This work presents the design and implementation of a four-section reconfigurable uniform impedance resonator (UIR) active filter. UIR active filter consists of λ_g/4 microstrip line resonators cascaded in series with parallel coupled lines (PCLs). An additional quarter wavelength section is added to the coupled line quarter wave resonator section and gives flexibility in the coupling length. The proposed active filter provides a gain as a means of compensation to loss incurred by passive circuitry. In addition, it gives high selectivity (-70 dB) and wide stopband. The wide stopband is the result of suppression of spurious frequencies which is accomplished by using shunt stub resonators at appropriate locations in the active filter. The bandwidth reconfigurability is achieved by varying the bias currents of the active devices as well as by tuning the varactor diodes. The UIR concept with active matching is implemented on an FR4 substrate (ε_r = 4.4), with passband gain of around 15 dB at 1.3 GHz, and out of band rejection is better than -35 dB at twice the centre frequency of 1.3 GHz.

In this paper, we study a double intelligent reflect surface (IRS) aided secrecy transmission design in multiple-input single-output (MISO) channel. Specifically, we investigate a joint active and passive beamforming design to maximize the secrecy rate, subject to multiple non-convex constraints. An alternating optimization (AO) method is proposed, where the unit modulus constraints are handled by the alternating direction of multipliers method (ADMM) and majorization-minimization (MM) methods. Simulation results show the superiority of the proposed design.

Measurements of the complex permittivity and permeability of solids at high electromagnetic field greater than 10 kV/m pose a significant challenge to RF connectors and input amplifiers of the measurement equipment. Specifically, difficulties arise in measuring materials with high imaginary permittivity or low impedance, which act as short circuits, either exceeding the measurement equipment damage threshold or that of the material under test, and/or inducing an unacceptable signal-to-noise in the collected data. In this work, we report the development of a new measurement technique where we introduce an outer air-gap between the material under test and the conductor of a coax airline. The introduced air-gap reduces the effective conductivity of the sample, mitigating damage to the materials under test and allowing for high power measurement. This study compares the ability of air-gap correction methods to recover the complex permittivity and permeability to within 10% of the value measured without an air-gap introduced.

A single-layer via-less rectangular patch antenna for automotive applications in C-band is proposed. To match the needs of a vehicular dedicated short range communication protocol, the resonant edge of the antenna is enlarged to narrow the beam-width in the H-plane, while at the same time a pair of thin slots serve as inhibitors for the higher modes, permitting adequate matching and polarization purity. The proposed single patch antenna presents a realized gain about 6.85 dB, H-plane beam-width narrower than ±32˚, E-plane beam-width larger than ±45.5˚, and return loss exceeding 20 dB with a 3 dB bandwidth of 500 MHz, with a minimum at 5810 MHz, hence suitable for coexistence of different communication standard in the C-band. Furthermore, its compact dimension permits the direct integration within a radio front-end.

This study presents a differentially driven log-periodic dipole array system with high isolation between reception and transmission ports for wideband full-duplex applications. The antenna system is composed of two pairs of log-periodic dipole arrays operating in the X-band spectrum from 8 GHz to 12 GHz. The system offers a low cross-polarization between E-plane and H-plane (less than -25 dB). The simulation results show high isolation S₂₁ < -60 dB through the entire X-band while the measured results reach S₂₁ < -45 dB in a reflective lab room. Furthermore, in order to verify the measured values, a modified 180º out-of-phase wideband power divider is used to feed transmitting and receiving ports. The second measured outcomes also attain total isolation greater than 45 dB for the entire band of interest. The proposed design is able to cover both orthogonal transmitted and received directions with reasonable gain values, high efficiency, and good impedance matching.

