Band Operation Research Articles

Ultrawideband Dual Circularly Polarized Waveguide Array Antenna for K- and Ka-Bands Satellite Communications

In the letter, a wideband dual circularly polarized (CP) waveguide antenna array is designed for K and Ka dual-band satellite communications. A multi-stage square waveguide structure is exploited into the radiating part to facilitate the excitation of a dual polarization response. A ridge waveguide polarizer is integrated to form the left-hand circular polarization (LHCP) and the right-hand circular polarization (RHCP). For a better arrangement of the feeding network, a transition structure with E-plane waveguides to double-ridge waveguides reduces the cross-sectional area of the feeding network. An 8 x 8 array antenna prototype was designed, fabricated and measured for demonstration purposes. The axial ratio (AR) and impedance bandwidth of the array antenna are more than 45%, according to simulation and measurement results. Input reflection coefficient and isolation lower than -15 dB for the dual CP from 19 to 30 GHz, the total antenna efficiency for the entire operating band exceeded 72%. For both polarizations, the peak gain ranges between 24.6 and 28.8 dBi from 19 to 30 GHz.

Decoupling and Wide-Angle Scanning Design of a Millimeter-Wave Phased Array Using Square-Ring Metasurface

A wide-angle scanning millimeter-wave (mm-wave) phased array using square-ring metasurface (SRMS) is presented in this letter. SRMS not only improves the element gain owing to enhancing the radiation efficiency and directivity of the antenna element, but also decreases the mutual coupling between elements as a partially reflective surface. Due to the reduced mutual coupling, both the active impedance matching and the total efficiency of the proposed array are significantly improved. Further, thanks to the improved active impedance matching and the small element spacing of 0.43 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength at the center frequency of 27 GHz in free space), the 3-dB scanning angle of the proposed array is significantly extended. Measured results show that the phased array achieves a wide 3-dB scanning angle greater than ±68° over a wide operating band of 24. 11-29.68 GHz (20.7%), which is very suitable for 5G mm-wave terminal applications.

Design and Analysis of Modified U-Shaped Four Element MIMO Antenna for Dual-Band 5G Millimeter Wave Applications.

A novel compact-slotted four element multiple input multiple output (MIMO) planar monopole antenna is proposed for 5G mmWave N257/N258 and N262 band applications. The antenna, with dimensions of 12 mm × 11.6 mm × 0.508 mm (1.036λo ×1.001λo×0.043λo where λo is computed at lowest cutoff frequency), is fabricated on a Rogers RT/duroid 5880 (tm) substrate with a relative permittivity of 2.2 and a dielectric loss tangent of 0.0009. The suggested antenna consists of four U-shaped radiating elements (patches) on top of the dielectric material and a slotted ground on the bottom. The radiating elements are fed by a 50-ohm microstrip line feed. To improve the impedance performance of the MIMO antenna, a rectangular strip of 1.3 mm × 0.2 mm and a couple of rectangular slots are added to each radiating element. The first operating band at 27.1 GHz, ranging from 25.9 GHz to 27.8 GHz, is achieved by using slotted U-shaped radiating elements. The second operating band at 48.7 GHz, ranging from 47.1 GHz to 49.9 GHz, is obtained by etching hexagonal slots on the ground. The antenna design achieves an isolation of >27 dB through the orthogonal positioning of radiating elements and slots on the ground. The designed antenna operates at 27 GHz (N257/N258) and 48.7 GHz (N262) bands, exhibiting stable radiation patterns, a peak gain of >5.95 dBi, radiation efficiency of >90%, an envelope correlation coefficient of <10-6, a total active reflection coefficient of ≤-10 dB, channel capacity losses of <0.03 bits/s/Hz, and a mean effective gain of ≤-3 dB. The simulated and measured results of the antenna show good agreement, making it well-suited for 5G mmWave communication applications.

