Characterizing the random errors at the elements of a phased array antenna leads to equations that estimate the associated performance degradation. The increase in sidelobe level and decrease in gain due to random errors is well established. This paper derives an expression that predicts the axial ratio degradation due to random errors in the circularly polarized elements of an array. In the case of small errors in an array of crossed dipoles, we found a simple expression for the axial ratio of the array under random errors at broadside.

The paper discusses the application of laser illumination and brightness amplification techniques for studying the process of high-temperature combustion of aluminum and iron nanopowders and their mixtures. The laser equipment for visualization based on solid-state laser illuminator, brightness amplifier on copper bromide vapors and high-speed camera is considered. These approaches allow the increase of monitoring distance to 50 cm, which is important for high-temperature processes imaging. The video images allow studying the surface morphology changes during high-temperature combustion identifying the main stages of the combustion, spreading of the heat wave and cooling.

In this paper, a novel wearable inkjet printed dual-band antenna is presented, which works at 2.45 GHz and 5.8 GHz for wireless body area network applications. The proposed antenna geometry is composed of two printed monopole elements, which are constructed from an analytical profile of an exponentially-decaying sinusoidal curve. The analytically parameterized curve allows for constructing on demand irregular and unique shaped miniaturized radiators. The antenna system is printed on a transparent flexible polyethylene terephthalate (PET) film. The wearable dual-band printed antenna with an overall size 45 x 40 x 0.135 mm³ is compact, light weight, and low profile, making it a suitable candidate for wireless body area network applications, when limited volume space for the worn unit is a requirement. Good agreement between numerical and measured data is achieved. Moreover, the overall far-field radiation performance of the wearable dual-band antenna is satisfactory, with measured peak gains of 1.81 dBi and 3.92 dBi, and a total computed efficiencies of 81% and 82% at 2.45 GHz and 5.8 GHz, respectively. The effect of bending the wearable antenna structure is also investigated, and only slight performance variations are observed.

Advancements in functionalities and operating frequencies of integrated circuits lead to the necessity to study Electromagnetic Compatibility/Electromagnetic Emissions (EMC/EMEs) from these devices. In this work, a methodology is developed, which combines near field electromagnetic measurements and 3D layout simulation of an Integrated Circuit (IC), to identify the sources of EME from a commercial IC. This methodology can help to narrow down the area of key importance with respect to EME sources, instead of the entire IC, before it is fabricated. Consequently, IC designers can optimize their design to minimize the EME before fabrication, saving cost and time significantly.

A very-low-profile, decoupled, hybrid two-antenna system top-loaded with a coupled strip resonator for isolation enhancement is demonstrated. Each hybrid antenna consists of one 2.4 GHz open slot and one 5 GHz monopole, formed on the two sides of the substrate. The two-antenna design is able to operate in the 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) wireless local area network (WLAN) bands and yet merely occupies a size of 5 mm × 40 mm (about 0.04λ × 0.32λ at 2.4 GHz). The loaded strip resonator is employed to reduce the mutual coupling in the 2.4 GHz band. With further capacitively grounding the decoupling strip using a grounded T strip, good isolation > 18 dB over the 5 GHz bands can also be achieved. Owing to its low profile of 5 mm, the proposed design can find some practical applications in the narrow-bezel notebook computers and is of the smallest footprint among those two 2.4/5 GHz antennas for notebook applications.

In this paper, a simple and effective side-lobe suppression technique is proposed by using integrated high refractive index matematerial (HRIM). It is known that current reversal, which occurs at the third harmonic of the dipole natural frequency, disturbs the omnidirectional radiation pattern of a dipole antenna, and the main beam splits into two side lobes. For suppressing the two side lobes and maintaining consistent radiation pattern purposes, two regions of HRIMs are integrated along the side-lobe radiation direction of a reflector-backed dipole antenna to tilt the two side lobes toward the broadside radiation direction. The HRIM is constructed with 2X3 H-shaped unit-cells periodically printed on the single side of dielectric substrates. The beam-tilting approach described here uses the phenomenon that the EM wave undergoes a phase shift when entering a medium of different refractive indices. Simulation and measurement results show that by implementing the HRIMs, the two side lobes are tilted toward the broadside radiation direction, and as a result, the side lobe is suppressed, and radiation consistency for the first and third harmonic resonances is realized. Moreover, the antenna gain for the third harmonic is achieved as high as 7.8 dBi, which is an increase of approximately 3 dBi compared with the fundamental resonance.

