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Robust Design Approach Towards GaN HEMT RF Front End Amplifier for High Power Transceivers
(National Institute of Technology Karnataka, Surathkal, 2024) Gupta, Manishankar Prasad; Sandeep Kumar
This research work focuses on the design and implementation of Gallium Nitride High Electron Mobility Transistor (GaN HEMT) based Microwave Low Noise Amplifiers (LNAs) and Power Amplifiers (PAs) with novel techniques for modern wireless broadband and dual-band communications. The Low Noise Amplifiers account for the majority of the system’s Noise Figure, while Power Amplifiers account for most of the high output power. As a result, front-end designs are being researched to improve the device’s signal to noise ratio (SNR) with highly linear output power. The primary objective of the proposed front-end is to produce low NF, small and large signal flat gain, excellent linearity, high efficiency, and high i/o power while minimum power consumption at the ultra-high frequency to microwave bands of operation. Firstly, a performance analysis of the GaN HEMT based low noise amplifier (LNA) using even-odd mode matching techniques has been developed. The proposed GaN LNA circuit provides a high input/output (i/o) power, and ultra-low noise over wideband ranging from 0.5 to 2.7 GHz with fractional impedance bandwidth of 138%. The proposed LNA circuit with the incorporation of input/output broadband stages relaxes 50Ω matching constraints and achieves high input and output power with good stability. The proposed LNA achieves a simulated/measured gain of 16dB/17dB. An ultra-low noise figure of 0.6 dB flat is achieved over a wideband. In addition, the high output power is achieved at 40dBm while input power is 25dBm. The fabricated GaN HEMT LNA circuit has consumed power of 120 mW. The area of the fabricated RF GaN HEMT LNA is 32 × 26 mm2 . Secondly, a GaN HEMT device to circuit approach towards LNA using defective ground bias (DGB) technique has been developed. This is the first MMIC GaN HEMT LNA design to offer dual-bands of operation in both L and S-bands to the author’s best knowledge. The proposed 0.15-μm GaN HEMT device is fabricated using slot radiation phenomenon, which achieved a high output power of 20W. To achieve an optimal noise, high i/o power, and almost flat gain at both L and S-band, the defective ground structure of bias topologies is modelled and optimized. An artificial ground defect is created to offer resonant properties, which utilizes frequency-selective properties to improve the performance of the LNA circuit. The dedicated LNA shows the benefits of compact size, extremely low noise figure of 0.74/1.6 dB, and high output power of 44 dBm. The compact GaN HEMT LNA could overcome the weak signal strength received by RF receivers for modern wireless communication systems. Thirdly, a high efficiency Rat-Race coupler (RRC) based compact GaN HEMT PA design over broadband has been developed. The RRC integrated PA design is proposed for the first time as per author best knowledge. The design methodology used a higher order two open stubs and a rat-race coupler (RRC) at i/o sections to control harmonics impedances. As a proof of concept, a PA is fabricated using a monolithic microwave integrated circuit (MMIC) with 0.15 μm gallium nitride high electron mobility transistor (GaN HEMT) process. The measured result shows that the designed PA achieves a flat power added efficiency (PAE) of 65% - 74 %, output power (Pout) of 44.8 dBm - 46 dBm, and drain efficiency (DE) of 72% - 85 %, over a record wide frequency of 1.8 GHz - 3.6 GHz, which is the highest one among all reported harmonic tuned PAs. Finally, a highly stable PA with three operating bandwidth points has been presented. A unique multi-harmonics-controlled network with three-paths impedance matching structure and proper bias topologies are combined to achieve excellent performance in terms of operating bandwidth, efficiency, and high i/o power. A buffer stage of impedance matching is generated by proposed three paths to reducing the harmonics, promoting the targeted fundamental bandwidth. To verify the methodology, a wideband PA is implemented with a 25-W wolfspeed Cree model CG2H40025F GaN HEMT device. The implemented PA is simulated and post-simulated, which provide a fractional bandwidth of 67 % over the frequency of 2 to 4 GHz, with DE of 54-65 %, PAE of 47-52 %, saturated output power of 43.1-44.6 dBm, and a gain of 7.1-9.5 dB. The above results show that PA realized by the proposed novel method is suitable for modern wireless applications. All the proposed GaN HEMT LNAs and PAs are fabricated using a MIC/MMIC process under the supply of 28V. The design of experiment (DoE) and statistical analysis are additional novel contributions towards robust proposed front-end amplifiers in this work. DoE is a new analysis technique to find the individual device parameter’s contribution to the final gain, NF, and return loss. Statistical analysis is also performed to find the yield so that the robustness of the proposed designs is satisfied. A novel harmonically controlled impedance matching techniques are used to design and analyze PAs.
