In this paper, an efficient wideband array adaptive beamforming (ADBF) approach based on keystone transform is presented. In order to eliminate the aperture effect of the wideband signal, the modified keystone transform is applied to remove the time delay between different array elements. Thus, the wideband array is equivalent to the narrowband array, and the orthogonal projection matrix of the target steering vector can be used to filter the desired signal in the training samples, which avoids the signal cancellation caused in the estimation of ADBF covariance matrix. Compared with theestablished algorithm of sliding window, this approach can significantly reduce the computational burden. The feasibility and effectiveness of the proposed method are validated through numerical simulations.
It is still a delusion that the transmitter coil is able to drive multiple loads (electrical/electronic devices) in multi-receiver Wireless Power Transfer (WPT) system. Nevertheless, it is found that for a fixed design, the number of receiver load coils that can be driven with their stipulated power level is not selected randomly rather with definite number. The circuit model analysis of series-series compensated multiple-receiver WPT system is proposed in order to estimate the number of loads with respect to the transmitter coil. Both theoretical simulation and experimental studies have proven this finding, and the results obtained are important for designing an effective multiple-receiver WPT system.
In order to solve the nonlinear and coupling problems of three-pole hybrid magnetic bearing, a six-pole outer rotor hybrid magnetic bearing (HMB) is proposed. Firstly, the structure and working principle of the six-pole outer rotor HMB are introduced. Secondly, the linearity and coupling characteristics curves between radial suspension force and control current are analyzed and verified by the finite element method. In comparison with the analysis results of the three-pole HMB, there is no electromagnetic coupling between radial two degrees of freedom of the six-pole outer rotor HMB, and the nonlinear problem of force-current characteristic is solved. Finally, an experimental platform is built. The research results show that the maximum bearing capacity of the six-pole outer rotor HMB is 32.3% higher than that of the three-pole HMB. The suspension force-current characteristic experiment shows that the suspension force-current properties of the six pole outer rotor hybrid magnetic bearing can be considered linear near the equilibrium position, and there is no magnetic coupling between two radial degrees of freedom of the six pole outer rotor HMB near the equilibrium position.
In this paper, we present the design of a cylindrical conformal transmitarray antenna for generating high-gain beam. A low-profile transmitted element with 3-bit quantization is designed. It can cover 360˚ transmission phase shift range with transmission magnitude below -2 dB. A prototype of the cylindrical conformal transmitarray antenna is fabricated and measured. The measured gain is 21.75 dBi with aperture efficiency of 42.7%, and the thickness of the transmitarray is only 0.1 wavelengths at operating frequency.
A novel and compact microstrip-line fed printed antenna for wideband circular polarization (CP) radiation is proposed. The designed antenna utilizes a crescent-shaped substrate, rotated L-shaped monopole, and defected ground structure (DGS) to achieve a wide 3-dB axial ratio (AR) bandwidth and 10-dB impedance bandwidth (ZBW) across the entire 5 GHz Wireless Local Area Network (WLAN) and Vehicle to Everything (V2X) operational bands. As the substrate of the proposed antenna is only 0.8 mm thick, it has a very low profile of 0.014λ in terms of free space wavelength (λ) at 5.5 GHz. The proposed CP antenna exhibits overlapping 10-dB ZBW and 3-dB AR bandwidth (ARBW) of 22.05% (4.80-5.99 GHz), along with broadside far-field patterns, gain greater than 2.5 dBi and efficiency above 85%throughout the desired operating band. Therefore, it is a good candidate for WLAN and V2X communication applications.
In this paper, an electrically-small microwave dipole sensor is used with machine learning algorithms to build a noninvasive continuous glucose monitoring (CGM) system. As a proof of concept, the sensor is used on aqueous (water-glucose) solutions with different glucose concentrations to check the sensitivity of the sensor. Knowledge-driven and data-driven approaches are used to extract features from the sensor's signals reflected from the aqueous glucose solution. Machine learning is used to build the regression model in order to predict the actual glucose levels. Using more than 19 regression models, the results show a good accuracy with Root Mean Square Error of 1.6 and 1.7 by Matern 5/2 Gaussian Process Regression (GPR) algorithm using the reflection coefficient's magnitude and phase.
The planar physical model of ultra-broadband unidirectional waveguide based on surface magnetoplasmons (SMPs) has been derived and calculated in detail, but the coaxial physical model of ultra-broadband unidirectional waveguide based on SMPs has not been reported. Based on the gyromagnetic properties of Ferrite (taken yttrium iron garnet as an example, abbreviated as YIG), a novel ultra-broadband unidirectional coaxial waveguide is proposed in this paper. The basic model of the waveguide is a multilayer coaxial waveguide system composed of metal-layer-YIG-YIG-metal wire. The magnetization vectors of two middle YIGs are equal and opposite. Theoretical analysis and simulation results show that the waveguide supports two unidirectional transmissions, and both unidirectional bands have excellent properties of immune scattering and back reflection. The waveguide system has the characteristics of simple structure, immune scattering, and ultra-broadband unidirectional band, which is expected to be used in all-photon communication system.
