By etching a half-wavelength hook-shaped slot on the ground and adding quarter-wavelength rectangle-shaped strips in the patch, a novel triple band-notched ultra-wideband (UWB) antenna is proposed. The triple band-notches are used to prevent interferences from existing bands at 3.3-3.9 GHz, 5.15-5.35 GHz, and 5.725-5.825 GHz. Fed by coplanar waveguide, the antenna is printed on a 30*30 mm² substrate. The parameters affecting antenna performance are simulated and analyzed. The simulated and measured results show that the proposed antenna achieves a wide bandwidth from 3 GHz to 11 GHz with triple band-notches. Radiation patterns and gain are also investigated and analyzed.

A compact slot-coupled endfire radiation antenna based on a tapering spoof surface plasmon polaritons (SSPPs) structure with high efficiency is proposed in this paper. A narrow slot balun is designed to feed the SSPPs structure rather than to work as the primary radiator. Simulated results show that the odd SPP mode is successfully excited on the tapering SSPPs structure, which contributes to the endfire radiation. Due to the high confinement of SSPPs, the proposed antenna shows low RCS within the frequency band of 1.5 GHz-4 GHz and 5.6 GHz-8 GHz. A prototype is fabricated and tested. Simulated and measured results show good agreement that the proposed antenna can provide stable endfire radiation patterns within the frequency band of 2 GHz-3.4 GHz. The maximum gain reaches 8 dBi, and the average efficiency over this bandwidth is 80%. The high-efficiency endfire SSPPs antenna with balanced broad band and high gain has a promising application in communication systems and integrated circuits.

A novel beam scanning microstrip leaky wave antenna based on liquid crystal material is proposed in this paper. Based on the dielectric anisotropy of the liquid crystal, the main beam angle of the antenna pattern can be easily adjusted with the changing of external bias voltages. Good agreement between simulated and measured results is found for the presented leaky wave antenna. Both the simulation and test frequencies of the antenna are set at 12 GHz. Besides, the measured data show that when the dielectric constant of the liquid crystal changes from 2.4 to 2.52, about 10 degrees tuning range of the main beam angle is achieved.

In this letter, a methodology for the generation of received irradiance/power time series for a GEO downlink concentrated on small aperture receiver terminals is reported. The synthesizer takes into account the atmospheric phenomena that degrade the propagation of the optical signal and especially the turbulence effects. For modeling the scintillation effects, Kolmogorov spectrum is assumed, and the Rytov's approximation under weak turbulence is also used. The time series are generated using the theory of stochastic differential equations. Finally, the proposed synthesizer is compared in terms of first order statistics with experimental data from the ARTEMIS GEO optical satellite link campaign with very good agreement.

A compact multiple-input-multiple-output (MIMO) antenna with very high isolation is proposed for ultrawideband (UWB) applications. The antenna with a compact size of 30.1×20.5 mm² (0.31λ₀×0.λ₀) consists of two planar-monopole antenna elements. It is found that isolation of more than 25 dB can be achieved between two parallel monopole antenna elements. For the low frequency isolation, an efficient technique of bending the feed-line and applying a new protruded ground is introduced. To increase isolation, a design based on suppressing surface wave, near-field, and far-field coupling is applied. The simulation and measurement results of the proposed antenna with the good agreement are presented and show a bandwidth with S₁₁ ≤ -10 dB, S₁₂ ≤ -25 dB ranged from 3.1 to 10.6 GHz making the proposed antenna a good candidate for UWB MIMO systems.

In this paper, we present our experimental study of the effect of the external DC magnetic bias field on the nonlinear properties of meta-atom loaded with ferrite elements of different shapes. It is demonstrated experimentally that the adjustment of the resonance frequency of the meta-atom loaded with the ferrite elements of different shapes is possible not only by the input microwave power but also by the external DC magnetic bias field. It is shown that as the external DC magnetic bias field is increased to a certain value, the resonance curve of the nonlinear meta-atom demonstrates bistability. In addition, we achieve significant enhancement of the meta-atom nonlinearity using the nonlinear properties of both ferrite and varactor diode.

