Discovering governing equations for transmission line is essential for the study on its properties, especially when the nonlinearity is introduced in a transmission line system. In this paper, we propose a novel data-driven approach for deriving the governing partial differential equations based on the spatial-temporal samples of current and voltage in the transmission line system. The proposed method is based on the ridge regression algorithm to determine the active spatial differential terms from the candidate library that includes nonlinear functions, in which the time and spatial derivatives are estimated by using polynomial interpolation. Three examples, including uniform and nonuniform transmission lines and a specific type of nonlinear transmission line for soliton generation, are provided to benchmark the performance of the proposed approach. The results demonstrate that the newly proposed approach can inverse the distributed circuit parameters and also discover the governing partial differential equations in the linear and nonlinear transmission line systems. Our proposed data-driven method for deriving governing equations could provide a practical tool in transmission line modeling.

This paper proposes an SRLSM with segmental stator pole. The segmented SRLSM which is known as SSRLSM was designed for domestic lift application. The SSRLSM was designed to fulfill the design target requirement where the lift must be able to transport a maximum 200 kg payload. This payload requires a motor with more than 2000 N thrust force at rated power of 1.5 kW. The rated current is 2.5 A. However, for the excitation current, the maximum current is taken twice of the rated current which is 5.0 A. The design of the SSRLSM was completed in two stages. The first stage is to design the stator pole length, l_st, while the second stage is to design the stator pole thickness, t_st. The designed models were simulated with FEM software. The simulation results show that the highest thrust produced in first stage is 6773 N. The thrust is produced by the model with stator pole length, l_st, of 120 mm. Meanwhile, in the second stage, the model with the stator pole thickness, t_st, of 20 mm produced the highest thrust. The thrust obtained from the model is 6903 N. Based on the analysis, the final model was selected. The model has the stator pole length, l_st, and stator pole thickness, t_st, of 120 mm and 20 mm, respectively.

Herein a circularly-polarized (CP) quad-band compact microstrip antenna is proposed. Its design involves one annular ring radiator having eight symmetrical slots along its boundary and three circular closed ring resonators (CRRs) on the bottom side of the substrate. Resonance frequencies of this antenna have been analyzed first and then tuned to excite desired modes via specially designed feed configuration by applying theory of characteristic modes (TCMs). Evolution process of the antenna geometry shows that the eight symmetrical slots in tandem with the CRRs generate wide impedance bandwidth (IBW), while measured quad CP bands are obtained through uses of an asymmetric ground plane resonating at 5.63 GHz (120 MHz), a cross-shaped slit at 7.69 GHz (650 MHz), a rectangular open loop at 9.91 GHz (1200 MHz), and a tuning stub in the feeding structure at 12.09 GHz (160 MHz). Series of parasitic strips augmented CP radiation and eliminate ripples in the radiation pattern. A low cost FR-4 substrate is used to fabricate the antenna with an optimized dimension of 35×30×1.6 mm³. The measured IBW ranges from 4.36-4.82 GHz, 5.50-5.78 GHz and 5.95 - beyond 14 GHz. The proposed antenna may find suitable applications in C band, X band, and 5 GHz WLAN devices.

In recent years, electrical impedance tomography (EIT) has attracted intensive interests due to its noninvasive, ionizing radiation-free, and low-cost advantages, which is promising for both biomedical imaging and industry nondestructive tests. The purpose of this paper is to review state-of-the-art methods including both algorithms and hardwares in EIT. More specifically, for the advanced reconstruction algorithms in mainstream, we offer some insights on classification and comparison. As for the measurement equipment, the structure, configuration modes, and typical systems are reviewed. Furthermore, we discuss the limitations and challenges in EIT technique, such as low-spatial resolution and nonlinear-inversion problems, where future directions, such as solving EIT problems with deep learning, have also been addressed.

In this paper, a compact two ports Multiple Input Multiple Output (MIMO) antenna for Ultra Wide Band (UWB) application has been proposed. The presented antenna consists of two symmetrical radiators, developed on an FR4 substrate with overall size of 34 × 18 × 1.6 mm³. The proposed antenna is fed with a 50 Ω microstrip line. The antenna has good impedance matching in the range of UWB band. The isolation is lower than -15 dB from 3.1 to 5 GHz and < -18 dB from 5 GHz to 11 GHz. Envelope Correlation Coefficient (ECC) < 0.01 and Diversity Gain (DG) > 9.96 dB. The performance of the proposed antenna is analyzed and examined in term of return loss, gain, radiation efficiency, ECC, DG, and isolation between two ports.

