A novel compact microstrip lowpass filter with ultra-wide stopband characteristic using square ring loaded resonators is proposed. A microstrip high impedance main transmission line loaded with five square ring loaded resonators is adopted in the design of the filter. Owing to the adoption of the square ring structure, the filter achieves compact size and ultra-wide stopband. A demonstration filter with 3 dB cutoff frequency at 0.72 GHz has been designed, fabricated and measured. Results indicate that the proposed filter is able to suppress the 19th harmonic response referred to a suppression degree of 15 dB, together with a small size of 0.054λ_g×0.070λ_g, where λ_g is the guided wavelength at 0.72 GHz.

An applicable and convenient method is critical for calculating the RCS (Radar Cross Sections) of chaff clouds. An improved method based on direct method [18] is proposed in this paper to promote efficiency, which is called SPMDM (Singular Points Meshing Direct Method). The tanh-sinh method is applied in SPMDM to compute the complex singular function in which the integral domain is meshed by the singular points. The practicability and accuracy of the SPMDM are confirmed through comparison with direct method. Results indicate that the SPMDM can significantly decrease calculation time and increase computing efficiency, especially in large-scale case or small relative error region.

Time domain reflectometry is frequently used to localize faults in electrical systems. Most existing literature on reflectometry in transmission lines considers symmetric faults that are either shorts between the two conductors or open circuits where both conductors are disconnected at the same location. This paper investigates spread spectrum time domain reflectometry (SSTDR) applied to asymmetric twin-lead transmission lines in which either only one conductor is disconnected or the reflectometry instrument itself is asymmetric. For asymmetric faults, we observe not only the expected dominant reflection corresponding to the location of the disconnection, but also an additional reflection from the end of the transmission line. In the second case, we leverage the asymmetric response of the SSTDR instrument to identify which of the two otherwise identical conductors has been disconnected.

The present work describes a unique planar wideband circularly polarized MIMO antenna for 4G and sub-6 5G band (1.35-2.6 GHz), with pattern diversity over the entire axial-ratio bandwidth. The design consists of two tri-branch planar inverted-F antenna (PIFA) antennas with a ground T-stub between the antennas, which is used to realize circular polarization and high isolation. The third antenna is an integrated sub-6 5G (4.45-4.7 GHz) and LTE band (786.7-807.7 MHz) antenna, which is folded above the ground and placed vertically around the side. It also provides circular polarization at LTE band. The 3 dB axial ratio bandwidth (ARBW) of the MIMO antenna is 1.05 GHz (1.47-2.52 GHz); impedance matching bandwidth (IMBW) is 1.25 GHz (1.35-2.6 GHz); and its isolation is better than 13.4 dB in the whole band. It has fabricated on an FR-4 substrate and is suitable for mobile handset.

A novel wideband microstrip patch antenna with nonuniform transmission line feed is presented using model predictive control. Nonlinear model predictive control (NMPC) is used to achieve a nonuniform transmission line that matches with the microstrip patch antenna. The transmission line is extended using cosine expansion with the impedance differential equation then being used as the dynamic NMPC equation to find the unknown coefficients of that cosine expansion. The transmission line is designed such that the impedance of the input port matches the impedance of the microstrip antenna at the resonance frequency and its adjacent frequencies. The proposed antenna's impedance is 5.15-5.85 GHz. In this bandwidth, the radiation pattern is stable; the cross polarization and back lobe are -30 dB and -20 dB respectively. The error in the impedance bandwidth is about 4.2%. The simulation and measurement results are considered satisfactory.