In this paper, a high-performance microstrip diplexer is designed and manufactured. The design is based on two pairs rectangular open-loop resonators band-pass filters and a novel zigzag junction. It operates at 3.5 GHz for fifth-generation 5G sub-6-GHz and 5 GHz for Wi-Fi communications. The proposed diplexer is considerably miniaturized with a global compact size of 30×17 mm2. In addition, it presents low insertion losses less than 0.5 dB at both channels in comparison with the previous diplexers. Moreover, the isolation is higher than 20 dB, and the return loss is better than 14 dB at the bandwidths. To confirm the simulation results, the presented diplexer is manufactured and measured where a good agreement is carried out.
A novel compact dual-band bandpass filter with wide stopband using stub-loaded stepped-impedance resonators is presented in this paper. The characteristics of the dual-mode resonator are investigated by using even/odd mode analysis. The center frequencies and bandwidths of the two passbands can be controlled by adjusting the geometric dimensions of the stub-loaded stepped-impedance resonators. Moreover, the filter has been implemented with five transmission zeros to improve the selectivity. A prototype of a dual-band bandpass filter centered at 3 and 4.35 GHz has been designed and fabricated. The measured bandwidths are 8.3 and 4.6%, and the corresponding insertion losses are 1.7 and 1.6 dB, respectively. A compact dual-band bandpass filter with sharp roll-off rate of 113.3/56.7/56.7/170 dB/GHz, wide stopband of 5.3 GHz, and isolation between two passbands of 25 dB is achieved. The measured results are in good agreement with the simulated ones.
In this paper, a textile based fractal monopole antenna is proposed with a defected ground structure for wearable application. The proposed antenna is designed on Flannel fabric with a thickness of 1 mm, which translates to 0.03λ at 10 GHz. The total dimensions of proposed antenna is 60 x 40 x 1 mm. The measured fractional bandwidth of the antenna is 110.1%. The proposed flannel based conductive ink antenna is characterized, and the results for washable fabric are illustrated. Both simulated and measured results are presented. The concept of application of low cost conductive ink on flannel fabric is demonstrated using conventional screen printing method. The antenna is characterized for commercial wash ability; the measurement results are invariant with the machine wash of the flannel fabric indicating robustness of the proposed method of fabrication of the antenna element.
This article reports an SDR (software-defined radio) operating as a receiver for near-field measurement, aiming at EMC pre-compliance tests. The SDR replaces professional-grade RF instrumentation with benefits, with the lower costs. Its software application is based on Open-source GNU-Radio, which grants a higher versatility to the signal processing and visualization, requiring a single laptop to analyze the data and control the whole system, in real time. Reported tests used two commercial PCB magnetic field probes, and a proof-of-concept near-field imaging is performed in an S-shaped transmission line at 1100 MHz.
A compact and broadband uniplanar Microstrip Antenna (MSA) is proposed for endfire radiation at sub-6 GHz 5G frequency band. The proposed antenna consists of a semi-elliptical radiating element and a U-shaped ground plane. The use of semi-elliptical radiating element results in a wide impedance bandwidth (BW) and compact size. The U-shaped ground plane further improves the bandwidth due to the increased coupling from radiating element to ground. An endfire radiation pattern, 3.8 dBi peak gain, and 49.8% bandwidth (BW) are achieved while a compact size of 0.47λ0×0.13λ0×0.008λ0 (where λ0 is the wavelength in free space at the center frequency) is kept. A parametric study based on CST-MWS simulations is also presented together with an equivalent circuit analysis to see the effects of various dimensional parameters of the uniplanar MSA with an elliptical radiating element. To validate the simulation results, prototype of the proposed antenna was fabricated and tested. The measured results are in good agreement with the simulated ones.
Crosstalk between interconnected lines is considered from two perspectives in this study. From a physical space perspective, the four transmission lines are reduced to two transmission lines. Meanwhile, the replacement of signal transmission of four-channels 2PAM (Pulse Amplitude Modulation) with signal transmission of two-channels 4PAM can reduce the quantity of transmission line and increase the space between the transmission lines. Thus, it can reduce the crosstalk. Under the same signal-to-noise ratio (SNR), the change in symbol error rate (SER) after signals of four-channels 2PAM are changed to those of two-channels 4PAM is given. Results show that the latter has an advantage in anti-crosstalk compared with the former in terms of the influence of crosstalk on SER. From the signal space perspective, applying signal linear combination transformation can convert the multiplexing signals in the interconnects into orthogonal mode. This process can cancel the crosstalk. In this study, the two methods are combined to save wiring while reducing crosstalk. ADS simulation results show that the eye pattern of 4 PAM signal recovers well by saving half the number of transmission lines.
This paper presents the design of a novel aperture coupled cylindrical dielectric resonator antenna with linear polarization and circular polarization. The linearly polarized cylindrical dielectric resonator antenna (LP CDRA) with proposed aperture and microstrip feed line excites three hybrid radiating modes (HEM111, HEM21δ and HEM13δ) in three impedance bands. The circularly polarized cylindrical dielectric resonator antenna (CP CDRA) with proposed aperture and flag shaped feed line excites six different hybrid radiation modes (HEM11δ, HEM21δ−like, HEM21δ, HEM12δ, HEM13δ, HEM14δ) in three impedance band and three CP bands. Different sense of CP is reported. The antennas operate in both C and X bands.
