for every generation, PCB design is becoming more and more challenging. The high-speed signal is getting more sensitive to the board layout impairments due to the dense placement of components. Therefore, a comprehensive scan including geometry, crosstalk, and noise coupling is necessary to ensure a quality eye at the receiver end for the concerned high-speed nets at 56Gb/s and beyond. In this paper, we offer a complete and automated full-board SI scan methodology. With such a methodology, subtle board layout defects are quickly pinpointed, including ground coverage, via stub length, trace necking, power via to signal via/trace spacing, and ground via to signal via distance, etc. Moreover, high-speed return loss and crosstalk scan in connector and ASIC pin fields are also implemented in an automated way with the help of the fast EM solver technology. As a result, the goal to have a confident PCB sign-off for the high-speed signals is achieved.

As more components are integrated into a denser area in electronic devices, the complexity of routing increases. A routing design resulting from routing tools may pass all design rule checks, but it can also result in signal integrity problems, which affect the performance of the entire link path, often not realized until the layout stage. In this paper, such designs are analyzed for their unintentional resonances in the insertion loss and the crosstalk of the signals. As an example, an unintentional power plane stub created by trace routing revisions adjacent to the signal trace behaves as a quarter-wavelength resonant structure. To avoid such unintentional resonances in high-speed signals, trace routing should be carefully designed and design rule checks must be improved to detect and warn the users of such potential signal integrity hazards.

During the last decade, the guided wave structures played a key role in numerous microwave systems. They have been deployed in many applications such as radar, remote sensing, and satellite applications. Furthermore, such guided wave structures have various advantages in a term of the strength of the structure, high power handling capability, efficiency, and small dimensions which make them more appealing to be employed in microwave frequency range applications. In this paper, design, analysis and comparison of structures for radar applications with enhanced performance using impedance matching, has been obtained. The $TE_{10}$ transmission enhancement obtained through two varieties, the first variety is the feeder with straight output ports and the second is the feeder with V-output ports for V-antenna applications. The enhancement transmission ratio (ETR) is the ratio of transmission of both structures with and without stub. Structures have been analyzed using HFSS and CST. The proposed structures presents ETR for TE 10 up to 17.7 and 28.8 at 11.43 and 8.12 GHz for both varieties respectively compared to the conventional feeders without stubs using HFSS simulator. The same structures present ETR for TE 10 up to 17.6 and 28.7 at 11.93 and 8.63 GHz using CST simulator. The proposed structures characteristics such as the magnitude of transmission coefficient, log scale distribution of current on surface and the ETR are obtained to demonstrate the performance of structures using HFSS and CST simulators.

A novel cross-shaped resonator composed of parallel coupled-lines for the design of high-selectivity single- and dual-band bandpass filters (BPF) is presented in this paper. The proposed resonator consists of four pairs of quarter-wavelength parallel coupled-lines two of which having one leg short-circuited. Even and odd mode analysis is performed for the exact derivation of the transmission poles. By adding a quarter wavelength open-circuited stub at the input and output ports two passbands can be created on each side of the operation frequency. To validate the theoretical analysis, the two filters are designed and simulated demonstrating the simple design procedure. Both single- and dual-band BPFs demonstrate an exceptional insertion loss of 0.23 and 0.77 dB respectively. The single –band BPF has a center frequency of 2.94 GHZ and a -3dB fractional bandwidth (FBW) of 50% with good filtering performance, sharp roll- off factor and return loss better than 25dB for the entire passband. The dual- band BPF is centered at 2.2/3.6 GHz having -3dB FBW of 10%/6.7% respectively.

This paper presents an impedance matching enhancement of a 1 × 4 rectangular microstrip antenna array designed for 5G applications in Ka-band. An efficiency comparative study between different impedance matching techniques, such as quarter-wave transformer, open-circuited or short-circuited length of transmission line (a stub) and smooth shapes tailored in the low corners of each antenna is presented. Indeed, an excellent input reflection coefficient $S_{11}$ value of −75 dB at 28 GHz and a bandwidth of 8.3% are achieved. In addition, radiation characteristics show a significant gain of 13 dB in E-plane. Due to its simple low-profile planar structure, which is easy to fabricate with no intricate process embroiled, and its attractive radiation characteristics, this planar antenna array meet the needs of 5G applications in Ka-band.

