Dipole Loop Research Articles

Realizing quasi-bound states in the continuum with stable resonant wavelength through compensation mechanism

All-dielectric metasurfaces underpinned by the physics of bound states in the continuum (BICs) have surged interest due to their spectral selectivity and strong light confinement. In this work, We propose a compensation mechanism for SP-BIC with stable resonance wavelength and controllable Q-factor. Here we take metasurfaces consisting of four nano-square disks as an example to break the symmetry of the unit cell by both x-compensation and y-compensation, respectively, and the resonance wavelengths are stable. The results show that the four nanodisks are excited in two modes with x-compensation and y-compensation when only C2 symmetry is preserved, and in one mode with x-compensation and y-compensation when only σx symmetry is preserved. Multiple decomposition results show that the loop dipole and magnetic dipole dominate the modes that retain only C2 symmetry excitation. In contrast, the magnetic dipole dominates the mode that retains only the σx symmetry excitation. Both modes excited by the compensation mechanism have stable resonances with high q-factors under the condition of preserving only C2 symmetry or only σx symmetry. Metasurfaces realized by the compensation mechanism may find promising applications in enhanced light-matter interactions such as lasers, sensing, strong coupling, and nonlinear harmonic generation.

Beam‐tilting antenna with low profile and increased gain for 5G mobile applications

AbstractA low‐profile beam‐tilting antenna with enhanced gain at millimeter‐wave frequency for future 5G mobile applications is designed, and measured results are presented. The mechanism of beam tilting is explained using the proposed printed rectangular loop dipole antenna (RLDA) with three directors that operate at 37 to 40 GHz. The proposed design includes a printed RLDA, one rectangular director sandwiched between two reverse L‐shape directors separated by a 0.05λ0 gap and located 0.35λ0 from the antenna. The measured results, which are well accepted with simulations, show that the antenna's main beam in the E‐plane tilts between ±20° with respect to the end‐fire direction over 37 to 40 GHz. A gain enhancement of 3 dB is obtained with no beam tilt, whereas a gain enhancement of 1.5 dB is obtained with the tilted beam in comparison to the printed RLDA. The proposed design is smaller in size, with a footprint of 10.2 mm × 5 mm (1.3λ0 × 0.64λ0).

Design of broadband dual‐polarized planar antenna with triple radiators

A wideband dual-polarized planar antenna with triple radiators is proposed for the LTE600/LTE700/GSM850/GSM900 base station in this paper. A novel concept of multi-radiator for multi-resonance by close coupling feed is presented and analysed . The proposed antenna is mainly composed of two pairs of loop dipole, L-shaped radiator, step dipole, two L-shaped feed lines, balun and reflector. The reflector is designed with a centrosymmetric partible baffle for directional radiations, which contribute to stable radiations as well. Owing to the novel closely coupling scheme for multi-radiators, three resonances are simultaneously excited within the desired band, producing a wide bandwidth of 47.7% (from 0.59 to 0.96 GHz) for |S11| < −15 dB with high isolation more than 30 dB. Moreover, an average gain of 8.8 dBi as well as stable radiation patterns are achieved simultaneously.

Second-Order, Single-Band and Dual-Band Bandstop Frequency Selective Surfaces at Millimeter Wave Regime

This communication presents the miniaturized low-profile second-order (SO) bandstop frequency selective surfaces (FSSs) for single- and dual-band resonances. The unit cell comprises two identical first-order (FO) elements in a back-to-back configuration with the metal grid in between. Two thin dielectric substrates separate the three metal layers. The proposed FO unit cell consists of intercell-connected spiral resonators (SRs) with capacitively coupled cross loop dipole. The SO filter response of the proposed FSS exhibits a wide stopband ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21} &lt; -10$ </tex-math></inline-formula> dB) bandwidth (BW) of 27.6%. The unit cell has the periodicity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.162\lambda _{0}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free space wavelength at the lower passband. The novelty of the proposed work is a miniaturized simple unit cell geometry, at the millimeter-waveband but not limited to it, with polarization insensitive and high angular stable filter response up to 60° with small variations in the BW. An unconventional four-unit cell element FSS is designed for dual-band SO stopband resonances with the BWs of 8.3% and 13.8%. Prototypes of both FSSs were fabricated and their measured results were found consistent with the simulated filter responses.