Wireless communication and/or wireless power transmission are highly desired in some of the practical environments fully enclosed by conducting walls. In this paper, a semi-analytical modal analysis is conducted for the purpose of characterizing wireless channels in a fully-enclosed space. The modal analysis is based upon an integral equation method. The cavity Green's function in the spectral domain (that is, expressed in term of cavity modes) is employed in the integral equation. The analysis results indicate that, when a transmitter and a receiver are symmetric to each other with respect to a certain cavity mode, the load of the receiver could be coupled to the transmitter with little dispersion, leading to excellent wireless channels with the potential of accomplishing efficient wireless communication and/or wireless power transmission. A cubic cavity with a side length of 1 meter is analyzed as a specific example, and the modal analysis results are verified by experiments. Measurement data agree with the theoretical analysis very well. As predicted by the theoretical analysis, excellent wireless channels associated with the TM₂₂₀ mode (with a bandwidth of 40 MHz), TM₃₁₀ mode (with a bandwidth of 10 MHz), and TM₃₁₁ mode (with a bandwidth of 20 MHz) are demonstrated inside a cubic box with side length of 1 meter.

A wideband patch array antenna with dual sense circular polarization (CP) is investigated in this paper. Four rotated hexagonal patches are sequentially distributed on the upper surface of substrate 1 to form a patch array. In order to widen impedance bandwidth, an annular feeding network with four rectangular branches is designed. At the bottom of the antenna, two orthogonally placed microstrip baluns are introduced to obtain the characteristics of left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). Meanwhile, four coaxial probes, passing through substrate 2 and substrate 3, are used to transmit the feeding signal between microstrip balun and the annual feeding network. The proposed patch array antenna is fabricated for verifying the feature of wideband and dual circular polarizations. The measured results show that the antenna has an impedance bandwidths of 70.2% (1.72-3.58 GHz) with an axial ratio (AR) bandwidth of 61% (1.85-3.48 GHz) and over 6.2 dBi gain at two ports. Moreover, the measured port isolation remains below -15 dB over the entire impedance bandwidth, and the measured radiation patterns with excellent directionality and symmetry at two ports indicate that the proposed antenna can be used for wireless applications.

Circular polarization is manifested by means of truncations on basic circular radiating patch with precisely designed asymmetric feed. The proposed truncated circular microstrip antenna (TCMA) yields impedance bandwidth (IBW) of 7.6 GHz, almost covering the FCC approved ultra wideband (UWB) frequency and 3-dB axial ratio bandwidth (ARBW) of 5.05 GHz spreading over two bands, enabling the antenna to be used for multiple applications in ultra wideband frequency range. A peak gain of 5.73 dBi is documented at 5 GHz which is within the circular polarization (CP) band. This single feed antenna is very simple to design and compact in size.

In this paper, an inkjet printed slotted disc monopole antenna is designed, printed and analyzed at 2.45 GHz ISM band on a polyethylene terephthalate (PET) substrate for early detection of brain stroke. PET is used as a substrate due to its low loss tangent, flexible, and moisture-resistant properties. By the implementation of slotting method, the size of this antenna is reduced to 40×38 mm². The printed antenna exhibits 480 MHz (19.55%) bandwidth ranging from 2.25 GHz to 2.73 GHz frequency. It shows a radiation efficiency of 99% with a realized gain of 2.78 dB at 2.45 GHz frequency. The Monostatic Radar (MR) approach is considered to detect brain stroke by analyzing the variations in reflected signals from the head model with and without stroke. The maximum specific absorption rate (SAR) distribution at 2.45 GHz frequency is calculated. The compact size and flexible properties make this monopole antenna suitable for early detection of brain stroke.

An effective and precise approach to the Wave Concept Iterative Process method modeling of magnetized graphene sheet as an anisotropic conductive surface is used to analyze the anisotropy of magnetostatically biased graphene and for studying an electrically doped magnetically biased graphene non-reciprocal antenna array for THz applications. The tuning of the performance of the array antenna is possible by varying the magnetic field and the chemical potential of graphene material. The return loss value decreases by increasing the magnetostatic bias and increases when the chemical potential increases.