This paper presents a quickly converging optimization technique for synthesis of filters with constant and frequency-variant couplings (FVC). Unlike the works so far appeared in the literature, the proposed technique is not based on the direct optimization of scattering parameters with assigned topology, but it consists of two procedures. Firstly, an FVC coupling matrix with assigned topology is suitably transformed by means of scaling and rotations for obtaining the new coupling matrix with constant couplings. Then, the cost function is constructed as a least squares problem involving both the eigenvalues of the new coupling matrix with constant couplings and that of the transversal coupling matrix. The solution is found via the solvopt optimization method. Two numerical examples with different topologies and specifications are synthesized to show the validation of the method presented in this paper.

In this paper, we systematically derive design equations for 3-way Bagley power dividers with arbitrary split ratios using interconnecting transmission lines with the same characteristic impedance. The exact value of the characteristic impedance for a specific dividing ratio is determined using these equations to achieve perfect input port matching. To validate the design procedure, two microstrip dividers with different split ratios, 1:3:1 and 1:10:1, are designed, simulated, fabricated, and measured. The desired split ratios are achieved at the design frequency, 1 GHz. Good agreement between simulated and measured results is obtained.

This paper investigates the performance of compact triple band-notched Multiple Input Multiple Output (MIMO) antenna for Ultra-Wideband (UWB) communication. Open-ended quarter wavelength slots are inserted on the radiators. These slots are used to obtain notch bands at WiMAX/C band, WLAN band and the X-band Satellite Communication System that ranges in 3.3-4.2 GHz, 5-6 GHz, and 7.2-8.6 GHz respectively. An I-shaped stub extends from the ground surface to minimize mutual coupling among radiating elements. Mutual coupling and Envelope Correlation Coefficient are found less than -15 dB and 0.2, respectively. The diversity characteristics like Mean Effective Gain Ratio and Total Active Reflection Coefficient are found around 1dB and less than -10.5 dB, respectively. The radiation efficiency of the radiator is more than 80% over the entire UWB frequency range. The proposed antenna is designed with the overall dimensions of 23×40×1.6 mm³.

A novel technique to design a wideband implantable antenna has been proposed by using magneto-dielectric material. The antenna is a half cutting of a coplanar waveguide fed antenna with symmetric geometry printed on a flexible substrate with 24 um thickness. A piece of magneto-dielectric sheet with 0.25 mm thickness is attached on the bottom layer of the antenna to tune the antenna bandwidth. The antenna is simulated in a one-layer body phantom. Simulation shows that the antenna has a wide bandwidth covering 902-928 MHz Industrial, Scientific, and Medical (ISM) band when the body phantom is filled with muscle. There are frequency bandwidth shifts when the body phantom is filled with different tissues of skin, small intestine, and stomach, respectively. The antenna has wide bandwidth covering ISM band in these tissues. Measurement has been done in meat mince. The measured bandwidth of proposed antenna is 810-1062 MHz. The proposed antenna has a compact size of 4 mm×12 mm×0.274 mm suitable to be applied in capsule endoscope, wireless pacemaker, etc.

In this letter, a microstrip dual-band band-pass crossover is proposed. By reducing the number of inner open stubs, miniaturization of a window-shaped crossover without reducing bandwidth can be achieved. An electromagnetic simulation and measurements are used to validate the compact (0.35λ × 0.35λ) crossover with a wide bandwidth.

Magnetic coupling resonance wireless power transfer (MCR-WPT) technology has been in development for over a decade. The output power of the MCR-WPT system achieves the maximum value at two splitting frequencies and not at the natural resonant frequency because frequency splitting occurs in the over-coupled region. In order to achieve excellent transfer characteristics, optimization approaches have been used in many MCR-WPT projects. However, it remains a challenge to obtain a constant output power in a fixed-frequency mode. In this research, two receiving coils are used in the MCR-WPT system to achieve a uniform magnetic field. First, a circuit model of the MCR-WPT system is established, and transfer characteristics of the system are investigated by applying the circuit theory. Second, the use of two receiving coils to achieve a uniform magnetic field is investigated. Constant output power is then achieved in a fixed-frequency mode. Lastly, the experimental circuit of the MCR-WPT system is designed. The experimental results are consistent with the theoretical ones. The topology of using two receiving coils results in optimum transmission performance. Constant output power and high transfer efficiency are achieved in the higher frequency mode. If the distance between the two receiving coils is appropriate and the transmitting coil moves between the two receiving coils, the fluctuation of the output power of the MCR-WPT system is less than 10%.