Direct Antenna Modulation (DAM) is explored recently in many wireless communication systems. In this paper, we explore the modulation process of electromagnetic signals in the antenna circuit design directly. The proposed antenna consists of two non-concentric elliptical patches for broadband applications to suit the spread spectrum applications. To perform a Differential Phase Shift Keying (DPSK) modulation, two identical antennas are fed by a two-branch microstrip line with a phase shift. Utilizing Computer Simulation Technology of Microwave Studio (CSTMWS) based on Finite Integral Technique (FIT), an optimization based-on numerical analysis is adopted for designing the transmission line configuration at the desired frequency bands. The other significant aspect that has been achieved in this research is reducing the patch size to be suitable for wearable devices. Therefore, a cylindrical substrate is utilized for bending the proposed antenna structure. The proposed antenna design shows a gain of 4.73 dBi and 2.5 dBi for the planar and folded antenna profile respectively. Two high-speed Positive Intrinsic Negative (PIN) diodes as switching elements of the RF signal are inserted between the identical antenna elements through a transmission line. Switch 1 (SW1) and switch 2 (SW2) are used to control the phase shift between the antenna elements by changing the switching state from (OFF-ON) and vice versa. The designed antenna is further investigated to realize the effects of radiation leakage from the antenna elements on the human body in the context of wearable applications. This study is conducted to the antenna performance when it is bent on a cylinder and compared to the flat case on four human body regions: arm, head, thigh, and chest. The proposed antenna based on PIN diodes is fabricated, measured, and tested. Using a 3D axis field strength meter, the proposed antenna system field strength is measured for different conditions at various locations of the human body. Finally, an excellent agreement is found between the obtained numerical results and measurements.

The ideality of operating environment of radar systems is extremely scarce while the demand for these systems is growing at a rapid pace. Technology of adaptation is therefore of primary concern in the design of their future strategies. The difficulty in finding a solution based on a single adaptive algorithm to deal with diverse noise environments has led to the development of composite adaptive procedure. Therefore, fusion of particular decisions of the single adaptive variants through appropriate rules provides a better final detection. This paper is intended to analyze the fusion strategy of cell-averaging (CA), order statistics (OS) and trimmed-mean (TM) schemes in heterogeneous environments. The tested target and the spurious ones are assumed to follow χ²-distribution with two- and four-degrees of freedom in their fluctuations. A closed form processor performance is derived. The results show that for the heterogeneous operation, this approach is more realistic. Particularly in multi-target situations, it exhibits higher robustness than CA, OS, or TM architecture. Additionally, our results reveal that it exhibits a homogeneous performance outperforming that of the Neyman-Pearson (N-P) detector which is the yardstick in the world of adaptive detection.

A method is presented for computing the equivalent resistance and the unknown components of simple series and parallel resistor networks. The approach consists in taking the product of a simple 2×2 matrix (N-1) times, where N is the total number of components in the network. The matrix approach originates from the study of continued fractions. Numerical computations only require an algorithm that handles matrix multiplication.

A circuit module for coupled transmission line channel transmission matrix (CTL-CTM) crosstalk cancellation is designed and simulated by using CMOS technology in a high-speed interconnection system. The module consists of an adder and a subtractor to realize analog addition and subtraction of digital signals. The adder is composed of CMOS transistor pair connected to an inverter at the next stage. The subtractor is composed of a current mirror as the load of CMOS differential pair. The crosstalk cancellation circuit module is simulated and verified by advanced design system (ADS) software. The designed adder and subtractor work well and have no significant difference with the ideal output, and the signal eye diagram recovered by the crosstalk cancellation circuit is of good quality, which solves the circuit implementation problem in the CTL-CTM crosstalk cancellation method.

A novel tunable dual-band bandpass filter (DBPF) with high selectivity and independently tunable passbands is proposed in this paper. Electric and magnetic coupling is employed in this design to create transmission zeros. The proposed tunable DBPF has the advantage of fully independent and controllable passbands due to the multipath propagation mechanism. The measured results of tunable DBPF show that the center frequency of the first passband can be shifted from 2.34 to 2.45 GHz when the bias voltage VL increases from 3 V to 15 V, and the second passband can be tuned from 4.73 to 5.04 GHz when the bias voltage VH varies from 6 V to 15 V. Moreover, the core circuit-size of the tunable DBPF is about 0.293 λ_g x 0.067 λ_g, where λ_g is the guided wavelength at 2.4 GHz. The proposed filter exhibits the merits of fully independent and tunable passbands, high selectivity, and compact size.