This paper presents a miniaturized quintuple band antenna for multiband operation with the aim of developing a small and simple structure antenna that can operate at multiband frequency. The proposed antenna contains a rectangular microstrip patch, a transmission line with 50 Ω coplanar wave guide (CPW) and six L-slots. By introducing these L-slots along the X and Y axis, in the radiating element, the antenna yields five resonance modes at 2.4, 3.5, 4.4, 6.09, and 7.7 GHz while keeping the size of 27.4 x 24 mm². The prototype of the proposed antenna is constructed and experimentally studied. The measured and simulated results prove that the proposed multiband antenna is suitable for Bluetooth, WLAN, WIMAX, LTE, and X band applications. The antenna is designed using FR4 lossy substrate material with relative permittivity ε_r of 4.4 and thickness of 1.6 mm.

A coplanar waveguide (CPW)-fed flexible dual-band antenna using graphene as conducting material and Kapton polyimide as a substrate is proposed. The antenna shows increased impedance bandwidth due to the use of CPW-feed having the values of 80.29% (1.64-3.84 GHz) and 6.31% (5.52-5.88 GHz), respectively. The antenna has an overall size of 0.38λ × 0.43λ at center frequency of 3.4 GHz. The proposed flexible antenna has gain values of 1.82 dBi and 1.68 dBi with efficiency values more than 86% which makes the antenna commercially viable for smart wireless products having space constraints.

A compact microstrip fed dual polarized Ultra Wide Band (UWB) monopole Multiple Input Multiple Output (MIMO) antenna for access point application in Wireless Body Area Networks (WBAN) is proposed. The antenna is elliptically polarized in the 6 to 10.6 GHz band. The proposed structure possesses high isolation with the introduction of Modified Serpentine Structure (MSS) that behaves as a decoupling unit (DU). To further reduce the coupling and to improve the impedance bandwidth, an Electromagnetic Band Gap (EBG) structure is introduced. The proposed antenna has a wide impedance bandwidth with S₁₁ < -10 dB in the UWB from 3.1-10.6 GHz and has a high isolation S₂₁ < -25 dB. The antenna has a fractional bandwidth of 106%. The radiation pattern of the antenna is omnidirectional. The Envelope Correlation Coefficient (ECC) is equal to zero, and the capacity loss is 0.264 which proves the diversity characteristics of the proposed antenna.

Complex interconnection structure is a common structure on printed circuit board (PCB). Herein, the paper proposes a method of crosstalk cancellation point at the crosstalk problem between microstrip lines in a complex interconnection structure. First, a model of the coupled transmission lines-channel transmission matrix (CTL-CTM) of the complex interconnection structure is established. Second, the CTL-CTM is simplified through the equivalence of crosstalk-coupling coefficient of parallel coupling microstrip lines to that of the complex interconnection structure. The eigenvalue of the simplified CTL-CTM is then decomposed, based on which the construction of crosstalk cancellation circuit is performed. Simulation results show that the proposed method can effectively improve the quality of eye patterns on complex interconnection structures.

This paper presents an efficient method for evaluating the flux linkage between two circular loops located on the top surface of a plane multilayer soil. The method consists of a rigorous procedure, which leads to expressing the flux as a sum of products of Bessel functions. First, the integral representation for the mutual inductance is cast into a form where the integration range is continued to the negative real axis. Subsequently, the non-oscillating part of the integrand is replaced with a rational approximation, arising from using a well-known least squares-based fitting algorithm. Finally, analytical integration is performed by applying the theorem of residues. As a result of the proposed method, the flux linkage between the loops is expressed as a finite sum of products of Bessel functions. Since no assumptions are made in the mathematical derivation, the obtained explicit expression is valid regardless of the operating frequency. Numerical tests are performed to show the advantages of the proposed method with respect to standard numerical integration techniques. In particular, it is seen how the use of the derived series representation for the inductance with 50 terms permits to achieve the same accuracy as conventional Gauss-Kronrod numerical integration technique, with the advantage of reducing the computation time by at least 8 times.

