Split Patch Research Articles

Few-shot learning under domain shift: Attentional contrastive calibrated transformer of time series for fault diagnosis under sharp speed variation

The domain shift of sample distribution caused by sharp speed variation dissatisfies the general assumption of stationary conditions, which renders a severe challenge for a majority of existing intelligent fault diagnosis methods. Moreover, data deficiencies in industrial applications further compromise diagnostic accuracy and reliability. To break the predicament of fault diagnosis under sharp speed variation with few samples, we developed an Attentional Contrastive Calibrated Transformer (ACCT) of time series. First, a plurality of convolution layers is used to capture low-level local structure features. Then, the transformer is applied to the sequences of split patches for modeling global dependencies and extracting the domain invariant features. Meanwhile, a data augmentation strategy based on regional mixing is used to enhance the generalization. Furthermore, to obtain a more discriminative feature representation, we designed a regularization based on unsupervised contrastive learning for calibration of attention distribution. The results demonstrated that transformers have an aptitude for analyzing time series data even under sharp variation, which do not need to deliberately consider extra modules for cross-domain disentanglement. The proposed method is superior to several advanced transformers in three case studies under speed transient conditions with few samples.

Hybrid phase error analysis for dual-polarized reflectarray antenna using asymmetric split patch element

ABSTRACT A hybrid phase error analysis for dual-polarized reflectarray antenna using asymmetric split patch element is proposed in this article. The asymmetric split patch consists of a four-leaf patch and two split rings of different size where small one makes the patch asymmeric along y-axis and large one is used for impedance matching. And a complete 360° phase shift is obtained by using variable-size approach and flipping split patch 180° along y-axis. Then, we use hybrid phase error analysis approach to analyze and optimize the influence of phase sensitivity, quasi-periodic influence and phase constant on the reflectarray antenna. The simulated results show that maximum of element phase sensitivity is reduced by 275°/mm and element quasi-periodic phase error is dropped by 38°. Furthermore, dual-polarized reflectarray composed of 676 asymmetric split patch elements is designed, fabricated and measured. The measured gain of the proposed antenna is 29.9 dBi @10.0 GHz with aperture efficiency of 46%. The −1 dB gain bandwidth is 12% @10.0 GHz. The measured results show that the proposed antenna can improve phase accuracy effectively by using hybrid phase error analysis approach with asymmetric split patch.

Multi-channel Calibrated Transformer with Shifted Windows for few-shot fault diagnosis under sharp speed variation

In engineering practice, mechanical equipment is mainly operated under the working conditions of sharp speed variations, which results the data distribution domain shift. Furthermore, the domain shift and the lack of data in engineering practice render severe challenges for existing intelligent mechanical faults diagnosis technologies. To this end, this paper proposed a Multi-channel Calibrated Transformer with Shifted Windows (MCSwin-T) for computing self-attention in each non-overlapping window which models the relations between the sequences of split patches. Meanwhile, a new partitioning approach is designed by shifting the windows and alternately use the two different partitioning approach to establish the connections across windows. To extract low-level features of the signal and maintain the positional information, a plurality of convolution layers is applied before transformer block. A normalized method which is a multi-channel multiplication of the vector generated by each residual block is also developed to calibrate activation and increase the stability of the optimization. To evaluate the effectiveness, the proposed method is compared with multiple advanced transformer methods in two case studies under speed transient conditions. The experimental results indicate the superiority and higher accuracy of the proposed method under few-shot domain shift condition.

Air-bridged Schottky diodes for dynamically tunable millimeter-wave metamaterial phase shifters

A low loss metamaterial unit cell is presented with an integrated GaAs air-bridged Schottky diode to produce a dynamically tunable reflective phase shifter that is capable of up to 250° phase shift with an experimentally measured average loss of 6.2 dB at V-band. The air-bridged Schottky diode provides a tuneable capacitance in the range between 30 and 50 fF under an applied reverse voltage bias. This can be used to alter the resonant frequency and phase response of a split patch unit cell of a periodic metasurface. The air-bridged diode die, which is flip-chip soldered to the patch, has ultra-low parasitic capacitance and resistance. Simulated and measured results are presented which verify the potential for the attainment of diode switching speeds with acceptable losses at mmWave frequencies. Furthermore the study shows that this diode-based unit cell can be integrated into metamaterial components, which have potential applications in future mmWave antenna beam-steering, intelligent reflecting surfaces for 6G communications, reflect-arrays, transmit-arrays or holographic antennas.