Self-Decoupled Dual-Band Shared-Aperture Base Station Antenna Array

A new decoupling concept for dual-band shared-aperture base station antenna arrays is proposed. By loading arrow-shaped decoupling structures in the hollowed regions of the low-band (LB) loop dipole arms, the LB antenna can yield partial reflection to the high-band (HB) antennas, canceling the HB-coupled wave. A dual-band base station antenna array is designed, fabricated, and measured based on this decoupling concept. With decoupling, the HB radiation patterns are restored. The copolarized in-band couplings between the HB antennas are reduced by about 9 dB, reaching >26.9 dB. The proposed antenna array possesses both cross-band and in-band decoupling abilities, without extra decoupling layer.

Theory and Analysis of the Loop Antenna and Ω-Shaped Loop-Dipole Antenna

This paper first examines and corrects Storer’s theory of circular loop antennas, and then investigates theoretically the proposed Ω-shaped loop-dipole antenna. Special emphasis is given to the analysis of the effect of the higher-order terms of the Fourier series as a remainder on the current distribution, input impedance, and radiation patterns of the thin-wire circular loop antenna. It is found that the remainder must be included in the calculation of the current distribution and input impedance but can be neglected to simplify the calculation of far-field radiation. Then, a theoretical model is proposed to analyze the radiation fields, directivity, and input impedance of the proposed Ω-shaped loop-dipole antenna based on the loop and dipole antennas’ theories. Analytical expressions for the radiation fields, directivity, and input impedance of the Ω-shaped loop-dipole antenna are derived. The theoretical and numerical results are compared for the Ω-shaped loop-dipole antennas of practical interests. They are in good agreement.

Advanced method for structure-strength-ductility assessment of dispersion-strengthened FCC metals using activation work, mean slip distance and constitutive relation analyses: Decoding the Haasen plot

The role of cross-slip activation on controlling dislocation mechanisms and deformation debris creation in a dispersion-strengthened matrix (DSM) face-centred cubic metal, GlidCop®, has been elucidated using experimental measurement of the strain rate sensitivity, S, the mean slip distance, λ, and constitutive relation analyses (CRA) from 78 to 473 K. If the stress for cross-slip activation is larger than that of DSM yield stress, geometrically necessary prismatic loops (GNPL) are generated, but the rate controlling kinetics is that of vacancy-drag for cube-textured copper wire-specimens. With increasing temperature, percolation continues to occur by Orowan looping. However, upon yielding, GNPL formation is replaced by various types of dipole loop creation due to dislocation intersections from multiple slip. Loops that convert to stacking fault tetrahedra are measurable, but opposite sign dipoles are dynamically annihilated by pipe diffusion reducing debris retention. The rate controlling mechanisms are identified in the temperature range in which S is constant and the activation energy to overcome the obstacle becomes identical to the measurable activation work. This study shows that cross-slip activation stress determined by CRA, when superposed on the yield stress versus temperature plot of DSM alloys, can identify the mechanism-change temperatures. Subsequent S versus temperature profiles, determined from a new method of Haasen plot analysis of up- and down-strain-rate change tests, can delineate the prime rate-controlling mechanisms, characterize the stored debris and determine whether non-shearing or shearing of particles had occurred. Hence, an advanced method to characterize plastic behavior of DSM alloys has been developed.

Ultrawideband Dual-Polarized Antenna for LTE600/LTE700/GSM850/GSM900 Application

An ultrawideband antenna is proposed for base station using loop resonator below the dual-polarized antenna. The designed loop resonator below is able to introduce new resonance to the antenna for ultrawideband operation. The energy is coupled by the loop dipole. This design can effectively enhance the bandwidth without using extra antenna space, which contributes to the multiarray arrangement in the future. Consequently, a full parameter wideband dual-polarized antenna is obtained. Simulation and measurement exhibit a wide bandwidth of 54.3% (|S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -15 dB) from 550 to 960 MHz with polarization isolation of more than 31 dB. Desirable stable radiation patterns are also obtained over the whole band. It is a good candidate for the future base station communication system, etc.