Subwavelength grating-based silicon photonic TE mode division multiplexer for C + L band operation

This paper reports a subwavelength grating (SWG) based multiplexer (MUX) on a silicon photonics platform capable of multiplexing three transverse electric modes. The designed MUX is simulated using a commercial 3D finite-difference time-domain solver and shows broadband operation over the whole C and L optical telecom bands from 1530 nm to 1625 nm wavelength range. The effective indices of the Bloch modes in the SWG waveguides are extracted from the band structure plot. The designed MUX consists of two co-directional coupling regions for fundamental to higher-order mode coupling, with each coupling stage consisting of single-mode and multimode SWG waveguides. The transmission characteristics, viz. transmittance, insertion loss, and return loss, are presented and discussed. The coupling lengths without the tapering regions for TE0–TE1 and TE0–TE2 mode couplings are 14μm and 1.48μm, respectively. The transmittance is >78% with the highest insertion loss and return loss of 1.1 dB and –15 dB, respectively. At 1550 nm, the transmission is >88%, insertion loss is <0.6 dB, and return loss is <−15 dB. A uniform under-etch and over-etch of 5 nm are taken for the fabrication tolerance study, which shows a maximum variation of 0.58 dB for the insertion loss with return loss <−14.6 dB at 1550 nm. Over the whole simulated range, the insertion loss is <1.4 dB, and return loss is <−14.6 dB with ±10 nm change in device dimension. A temperature tolerance study with 50 °C and 100 °C rise in temperature has been done, and the device retains its broadband operation over the simulated range. The maximum increase in insertion loss is 0.1 dB for the TE0–TE2 coupling, while the overall return loss of the device decreases to <−20 dB for the TE0–TE1 coupling.

Fully-Metallic Additively Manufactured Monolithic Double-Ridged Waveguide Rotman Lens in the K/Ka-Band.

This paper reports on the design and experimental validation of a fully-metallic double-ridged waveguide 10 × 10 Rotman lens additively manufactured as a single part. The wide band operation of this quasi-optical beamformer enables us to cover the uplink and downlink frequencies allocated to satellite communications in the K/Ka-band, from 17.3 GHz to 30 GHz. The feeding port design was adjusted to enable vertical printing, thus minimizing the use of supporting structures. A prototype was manufactured and tested. The reported results indicate losses in the range of 0.5 dB in the lower-frequency band and 0.8 dB in the upper-frequency band, including the waveguide transitions added for test purposes. The measured reflection and coupling coefficients remain below -11.5 dB over the operating band. The standard deviation of the residual phase error across the array ports is below 5° in simulation and below 10° in measurements. Array factors synthesized using the scattering parameters confirm the good stability of the beamforming functionality over the wide frequency band analyzed. This monolithic design is a promising step toward more integrated antenna systems, such as a compact dual-stack configuration for planar array design.

Low-profile dual-polarized differential-fed filtering antenna and its novel array with low sidelobe level

This paper presents a single-layer dual-polarized filtering antenna with good out-of-band suppression. By using inherent characteristic of the patch’s eigenmode and meanwhile merging four filtering strategies, i.e., parasitic patches, slot on the driving patch, and defected groundstructure (DGS), a low-profile filtering antenna design with five radiation nulls has been realized. With the designed filtering antenna, a conventional 1×2 array with a spacing of 0.91λ is first developed. In order to reduce the sidelobe level of the array, a sharing patching scheme is introduced to decrease the interspace between the elements as 0.44λ, with the same physical size as the conventional array. In addition, a concept to measure total isolation between two kinds of the polarized ports in the array, i.e., SddVH, has been derived for the first time. The prototype of the proposed array is fabricated with a profile of 0.038λ. Measured results indicate that the designed novel array has an operational band of 3.53–4.06 GHz, SddVH better than 41 dB, a sidelobe level below −18 dB, and a suppression level above 20 dB with the stopband up to 0.5 GHz and 5 GHz.

Overlapping filter bank convolutional neural network for multisubject multicategory motor imagery brain-computer interface