Influence of Raw Materials and Binding Agents on Engineering Properties of Fly Ash based Pelletized Aggregates
(National Institute of Technology Karnataka, Surathkal, 2024) Sharath, B P; Das, Bibhuti Bhusan
Analysis and Prediction of Road Accident Cost
(National Institute of Technology Karnataka, Surathkal, 2024) P H, Sumayya Naznin; Ravi Shankar, A. U.; Mohan, Mithun
Road traffic accidents (RTAs) significantly impact a country's economic advancement by consuming a large portion of its Gross Domestic Product (GDP), especially in developing countries. The proportionality of road accidents with urbanization mandates road accident cost analysis as a prime component in the planning and designing of road projects. The quantification of accidents and their associated parameters remains challenging, as it demands a meticulous approach. Moreover, allocation towards road safety infrastructure should be based on a cost-benefit analysis to ensure the most efficient use of available resources in formulating road safety policies, reinforcing the significance of road accident cost estimation. Different countries use varying methodologies for this estimation, rendering international comparisons unreliable. Notably, the existing methodologies mainly focus on developed countries, leaving a gap in the literature for developing nations. Human Capital (HC) and Willingness to Pay (WTP) are two commonly used approaches for estimating accident costs. The HC method, using diverse data sources such as police accident databases, questionnaire surveys, private hospital records, and vehicle garage bills (considering collision types), provides a component-wise breakdown of costs. The RTA cost estimation using the HC method reveals the loss of productivity, accounting for 49% of total costs, as the most significant component. Medical costs comprised 24%, vehicle damage 10%, human costs 16%, and administrative costs accounted for a mere 1%. However, this method overlooks intangible factors like pain, grief, and suffering (PGS) along with the contribution of post-retirement victims and caregivers of RTA victims. In contrast, the WTP-stated preference methodologies, Contingent Valuation (CV), and Discrete Choice Experiments (DCE) used in this study provide insight into the intangible costs, although with varying degrees of accuracy. Notably, WTP-CV estimates tend to have a lower bound, whereas WTP-DCE estimates are substantially higher. WTP-CV payment card approach reveals that accident costs are mostly influenced by population and risk reduction, with socioeconomic factors and driving behaviour also playing a major role. Meanwhile, the WTP-DCE method indicates that travel attributes have a greater impact on WTP than socioeconomic factors. Taking into account the limitations of both HC and WTP, a Hybrid method is proposed. This approach modifies the conventional HC method by incorporating the concept of Value of Statistical Life (VSL) to account for intangibles such as PGS. It also acknowledges the contributions of post-retirement victims and caregivers of RTA victims. The VSL concept, in conjunction with the Maximum Abbreviated Injury Scale (MAIS), enables a more comprehensive cost estimation, with PGS comprising 56% of total costs in the Hybrid method. In contrast, the productivity loss is reduced to 17%, ensuring the method is not solely focussed on lost productivity. Considering the nation's economic situation, using the weighted average method, the VSI for grievous and minor injuries was determined to be 19.4% and 3.6%, respectively, which can be implemented in regions with similar socioeconomic profiles. A Python-based program is developed, making this methodology more accessible and applicable. This tool can evaluate the severity of an accident, computing the resultant loss. A similar tool is also developed for calculating court-awarded compensations. The comparison results indicate that the cost and compensation differences are substantial and that compensation is typically less than the RTA cost, as it is predominantly based on the subjective judgment of the court. Using an expert opinion survey, the Hybrid method was adjudged as the best suited method for RTA cost estimation for accidents of different severity as more than 60% of the experts chose the RTA cost estimated using the Hybrid method over the other methods across various test scenarios. In conclusion, while the Hybrid methodology provides a more holistic perspective of accident costs, it still provides an estimate with a lower bound. This study does not consider some costs, such as infrastructure damage and traffic congestion. However, the approach highlights the imperative need to comprehend and estimate the true economic and intangible effects of road accidents, particularly in developing nations.