As computing power and algorithmic advances have evolved rapidly in the recent past, it is now feasible to solve complex electromagnetic (EM) problems involving scattering, radar cross section, antenna design, microwave circuit design, artificial EM materials etc., using full-wave numerical methods. Several general-purpose commercial software packages are routinely used in industry in all these domains for EM analysis or design. However, the task of processing large sets of data output from these design studies and analyses is generally beyond the realm of commercial software packages, and the designer spends many hours writing problem-specific computer programs to extract the desired performance parameters. Some examples where auxiliary processing is needed for the extraction of EM parameters of interest include determination of coupling coefficients or the unloaded quality factor of a dielectric resonator, de-embedding feed lines from antenna currents, removal of discontinuity effects, and the extraction of equivalent circuit models. The same considerations as simulated data apply to the parametric analysis of measured data in the presence of noise. This paper presents a versatile data-driven spectral model derived from a state-space system representation of the computed or measured EM fields, from which all the parameters of interest can be extracted. An attractive feature of the state space method is its ability to identify a small number of the system transfer function poles uniquely associated with a specific scattering mechanism or modal response, thereby enabling its isolation from the total response for detailed study. For example, using SSM, specular reflection and creeping waves on a smooth convex surface can be analyzed and the diffraction at the edges can be isolated from the composite RCS of a large body. The desired field parameter is extracted or estimated from synthetic or measured data using a linear system of a relatively small model order that characterizes the specific modal response of interest. Illustrative examples will be presented to demonstrate the usefulness of the proposed approach for parametric extraction.

This paper presents a high gain dielectric resonance antenna (DRA) array for vehicular wireless communication and 5G system in millimeter wave band, which takes the advantage of low side lobe level (SLL). The planar antenna array is composed of 8×8 rectangular DRA elements, whose operation mode is the fundamental mode TE₁₁₁. The beamforming weights of the array are designed based on the principle of Dolph-Chebyshev distribution to suppress the antenna SLL. The planar array consists of 8 linear sub-arrays, which are fed with standing-wave series resonance method respectively. The excitations of sub-array elements are precisely adjusted based on the aperture coupling model. Furthermore, the series-parallel hybrid feed network and parallel-cascaded feed network are applied to unequally feed the sub-arrays in accordance with Chebyshev polynomials. The measurement results of prototype validate the design solution of antenna array. The impedance bandwidth is 570 MHz (25.77 GHz-26.34 GHz) for reflection coefficients less than -10 dB, and the antenna gain and SLL are 20.5±1 dBi and 20 dB, respectively. Due to the advantages of miniaturization and narrow beam, the proposed DRA antenna array is adequate for vehicle communication equipment.

Novel substrate integrated waveguide bandpass filters are presented by using a complementary split-ring resonator. The proposed stepped impedance octagonal octagonal complementary split-ring resonator (SI-OCSRR) presents high miniaturization compared to the classical octagonal complementary split-ring resonator (O-CSRR). Additionally, two different filter configurations consisting of two cascaded cells with different coupling between the CSRR are proposed. A comparison between the proposed filters and the other ones reported in the literature has proven the advantages of the proposed filters, namely compact size, high in-band return loss, and ease of integration. A good agreement between the simulated and measured results has been reached, which verifies the validity of the design methodology.

This paper presents the design and fabrication of HE₁₁ miter bend along with a TM₁₁ to HE₁₁ mode converter and corrugated up-taper, which are the integral parts of a transmission line system (TLS) that carries 200 kW microwave power at 42 GHz from Gyrotron to plasma or calorimetric dummy load. It has a hybrid (HE₁₁) mode. The HE₁₁ mode transmission loss in miter bend is derived using mode-matching techniques and gap loss theory. The gap length (L) in a waveguide of diameter (D = 2a) at a wavelength (λ) for the predicted loss (D ≥ λ) is approximately 1.7[Lλ/2a²]^3/2 dB. The HE₁₁ miter bend design incorporates a demountable cooling assembly with a flat mirror. The design and optimization of the proposed miter bend were carried out using CST-microwave studio software. Finally, HE₁₁ miter bend was fabricated along with integrated assembly. The proposed HE₁₁ miter bend with mode converter and corrugated up-taper gives the transmission efficiency of 95.64%.

Nonlinear effect on optical properties of one-dimensional photonic crystal (1D-PC) of the type (HL)ⁿ (LH)^m (LLHH)^k was investigated. It is an asymmetric hybrid Fabry-Perot resonator type of 1D-PC structure which is composed of linear (H layers) and nonlinear (L layers) materials. The linear and nonlinear transmission spectra are graphically illustrated using a numerical approach based on the Transfer Matrix Method (TMM). Results show the appearance of a Perfect Transmission Peak (PTP) in the photonic band gap which makes the structure constitute a monochromatic filter. By analyzing this PTP it is shown that the Full-Width at Half-Maximum (FWHM) depends not only on the number of symmetry layers of the studied 1D-PC but also on the refractive index of the nonlinear layers. The change of the refractive index (Kerr effect) causes a dynamically shift in the band gap including the resonance peak. As a result, such a structure has the potential to be used for designing optical filters and nonlinear optical devices.