BackgroundMotor imagery brain-computer interfaces (BCIs) is a classic and potential BCI technology achieving brain computer integration. In motor imagery BCI, the operational frequency band of the EEG greatly affects the performance of motor imagery EEG recognition model. However, as most algorithms used a broad frequency band, the discrimination from multiple sub-bands were not fully utilized. Thus, using convolutional neural network (CNNs) to extract discriminative features from EEG signals of different frequency components is a promising method in multisubject EEG recognition.MethodsThis paper presents a novel overlapping filter bank CNN to incorporate discriminative information from multiple frequency components in multisubject motor imagery recognition. Specifically, two overlapping filter banks with fixed low-cut frequency or sliding low-cut frequency are employed to obtain multiple frequency component representations of EEG signals. Then, multiple CNN models are trained separately. Finally, the output probabilities of multiple CNN models are integrated to determine the predicted EEG label.ResultsExperiments were conducted based on four popular CNN backbone models and three public datasets. And the results showed that the overlapping filter bank CNN was efficient and universal in improving multisubject motor imagery BCI performance. Specifically, compared with the original backbone model, the proposed method can improve the average accuracy by 3.69 percentage points, F1 score by 0.04, and AUC by 0.03. In addition, the proposed method performed best among the comparison with the state-of-the-art methods.ConclusionThe proposed overlapping filter bank CNN framework with fixed low-cut frequency is an efficient and universal method to improve the performance of multisubject motor imagery BCI.

In-situ compression with acoustic emission detection of high pressure torsion deformed Cu38Zr54Al8 metallic glass micropillars

In-situ compression of Cu38Zr54Al8 metallic glass micropillars in a scanning electron microscope was performed together with continuous acoustic emission recording on samples in the as-cast state and after pre-deformation by high pressure torsion. A size effect was detected in both shear band operation and acoustic emission signal, irrespective of the preliminary deformation. This phenomenon was explained by the size dependent compliance of the pillar/indenter system. Differences between acoustic emission signals from the as-cast and pre-deformed states indicated changes in the shear band formation mechanism due to high pressure torsion. These differences were clear in the elastic regime of the in-situ compression and supported the role of rejuvenation in stabilization of unstable shear bands.

A highly robust RF 65 nm CMOS power amplifier design using Quasi-Newton control algorithm for wireless system

This article reports a novel robust approach towards CMOS power amplifier (PA) using Quasi-newton (QN) control algorithm in 65 nm CMOS process which provides best performance parameters over redundant wide bandwidth ranging from 2.4 to 16.4 GHz frequency band. Each stage are designed and optimized using QN algorithm to get desired goals such as high linearity, small group delay variations and high PAE across the entire frequency band of interest. Moreover, pole-zeros compensation technique is adopted and derived to get better stability of the proposed PA. The simulation and measurement results of PA achieved a small signal power gain of 10.5–16.8 dB with input return loss of better than 10 dB over the frequency band of 2.4 GHz to 16.4 GHz. A small group delay variation of ±58 ps over full frequency band of operation is achieved by optimizing the design parametric analysis. It is also observed that within the frequency of 6.5 to 14.6 GHz, an excellent small group delay variation of only ±11 ps is achieved and this is due to stage-2 tuning compensation technique. It also demonstrates the achieved input power in 1 dB compression points are −3.1 to 4.3 dBm, leading to maximum power added efficiency of 36.3%, respectively. The proposed PA consumes a lower DC power of 20.5 mW under supply voltage of 1.5. In addition, Process, voltage and temperature (PVT) analysis is executed at different conditions in order to achieve a robustness of the proposed PA over the entire band of operation.

Wideband switchable linear polarization rotator based on metasurface

The realization of dynamic polarization rotation based on the metamaterial or metasurface is always a concerned issue in electromagnetic manipulation. In this Letter, a transmission-type switchable metasurface is proposed, which can rotate the linear polarized (LP) wave to arbitrary angle among ±45° in a wide frequency band. The polarization rotation metasurface (PRM) consists of a polarization conversion surface and a partially reflective surface. By controlling the resistances of PIN diodes, the PRM can change the polarization angle of transmitted LP wave. To verify the design, a prototype of the proposed PRM is fabricated and tested, and the simulated and measured results are in good agreement. According to the measured results, the fractional bandwidth at each state of prototype is larger than 20.4%. The overlapping operational band of the prototype is from 3.03 to 3.60 GHz, where the transmission coefficient remains higher than –2 dB, and the axial ratio of transmitted wave is higher than 15 dB. The proposed design may have the application potential in target detection, wireless communication, and polarimetric imaging.