A novel dual-band conical-helix/monopole antenna is proposed to operate as an on-body central antenna for Wireless Body Area Network (WBAN). The proposed antenna communicates in three ways: (i) off-body communication through its end-fire radiation with the ceil-mounted WiMax antenna at 5.8 GHz, (ii) on-body communication through its broadside radiation with the on-skin biosensor antennasat 3.0 GHz, and (iii) in-body communication with the in-body (implanted) biosensor antennas at 3.0 GHz. The characteristics of the proposed antenna are investigated through electromagnetic simulation and experimental measurements where a prototype of this antenna is fabricated for this purpose. The antenna is matched with 50 Ω coaxial feeder over the dual frequency bands, mounted on a copper circular disc, and covered with a very thin dielectric radom for mechanical protection. Such an antenna covered by the radom is shaped like a hemispherical button that can be attached to patient clothes and, hence, it can be considered as a wearable antenna. The radiation patterns obtained by experimental measurements show good agreement with those obtained by the CST® simulator and are shown to be appropriate for communication with the ceil-mounted WiMAX antenna and the biosensor antennas at 5.8 GHz and 3.0 GHz, respectively. The distribution of the microwave power density near the body surface is evaluated by simulation and experimental measurements to ensure the realization of the electromagnetic exposure safety limits. The Specific Absorption Rate (SAR) distribution inside the human tissues of concern is evaluated showing a safe level of electromagnetic exposure. Quantitative assessment of the WBAN communication system performance is achieved when the proposed antenna is employed as an on-body central antenna for the WBAN. Thanks to the optimized design of the proposed antenna the Bit-Error-Rate (BER) is shown to be very low even when the input power fed to the antenna is only 1 mW.

A novel analytical method suitable for coupled electromagnetic field of a circuit is proposed in this paper. In a high frequency circuit and high-frequency converter, skin effects are obvious, and the variations in resistance and inductance values depend on frequency. In addition, the voltage and current distribution changes of a high frequency circuit generated with a high-frequency converter during dynamic switching process are complicated and depend on time. A novel analytical method suitable for coupled electromagnetic field of circuit in parameter optimization design of high-frequency circuit and high-frequency converter is proposed in this paper. The proposed method considers the influence of skin effect and coupled electromagnetic field on parameter variation simultaneously. According to the law between parameter variation and line length, the calculation process of parameter optimization will be simpler and more effective.

Mathematical expressions for the components of the magnetic field produced by a conically-shaped current sheet and by a tightly-wound conical coil are presented. The conical current sheet forms the frustum of a cone. In the limit as the top radius of the frustum approaches the bottom radius, a cylindrical current sheet is formed. Mathematical expressions for the magnetic field produced by a cylindrical current sheet are then compared to known and published results.

With the rapid development and in-depth research of non-contact bio-radar-based detection technology, researchers have recently been putting more emphasis on target identification. Living status identification, a hotspot of target identification research, is particularly useful in search and rescue missions. During such missions, in order to rescue victims and provide corresponding medical support in a timely manner, it is necessary to acquire the survival information of victims, especially when they are injured. Hence, the vital signs extracted from a radar signal should be considered as the crucial parameters to reflect the living status. To determine living status through analyzing vital signs, this study utilized a bio-radar system to continuously monitor hemorrhagic animals, which simulated injured persons with hemorrhagic symptoms. Moreover, we defined and classified three survival periods based on changes in vital signs combined with a K-nearest neighbor algorithm (KNN) classifier. Experimental results show that we can approximately determine the current living status of animals with this method, which can aid in providing information for on-site rescue and follow-up medical treatment.

The management of the current pandemic COVID-19 has been challenging and complex. The main and only successes have been achieved with non-pharmacological interventions (NPI). When tracking, monitoring, and early intervention at home have been delivered to citizens, the contagion can be controlled. In the current pandemic, various methods have been applied to track the COVID-19 virus, such as Korea's mobile phone tracking system. We propose a method based on a wearable bracelet prototype able to detect biomedical parameters, which can be very useful to monitor the virus infection when the patient develops symptoms, such as a high temperature or low blood oxygenation. In particular, the prototype bracelet can measure the blood oxygenation using an infrared optical sensor and measure the temperature of the patient. The bracelet can record the identification number of other bracelet devices that came in proximity. The bracelet is equipped with a built-in low power Bluetooth, aimed to send the recorded data to a smartphone or another device in order to connect them with proper geo-localization and to the web. The identification number of the patient device can be used to trace the number of people and whom he has been in contact with, immediately by the sanitary authorities. Moreover, the bracelet can be used for monitoring the patient's health at home, avoiding the hospital's overcrowding. The proposed system not only can effectively localize the trace path of patients positive to the COVID-19 virus or to other respiratory diseases, but also can provide an evolution of the patient symptoms and monitor people in-home quarantine. The system is simple and could be an efficient tool to track any other future pandemics.