Enhanced cross-polarization isolation of loop-dipole antenna array backed by dielectric cavities for 5G base stations

Various decoupling methods were proposed and investigated for multiple-input multiple-output (MIMO) Base Station (BS) systems. These methods can effectively decouple the dual-polarized co-polar signal but fail to decouple the cross-polarized signal, similarly limiting the BS's overall decoupling performance. In this paper, different antenna arrays are designed to illustrate the coupling mechanism of cross-polarized BS antennas, and a comprehensive study of the relationship between antenna configurations and mutual couplings is conducted. It is shown that compact size antenna elements enlarge the edge-to-edge separation, and the loop-shaped dipole elements reduce the cross-polarization couplings. Finally, the array-antenna decoupling surface (ADS) method is applied in a 2×2 array composed of the designed antennas. Thanks to the improved antenna unit, the decoupling task is eased, and a better decoupling performance is achieved compared with the original ADS work.

Pattern-Reconfigurable Loop–Dipole Antenna for Electromagnetic Pleural Effusion Detection

Electromagnetic pleural effusion detection requires wideband and pattern-reconfigurable antennas to scan the chest area. Thus, a wideband and low-profile unidirectional loop-dipole antenna with planar structure that is capable of scanning in the azimuth plane is proposed. The antenna consists of a one-wavelength loop, a modified half-wavelength bow-tie dipole, and two parasitic directors to achieve wide operating bandwidth and high front-to-back ratio (FBR). The dipole antenna is directly fed using coaxial cable, whereas the loop is excited using offset proximity coupling. The unidirectional radiation pattern is achieved by quasi-Yagi mode at lower frequencies and a combination of loop and dipole modes at higher frequencies. The parasitic directors are utilized to alter the current distribution on the loop and, thus, enable beam switching in different directions. To verify the proposed concept, two p-i-n diodes are used to change the current nodes on the loop and, hence, switch the radiation pattern from 200 to 00 and +200 in the azimuth plane. The proposed antenna, which has the compact size of 0.32λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.2λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.004λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is wavelength at the lowest operating frequency), has a wide fractional bandwidth of 55% at 0.8-1.4 GHz, which is suitable for pleural effusion detection. The antenna has a peak gain and an FBR of 5 dBi and 14 dB, respectively.

Computational Analysis of a Dual Loop Dipole Antenna and Its Interleaving Array for Improving Transceiver ∣B1∣-field for MRI

This article intends to present the electromagnetic (EM) insight of the operation of a double loop shaped dual loop dipole (DLD) antenna as a single-channel transceiver coil and in an array configuration of multi-channel transceiver coil, designed to provide high signal-to-noise ratio (SNR) by using numerical simulations for 300 MHz magnetic resonance imaging (MRI). Thus, this section includes the comparison of DLD antenna and commonly used loop coils through EM simulations. The use of a DLD antenna is proposed to address the length issue that traditional straight dipole have by making a spiral type in a loop style, while having the same effective physical length of the straight dipole. The magnetic flux density (∣B1∣)-fields of the DLD antenna and the traditional loop coil are compared by field maps acquired by EM simulations. In addition, the DLD antenna has been extended to a 7-channels array, for which the magnetic field coupling between each coil is analyzed and presented through the noise correlation matrix. The use of the DLD antenna exhibits higher ∣B1∣-field intensity while keeping the similar uniformity than a surface loop coil. We use the DLD antenna 7-channel array to observe its utility as multi-channel with short distance overlap between elements; each element is approximately 37 mm away from neighboring element. Transceiver array arrangements also show improved coil performance, especially the interleaving configuration with loop coil indicates lowered mutual inductance coupling at calculated noise correlation matrix. The proposed DLD antenna is expected to induce rapid imaging and high ∣B1∣-field, when expanded to multi-channel planar or volume configuration since it can maximize the number of configuring coil elements within limited imaging area leading effective parallel imaging and deeper penetration depth due to the traveling wave.