An aperture coupled printed antenna using frequency selective surface (FSS) reflector is reported in this paper. The proposed antenna includes two layers of FSS reflectors designed with an array of 7×5 crossed elements on the top substrate to achieve wideband, high gain and improved directivity. The antenna implements an aperture coupled radiating element on the bottom substrate which serves as a source feed antenna to the FSS reflector. The proposed structure has an overall dimension of 30×32×1.6 mm3 operating between 6.5 and 8.3 GHz with an impedance bandwidth of 1.8 GHz. The results reveal that the impedance bandwidths in excess of 82.3% and 44.5% have been achieved compared to the source feed antenna and antenna with single layer FSS, respectively. Further, the peak gain of 6.25 dB is also achieved in the operational frequency band with a two-layer FSS which is 29.4% and 15.8% more than the antenna without FSS and antenna with single FSS layer. Due to compact structure, wideband, high gain, and fabrication simplicity, the proposed antenna may be suitable for long distance communication systems.
In this paper, a single band two element MIMO antenna for future 5G wireless applications at 5 GHz is presented. The antenna consists of T over T shaped meander micro strip lines printed on the front side and defected ground structure on the back side of an RT Rogers 5880 substrate, which are able to excite a resonance mode. The antenna operates at 4900 to 5060 MHz (|S11| < -10 dB) covering the 5G NR band n79. The antennas are to be placed symmetrically along the edges at the corners of the Smartphone panel. The isolation in the case of two elements MIMO antenna is enhanced by an I-shaped ground slot. The mutual coupling reduction is facilitated by 10 mm neutralization line (NL) at both hands. The prototype is fabricated to validate the proposed model. The measured results show good accordance with simulated results. The main performance results wherever possible of the proposed design are calculated, compared and analyzed with the measured results.
A wideband magneto-electric (ME) dipole with characteristics of dual-circular polarization is presented in this paper. The proposed antenna is composed of four horizontal radiation patches, four pairs of vertical radiation patches, a ground plane, a pair of wideband feeding networks, and novel crossed feeding structures which work as wideband 3-stage impedance matching transitions. The feeding networks which contain a Wilkinson power divider and a coupled-line phase shifter are printed on the bottom of the ground plane, and they can provide stable two-way output wideband signals with quadrature-phase. The proposed antenna works as a ME dipole with a wide operation bandwidth of 53.2% (S11 < -10 dB, and Axial Ratio (AR) < 3 dB) from 1.71 GHz to 2.95 GHz for right-hand circular polarization (RHCP) and 62% from 1.7 GHz to 3.25 GHz for left-hand circular polarization (LHCP), respectively.
Novel microstrip single-band and dual-band bandpass filters (BPFs) are presented in this paper. Firstly, a pair of open-ended stubs of less than λ/4 in length is connected to a uniform impedance resonator (UIR) at two symmetrical positions with respect to its centre, and at the same time other two open-circuited stubs with different lengths are loaded in the middle of the resonator. By virtue of parallel-coupling structure at I/O ports, a single-band BPF is constructed centered at 2.2 GHz with 10.6% 3-dB bandwidth, and two transmission zeros are implemented at the right side of the passband. Next, the L-shaped I/O coupled lines are applied to suppress the inherent spurious response of the stubs-loaded resonator. As a result, a dual-band BPF with two passbands at 2.2 GHz and 5.2 GHz, which is self-contained with three transmission zeros between the two passbands, is constituted. Finally, the proposed bandpass filters are designed and fabricated to provide an experimental validation for the predicted performances.
We present a capacitive wireless power transfer (C-WPT) system using rotating capacitors for wireless sensor system (WSS) on propulsion shaft. In order to supply stable power to the WSS consisting of four sensors, a controller, and a radio module, we designed the rotating capacitor connected in parallel with multiple plates that minimizes the change in capacitance of the power coupling capacitor of the C-WPT system. A Class-E converter and transformers topology are utilized to drive the C-WPT system for WSS. The fabricated C-WPT system transmitted stable power even when the rotational speed of the shaft was changed from 100 to 300 revolution per minute (rpm), and achieved power of 20.48 W and transmission efficiency of 64.29%.
In this letter, a new bandpass frequency selective surface (FSS) with sharp sidebands is proposed to suppress electromagnetic interferences caused by the fifth generation (5G) mobile communication to fixed C-band satellite system. The proposed design is composed of three cascaded layers separated by air space, whose unit cell geometry comprises metal square loops, square slots and their evolvement. As the overall configuration yields high-order bandpass characteristics with multiple transmission poles and zeros, a flat passband covering 3.7-4.2 GHz is obtained, while the out-of-band shielding effectiveness mostly remains better than 20 dB over frequency lower than 6.5 GHz. Good angular stability and polarization independency are also achieved due to structural symmetry. A prototype was fabricated and measured, whose results agree well with the full-wave simulation.