Dual-Band Dual-Polarized Shared-Aperture Grid Antenna With Large Frequency Ratio

In this letter, a dual-band dual-polarized shared-aperture grid antenna with a large frequency ratio is presented. To achieve shared aperture and large frequency ratio, a millimeter-wave (mm-Wave) partially reflective surface (PRS) is embedded into a microwave patch antenna. A periodic circular grid patch is adopted not only as the microwave antenna but also as the mm-Wave PRS antenna. The mm-Wave PRS antenna is centrally excited by a cross-shaped waveguide with two coaxial connectors, and the microwave patch antenna is driven by a pair of orthogonal L-shaped probes, resulting in polarization diversity in both bands. A compact microstrip resonant cell (CMRC) and a metal post are designed to reduce the couplings between different ports. For demonstration, a prototype operating in the 3.5 GHz and 28 GHz bands is fabricated and measured. The overlapped measured -10 dB impedance bandwidths between the orthogonal ports cover 3.41–3.59 GHz (5.14%) and 26.62–30.26 GHz (12.8%) in the low and high bands, whereas the measured peak realized gains of 8.75 dBi and 12.79 dBi are obtained, respectively. All port-to-port isolations are larger than 20 dB over the bands of operation.

High-Gain and Wideband Circularly Polarized Endfire Leaky-Wave Antenna Array Based on the Complementary Dipole

A circularly polarized (CP) endfire leaky-wave antenna (LWA) array with the merits of high-gain and broad operation band is proposed in this communication. This array configuration is composed of double-row antenna cells arranged linearly, which derives from the performance of the complementary dipole (loop and electric dipole). By introducing the coupling loop and the electric dipole along both side of a metallic parallel strip line (PSL), the effective radiation is generated from this structure due to the periodic perturbation. Based on the intrinsic 90° phase differences of the complementary dipole, CP performance is easily achieved by turning the antenna unit size reasonably. Similar to the yagi antenna, this linearly antenna array achieves an endfire radiation. A fabricated prototype has verified the design concept, which shows that the proposed antenna has a relative impedance bandwidth of 51.1%, 3dB axial ratio (AR) bandwidth of 25%, and the gain of 1.1-13.59dBi within the operation band.

A Compact Ultra-Wideband Monocone Antenna with Folded Shorting Wires for Vehicle-to-Everything (V2X) Applications

In this paper, a capacitively-fed, ultra-wideband (UWB), and low-profile monocone antenna is proposed for vehicle-to-everything (V2X) applications. The proposed antenna consists of a monocone design with an inner set of vias. Additionally, an outer ring is added with a small gap from the monocone and shorted with six folded wires of different lengths to extend the operating band. The proposed antenna covers the frequency range from 0.75 GHz to 7.6 GHz and has a 164% fractional bandwidth, with a gain value varying between 2 and 10 dBi. The dimensions of the antenna are 0.37λL × 0.37λL × 0.067λL. The antenna was fabricated using a 3D printer with low-cost polylactic acid plastic (PLA) material and then sprayed with aerosol copper nanoparticles. The efficiency was approximately 90% throughout the frequency bands of interest. Finally, the proposed antenna was installed on a vehicle and tested with an OBU (onboard unit) and a RSU (roadside unit) in the field. The results show a longer wireless communication range for V2X applications.

A Wideband Rotary-Joint-Free H-Plane Horn Antenna With 360° Steerable Radiation Pattern Using Gap Waveguide Technology

Considering the limitations of electronically steerable antennas such as limited steering span, gain degradation for large steering angles, complexity, and cost, this paper is focused on the design of a simple mechanically steerable H-plane horn antenna. It is shown that since there is no need for an electrical connection between the top and bottom sections of a gap waveguide, if a sectoral horn is properly designed and realized using this technology, the pattern of the antenna can be easily steered without a rotary joint. To demonstrate this concept, a rotary-joint-free H-plane horn antenna is designed, and its performance is predicted using EM simulations. The antenna offers a wide operating band covering almost the entire Ku band and provides a full 360-degree continuous steering span. Additionally, the proposed antenna benefits from a constant gain over the full range of steering angles. This is in contrast to phased array antennas whose gain degrades when the main beam is steered away from the broadside. The proposed concept and computed characteristics are verified by good agreement between the simulated and measured characteristics of the fabricated prototype.