Prawn Exoskeleton Derived Calcium Phosphates and their Composites for Bone Regeneration
(National Institute of Technology Karnataka, Surathkal., 2024) Perabathula, Satish; Mandal, Saumen
In the present study, various calcium phosphates like hydroxyapatite (HA), biphasic calcium phosphates (BCP) and β-tri calcium phosphate (β-TCP) were synthesized from prawn (Fenneropenaeus Indicus) exoskeleton powder. The obtained calcium phosphates were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photo electron spectroscopy (XPS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA). The calcination temperature of 723 C was appropriate for the thermal decomposition of calcite to calcium oxide (CaO). Hydroxyapatite and biphasic calcium phosphates are derived from prawn shell biowaste through a wet chemical treatment of CaO. Hydroxyapatite dense scaffolds sintered at 1100 C showed compressive strength of 26.5 MPa. In biphasic calcium phosphates, the specimens sintered at 1100 C showed the compression strength of 56.8 MPa. X-ray diffraction (XRD) pattern revealed the phase-pure crystalline rhombohedral crystal structure of β-TCP with an average crystallite size of ~25.8 nm, prepared at 1100 C through solid state reaction approach with Ca:P ratio of 1.5. Furthermore, the SEM and EDS opened up well sintered uniaxial grains and the presence of trace elements like Fe, Mg, Si, and Na. A major objective of this work is to explore the mechanical properties of calcium phosphates and their composites with clay. In this study, a cost-effective method to prepare HA-clay composite was demonstrated via the mechanical mixing method, where kaolin and bentonite were used, because of their biocompatibility. Addition of 20 % kaolin to HA enhanced the compressive strength by 33.7 % and addition of 30 % bentonite to HA enhanced the compressive strength by 6 times when compared with bare HA.
Investigation on Synergistic Effect of Biomineralization and Ash-Based Soil Stabilization
(National Institute of Technology Karnataka, Surathkal, 2023) Kothuri, Mahindra; Devatha, C. P.
Waste management is an intricate and pressing global challenge that demands our immediate attention and concerted efforts to address the environmental impacts resulting in widespread pollution and adverse effects on human health. To combat these challenges, it is imperative to develop innovative and eco-friendly solutions that mitigate the negative consequences of waste and promote sustainable practices for a cleaner and healthier future. Waste materials, including biomedical ash and ferrochrome ash, contain toxic heavy metals such as Pb, Ni, and Cr, which pose risks to the environment and human health. Hence, the present study aims to assess the effect of biomineralization to immobilize the heavy metals and allowing the safe application of biomedical ash (BMA) and ferrochrome ash (FCA) in enhancing the properties of black cotton soil (BCS). The research objectives encompass evaluating microbial growth in waste ashes, identifying the optimal protein source for bacterial urease production, optimizing nutrient medium composition for enhanced biomineralization, and analyzing the impact of biomineralization on the engineering properties of waste ashes as environmentally friendly soil stabilizers. To address these objectives, a three-stage methodology has been adopted. In the first stage, the investigation focused on the presence of bacteria in waste ashes. Indigenous urease-positive bacteria were isolated using the serial dilution technique with Christensen's agar medium and identified through 16SrRNA analysis. The study identified Bacillus cereus and Lysinibacillus sphaericus as suitable urease-positive bacteria for biomineralization in BMA and ferrochrome ash FCA, respectively. The performance of different legumes as protein sources were compared by monitoring pH, optical density, and urease activity over time. Blackgram and soybean were identified as the most suitable protein sources for bacterial growth and urease activity. The second stage of the research involved integrating biomineralization into biomedical ash for stabilizing black cotton soil. Response surface methodology (RSM) using a central composite design (CCD) was employed to model the role of protein, vitamin, and carbon sources in urease activity. The study determined the optimal combination ii of 23.47 g/L black gram, 3.45 g/L yeast extract, and 0.03 g/L dextrose while also observing that the dosage of protein and vitamin sources significantly impacted bacterial growth and urease activity. The production of mineralized biomedical ash consisted of combining equimolar urea & calcium chloride (1 M) and the acquired bacteria