A filtering rectangle dielectric resonator antenna (DRA) with high band-edge selectivity is proposed in this paper. The DRA is fed by a simple hybrid feeding structure consisting of a microstrip-coupled slot on the bottom and a thin metallic strip on the side of DRA to excite the fundamental TE^y_1δ1 mode. The feeding structure establishes a cross-coupled mechanism which includes electric and magnetic coupling; thus, introducing two radiation nulls at the band edge without any filtering circuits. By using the designed hybrid feeding structure, a bandpass filtering response is obtained. For enhancing band-edge selectivity, a shorted stub is introduced to weaken the coupling between the two microstrip stubs of the feeding structure. A wide impedance bandwidth of 19% and a flat gain of around 5.6 dBi are realized. To validate the design, a prototype is fabricated and measured, showing a favorable agreement with the simulated results.

In this article, we design a reconfigurable bandwidth based on a concentric ring slot antenna using graphene. The developed antenna has good agreement between simulated and experimental results. The use of graphene in Terahertz (THz) has shown better performance than metal, and the variation in the chemical potential of graphene provides excellent performance properties, good return loss reaching -33.288 dB, bandwidth reconfiguration from 255 GHz to 406 GHz, and a good gain. These results are promising for THz applications and particularly for the application of medical imaging. The modeling and validation are performed using the CST Simulator.

In this paper, a novel dielectric resonator antenna has been numerically simulated and experimentally demonstrated. The proposed design, comprising an Indium Tin Oxide (ITO) coated glass slide placed on a microstrip transmission line, is intended for WLAN and Wi-Max applications. The antenna shows a maximum bandwidth of 2.15-7.65 GHz and 10.36-11.78 GHz and a gain ranging from 2.21 to 6.44 dB. The novelty of the design lies in the use of ITO coating on glass to enhance as well as regulate the antenna bandwidth. Parametric variations have been investigated to analyse the topology for understanding the effect of the design parameters on gain, bandwidth, and reflection coefficient. A prototype has also been fabricated, where different ITO sheets have been mounted to measure the response. The proposed geometry has been found to be better and competent enough with respect to antenna parameters than existing Ultrawide Band antennas.

A wideband end fire antenna architecture in planar technology with fewer turns: helix antenna in planar technology adopting thickness of quarter wavelength is suggested. A wideband 24 GHz helix antenna with 2.25 turns in Rogers compressed RT 4350 technology is presented. The antenna has a bandwidth of 6.2 GHz for S₁₁, gain of 9.3 dBi, half power width of 39.5° and 39° respectively in X-Z and X-Y planes. This helix antenna is characterized by wide bandwidth, high gain, high half power width, compactness and high gain turn ratio. It could also be utilized in antenna design for other frequency bands with compressed PCB technology, as well for on-chip THz antenna design.

The proposed antenna structure is excited for multiple operational modes by means of meandered strips. The compact planar monopole antenna is demanded enormously for handheld devices especially automatic meter reading and tablet devices. Due to Chu limit, it is extremely vital to miniaturize an antenna by balancing tradeoff between bandwidth and radiation efficiency. The designed antenna is formed by two interconnected broad monopole open slots which covers multi-bands for smart energy meter and tablet computer applications. The cost effective FR4 laminate of size 50 x 200 mm² (0.4λ x 1.6λ) is employed to match standard tablet computer communication module dimensions. The impedance bandwidth, for all excited resonant modes, is above typical requirement of 2%, and the VSWR is well below the necessary requirement of 1.5. The peak gain ranges from 0.94 dBi to 1.92 dBi. Radiation patterns along with other antenna parameters are satisfactorily meeting the demand of Wireless Energy Meter and Tablet Devices. The effects of varying dimensions of a monopole on the radiation characteristics have also been presented. The return loss and radiation patterns computed through simulations are validated through experimental measurements in an anechoic chamber environment.