This paper proposes a coplanar waveguide-fed slot antenna with vertical rounded bow-tie slots for wideband harmonic suppression. Higher-order harmonics up to nine times the fundamental resonant frequency (9f_o) of the slot antenna was successfully suppressed by adding the slots in the middle of the two slot arms. A prototype of the antenna that resonates at 1 GHz was fabricated. The measured input reflection coefficient of the antenna remains over -3 dB at up to 9.15 GHz, which demonstrates the wideband harmonic suppression capabilities.

This paper presents a piezoelectric transducer-tuned fourth-order bandpass filter (BPF). The proposed filter consists of four open-loop resonators which form cascaded quadruplet (CQ) sections with a capacitive cross coupling. There are two transmission zeros (TZs) in the lower and upper stopband to further improve the selectivity of the filter. The structure parameters are optimized by using High Frequency Structure Simulator (HFSS). The piezoelectric transducer (PET) together with a dielectric substrate is used as a tuning element. The effects of the PET on the coupling coefficient and external quality factor are analyzed. The designed tunable filter has been manufactured and measured. The measured results show that the center frequency of the filter changes from 2.48 GHz to 2.28 GHz; the insertion loss basically keeps constant; 3 dB bandwidth of the filter changes from 156 MHz to 168 MHz over the tuning range; and the positions of the TZs in the stopband move synchronously as the center frequency varies.

To improve computational efficiency of traditional method for solving separable multi-objects scattering problems, each subdomain impedance matrix is sparsified by biorthogonal lifting wavelet transform (BLWT) without allocating auxiliary memory, and a sparse underdetermined equation is constructed by enjoying the prior knowledge from known excitation in wavelet domain, then orthogonal matching pursuit (OMP) is employed to fast and accurately solve the sparse underdetermined equation under compressive sensing (CS) framework. Numerical results of separable perfectly electric conduct (PEC) multi-objects are presented to show the efficiency of the proposed method.

Transmission/reflection method is widely used in microwave engineering for determining dielectric properties of materials, and significant uncertainty will arise in the results if the thickness of the samples is small. In this paper, we propose animproved algorithm for deducing complex permittivity of thin dielectric samples with the transmission/reflection method. With the proposed algorithm, the real and imaginary parts of the complex permittivity will be treated separately, and two independent weighting factors, β_re and β_im, will be used to minimize the uncertainty in both parts ofthe complex permittivity. Numerical calculations as well as experimental measurements on undoped and boron-doped diamond films were conducted within the frequency range of 18.5-26.5 GHz to demonstrate the effectiveness of the algorithm. It is verified that among the various iterative algorithms which could be used to derive complex permittivity, the proposed algorithm is the most advantageous inreducing uncertaintieswhen thin dielectric samples are dealt with.

This paper evaluates the performance of different configurations of MIMO antenna operating in the 5G band with the effect of user's hand in data mode and suggests an optimized configuration to mitigate hand effects. A dual-band four-element MIMO antenna is used. All antenna elements (AEs) are identical planar inverted-F antenna (PIFAs) with a lower frequency band (LB) from 3.3 to 3.8 GHz and an upper frequency band (UB) from 5.2 to 6 GHz. In addition, four different configurations to place the AEs on the chassis are selected including worst and optimized configurations as well two intermediate cases. Results show that similar values of ECC are produced for both cases without and with user hand. These values are less than 0.20 on most frequency range, except the worst case configuration which has some high ECC values close to unity. Unlike ECC, TE is severely affected by user's hand as well as by the different configuration. TE of each AE under hand effect is degraded differently according to the thickness of hand tissue that covers it. TE in the optimized configuration without user's hand ranges between 50 and 95% in both frequency bands. However, this range deteriorates when user's hand effect is considered, between 40% and 15% in LB, and from 35% to 41% in the UB. Multiplexing efficiency analysis reveals that MIMO performance is mainly determined by TE, and the impact of the low ECC is insignificant. This indicates that improving the performance depends on improving the TE of AEs and optimizing their positions on the chassis to reduce interaction with user's hand. Moreover, the loss in ergodic capacity due to user's hand compared with free space is increased from 5 to 40% in the LB, and it is more stable in the UB and ranging between 12 and 17%.

