A compact, gain-enhanced, linearly tapered slot antenna (LTSA) with hook-shaped slots in the ground plane and a combined director, consisting of a metallic strip director and double-sided metamaterial (DS-MTM) loading surrounding it, is proposed for ultra wide band (UWB) applications. Hook-shaped slots are appended in the ground plane for miniaturization, whereas a combination of the metallic strip and DS-MTM loading placed above the LTSA is used for gain enhancement. Performance of the proposed combined director is compared with other commonly used director configurations in the literature, such as single strip director, two strip directors, and two-layers of DS-MTM. It was found that gain enhancement effect of the proposed combined director is the greatest over the UWB band, compared to other director configurations. The fabricated prototype of the proposed antenna operates from 2.83 GHz to 11.31 GHz (119.9%) for a voltage standing wave ratio less than 2 with moderate gain of 3.2-7.5 dBi. The dimensions of the proposed LTSA in terms of the free space wavelength at the lowest frequency (λ0) are 0.28λ0 × 0.30λ0 × 0.0075λ0 (30 mm × 32 mm × 0.8 mm), which are very compact.
In this paper, the possibility of synthesizing a linear antenna array for multiple objectives with the thinning approach is demonstrated. The thinning space is constrained to three cases (side, central, and random) parts instead of a fully filled linear array. In the case of the side part, a set of elements located on both edges of the array are removed with the optimized elements close to the center remaining unchanged. As in the case of the central part, only a set of elements close to the center are removed. In the case of a random selection of elements, the cancellation process is carried out randomly within the sides and the center. Since the amplitude weights of the elements located on the edges of the array have a small amplitude excitation, the method of side thinning gives better results than the other two cases. Moreover, in cases of side and random thinning, the last element of each side is excluded from the thinning process to maintain the aperture size. The convex algorithm (CA) is used to perform such thinning optimization. CA optimization efficiently computes a multi-objective function in coordination with the thinned array technique, such as preserving the main beam width in all cases with the reduction of the sidelobe levels, generating one or more nulls, and steering the main beam in a certain direction. The simulation results, in all cases, show that 30%-40% of the array elements can be turned off with achieving a multi-objective radiation pattern.
A multiband fractal monopole antenna has been developed for wireless applications. A triangular monopole antenna is considered for this design to achieve the requirement of WLAN and WiMax. Annular rings are etched out from the basic antenna using the fractal concept. To increase its electrical length, notches are introduced at the edges. The volume of an antenna is 54×57×1.6 mm3. Various changes in the ground plane have been done to get the optimum result. The frequency bands at which the antenna resonates are 3.5 GHz, 5.35 GHz, and 6.1 GHz. These bands are best suitable for the WiMax (3.5 GHz) and wireless local area network (5.35 and 6.1 GHz) applications. The simulated and the experimental results show a good match.
The paper presents a new compact directional antipodal Vivaldi antenna that can be employed in modern imaging applications. To obtain wide-band impedance bandwidth in the proposed antenna, a stair case slot is introduced in both the tapered region along with a triangular ground plane. In addition, by means of introducing a parasitic patch close to the centre of radiators, a more directional radiation characteristic is attained within the operational bandwidth. Based on the simulation results, the antenna designed on FR4 substrate provides a wide impedance bandwidth (S11 < -10 dB) of 6.2 GHz i.e., between (3.8-10 GHz) with a gain between 3.5 to 7.5 dB suitable for variety of imaging applications. The designed single feed antenna is compact, low profile and trimmed to provide a triangular geometry with light weight. To validate the directional radiation performance of the antenna, it is fabricated and integrated with a signal generator and spectrum analyzer to obtain the image of a uniform target object i.e., cylinder using the standard back projection Radon transform algorithm. The proposed setup along with the algorithm are promising for the civil and medical applications on applying to other shapes of objects.
To reduce the loss of a drive motor and improve the output efficiency of the drive motor, this paper explores the influencing factors of core loss of an embedded combined magnetic pole drive motor (ECMPDM) for new energy vehicles. The mathematical model of the core loss of the drive motor is established. The monitoring points are selected in different areas of the stator to analyze the distribution of magnetic density, and the correctness of the model is preliminarily verified. Taking the motor core loss as the primary objective of optimization, the multi-objective optimization of the stator slot structure size is carried out by the response surface analysis method. The average value of the stator core loss and the radial magnetic density amplitude of the B point is taken as the two optimization objectives, and the optimal solution of the model is selected by the Pareto frontier distribution diagram. The optimal stator structure is analyzed, and the core loss value is calculated by three methods and compared with the simulation value. The prototype experiments of the optimized motor are carried out, and the no-load core loss experiment, the rated voltage characteristic experiment, and the peak power characteristic experiment are carried out, which verify the rationality of the optimized size and structure of the embedded combined magnetic pole drive motor for new energy vehicles and provide a possibility for the analysis of the temperature field of the embedded combined magnetic pole drive motor for new energy vehicles.
