| 1. |
- Aminoroaya, Alireza, et al.
(författare)
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Facile encapsulation of cyanoacrylate-based bioadhesive by electrospray method and investigation of the process parameters
- 2024
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Ingår i: Scientific Reports. - : Nature Research. - 2045-2322. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Polymer microcapsules containing cyanoacrylates have represented a promising option to develop self-healing biomaterials. This study aims to develop an electrospray method for the preparation of capsules using poly(methyl methacrylate) (PMMA) as the encapsulant and ethyl 2-cyanoacrylate (EC) as the encapsulate. It also aims to study the effect of the electrospray process parameters on the size and morphology of the capsules. The capsules were characterized using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and field-emission scanning electron microscopy (FE-SEM). Moreover, the effects of electrospray process parameters on the size were investigated by Taguchi experimental design. FTIR and TGA approved the presence of both PMMA and EC without further reaction. FE-SEM micrograph demonstrated that an appropriate choice of solvents, utilizing an appropriate PMMA:EC ratio and sufficient PMMA concentration are critical factors to produce capsules dominantly with an intact and spherical morphology. Utilizing various flow rates (0.3–0.5 ml/h) and applied voltage (18–26 kV), capsules were obtained with a 600–1000 nm size range. At constantly applied voltages, the increase in flow rate increased the capsule size up to 40% (ANOVA, p ≤ 0.05), while at constant flow rates, the increase in applied voltage reduced the average capsule size by 3.4–26% (ANOVA, p ≤ 0.05). The results from the Taguchi design represented the significance of solution flow rate, applied voltage, and solution concentration. It was shown that the most effective parameter on the size of capsules is flow rate. This research demonstrated that electrospray can be utilized as a convenient method for the preparation of sub-micron PMMA capsules containing EC. Furthermore, the morphology of the capsules is dominated by solvents, PMMA concentration, and PMMA:EC ratio, while the average size of the capsules can be altered by adjusting the flow rate and applied voltage of the electrospray process.
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| 2. |
- Asli, Javad Bagheri, et al.
(författare)
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A Parallel-Path Amplifier for Fast Output Settling
- 2023
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Ingår i: NEWCAS 2023 CONFERENCE PROCEEDINGS. - : IEEE. - 9798350300246 - 9798350300253
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Konferensbidrag (refereegranskat)abstract
- Pushing CMOS technology to the nanometer range is detrimental to analog circuits’ performance due to the reduction of gain and slew rate of amplifiers, so the classical approaches need to be revisited for adjustment in advanced nodes. This paper presents a parallel-path amplifier used as a switched-capacitor (SC) amplifier. The proposed amplifier includes a high bandwidth and slewing path parallel to a high gain path. The high bandwidth and slewing path, named the feedforward path, provides high charging/discharging currents to decrease the slewing time of the amplification phase, significantly (60%). In parallel, the high gain path provides sufficient open-loop DC gain for final settling (59 dB). The feedforward path is enabled/disabled by control signals provided through a hysteresis detector and by considering the status of the feedback voltage. The proposed amplifier is designed and fabricated in 65nm CMOS technology as a multiplying digital-to-analog converter (MDAC) in a pipeline ADC. The chip is under fabrication, and this paper covers post-layout performance of the proposed amplifier. The results reveal that enabling the feedforward path guarantees the amplifier to have a constant error (\lt2 mV) for an extensive range of input voltages (300 mV Vin 900 mV) compared to its standalone high gain path. At the same time, the static current of the feedforward path is minimal (\lt 100 µ A), and it can drive large load capacitors. © 2023 IEEE.
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| 3. |
- Bagheri, Alireza, et al.
(författare)
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A 16 × 16 45° Slant-Polarized Gapwaveguide Phased Array With 65-dBm EIRP at 28 GHz
- 2023
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 71:2, s. 1319-1329
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Tidskriftsartikel (refereegranskat)abstract
- A high equivalent isotropic radiated power (EIRP) active phased array antenna is proposed for fifth-generation (5G) communication systems at 28 GHz. The numerical design, measurements of a fabricated prototype, and performance analysis are presented. The antenna design is based on the gapwaveguide technology and consists of $16 \times 16$ single 45° slant-polarized elements. The proposed design uses a low complexity printed circuit board (PCB) structure with only six layers, i.e., a half of the existing wideband solutions. The array antenna incorporates up/downconverter integrated circuits (UDCs) and $1 \times 4$ transceiver beamformer integrated circuits (BFICs). Moreover, a compact and highly efficient transition at the end of each channel of the BFICs has been designed to interconnect the antenna elements with the PCB. The antenna's front-end loss, which includes the feed line, mismatch, and ohmic losses, is only 1.3 dB. The array covers the scanning range of ±60° in the azimuth plane and ±10° in the elevation plane. The $S_{11} < -10$ dB frequency bandwidth is from 26.5 to 29.5 GHz. The maximum EIRP of the antenna is 65.5 dBm at saturation point. The presented design offers a compact, robust, and low-loss performance solution meeting the high transmission power requirements of 5G applications.
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| 4. |
- Bagheri, Alireza, et al.