Optimization design is a satisfactory way to improve the performance of magnetic bearing (MB). In this paper, a multi-objective genetic particle algorithm of swarm optimization (GAPSO) is proposed for homopolar permanent magnet biased magnetic bearings (HPRMBs). By assigning different inertia weights to each objective function, the multi-objective function is transformed into a new single objective function for optimization. In order to ensure the diversity of particles in the optimization process, genetic algorithm is used to cross-mutate them, which enhances the global search ability of particle swarm optimization. After optimization with GAPSO, the levitating force of the MB is increased by 22.3%, the volume decreased by 26.6%, and the loss reduced by 33.9%. The optimization results show that the multi-objective optimization based on GAPSO can effectively improve the performance of HPRMB.

In this paper, a novel compact dual band-rejected ultra-wideband (UWB) multiple-input multiple-output (MIMO) Vivaldi antenna is introduced and fabricated. The MIMO antenna with a small size of 26 × 28 mm² contains a modified ground plane and two microstrip-slot balun structures. A T-slot is etched on the ground to achieve miniaturization and high isolation, and the simulated |S₁₁| of -10 dB impedance bandwidth is from 2.7 to 10.9 GHz. An isolation of better than 15 dB is acquired over the UWB range (3.1-10.6 GHz). Meanwhile, by introducing two split ring resonator (SRR) slits on the ground and adding two split ring resonators (SRRs) close to the microstrip-slot balun structures, dual band rejection at both WLAN (5.15-5.85 GHz) and IEEE INSAT/Super-Extended C-band (6.7-7.1 GHz) can be achieved. The MIMO antenna has high gain and very low envelop correlation coefficient (ECC < 0.02). The measured results agree with the simulated ones, demonstrating that the UWB MIMO Vivaldi antenna is suitable for the UWB diversity applications.

This paper proposes low profile, high gain and wideband circularly polarized (CP) microstrip antennas (MSA), using gap coupled parasitic patches (PPs) on superstrate layer. Printed and suspended probe fed, CP MSAs are designed on a 1.59 mm thick FR4 substrate, and an array of closely spaced hexagonal PPs are printed on the bottom side of the 1.59 mm thick FR4 superstrate and placed at a height about λ₀/8, above the ground plane, where λ₀ is the free space wavelength, corresponding to the central frequency of the operating frequency band. The gap coupled hexagonal PPs are not only used to enhance the axial ratio bandwidth (AR BW) and gain of the antenna, but also used to reduce impedance and gain variation of the antenna over the operating frequency band. `Ant9' is a suspended MSA with 7 hexagonal PPs. A prototype `Ant9' is fabricated and tested, which provides a peak gain of 9 dBi, S₁₁ < -10 dB, gain variation < 1 dB, and AR < 3 dB over 4.9 to 6.45 GHz frequency band. ARBW of 27.3% is achieved. The proposed `Ant9' covers three frequency bands viz., 5.15 to 5.35 GHz, WLAN band, 5.725 to 5.875 GHz, ISM band, and 5.9 to 6.4 GHz, Satellite C band. The space fed antenna configuration reduces the cross polar radiation level (CPL) and increases the efficiency of the antenna. A prototype antenna is fabricated and tested. The measured results agree with the simulation ones. The overall size of `Ant9' is 0.96λ₀×0.96λ₀×0.136λ₀.

A dual mode shared aperture antenna consisting of two planer arrays of ring antennas is designed for L and S bands. The array of larger dimension surrounds the array of smaller dimension. The antennas are isolated from one another and fed separately. The antenna dimensions are optimized and prototyped. The antennas radiate separately in L and S bands with least coupling or no coupling. Measured results are in agreement with the simulations, depicting good performance in terms of impedance bandwidth, isolation, and gain.