Evaluation of a 16-channel transceiver loop + dipole antenna array for human head imaging at 10.5 tesla.

We evaluated a 16-channel loop + dipole (LD) transceiver antenna array with improved specific absorption rate (SAR) efficiency for 10.5 Tesla (T) human head imaging apsplications. Three different array designs with equal inner dimensions were considered: an 8-channel dipole antenna, an 8-channel loop, and a 16-channel LD antenna arrays. Signal-to-noise ratio (SNR) and B1 + efficiency (in units of μT per √W) were simulated and measured in 10.5 T magnetic resonance imaging (MRI) experiments. For the safety validation, 10 g SAR and SAR efficiency (defined as the B1 + over √ (peak 10 g SAR)) were calculated through simulation. Finally, high resolution porcine brain images were acquired with the 16-channel LD antenna array, including a fast turbo-spin echo (TSE) sequence incorporating B1 shimming techniques. Both the simulation and experiments demonstrated that the combined 16-channel LD antenna array showed similar B1 + efficiency compared to the 8-channel dipole antenna and the 8-channel loop arrays in a circular polarized (CP) mode. In a central 2 mm × 2 mm region of the phantom, however, the 16-channel LD antenna array showed an improvement in peak 10 g SAR of 27.5 % and 32.5 % over the 8-channel dipole antenna and the 8-channel loop arrays, respectively. We conclude that the proposed 16-channel head LD antenna array design is capable of achieving ~7% higher SAR efficiency at 10.5 T compared to either the 8-channel loop-only or the 8-channel dipole-only antenna arrays of the same dimensions.

A Miniaturized Wideband Dual-Polarized Antenna Based on Mode-Control Principle for Base-Station Applications

In this paper, a miniaturized wideband dual-polarized antenna and its array are proposed and demonstrated for practical base-station applications. “Mode-control” principle is employed to facilitate both miniaturization and bandwidth-enhancement of the proposed antenna element. To be more specific, by inserting meander lines into a traditional crossed loop-dipole antenna, its first resonant mode can be shifted to a lower frequency without increasing the aperture size, implying that a total size reduction can be achieved. Meanwhile, by embedding a pair of crossed straight strips into the coupling region of the crossed loop-dipole antenna, its second resonant mode can be moved to a higher frequency with a good impedance matching, thereby improving the impedance bandwidth significantly. A prototype of the proposed antenna with a small radiator size of only 0.33λ x 0.33λ (λ is the wavelength at the center frequency of 2.2 GHz) is designed, fabricated and measured. Measurements show that in the target frequency band from 1.71 GHz to 2.69 GHz, i.e., 2G/3G/4G bands, a relatively good impedance matching with the VSWR of less than 1.65 and a high isolation of greater than 28 dB are obtained by the proposed antenna element. Also, a stable gain of 8.7±0.5 dBi and a stable 3-dB beamwidth of 64.8±2.7° at the H -plane are respectively achieved. A multiple-input-multiple-output (MIMO) antenna array consisting of two subarrays with electrical down-tilt is further developed for practical base-station applications. Each subarray is composed of ten antenna elements. The overall width of the array is only 260 mm, which is much narrower than that of typical industrial products (~305 mm). Measured results show that the antenna array has also achieved good performances such as wide impedance bandwidth, high isolations among different ports, and stable radiations over the 2G/3G/4G bands.