A copper strip and conductive paint-based low profile stripped helical antenna for circular polarization over wide axial-ratio (AR) bandwidth are presented. Impacts of strip widths and geometric parameters of the helix on antenna performance (impedance bandwidth, reflection coefficient, AR, gain) are analyzed thoroughly. In terms of performance parameters, the proposed design is also compared with traditional designs of wire and strip-based helical antennas. Proper impedance matching in the proposed design is achieved by the non-conformal placement of the strip. For easing the fabrication complexity, the antenna is again simulated with a dielectric-based supportive structure, and the impact of this additional support is discussed. The antenna is then constructed on a 3D printed polylactic acid (PLA) based structure. Finally, the 1.3-turn strip-based helical antenna with a radius of 18 mm provided impedance and 3-dB AR bandwidths of 99% and 82.52%, respectively. The maximum gain of 9.40 dBi was found at 2.05 GHz in 3-dB AR bandwidth. The height of the presented antenna is 0.35 λ0, where λ0 is the free space wavelength at the frequency of 2.65 GHz. Low profile and wide AR bandwidth facilitate the use of this antenna in space communication.
Embroidery has been recently introduced as a new method to realize sensors especially for wearables. In this paper, we present a slot-loaded embroidered patch antenna to provide a simplified setup which allows the antenna to act as a stand-alone resonator. The design procedure, simulation and implementation of an embroidered sensor are presented and discussed. It is demonstrated that this structure can be used without any need for external antennas as a wireless sensor. To demonstrate the feasibility of this technique, the design process using a slot-loaded antenna to achieve a high Q antenna, fabricated on an FR4 substrate, is presented and discussed. This structure is then manufactured, with practical results shown to agree with simulated results. Using this as a basis for subsequent designs, an embroidered slot-loaded patch is presented and discussed. We demonstrate this capability in an experiment where a set of solvents inside plastic bottles were interrogated using the embroidered antennas.
This article was removed from the website on February 8, 2023, because it has been found to violate plagiarism rule of our journal.
The C-band RDRA with a defective ground structure operated at resonant frequency 6.2 GHz is best suitable for satellite uplink applications. In the C-band, the broad aperture slot and pentagonal-shaped defective ground structure (DGS) offer excellent isolation and great efficiency. The simple prototype of designed pentagonal DGS RDRA is fabricated, tested, and validated. The proposed C-band RDRA has a fractional bandwidth of 12.14%, a return loss of -30 dB, a gain of up to 7.95 dB, and a minimal VSWR at the resonance frequency of 6.2 GHz. It offers a broad beamwidth of 110.87˚ in the E-plane, 43.73˚ in the H-plane, and 91.5% efficiency.
Microwave imaging of small scatterers is an inverse scattering problem, and recently, the MUSIC algorithm has been proposed to solve this type of problem. The MUSIC algorithm, by assuming that the number of targets is a priori known, can locate the scatterers from the peaks of the well-known pseudospectrum. The noise and multiple scattering create ambiguity to detect the number of targets. Usually, information-based algorithms such as Akaike information criterion (AIC) and minimum description length (MDL) are employed for source number estimation. However, in the cases of low signal-to-noise ratio (SNR) and close targets, the performance of these methods is seriously degraded. In the present work, we propose a two-step approach to enumerate the scatterers in microwave imaging applications for cases where traditional methods fail. Firstly, the MUSIC algorithm is applied to locate all possible targets by assuming the maximum number of targets, and secondly, we can discriminate between the real and unreal targets by using a novel formula that acts as a spatial filter. The efficiency of the proposed method has been examined through various simulation tests using numerical and experimental datasets, and the results verify that the method can accurately specify the location and the number of scatterers in 2D microwave imaging applications.
In this paper, a flexible full-duplex antenna is proposed with robust performance and high isolation for 5.8 GHz using foam and PET paper. The patch of the antenna is modified by corner cut and inset feeding, while the defected ground structure is used to improve isolation between transmit and receive ports. Silver nanoparticle ink is used for printing the antenna in an inkjet printer. The fabricated version supports simulated results by showing acceptable performance in desired bandwidth. Bending tests and human body loading experiments are carried out on the fabricated antenna to demonstrate antenna's effectiveness for wearable applications. To the best of authors' knowledge, this is the first flexible full duplex antenna designed, achieving a high isolation level of -50 dB. Moreover, wide bandwidth, improved gain, radiation efficiency, low cost, easy fabrication, and robust performance make it a good option for 5.8 GHz wearable applications.