This paper aims to present a miniaturized dual polarized circular slot antenna for ISM band applications. The proposed compact antenna of size 95×95×1.6 mm3, consist of circular slot with two ports placed in opposite direction. The Port 1 is excited by a 50 Ω microstrip line with a triangular stub and port 2 is excited by a microstrip line with stepped triangular patch due to which the impedance bandwidth (BW) of proposed antenna is enhanced and radiated with horizontal and vertical polarizations. The proposed circular slot antenna achieved a 10 dB return loss bandwidth for port 1 of 60.6% (1.54-2.89 GHz) and port 2 of 53.7% (1.73-3.0 GHz) with isolation of 40 dB in the entire band and achieved a realized gain of 2.50 dBi at 2.45 GHz. The simulated results of proposed antenna show good radiation characteristics for ISM band applications.

A bandpass filter has been presented in this paper with its design, which has been substantiated by its analysis followed by confirmed and authentic results. The authors have used a simple approach and method to realize the three transmission poles and two transmission zeroes for application in the Ku-band. The resonant frequency is achieved by the implementation of half-circular-shape (HCS) patch and stubs as well. At first, the 50-Ohms input impedance is provided by the use of the microstrip transition. Apart from this, four open stubs, along with two HCSs patches, are executed on the radiation of the structure. The merits of HCS patch and stubs is to produce the resonant frequency. Moreover, a stub is placed on each side of the port. The length of each stub that is placed on either side of the port is equivalent to half of the guided wavelength. Additionally, to eliminate the unwanted noise and improve the fractional bandwidth, the feed-line and stub gap plays a primary role in the design. The designed filter can be used for Ku-band applications.

The deterioration of the sidelobe level (SLL) will significantly reduce the performance of the antenna used for satellite communications. Sidelobe level suppression is often neglected in the design of Variable Inclination Continuous Transverse Stub (VICTS) antenna with high-gain and wide bandwidth. A VICTS antenna operating at 13 GHz-15 GHz with low SLL design is presented in this paper. The radiation plate of the antenna is composed of two sets of radiation stubs with different radiation efficiency. By using the parallel plate waveguide (PPW) and nonlinear slow-wave structure with gradually decreasing height, the aperture field of the antenna is controlled to be tapered to suppress the SLL. The simulation results show that the SLL can be kept below -19 dB and the return loss is less than 15 dB in the scan range of 6.7° to 53.4°.

The recent developments in microwave systems, put high requirements to antenna arrays for RFID and radar applications, in terms of pattern shape and side lobe specs. The presented paper discusses an inexpensive approach for amplitude distribution control of aperture-coupled microstrip patch antenna, as a building block of more complex array systems.

Two types of short-circuited stub-embedded ring resonators (SERRs) are proposed in this paper. The resonant modes of the SERR can be designed by properly choosing the short-circuited point on the resonator. When the short-circuited point is set at the open-end of embedded-stub, type A resonator is realized and large frequency ratio of harmonic to fundamental frequency can be achieved. Simultaneously, wide stopband can be realized. When the short-circuited point is set at the loop portion of SERR, type B resonator is realized and low frequency ratio of harmonic to fundamental frequency can be achieved. These characteristics of the resonators type A and type B are explored and combined in a diplexer with common resonator part. Each channel of the diplexer are constructed by using the type A resonators for wide stopband, and then combined via a type B resonator for designated frequencies. A third-order diplexer operating at 3.45/5.8 GHz for fifth generation of mobile communications (5G) and wireless local area networks (WLAN) is designed, fabricated, and measured. Measured results agree well with the simulated ones, which confirms the proposed design methodology.

A novel method to design stripline filters with shielding structure is presented in this paper. By applying a shielded substrate integrated cavity a fully closed, 3rd-order filter with low loss is proposed for 5G N79 band. The shielding vias and copper layers form an enclosed cavity for the stripline filter composed of two gradient impedance resonators (GIR) and one stepped impedance resonator (SIR), which removes the radiation loss and improves the selectivity performance. A transmission zero is obtained by equating the gradient and low impedance parts of the GIR to an open-ended quarter wavelength stub. On the basis of this filter, a 2nd filter is designed by introducing a defected ground structure (DGS) and quarter wavelength stubs, which expands the passband and stopband. Both filters are fabricated and measured. The measured results are in good agreement with simulation, which validate the proposed design methodology. The minimum insertion loss is 0.46 dB and 0.25 dB for these two filters, respectively. The two filters are good candidates for 5G N79 applications.

This paper presents a development of a compact ultra-wideband (UWB) slot antenna using stair-step impedance technique with a pentangular stub for 5G application. The proposed antenna is miniaturized and fabricated on a very cheap FR4 substrate with a dimension of 20x22 mm2. Also, the stair-step segments and a pentangular stub in the slot antenna provide improving the impedance bandwidth. The stair-step segments are used to tuning at a lower frequency, and a pentangular stub provides to tuning the higher frequency. The proposed antenna can operate the frequency range between 3.1 GHz to 14 GHz. The radiation pattern is bidirectional throughout the operating frequency range, while the average antenna gain is about 3.5 dBi.