Effect of Rapid Body Weight Loss on Balance and Functional Mobility in Obese Individuals after Laparoscopic Adjustable Gastric Banding Operation

The purpose of this study was to evaluate the effect of rapid weight loss on static balance and functional mobility among excessively obese patients undergoing Laparoscopic Adjustable Gastric Banding (LAGB) surgery. Subjects (8 females; BMI &amp;gt;35 kg/m2) underwent baseline measurements before LAGB surgery, followed by subsequent evaluations at 6 weeks, 12 weeks, and 24 weeks during the follow-up appointments. During each evaluation, various assessments were conducted, including measurements of anthropometry such as body weight, height, hip and waist circumference, as well as functional tests for static balance, 10-meter walk, and timed get-up-and-go. There were statistically significant changes in weight, BMI, waist circumference, hip circumference, abdominal circumference, waist-hip ratio, static sway eyes open, timed up-and-go, 10-meter walk, and steps in 10-meter walk test values (p&amp;lt;0.001) between the baseline and the postoperative measurements. However static sway values under eyes closed condition were not statistically significant. In the 24-week follow-up, the weight loss, reduction in abdominal circumference, increase in walking speed against time and step count, and recovery in functional movements were shown to persist. Also, reduction in static balance surface oscillation confirmed the improvement of balance control.

Predicting Water Quality Distribution of Lakes through Linking Remote Sensing–Based Monitoring and Machine Learning Simulation

The present study links monitoring and simulation models to predict water quality distribution in lakes using an optimized neural network and remote sensing data processing. Two data driven models were developed. First, a monitoring model was established that is able to convert spectral images to TDS distribution. Moreover, a simulation model was developed to generate a TDS distribution map for unseen scenarios for which no spectral images are available. Outputs of the monitoring model were applied as the observations for training the simulation model. The Nash–Sutcliffe model efficiency coefficient (NSE) was utilized in the system performance measurement of the models. Based on the results in the case study, the monitoring model was sufficiently robust to convert the operational land imager spectral bands of Landsat 8 to the TDS distribution map. The NSE was more than 0.6 for the monitoring model, which confirms the predictive skills of the model. Furthermore, the simulation model was highly reliable in generating the TDS distribution map of the lakes. Three tests were carried out to demonstrate the reliability of the model. When comparing the results of the monitoring model and simulation model, an NSE of more than 0.6 was found for all the tests. It is recommendable to apply the proposed method instead of conventional hydrodynamic models that might be highly time consuming for simulating water quality parameters distribution in lakes. Low computational complexity is the main advantage of the proposed method.

A Novel High Isolation 4-Port Compact MIMO Antenna with DGS for 5G Applications.

This paper presents the design and realization of a simple and low-profile, four-port multiple-input-multiple-output (MIMO) antenna operating in a mm-wave band supporting 5G communication technologies. As part of the design methodology, the initial stage involved the development of a conventional monopole patch antenna optimized for operation at 26 GHz, which was matched to a 50 Ω stepped feed line. Afterward, a square-shaped defected ground structure (DGS) with semi-circle slots on the edges was placed on the ground to improve the isolation, and the circular and rectangular slots were incorporated as DGSs to optimize the antenna impedance bandwidth. Etching semi-circular-shaped slots on the ground plane achieved more than 34.2 dB isolation in the 26 GHz operating band. In addition, an arrangement of four symmetrical radiating elements was positioned orthogonally to minimize the antenna's physical size and improve the isolation. The proposed MIMO antenna's overall dimension was 25 × 25 mm2, which was printed on a Rogers 5880 substrate at a width of 0.787 mm and εr = 2.2. The proposed antenna covered the 5G mm-wave band with a 10 dB bandwidth ranging from 25.28-28.02 GHz, whereas the maximum gain attained for the proposed structure was 8.72 dBi. Additionally, the implementation of these slots effectively mitigated mutual coupling, resulting in reduced envelope correlation coefficient (ECC) values. Furthermore, other MIMO performance metrics, including channel capacity loss (CCL), mean effective gain (MEG), and diversity gain (DG), were analyzed for the proposed structure. The obtained results indicate its suitability for various usage areas, such as smart devices, mobile phones, and sensors in 5G applications.