Scheimpflug LIDAR has attracted considerable attention in the recent years, and has been widely applied in many fields due to its infinite depth of field. In this study, we reconstruct a series of formulas to demonstrate the Scheimpflug principles, with reference at the hinge point. These formulas based on directly measurable parameters are simple in form. Base on this, we report a new calibration for the Scheimpflug system, without measuring the instrument parameters. We also confirm that the result of calibration is accordance with the actual setting of the system. To take full advantage of the infinite depth of field of the Scheimpflug system, we have designed and carried out the system, combining with a rotary stage, to obtain the entire volumetric profile for a target of interest in a cycle rotation. To the best of our knowledge, this is the first time Scheimpflug system is utilized to perform a three-dimensional volumetric profile measurement.

This paper presents a high gain Fabry-Perot antenna with radar cross section (RCS) reduction property. A receiver-transmitter metasurface is designed and used as the partially reflective surface (PRS) of the antenna to realize high gain and wideband RCS reduction. Firstly, the working principle of the unit cell is similar to the reception and radiation of two patch antennas. The unit cell is designed to present high reflectivity through tuning the impedance matching between two patches. This can ensure that the antenna obtains high gain. Then, the ground plane in the middle makes the reflection phase from different sides of the unit cell be tuned independently. Two unit cells with same reflection phase from the bottom side and 180° reflection phase difference from the top side are obtained through tuning the size of the transmitter patch. With the improved chessboard arrangement of these two unit cells, the incident wave can be scattered into many directions. So the metasurface presents a good RCS reduction property. More importantly, thanks to the high reflectivity of the metasurface, almost all the electromagnetic waves from the outside are reflected and rarely enter the cavity. Therefore, the antenna achieves good in band RCS reduction. The measured results of the fabricated antenna agree well with the simulated ones, which verify the correctness of the design. The antennas reaches the maximum gain of 18.2 dBi at 10 GHz. Wideband RCS reduction and good in band RCS reduction are also obtained by the antenna.

Electromagnetic-circuital-thermal multiphysics simulation is a very important topic in the field of integrated circuit (IC), microwave circuits, antennas, etc. This paper gives a comprehensive review of the state of the art of electromagnetic-circuital-thermal multiphysics simulation method. Most efforts were focused on electromagnetic-circuital co-simulation and electromagnetic-thermal co-simulation. A brief introduction of related theory like governing equations, numerical methods, and coupling mechanisms is also included.

A variety of psychological scales are utilized at present as the most important basis for clinical diagnosis of mood disorders. An experienced psychiatrist assesses and diagnoses mood disorders based on clinical symptoms and relevant assessment scores. This symptom based clinical criterion is limited by the psychiatrist's experience. In practice, it is difficult to distinguish the patients with bipolar disorder with depression episode (bipolar depression, BD) from those with major depressive disorder (MDD). The functional near-infrared spectroscopy (fNIRS) technology is commonly used to perceive the emotions of a human. It measures the hemodynamic parameters of the brain, which correlate with cerebral activation. Here, we propose a machine learning classification method based on deep neural network for the brain activations of mood disorders. Large time scale connectivity is determined using an attention long short term memory neural network and short-time feature information are considered using the InceptionTime neural network in this method. Our combined method is referred to as AttentionLSTM-InceptionTime (ALSTMIT). We collected fNIRS data of 36 MDD patients and 48 BD patients who were in the depressed state. All the patients were monitored by fNIRS during conducting the verbal fluency task (VFT). We trained the model with the ALSTMIT network. The algorithm can distinguish the two types of patients effectively: the average accuracy of classification on the test set can reach 96.2% stably. The classification can provide an objective diagnosis tool for clinicians, and this algorithm may be critical for the early detection and precise treatment for the patients with mood disorders.

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.