(författare)
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Comparing 5G hybrid beamforming in indoor environments-collocated vs distributed mmWave arrays
- 2024
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Ingår i: FRONTIERS IN COMMUNICATIONS AND NETWORKS. - : FRONTIERS MEDIA SA. - 2673-530X. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies the performance of hybrid digital-analog multi-user multiple-input multiple-output (MU-MIMO) downlink communication based on various antenna systems for 5G applications. The analysis is focused on comprehensive numerical simulations comparing hybrid beamforming schemes for collocated vs distributed phased array antennas (PAA) deployments in two indoor office environments. This study uses measured beamforming radiation patterns from two 28 GHz state-of-the-art PAAs. The channel models employed are the standardized statistical 3GPP 38.901 indoor channel models implemented in the QuaDRiGa software. A beam selection algorithm is implemented to maximize the achievable sum rate, assuming either matched-filtering or zero-forcing precoding. The evaluated figures of merit are the gain of the RF power amplifier, the per-user signal-to-interference-plus-noise ratio (SINR), and the resulting achievable sum-rate capacity. Based on the results, the distributed deployment scenario always shows a higher SINR and achievable sum-rate capacity at the user locations while requiring a lesser amplification of the conducted power. Specifically, the largest PAA with slant-polarized 16 x 4 elements producing 16 horizontal analog beams in combination with zero-forcing digital precoding proved to be the best solution in both open and mixed indoor office environments in absolute values. On the other hand, the array based on the same type of elements but in a more compact realization with 4 x 4 elements, but with beams arranged as 8 horizontal times 2 vertical, offered the most significant relative gains.
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| 5. |
- Bagheri, Alireza, et al.
(författare)
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Micro strip to Ridge Gap Waveguide Transition for 28 GHz Steerable Slot Array Antennas
- 2020
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Ingår i: 2020 14TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP 2020). - 2164-3342. - 9788831299008
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Konferensbidrag (refereegranskat)abstract
- In this paper three types of contactless vertical transitions from microstrip to double ridge waveguide are presented. The designs are compact in size and robust, with improved isolation by employing a pin structure, making them ideal for SG mmWave phased arrays. All transitions cover the 26.5 - 29.5 GHz band, their dimensions are less than half a wavelength in pitch and have insertion losses less than 0.6 dB. The three designs apply different matching strategies and offer a trade-off between bandwidth and PCB areas. Finally, the behavior within an array configuration is analyzed.
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| 6. |
- Bagheri, Alireza, et al.
(författare)
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Minsum m watchmen’s routes in Stiegl polygons
- 2023
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Ingår i: XX Spanish Meeting on Computational Geometry. ; , s. 41-44
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Konferensbidrag (refereegranskat)abstract
- We present an O(n2 · min{m, n}) time and O(n · min{m, n}) storage algorithm to compute the minsum set of m watchmen routes given their starting points in a Stiegl polygon ― a staircase polygon where the floor solely consists of one horizontal and one vertical edge ― with n vertices.
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| 7. |
- Bagheri, Alireza, et al.
(författare)
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TX Beamforming EVM Performance of a 65 dBm-EIRP Slant-Polarized Gapwaveguide Phased Array at 28 GHz
- 2023
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Ingår i: 17th European Conference on Antennas and Propagation, EuCAP 2023.
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Konferensbidrag (refereegranskat)abstract
- The transmit error vector magnitude (EVM) performance measurements of a slant-polarized 28 GHz gapwaveguide-based phased array is analyzed in this paper. The performance is studied by using a large range of signals, with varied powers, symbol rates, and quadrature amplitude modulation (QAM) orders. The measurements have been conducted for four different scanning angles. A non-standardized over-the-air (OTA) link between the phased array and the receiver in a laboratory environment is used. The results show that the phased array antenna supports a 31 dB effective isotropic radiated power (EIRP) dynamic range at a maximum 2% EVM when transmitting a 64QAM modulated signal with 250 MS/s symbol rate at all scanning directions.
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| 8. |
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| 9. |
- Yong, Wai Yan, et al.
(författare)
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An Overview of Recent Development of the Gap-Waveguide Technology for mmWave and Sub-THz Applications
- 2023
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Ingår i: IEEE Access. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2169-3536. ; 11, s. 69378-69400
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Forskningsöversikt (refereegranskat)abstract
- The millimeter-wave (mmWave) and sub-terahertz (sub-THz) bands have received much attention in recent years for wireless communication and high-resolution imaging radar applications. The objective of this paper is to provide an overview of recent developments in the design and technical implementation of GW-based antenna systems and components. This paper begins by comparing the GW-transmission line to other widely used transmission lines for the mmWave and sub-THz bands. Furthermore, the basic operating principle and possible implementation technique of the GW-technology are briefly discussed. In addition, various antennas and passive components have been developed based on the GW-technology. Despite its advantages in controlling electromagnetic wave propagation, it is also widely used for the packaging of electronic components such as transceivers and power amplifiers. This article also provided an overview of the current manufacturing technologies that are commonly used for the fabrication of GW-components. Finally, the practical applications and industry interest in GW technology developments for mmWave and sub-THz applications have been scrutinized.
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