This paper introduces a new technology for a high-speed, high-power mobile form-factor tuner utilizing gas discharge tube plasma cells as switching components. To the best of our knowledge, this represents the first plasma-enabled RF matching network. Technology development is reviewed, the fabrication and measurement of a proof-of-concept switched stub impedance tuner are presented, and techniques for improvement are discussed. The proof-of-concept impedance tuner functions with a 27% bandwidth from 3 to almost 4 GHz and shows a power gain better than -2.5 dB across all switching state-frequency combinations at a 50 W input power level with spread coverage of the Smith chart. State change transient timing is measured to be on the order of 500 ns. This technology demonstration highlights the potential of miniaturized, rapidly-tunable, high-power, plasma-based RF devices., Comment: 4 pages, 7 figures, published in IEEE Wireless and Microwave Technology Conference (WAMICON), 2021

A novel CPW fed UWB antenna with 4GHz/5.48GHz/7.5Ghz triple notch band features has been proposed. The antenna which has a dimension of $35.4\text{mm}\times 28.8\text{mm}$ , is composed of pentagonal radiating stub with CPW framework. The ultra wide band from 3.03GHz to 11.1GHz frequency range has been obtained and by inserting three simple L shaped regular slots at the ground plane and the stub and optimized in order to achieve desired stop band characteristics. The triple frequency band notched characteristics has been achieved at IMT (International Mobile Telecommunications) advanced system 4th generation mobile communication system (3.4-4.2GHz), WLAN (5.15-5.3GHz) and X Band satellite communication(downlink) (7.25-7.75GHz). The antenna shows broad bandwidth, good impedance match and omnidirectional radiation patterns in the entire frequency range.

International audience; In this paper, an ultra-low-profile wideband continuous transverse stub (CTS) array is presented. The antenna module is fully realized in multilayer printed circuit board (PCB) technology, comprising 9 dielectric substrates. Particularly, the radiating part consists of long slots etched on the top of the eighth dielectric substrate. The slots are parallel-fed by a corporate feed network made of vertical parallel-plate waveguides (PPW), using via-fences. A pillbox system, embedded into two substrates, is employed to feed the slots with a line source. The antenna module is low cost and presents a very low form factor. A prototype was fabricated and measured in the K/Ka-band. The antenna array provides a pencil-beam radiation for angles of scanning as far as ±24° along the azimuth plane parallel to the slots. The input reflection coefficient is below -10 dB in the frequency range 19-31 GHz (48% of relative bandwidth). The maximum realized gain is 21 dB at 29 GHz.

This paper presents a patch antenna designed for Ultra High Frequency (UHF) Radio Frequency IDentification (RFID) reader achieving polarization and frequency agility by employing a reconfigurable feeding network inspired by stub theory. The switchable polarization improves the polarization efficiency in comparison with standard circular polarized antennas, while the frequency reconfigurability allows to use the same design to cover the European and US frequency bands. As further optimization, the patch antenna, has reduced size, for improving system integration. The combination of antenna and reconfigurable feeding network has been tested through simulations, showing a good matching over the two RFID frequency bands, while switching among four linear polarizations. The simulated results have shown a good polarization purity, however, the total efficiency is limited by the switching elements. Nevertheless, being a compact and low-cost solution, the proposed frequency and polarization reconfigurable feeding network is a good alternative to standard circular polarized designs.

The antennas are an essential part of wireless communication system. Ultra-wide band communication has the high demand for high data rate and low power. Although UWB transmits more information at low energy state, the diffraction and reflection between two interacting antennas cause multipath fading. Multiple-Input Multiple-Output (MIMO) is used to overcome this disadvantage produced by Ultra-wideband (UWB) technology. The task is to layout a textile MIMO antenna which operates at UWB frequency. So, we come up with the structure which is made out of jean material whose $\epsilon \mathrm{r}$ is 1.6 and loss tangent is 0.02. The 'T' shaped stub is made in ground plane to improve port isolation. The antenna has dimensions of $(36 \times 55 \times 1.5)$ mm3 and covers better frequency range of 2.2712.33GHz. The proposed antenna was designed using HFSS software.

The reactance-to-reactance transformer (RRT) technique is proposed in this paper for applying in the tuning circuit to miniaturize the tuning stub. These associated RRT formulas are derived based on conjugately characteristic-impedance transmission line (CCITL) equations and the ABCD parameters. The proposed RRT analytical formulas are applied to both short- and open-circuit tuning stubs. Then, the physical length, electrical length and reflection coefficient are observed at the operating frequency of 2.4 GHz. Simulation results prove that the proposed RRTs can be applied to shorten the tuning stub length compared to that of the conventional single stub tuning.