Surface ship imaging technology is widely used in military and civilian applications. To resolve the problem of imaging moving target positioning blur on sea surface, this paper proposes a method for estimating the velocity of moving target using velocity synthetic aperture radar (VSAR). Firstly, the paper analyzes the imaging mechanism and constraints of VSAR method and establishes an imaging model based on phased array radar for surface ships. Then, the rate-frequency estimation method of the multi-antenna image domain is used to correct the azimuth offset, and the image moisture algorithm is used to estimate Doppler frequency modulation. Therefore, the adaptive focusing of the target image is completed. Finally, this method is used to simulate and calculate the surface motion ship to realize continuous dynamic imaging of the moving ship. Compared with the traditional single-channel SAR radar and track-interfering radar (ATI) algorithm, the rate-frequency estimation algorithm solves the shortcomings of the azimuth positioning accuracy and improves the positioning performance of the moving target ship under large-area sea conditions.

This paper presents a detailed analysis of the human body limb movement influence on the radiation pattern of a wearable antenna during different activities. The analysis is carried out at 3, 6, 9 GHz of the 3-10 GHz UWB range of frequencies. Simulations are carried out on a human body model in CST microwave studio with a compact wearable antenna to obtain the body-worn antenna radiation patterns for lower and higher frequencies. This study gives an insight into the variation of the radiation patterns of a compact UWB antenna depending upon the position of the wearable antenna on the body. Results conclude that the radiation pattern of the wearable antenna changes significantly in terms of shape, size, level of distortion and direction of maximum radiation with different limb movement activities and also depends upon the placement of the antenna on the limbs. The coverage area of the wearable antenna radiation pattern becomes highly directive and shrinks in coverage area for the shoulder/thigh node in comparison to the wrist/ankle wearable node by 10-15%. The bending of the limbs leads to deformation and reduction in area of the radiation pattern with values as high as 30-40% compared to free space scenario as the bending angle between the upper and lower arm/leg reduces. The analysis presented gives directional information regarding maximum radiation and the field strength of the radiation pattern for various activities performed. The present study reports results on the influence of the wearable antenna position, on detection and tracking performance of RF and microwave biomedical devices/sensors suitable for various healthcare applications such as tracking of human subject, patient monitoring, gait analysis, physical exercises, yoga, physiotherapy, and rehabilitation.

An effective numerical technique is demonstrated for the plane wave scattering from an infinite periodic array of hollow circular cylinders of finite length. The cylinders are made of infinitely thin perfect conductor and allocated in the axial direction. We formulate the boundary value problem into a set of integral equations for the unknown electric current densities flowing in the circumferential and longitudinal directions. Employment of the Galerkin method allows us to solve simultaneous linear equations for the expansion coefficients of the unknown current, from which we can find the field distributions in both far and near regions. The procedure of analytical regularization makes the linear system into the Fredholm second kind that is contributory to stable and rapidly convergent results. Resonance is detected as abrupt changes in the total scattering cross sections for each grating mode, and it is accompanied by the formation of circular cavity mode pattern in the cylinder.

Chipless RFID with small, printed metal tags have been proposed as a cost-effective alternative to chip-based technologies. A potentially viable configuration is to image the patches of different shapes, sizes, and orientations within a tag with a tabletop-scale synthetic aperture radar (SAR), operating in the V or W band. Information is encoded into, e.g. polarization, resonance characteristics, and phase of the scattered signal. The effect of electromagnetic coupling and sidelobe interference between closely spaced metal patches on SAR image has not been addressed in prior studies. To be specific, we analyze 60 GHz circular SAR (CSAR) imagery of subwavelength patches separated by distances on the order of wavelength. The scattered field is calculated with the method of moments (MoM) to account for EM interaction. The field is then used to form CSAR image with the polar formatting algorithm (PFA). Significant distortion of the CSAR image is found at this scale. Sidelobe interference causes image distortion and up to 7 dB of intensity modulation with patch separation. EM coupling produces an ``interaction image,'' an artifact that extends between the patches. The source of this effect is traced to induced currents and charges residing on the patches' inner edges. Increasing system bandwidth or changing the incidence angle has minimal effect on both classes of image artifacts, highlighting the importance of accounting for them in practical system design and subsequent information processing.