The electrical network model and differo-integral method (D-IM) were applied to electrical parameters estimation of nonhomogeneous composite materials. The laminar composite is arranged of conductive unit cells with adjustable geometry. Modification of unit cell's internal geometry results in change of composite's effective properties. Stationary electric and magnetic fields of exemplary structures were numerically analyzed. Theoretical computations along with network model were verified by experimental measurements of 10 fabricated samples. Obtained results indicate that D-IM is a valuable tool for qualitative and quantitative estimation of electrical parameters.

A simple and efficient explicit solution is derived for the mutual inductance of two non-coaxial coplanar circular loops, which is valid in the quasi-static as well as non-quasi-static frequency ranges. The solution is obtained by rigorously evaluating the Sommerfeld Integral describing the inductance, starting from expanding the integrand into a power series of the loop radius. As a result, a sum of simpler integrals is obtained, and term-by-term analytical integration is straightforwardly performed. The inductance is finally expressed as a series of spherical Hankel functions, with algebraic coefficients depending on the electrical size of the loops. Conducted numerical tests lead to conclude that, accuracy being equal, the proposed expression offers advantages in terms of time cost over conventional numerical integration techniques.

This paper presents an application of integral type optimal control scheme for rotor positioning of a hybrid magnetic bearing (HMB) in one degree of freedom (1-DOF) using low bias current. It is observed that higher biasing current enhances the linearity and disturbance rejection capability but at a cost of higher copper loss in the actuator. So, selection of biasing in an HMB system is very crucial. In the proposed scheme the dc biasing current can be varied by adjusting the axial offset to the rotor magnet. Analysis has been conducted to achieve the optimal biasing current for better performance of the HMB. A prototype of the HMB system has been fabricated and tested which represents quite satisfactory axial vibration characteristics under low biasing current.

We consider the Global Navigation Satellite System Reflectometry (GNSS-R) for land applications. A distinct feature of land is that the topography has multiple elevations. The rms of elevations is in meters causing random phases between different elevations, which affect the coherent wave that has definite phase and the Fresnel zone effects as shown previously by a Kirchhoff numerical simulator (KA simulator). In this paper, we develop a physical patch model that is computationally efficient. The entire area within the footprint is divided intopatches. Each patch is small enough to satisfy the plane wave incidence and is large enough to ignore mutual wave interactions between patches. The bistatic scattering cross section of each patch for the coherent and incoherent field is computed. The bistatic cross section of plane wave incidence is obtained from lookup tables (LUTs) of the numerical 3D solution of Maxwell equations (NMM3D). The SWC represents the summation of weighted coherent fields over patches. The SWICI represents the summation of weighted incoherent intensities over patches. The formula of the received power is the sum of powers from the SWC and SWICI (the SWC/SWICI formula). The weighting factor of each patch is based on thegeometry, spherical waves, and the considerations of field amplitudes and phase variations. We also present an alternative formula, the ``correlation'' formula, using the summation of power from each physicalarea and correlations of SWCs from areas. The SWC/SWICI formula and the ``correlation'' formula are shown analytically to be the same. Results are compared with the KA simulator and two common models (the coherent model and the incoherent model). Results of the patch modelare consistent with the KA simulator. For the simulation cases, the results fall between the coherent model and the incoherent model. The patch model is much more computationally efficient than the KA simulator and the results are more accurate. In examples of this paper, the patch model results are independent of patch size as long as the patch size smaller than 50 m and much larger than the wavelength of GNSS-R frequency.

In this work, a novel planar four-port microstrip triplexer is designed and analyzed to operate at 1.9 GHz, 2.5 GHz, and 3.35 GHz for wireless communication applications. The proposed structure consists of a compact patch and spiral cells. The main advantage of this triplexer is its very compact size, with a cross size of only 15 mm×15 mm (0.017λ_g²). Sharp frequency response at the edges of all passbands, low insertion losses (0.25 dB, 0.4 dB and 0.11 dB), and high return losses (45 dB, 54 dB and 40 dB) in all channels are the other advantages of the designed triplexer. Additionally, the triplexer has reasonable isolations (S₂₃, S₂₄, S₃₄), better than 20 dB. To verify the design method, both EM simulation and measurement results are obtained. The comparison shows that the measured and simulated results are in good agreement, which proves the feasibility of this work.