Flexible microwave metasurface absorber with reconfigurable absorption intensity in ultra-wideband

This article proposes a flexible metasurface absorber (MA) with reconfigurable absorption intensity in an ultra-wideband spectrum. Due to the utilization of an ultrathin polyimide substrate, the MA is endowed with superior flexibility over previous rigid designs. The pattern of the MA consists of a fourfold symmetrical metal strip and four PIN diodes, which simultaneously activate multiple resonances to generate a wide operating band. By adjusting the voltage of the PIN diodes embedded in the strips, the MA can execute various stages of reconfigurable absorption intensity through varying states of ohmic loss. When the PIN diodes are off, MA is switched to a reflector. In addition, the results of the equivalent circuit simulation confirm the feasibility of the design. Finally, an MA sample is fabricated and measured, and good agreement is obtained between the measured and simulated results. The MA achieves a reconfigurable absorption intensity varies from −16.8 to 0 dB over an ultra-wide frequency range of 5.6–16.98 GHz, with relative bandwidth up to 100.8%. As expected, the designed MA features excellent characteristics both in plane and curved states.

Independently Tunable Triband Patch Antenna with Band-Notched Characteristics for X-Band Applications

This paper presents a triband antenna with a simple design for X-band applications. The proposed antenna is designed based on a patch with a truncated corner slot and complementary split-ring resonators in the ground plane. In this way, the antenna exhibits three operating bands and its resonant frequencies can be controlled independently by changing dimensions of the slot in the patch and the resonator structures in the ground plane. In addition, due to the antiresonant behavior of the complementary split-ring resonator structures, the antenna exhibits a notch-band characteristic at 10.7 GHz. A parametric study is performed to provide a detailed understanding of the independent resonance tuning behavior of the antenna. Both simulated and measured results of the proposed antenna are presented, which are in good agreement. The proposed antenna shows three operating bands in the X-band including (with absolute and relative bandwidths) 9.4–9.7 GHz (300 MHz, 3.14%), 10.3–10.6 GHz (300 MHz, 2.86%), and 11.05–11.32 GHz (297 MHz, 2.66%). In addition to that, a notched band of 10.6–11.05 GHz is introduced to exclude operation in the frequency bands of radiometric observation systems (10.6–10.7 GHz). To the best of our knowledge, this work is unique in its combination of independent tuning of three frequency bands of operation with single-layer implementation in the X-band. Such a structure provides additional degrees of freedom to the antenna design, customizing operation in the required bands while avoiding operation in other bands.

External tie line power fluctuations smoothing strategy of new urban power grid

In a net-zero carbon power grid (NZCPG) with a relatively high proportion of renewable energy sources, significant power fluctuations occur, severely constraining the development of both the NZCPG and the New Urban Power Grid (NUPG). In the NZCPG, the proportion of traditional hydro and thermal power units used to mitigate power fluctuations has decreased. It is necessary to explore the load resources in the NUPG to stabilize the power fluctuation between the NUPG and the NZCPG, and to reduce the operating pressure of the NZCPG. Firstly, this paper proposes a method for developing external tie line schedules based on the load operation band (LOB) to relax the constraints on the schedule for the NZCPG. Secondly, A revised load response aggregation model is proposed to improve the aggregation accuracy under uncertainty factors by online correcting their impact on the load response characteristics. Thirdly, considering the flexible loads in NUPG can only compensate for a part of the power fluctuation, this paper proposes a method to judge the power fluctuation that these loads can offset. Two PFS optimal strategies are proposed among NUPG partitions considering deviation penalty and within each NUPG partition reducing the number of participated load-users. This paper focuses on the PFS in bulk NZCPGs other than in the distribution grids and microgrids. Our work can effectively smooth the power fluctuation within NUPG regulation capability meanwhile reducing the number of participated load-users. Fourthly, a method is proposed to judge the power fluctuation beyond NUPG regulation capacity in NUPG. Using the actual load response capacity, the over-amplitude/time layered smoothing strategy with optimal load is proposed, which can offset the power fluctuation of the bulk NZCPG to the largest extent. Finally, the IEEE-39 system is used to verify the effectiveness of the proposed methods.© 2017 Elsevier Inc. All rights reserved.