Wideband Circularly Polarized Split Patch Antenna Loaded With Suspended Rods

A novel single-fed wideband circularly polarized (CP) split patch antenna with two suspended metal rods is proposed in this letter. The proposed antenna has two semi-circular patches with a suspended metal rod loaded on each patch. The antenna is fed by a coupling slot and a hammer-headed microstrip line on the opposite side. Two inclined semicircular patches are combined with slot to form a CP radiation at low-frequencies band; furthermore, two suspended metal columns form a loop-type antenna at high-frequency band, which are combined with the slot forming another CP resonance point. The combination of these two CP resonance points broadens the CP bandwidth which is indicated by the AR curve. The proposed antenna has a simulated 3 dB AR bandwidth of 22.58% (4.87-6.11 GHz) and a wide -10 dB impedance bandwidth of 48.75% (3.8-6.25 GHz). The overall electrical size of the antenna including the ground is 0.46 × 0.46 × 0.154 λ0 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (with λ0 being the free-space wavelength at 5 GHz). The measured peak gain of the antenna is greater than 8 dBic from 5 to 6 GHz. A 2 × 2 antenna array based on the proposed antenna element is also implemented and experimentally verified. The 2 × 2 array has a 3 dB AR bandwidth of 49.7% (4.02-6.68 GHz). This proposed antenna and its array exhibit a very novel structure and an interesting working principle while demonstrating excellent CP radiation performance. They could be applied in various 5G or other communication systems, which require CP radiation.

A compact wideband antenna with detailed time domain analysis for wireless applications

In this research paper, a compact wideband monopole antenna of the dimensions 20 � 20 � 1:6 mm3ði:e: total volume ¼ 640 mm3Þ is presented. The proposed antenna configuration has simplified design in which the ground plane, as well as the radiating patch, are on the same plane. This design renders one side of the substrate consummately empty resulting in an overall design which is more facile to fabricate. It is excited by Coplanar Waveguide (CPW) feeding technique. The proposed structure has a fractional bandwidth of 40.56% (4.3–6.45 GHz) in simulation and 34.41% (4.4– 6.38 GHz) in measurements for S11 < �10 dB criteria. It has linearly increasing gain over its entire oper�ational bandwidth and has a maximum peak realized gain of 4.7 dB at 6.4 GHz in simulation and about 3.8 dBi at 6.3 GHz in measurement. The designed antenna is suitable for WLAN and WiMAX of the range corresponding to 4.70–6.19, 5.5–5.7 and 5–6 GHz. To overcome the major drawback of narrow band�width in printed patch antenna, the uniquely designed split patch technique is used to achieve wide bandwidth. The antenna time-domain analysis is detailed by keeping it in side-to-side and face-to-face orientations. This analysis resulted in a stable performance which is very much required from a wideband antenna. All the necessary antenna simulations are done using HFSS and are validated by fabricating a model of it

Bandwidth Enhanced Circularly Polarized Fabry–Perot Cavity Antenna Using Metal Strips

This paper introduces a novel single feed wideband Tai Chi-shaped circularly polarized (CP) antenna that utilizes a Fabry-Perot cavity (FPC) with a 3D printed structure to increase the antenna gain and axial ratio (AR) bandwidth. Besides, a novel method is proposed for AR bandwidth enhancement. Some simple metal strips are introduced, which could adjust the phase of the particular electric field component. By placing the metal strips at an optimal position, the AR bandwidth of the antenna could be effectively broadened. Note that this method has little effect on the other antenna performance and it does not require additional structural changes. The proposed method to increase the axial ratio bandwidth is very simple and effective. The Tai Chi-shaped antenna consists of two separate small patches and two suspended metal rods. The two small patches are 180° out-of-phase excited which are centro-symmetrically placed to form a larger and complete circular patch. The two small patches and the total split patch generate two minimum AR points, which substantially broadens the AR bandwidth. Adding two layers of FR4 substrate to the antenna constitutes an FPC, and the antenna peak gain is increased from 9.42 dBic to 14.44 dBic. In addition, the AR bandwidth has been increased from 27.73% to 44.42%. In order to further increase the AR bandwidth of the CP antenna, some simple metal strips have been added to the FPC substrate. The AR bandwidth has been enhanced from 44.42% to 53.46% (4.07 - 7.04 GHz). Compared with other CP antennas with FPC, our proposed antenna shows advantages in terms of substantially broadened impedance and AR bandwidth, high gain, and low fabrication cost.