A 4-port planar multiple-input multiple-output (MIMO) antenna system design is proposed. The antenna elements are modified meandered wideband antennas which cover frequencies from 674 MHz to 1 GHz, 1.9 GHz to 2.1 GHz, 3.175 GHz to 3.476 GHz, 4.529 GHz to 4.761 GHz and 5.254 to 5.513 GHz for long term evolution (LTE), Internet of Things (IoT), and sub-6 GHz applications and thus can be used for robotic navigation, logistics, healthcare, tracking, transportation etc. Due to very small envelope correlation coefficient (ECC) between the ports (< 0.5), the MIMO configuration can be efficiently implemented which helps in increasing the data rates. It is very compact in size and thus can be used for portable handheld devices. Since there is the problem of current localization due to common ground, the future work aims at minimizing coupling and improving the impedance matching using novel decoupling networks. These MIMO antennas are connected to a common slotted ground plane. Antenna simulation has been done using Computer Simulation Technology (CST) Microwave Studio Suite simulator. A low cost FR-4 substrate with dimensions 65 mm × 90 mm × 1.6 mm has been used for antenna fabrication, and experimental results are obtained using an anechoic chamber and a vector network analyser. ECC and realized gain of the antenna are also obtained experimentally and are almost similar to the simulated results.
In order to improve the practicability and versatility of ultra-wideband (UWB) antennas, a reconfigurable band notch antenna is proposed in this paper. It has a compact size of 18 mm×16 mm×1.6 mm. The reconfigurable band notch function is realized by two small tunable units. The tunable unit makes up of a split ring resonator (SRR), a dielectric substrate, and a varactor diode. The simulation results show that the antenna combines the functions of band notch emergence, removal and movement. The applied reconfigurable method can effectively broaden the continuous movement range of band notch. The measurement proves that the antenna has the band notch reconfigurable function, and the measured results are in good agreement with the simulation ones. The radiation patterns are measured, which are stable and consistent under two modes with and without band notch, showing omnidirectional radiation characteristics. These research results provide reference value for the design of band notch UWB antenna shielding civil narrowband communication band.
To further improve fault diagnosis performance, a new hybrid feature selection approach combined with whale optimization algorithm and extreme learning machine is presented in this study. Firstly, three filter methods based on different evaluation metrics are employed to select and rank 25 input features derived from gases concentration values, gases ratio and energy-weighted dissolved gas analysis. Then, feature fusion approaches are applied to aggregate feature ranks and form a lower-dimension candidate feature subset. Afterwards, the whale optimization-based extreme learning machine model is implemented to optimize parameters and select optimal feature subsets. The accuracy of the model is used to evaluate the fault diagnosis capability of the concerned feature subsets. Finally, novel subsets are determined as the optimal feature subset to establish a fault diagnosis model. According to the experimental results, the average accuracy of the proposed approach is better than that of other conventional methods, which indicates that the optimal feature subset obtained by the proposed method can significantly promote the fault diagnosis accuracy of the power transformer.
In the conventional virtual synchronous generator (VSG) dual adaptive inertia and damping control schemes, the inertia J and damping D exhibit different variation patterns in different time intervals and are mutually constrained. To address this problem, an adaptive neural-fuzzy network inference system (ANFIS)-based dual adaptive inertia and damping VSG control technique applied to the direct-drive permanent magnet synchronous wind generator (D-PMSWG) system is proposed in this paper. In ANFIS-VSG, the controller is designed on the basis of the ANFIS control principle, and the input and output data are collected by PID control. The Sugeno-type ANFIS controller model is adopted to train the fuzzy inference system (FIS) online. Moreover, the virtual inertia and damping coefficients can be dynamically adjusted in real time according to the frequency variation without taking the different variations and mutual constraints of inertia J and damping D in different intervals into consideration, so the design difficulty and calculation process can be simplified, and the accuracy of the proposed control algorithm is enhanced through training. Furthermore, when the system is subject to load changes, integrating into the grid from an islanded state, and when the output power sets value steps, the power-frequency characteristics and the anti-interference capability of the three-phase output current of VSG can be improved. Finally, the proposed control strategy is simulated and analyzed based on Matlab/Simulink simulation software, which proves the correctness and effectiveness of the proposed control algorithm.
A novel balanced-to-balanced differential-mode negative group delay (NGD) microwave circuit with excellent common-mode suppression is proposed. The proposed circuit consists of two sections of coupled lines, six transmission lines, and four open-circuited stubs. The coupled lines combined with the open-circuited stubs produce the NGD characteristic, which is connected by the λ/2 transmission lines to form a balanced structure for excellent common-mode suppression. To verify the proposed balanced circuit, a microstrip circuit prototype with a center frequency of f0 = 1.0 GHz is designed, fabricated, and measured. When the prototype is excited in differential mode, the measured NGD time at f0 is -3.45 ns with an NGD bandwidth of 16.6 MHz (991.7-1008.3 MHz), insertion loss of less than 2.88 dB, and return loss of more than 11.7 dB. Furthermore, the measured common-mode suppression is greater than 41 dB in the NGD band.