A wireless charging system for electric vehicles has two parts which are located inside and outside the vehicle respectively, and energy is transmitted from the outside part to inside part through a loosely coupled transformer. The energy transmission efficiency is directly related to the power conversion efficiency of the entire wireless charging system. This paper aims to improve the transmission efficiency of the DC transformer of the wireless charging system through studying compensation design method of DC transformer. A dual-tap rectifier is applied at the secondary side of the transformer, and a capacitor is connected in series on the primary side. Two capacitors are connected in series on the secondary side. By quantitative analysis on DC transformer efficiency, the relationship among efficiency, switching frequency and compensation parameter is obtained. The compensated DC transformer realizes soft switch and further improves transformer efficiency. Finally, simulation and experiment on the wireless charging system with magnetic induction are conducted to verify the improved transformer design. The simulated and experimental results show that the average compensated DC transformer efficiency has been improved by 1.248%. Thus the designed DC transformer can effectively improve the energy transmission efficiency, and reduce voltage stress of the power device.

A simple, small-sized, printed monopole antenna loaded with a chip inductor for achieving dual-band operation in notebook computers is introduced. The design consisted of a simple 5 GHz monopole, a chip inductor, and a tuning end portion. With the inductor inserted at the end of the 5 GHz monopole and connected to the tuning portion, the lower band resonance in the 2.4 GHz band can be attained, together with a reduced design footprint for 2.4 GHz operation. The frequency ratio of the upper and lower bands were also controllable by inductance values. The results showed that the antenna was capable of operating in 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) wireless local area network (WLAN) bands and yet occupied a small size of 5 mm × 12 mm (about 0.04l × 0.09l at 2.4 GHz) only.

Since passive millimeter wave synthetic aperture interferometric radiometer (SAIR) has the advantages of high spatial-resolution and large field of view, it is an attractive tool for wide area surveillance. Among the SAIRs, the Rotating Scanning SAIR (RS-SAIR) with linear sparse array is a popular system with low redundancy and high reliability. According to the detection mechanism of RS-SAIR, we extend RS-SAIR to deal with higher-order moving target detection (HMTD) for the first time in this paper. In the proposed HMTD method, the 2D time-projection image is constituted by the 1D projection images measured by RS-SAIR firstly. Then, the projection trajectory of moving target can be extracted from the time-projection image. Finally, the positions and motion parameters are estimated by fitting the moving target's trajectory. Simulation results indicate that the position and motion parameters of higher-order moving target can be well estimated with high real time and accuracy by the proposed HMTD method.

Recent studies show that the frequency dependent soil properties can significantly influence transient grounding resistance and, subsequently, lightning protection and reliability of the electrical grid. However, these properties require further research: for example, it is not clear what factors (apart from the low-frequency resistivity) should be taken into consideration to determine accurately the properties for a particular soil (without conducting laborious measurements). Additional experimental data are needed. When measurements are conducted, the electromagnetic coupling between circuits can cause significant measurement error at frequencies about several MHz. In order to estimate this error, it is convenient to use a calculation method, as in this case, it is possible to set particular frequency dependent properties for the ground and compare those with the calculated ones (using an electrode array). In the article, the electromagnetic coupling error is examined for several commonly used electrode arrays using the finite difference time domain method. This method allows simulating wires with innite length, which is important for modeling pole-dipole and pole-pole arrays. Its drawback for this type of calculations, however, that it is relatively time-consuming. It was found that among the considered array configurations the error is smallest for the dipole-dipole arrays with the perpendicular allocation of the measurement wires and the pole-dipole array. By increasing the distance between particular parts of measurement wires, one can significantly reduce the error for some other arrays.