Design and Testing of Bipolar Pulsed-Power Supply With High Efficiency and Power Density for Strategic Mineral Exploration

In this paper, a 25-kW bipolar pulsed-power supply for strategic mineral exploration has been described. A 500-V, 12.5-A unit module consisting of a highly efficient LCC resonant converter and a full-bridge-based bipolar pulse-switching unit is designed. The LCC resonant converter has a trapezoidal-shaped resonant current for reduced conduction loss. For achieving high power density, the leakage inductance of the transformer is used as resonant inductance without an external inductor. Moreover, the designed gate drive circuit based on the repetitive short pulse is proposed to operate the frequency range from dc to 8 kHz and reduce the size of the gate transformer. Four modules are connected in series and parallel in order to operate the power supply in either loop mode or grounded dipole mode. Depending on the load condition, the pulse power source capable of delivering the required high voltage and low current (2 kV, 12.5 A) or low voltage and high current (500 V, 50 A) is operated either in grounded dipole mode or loop mode, respectively. In order to satisfy the output voltage balancing of the four modules, the third wire is wound to compensate for the transformer of the LCC resonant converter. Finally, the design of the bipolar pulsed-power supply has been verified based on the experimental results of the field test.

Internal Reconfigurable Dipole–Loop Antenna Array for High Reception Rate of Wideband UHD-TV Applications

An internal reconfigurable Dipole–Loop antenna array, covering the entire ultra-high frequency (UHF) band for ultra-high definition television (UHD-TV) applications is presented. The internal antenna array is used to overcome the influence of electromagnetic interference when integrating the antenna element inside the TV model and to increase the gain and reception rate of receiving signals for television broadcasting. The antenna array is designed based on the Dipole–Loop antenna elements, placing on substrate material PC-ABS (polycarbonate-acrylonitrile butadiene styrene: er = 3.5, tan δ = 0.005) of the bezel frame in the TV model. By simultaneously switching PIN diodes with two ON/OFF states, the antenna array can be frequency reconfigured to achieve a wide operating bandwidth for UHF (470–771 MHz) band. The spacing between the antenna elements in the array at each mode is chosen as 0.5λ0 (λ0 represents the free space wavelength of the highest frequency in the operating band). The proposed antenna array is designed, fabricated, and tested for experimental verification. Measurement results show that the antenna array is good for high reception rate of UHD-TV applications, with a − 6 dB impedance bandwidth of 51.6% (460‒780 MHz), covering the whole UHF band. The 3 dB gain bandwidths of 42.5% and 54.6% are obtained with peak realized gains of 9.6 dBi and 8.5 dBi for the horizontal and vertical polarizations, respectively. In addition, the diversity performance parameters are obtained and evaluated using the mean effective gains of the elements, and the diversity gain using both simulation and measurement results. It shows that the proposed antenna array can receive multi-side signals, applied in diversity and MIMO systems.

Wideband internal dipole–loop antenna with switchable and tunable frequency operation for ultra‐high‐definition television

This study presents the implementation of an internal antenna for ultra-high-definition televisions (UHD TVs), which has encountered challenges such as inherently narrow impedance bandwidths, limited space, and the effect of material properties of the TV to the antenna performance. The proposed antenna consists of a pair of rectangular arms (the dipole mode), which are fed by the coaxial cable, these arms are also connected to the ground plane (the loop mode) through two shortings that excite an additional resonance mode. In addition, reconfigurable antennas also offer attractive potential solutions to solve the challenging antenna problems related to narrow bandwidth using the ability to switch and tune operation frequency. Herein, a frequency reconfigurable dipole–loop antenna which can cover the entire ultra-high-frequency band (UHF: 470–771 MHz, BW: 47.4%) is achieved using PIN diodes for switchable frequency and varactor diodes for tunable frequency. A 49-inch UHD TV is used for the practical implementation experiment. The TV bezel ( ԑ r = 3.5, tan δ = 0.005) is used as the substrate for the antenna design. The designed antenna for UHD TV applications achieves good impedance matching and stable radiation characteristics in the UHF band, considering S 11 = − 6 dB (VSWR 3:1) as the impedance matching criterion.