Energetic ion or electron beams cause plasma instabilities. Depending on plasma and the beam parameters, an ion beam leads to change in the dispersion relation of Alfven waves on interacting with magnetoplasmas as it can efficiently transfer its energy to the plasma. We have derived dispersion relation and the growth rates for oblique shear Alfven wave in hydrogen plasma. The particles of the beam interact with the Shear Alfven waves only when they counter-propagate each other and destabilize left-hand polarized mode for parallel waves and left-hand as well as right-hand polarized modes for oblique waves, via fast cyclotron interaction. The collisions between beam ions and plasma components affect the growth rate and the frequency of generated Alfven waves, differently for right-hand (RH) and left-hand (LH) polarized oblique Alfven modes. For (ω + kzvbo > ωbc), the most unstable mode is the LH polarized oblique Alfven mode, and it is the RH polarized oblique Alfven mode for (ω + kzvbo < ωbc), which shows a polarization reversal after resonance condition. Numerical results indicate that the growth rates increase with increase in angle of propagation. The maximum growth rate values in the presence or absence of beam increase due to obliquity of wave.
Chirp sequence has been adopted in automotive applications for its simple generation and flexible integration within radar-centric systems. Besides, recent studies have shown its ability to carry data between communicating vehicles in the surroundings. Since the parameters adopted from current automotive radar sensors can differ at the transmitter side dependent on the automotive supplier, the carrier alignment of the communication receiver of one of the communicated nodes might not concur with the one in the transmitter. This paper presents a novel two-stage synchronization method for communication-assisted chirp sequence (CaCS) signals. The proposed synchronization method applies a sequence of up- and down-chirp as a preamble to estimate frequency and time offsets during the transmission. The suggested synchronization scheme supports partial chirp modulation systems and can be adapted for similar radar-centric systems that employ chirp modulation. The former stage performs a coarse synchronization, reallocates the receive carrier frequency, and corrects eventual time offsets between the communication receiver from one CaCS-node and the transmitter of another node. The carrier allocation at the communication receiver side is based on a combination of spectrum sensing via short-time Fourier transforms and image processing to estimate the transmitting signal pattern (slope, frequency offset, and delay). The latter stage, in its turn, relies on range-Doppler estimation to perform a fine correction of time and frequency offsets and compensates residual offsets of the coarse synchronization stage. Furthermore, the paper analyzes the case of a multi-user scenario with mutual interference between the signals that affects the synchronization and communication data detection. Besides, measurements are provided based on two completely unsynchronized software-defined radios to validate the proposed method. The study also illustrates the influence of the signal-to-noise ratio on the proposed method and verifies it with simulations in MATLAB. As a result, the offsets at the investigated CaCS-node are returned to recover the transmitted data correctly.
In this paper, the effect caused by the suspension force windings on the torque windings in a bearingless synchronous reluctance slice motor (BsynRSM) is analyzed, and a new slide model observer is proposed to reduce the speed estimation vibration caused by this effect. Firstly, the effect of suspension force windings is analyzed in a Maxwell model. The suspension force windings will generate an asynchronous torque and current, which are similar to superimposing an asynchronous motor on the original motor. And a special Matlab/Simulink model is built. Secondly, the effect of current and torque generated by suspension force windings on speed sensorless is analyzed. The sliding mode observer (SMO) is studied considering the effect of suspension force windings. Simulation result shows that the current generated by suspension force windings of the BsynRSM will cause the estimate speed vibrating with the rotor vibration, and the frequency of speed estimation vibration is much higher than the additional current and torque generated by the suspension force windings. Thirdly, an improved SMO is proposed. By using the improved SMO, the amplitude and frequency of the speed estimation are obviously reduced. Finally, the improved SMO is verified on the experimental platform, which proves the feasibility of the method.
Cellular UHF (Ultra High Frequency) transceiver networks and base transceiver station antenna systems comprise high power phase shifters for changing and adjusting the phases or delays of high-power transmitting signals delivered to antenna elements. In this work, theoretical and practical adjustment method of amplitudes and phases for electronic steering of a phased array antenna pattern are illustrated. In otherwords, a high power phase shifter with an asymmetric power divideris designed. The phases are changed and adjusted progressively, and thus the beam direction changes from -60° to 60°. The UHF phase shifter has been simulated in Advanced Design System (ADS) and CST STUDIO SUITE SPARK3D and measured. The simulations show that the designed and manufactured UHF phase shifter can also handle more than 20 KW and can be redesigned to reach up to more than 100 KW RF (Radio Frequency) power (microstrip/stripline structures) and can control/change phases of transmitting/receiving antennas. The phase shifter can be designed on any low loss substrate. By using this method in planar high power phased array antenna systems, 360° planar beam tilting is also achievable.zzz