with biomedical ash. Leachate extracted from mineralized biomedical ash demonstrated reduced concentrations of Hg (97 %), Cr (96 %), Zn (97 %), Pb (93 %), Fe (94 %), Cu (93 %), Cd (98 %), Ba (87 %), As (96 %), Ti (88 %), and Se (86 %), indicating the effectiveness of biomineralization in immobilizing heavy metals. To assess the influence of mBMA on soil characteristics, black cotton soil (BCS) was subjected to different proportions (10 %, 20 %, 30 %, and 40 %) of mBMA. At 40 % soil replacement (m40) by mBMA, the soil’s liquid limit (LL), plastic limit (PL), plasticity index (PI), and free swell index (FSI) were 47 %, 34 %, 13 %, and 14 %, respectively. The corresponding values in the same order are 53 %, 25 %, 27 %, and 114 % for BCS. The optimal moisture content (OMC) shifted from 22 % for BCS to 26 % for m40. The corresponding maximum dry density (MDD) reduced from 1.596 g/cm3 for BCS to 1.458 g/cm³ for m40. These values indicate improved soil consistency and reduced compressibility due to adding mBMA to BCS. Notably, the highest unconfined compressive strength (UCS) of 147 kPa was observed for m30 (30 % BCS replaced with mBMA). UCS of BCS was determined as 35 kPa. Characterization studies (XRD, FEGSEM, FTIR, TGA) were conducted on mBMA. X-ray diffraction analysis detected significant amounts of calcite while scanning electron microscope images revealed the presence of dense matter connecting the ash particles, which was identified as calcite formed during biomineralization. Fourier transform infrared absorption bands corresponding to carbonates further supported the occurrence of biomineralization. A 10 % weight reduction in the characteristic thermal decomposition range for calcium carbonate also confirmed its presence due to biomineralization. Calcite was identified in mBMA through XRD, with peaks observed at 23.03 °, 29.38 °, 25.47 °, 31.34 °, 35.98 °, 39.41 °, 43.15 °, 45.44 °, 48.48 °, and 57.40 °. Dense matter connecting the ash particles was observed in FESEM images of mBMA. It is believed to be the calcite formed during biomineralization. The carbonate presence was backed iii by the FTIR absorption bands at 711.6 cm-1, 873.6 cm-1, and 1420.3 cm-1. A 10% weight reduction in the characteristic thermal decomposition range (570 °C to 660 °C) for calcium carbonate confirmed its advent during biomineralization. In the third stage of the present study, FCA was employed in conjunction with biomineralization to stabilize BCS. Through optimization of the quadratic model, an ideal combination of 20 g/L soybean, 3 g/L yeast extract, and 0.125 g/L dextrose was determined for maximum optical density (1.946) and urease activity (27 m.mol urease/min). To stabilize the black cotton soil, soil bacteria were used with ferrochrome ash. The study involved assessing the extent to which ferrochrome ash could replace the black cotton soil and analyzing the impact of bacterial optical density, urea, and calcium chloride on enhancing the soil's unconfined compressive strength. The soil composite with the highest UCS of 350 kPa (TC5) comprised 40 % FCA, a bacterial medium with an optical density of 1.12, 0.5 g urea, and 0.5 g calcium chloride. A quadratic model was employed to investigate the impact of ferrochrome ash, bacterial density, calcium chloride, and urea concentrations on the unconfined compressive strength. The model indicated FCA as the primary contributor for the UCS improvement. The leachate of TC5 demonstrated reductions in heavy metal concentrations with efficiencies of 95% for Ni, 97% for Cu, 98% for Fe, 99% for Cr and Zn, and 100% for Pb, Cd, Ti, Hg, and As. The XRD analysis of TC5 revealed peaks at 20.61 °, 26.39 °, 28.08 °, 29.20 °, 31.08 °, 36.29 °, 39.21 °, 42.20 °, 43.16 °, 49.92 °, and 55.17 °. Additionally, peaks of FCA were observed at 28.32°, 40.54 °, and 50.23 °, while peaks of BCS were observed at 20.96 °, 26.72 °, 36.63 °, 39.58 °, 40.41 °, 42.53 °, 45.92 °, and 50.24 °. SEM of TC5 contained rhombohedral crystals of calcium carbonate and spherical particles of FCA on the flaky surface of the clayey soil. The FTIR profile of TC5 contained a characteristic absorption band for carbonate at 1457 cm-1, which was absent in the spectra of BCS and FCA. Other bands at 993 cm-1 and 1633 cm-1 indicate C-S-H formation. TGA analysis of TC5 exhibited an 18% weight loss in the temperature range iv of 590 °C to 810 °C, indicating the decomposition of calcium carbonate formed during biomineralization. These findings have important implications for waste management strategies, providing valuable insights into the potential of BMA and FCA with biomineralization in mitigating environmental risks and deriving value from waste.