Broadband Wireless Optical Nanolink Composed by Dipole-Loop Nanoantennas

In this paper, a broadband wireless optical nanolink with plasmonic optical nanoantennas is theoretically proposed and analyzed. The nanolink is formed by linear dipole-loop nanoantennas for transmitter and receiver. The analysis is performed using the linear method of moments with equivalent surface impedance, where we apply a voltage source in the transmitting antenna and connect a load in the receiving antenna. The power received in the load is investigated as a function of frequency and distance between transmitter and receiver. In addition, a comparison is made between this wireless nanolink with a bifilar optical transmission line. The results show that the proposed nanolink, with dipole-loop nanoantenna, can increase the operating bandwidth in the range of 179.1–202.5 THz, when compared with conventional nanolink based only on dipole antennas. In addition, wireless nanolinks, based on dipole or dipole-loop antennas, are more suitable than wired nanolink for distances above approximately 22 μm.

Type of active impulse noise suppressing method based on double‐loop antennas in very low frequency/ultra‐low frequency coupling communications

Very low frequency/ultra-low frequency coupling communication systems suffer from severe disturbance from non-Gaussian impulsive noises which producing significant long tails. Considering the significant in-band parts of the impulse, traditional noise-suppression methods are not adequate in improving the signal-to-noise ratio (SNR), and the performance of existing dipole–loop double antennas active noise suppression systems are limited to a low level due to the different directionality of the antennas. A new double-loop antennas active noise suppressing system was proposed, in which one multi-turn loop antenna was employed to receive the useful signals, and one single-turn loop was employed as the noise reference antenna. A mathematical morphology processor and a time-switch filter were employed to extract the impulsive noise, and the digital equivalent model of the multi-turn loop antenna was established filtering the extracted impulsive noise to obtain a duplicate transient, which is highly correlated with the transients received from the multi-turn loop antenna. The system SNR was improved by subtracting the transient duplicate from the received signals. Simulations were carried out with Monte Carlo method, showing that the SNR can be improved with the gain of about 18 dB with communication error rate extremely reduced by orders of magnitude. Experiment system was also designed and established to verify the feasibility and efficiency, and a 50 m communication experiment in an industrial environment showed that the error rate can be decreased from 0.2 to 0.06% while employing the proposed noise suppression method.

A Wideband Dual-Polarized Antenna With Two Independently Controllable Resonant Modes and Its Array for Base-Station Applications

A wideband dual-polarized antenna with two independently controllable resonant modes for 2G/3G/4G bands is proposed. Its radiator mainly consists of two crossed stepped-width loop dipoles loaded with two crossed straight dipoles. Two approaches are adopted to design the proposed antenna with large freedom. First, by replacing the traditional uniform-width loop dipole with a stepped-width one, the first resonant mode can be adjusted independently by controlling the width ratio of the loop. Second, a pair of crossed straight dipoles are embedded into the gap of the crossed loop dipoles, and the second resonant mode can be controlled independently by altering the length or position of the straight dipoles. Measurements show that the antenna achieves an impedance bandwidth of 54.5% with VSWR< 1.5 (1.68–2.94 GHz) and isolation of greater than 28.5 dB within the bandwidth. Also, an antenna array with ten elements is developed with electrical downtilt from 0° to 8° for practical base-station applications.

A Multimode Wideband ± 45$ ^{\circ}$ Dual-Polarized Antenna With Embedded Loops

A wideband dual-polarized antenna is proposed for base station applications. Compared to the conventional crossed loop dipole antennas, additional loops are embedded into original loops to generate a new resonant mode. Therefore, a multimode antenna with an enhanced impedance bandwidth is completed. A prototype of the proposed antenna is designed, fabricated, and tested. The measured impedance bandwidth of two ports is 51% with Return Loss > 15 dB from 1.68 to 2.83 GHz, and the isolation between two ports is greater than 27 dB. The measured results also show that a stable radiation pattern with 65.4o ± 2.4 $ ^{\circ}$ half-power beamwidth in the horizontal plane for slant 45 $ ^{\circ}$ polarization and a stable gain of 8.8 ± 0.7 dBi are achieved from 1.7 to 2.7 GHz.