The efficiency of the standard tapered windows as applied to sidelobe suppression in compressed pulses with linear frequency modulation (LFM) or chirp pulses corresponds to the literature data only in the case of rather great values of the pulse duration-bandwidth product B≥100. With comparatively small values of B (several dozens or so) the side-lobe levels prove to be essentially greater than those announced in the literature. In the paper, the output signal of the chirp-pulse compression filter is analyzed in order to look into causes of discrepancy between the sidelobe level obtainable using standard tapered windows and the literature data. Expressions are derived for estimating the maximum number of zeros and maxima in the response of the optimum filter of chirp-pulse compression and separation between adjacent and ``like'' (with the same numbers) zeros and maxima in dependence on the signal duration-bandwidth product. The amount of loss in the signal-to-noise ratio due to application of smoothing functions is determined. The case of applying window functions in the form of cosine harmonics of the Fourier series, which describes a rather great number of the standard windows, is analyzed in detail. Analytical expressions are presented for the output signal of the chirp-pulse compression filter on the basis of such windows and the amount of loss in the signal-to-noise ratio. A comparative analysis of the Hamming and Blackman windows is made in dependence on the pulse duration-bandwidth product B. It is shown that application of the Hamming window is more efficient up to B≈80. For greater values of B, the Blackman window shows a higher efficiency. As B increases, the efficiency of both windows steadily increases asymptotically approaching the figure declared in the literature. Coefficients of window functions containing 2 cosine harmonics of the Fourier series have empirically been selected which made it possible to reduce the sidelobe level by approximately 0.34 dB for B=21 and by more than 1 dB for B=7 as compared with the Hamming window. The obtained results allow concluding that the optimization problem for the window function parameters in the case of small values of the pulse duration-bandwidth product should be solved individually for each specific value of B. Most likely it would be impossible to obtain the extremely low sidelobe level; however, a certain improvement of the characteristics of the chirp-pulse compression filter seems quite possible.

Electrically small antennas are of intense and increasing academic and industrial interest due to the advent of ubiquitous RFID devices and more generally within the Internet of Things (IoT) applications. For most of these applications antennas will have to be as small as possible, when being integrated within a transceiver, while maintaining significant efficiency values. Of particular interest are antennas that can radiate omnidirectionally along a planar surface, thus establishing optimal connectivity capabilities for devices surrounding the corresponding transmitter. Such antennas are important not only for energy harvesting but also for near-field wireless charging applications. In this paper, we report an electrically small antenna of size ka ≈ 0.25, where a is its effective radius and k the wave vector at operating frequency. The antenna geometry is a 3-dimensional folded meandering loop and contains its own ground, so that it becomes insensitive to the integration environment. The radiation efficiency of the antenna is 70%, and it radiates as a vertically polarized dipole. The operating frequency chosen in this paper targets RFID/IoT applications at 915 MHz, and the impedance matching bandwidth, as realized, is narrow but appropriate for such applications and may be further increased if appropriate matching networks are used.

A high impedance surface has far-reaching potential in wireless applications, but realization of the surface operating at sub-GHz ranges is challenging due to its size limits in practical applications. Here, we present a novel inductive technique based on multi-turn square spiral loops. The introduction of the spiral loops to a mushroom-shaped high impedance surface provides additional current path, thereby results in a dramatic increase in its total inductance at given dimensions, and therefore leads to a significant reduction in a resonant frequency of a high impedance plane. Electromagnetic simulation results reveal that a resonant frequency shifts downward 1 GHz at a given dimension, and they are in good agreement with results from an analytical model for the proposed structure. Experimental measurements suggest the feasibility of the proposed approach.

The rectangular cavity is investigated and applied in the field of the radar cross section reduction (RCSR) of patch antennas for the first time. An integrated and efficient design technique is presented which uses both a slotted rectangular cavity and reflective phase cancellation by a simple artificial magnetic conductor (AMC) element. On condition that ensuring the radiation performance of the patch antenna does not deteriorate, the in-band radar cross section (RCS) of the antenna can be reduced by 12.2 dB at 7.6 GHz just relying on a type of phase-regulated AMC elements. On this basis, the rectangular cavity walls were first loaded surrounding the above-mentioned low-RCS patch antenna. The relative bandwidth (in which RCS was reduced by more than 8 dB) went from 3.33% to 50% in the RCSR ohttps://www.baidu.com/?tn=62095104_43_oem_dgf the antenna. Meanwhile, the RCS could be reduced by an additional 5 dB at its working frequency (7.6 GHz).

Average bit error rate (BER) performance of on-off keying (OOK) modulation in a free space optical (FSO) system, which is based on adaptive threshold technique under atmospheric turbulence described by exponentiated Weibull (EW) distribution, is studied and compared with that of using fixed threshold technique. In order to solve the adaptive threshold, the equation is simplified by using the generalized Gauss-Laguerre polynomial function, which significantly improves the operational efficiency. The simulation results show that the adaptive threshold varies with the average transmitted power under different noise variances, receiving aperture sizes and turbulence conditions. Compared with the fixed threshold technique, the adaptive threshold technique can greatly improve the BER performance of FSO communication system.