U-joint Double split O (UDO) shaped with split square metasurface absorber for X and ku band application

This paper reports, a metasurface absorber which is U-joint loaded Double Split O shaped with a square split patch at the center and Double Negative (DNG) property. The proposed absorber shows significant absorption for potential applications like radar signal absorption and satellite communication, remote sensing, RF shielding. The vertical U joint and split O mutually creates substantial resonance and expedite by the center square patch, to cover two consecutive X and Ku band absorption peaks at 11.56 GHz with 82.31%, 12.27 GHz with 98.91% and 14.19 GHz with 97.79%. Besides, balanced geometrical shape with insensitivity polarization for TE and TM mode wave propagation enhances the robustness and tunability of the structure. The absorption mechanism analyzed and discussed with the Finite Integration Technique (FIT). Characterization of S-parameter executed with an established method for dielectric property extraction and finally compared the proposed absorber with existing literature.

Transinguinal preperitoneal repair with the Polysoft patch: prospective evaluation of recurrence and chronic pain

The Polysoft patch was conceived to facilitate performance of the transinguinal preperitoneal patch method and combine the advantages of patch placement in the preperitoneal space and the open inguinal approach. The aim of this prospective study was to evaluate the rate of recurrence and chronic pain at midterm follow-up. In a cohort of 200 hernia repairs involved in a prospective evaluation, midterm results of 171 cases operated on from 1 July 2004 to 31 December 2005 were assessed. The anesthesia was spinal in 136 (79.5%) cases, local in 26 (15.2%), and general in nine (5.3%). A questionnaire was sent to patients on 30 November 2006 asking about recurrence, chronic groin pain, and satisfaction. With a median follow-up of 21.9 months (11.6-29.4), 167 (97.7%) patients were evaluated, two were dead, and two were lost to follow-up. There were two (1.2%) recurrences that were reoperated on; both consisted of an indirect sac that protruded between the branches of the split patch. Eleven (6.6%) patients alleged the feeling of a foreign body, and 12 (7.2%) reported pain that occurred occasionally or upon effort but did not prevent activity. In one case, the pain present before operation was unchanged, and in three cases, the pain could clearly be attributed to an origin other than the hernia repair. No case of pain that impaired activity was observed. With regard to results, 98.2% of patients were satisfied and 97.6% declared that they would adopt the same method in case they had to be operated on for another hernia. These results suggest that the technique provides a low rate of recurrence and a low percentage of chronic pain that did not impair activity.

Fair Surface Reconstruction Using Quadratic Functionals

AbstractAn algorithm for surface reconstruction from a polyhedron with arbitrary topology consisting of triangular faces is presented. The first variant of the algorithm constructs a curve network consisting of cubic Bézier curves meeting with tangent plane continuity at the vertices. This curve network is extended to a smooth surface by replacing each of the networks facets with a split patch consisting of three triangular Bézier patches. The remaining degrees of freedom of the curve network and the split patches are determined by minimizing a quadratic functional. This optimization process works either for the curve network and the split patches separately or in one simultaneous step. The second variant of our algorithm is based on the construction of an optimized curve network with higher continuity. Examples demonstrate the quality of the different methods.

Dual FET active patch elements for spatial power combiners

A novel dual-FET active patch antenna element and arrays for quasi-optical power combining are described. The circuit uses two FET's that symmetrically load a split patch antenna. The configuration of the devices decreases H-plane cross-polarization dramatically. The power combining was achieved by injection locking through mutual coupling. An equivalent isotropic radiation power of 0.88 W for a 2-element dual-FET patch antenna array has been obtained. For a 2/spl times/2 array, an equivalent isotropic radiated power of 2.99 W was achieved. The circuit is planar and amenable to monolithic circuits. >

Novel FET active patch antenna

A novel dual-FET active patch antenna element for quasi-optical power combining arrays is described. The circuit uses two FETs which symmetrically load a split patch antenna. The push-pull operation of the devices decreases H-plane crosspolarisation dramatically. A power output of 47 mW was achieved at 8.1 GHz.