| 1. |
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| 2. |
- Chandra, Rohit, et al.
(författare)
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A Link Loss Model for the On-body Propagation Channel for Binaural Hearing Aids
- 2013
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 61:12, s. 6180-6190
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Tidskriftsartikel (refereegranskat)abstract
- Binaural hearing aids communicate with each other through a wireless link for synchronization. A propagation model is needed to estimate the ear-to-ear link loss for such binaural hearing aids. The link loss is a critical parameter in a link budget to decide the sensitivity of the transceiver. In this paper, we have presented a model for the deterministic component of the ear-to-ear link loss. The model takes into account the dominant paths having most of the power of the creeping wave from the transceiver in one ear to the transceiver in other ear and the effect of the protruding part of the outer ear called pinna. Simulations are done to validate the model using in-the-ear (ITE) placement of antennas at 2.45 GHz on two heterogeneous phantoms of different age-group and body size. The model agrees with the simulations. The ear-to-ear link loss between the antennas for the binaural hearing aids in the homogeneous SAM phantom is compared with a heterogeneous phantom. It is found that the absence of the pinna and the lossless shell in the SAM phantom underestimate the link loss. This is verified by the measurements on a phantom where we have included the pinnas fabricated by 3D-printing.
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| 3. |
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| 4. |
- Chandra, Rohit, et al.
(författare)
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An Analytical Link Loss Model for On-Body Propagation Around the Body Based on Elliptical Approximation of the Torso with Arms' Influence Included
- 2013
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757. ; 12, s. 528-531
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Tidskriftsartikel (refereegranskat)abstract
- An analytical model for estimating the link loss for the on-body wave propagation around the torso is presented. The model is based on the attenuation of the creeping waves over an elliptical approximation of the human torso and includes the influence of the arms. The importance of including the arms’ effect for a proper estimation of the link loss is discussed. The model is validated by the full-wave electromagnetic simulations on a numerical phantom.
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| 5. |
- Chandra, Rohit, et al.
(författare)
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An Approach to Analyze the Movements of the Arms while Walking using Wearable Wireless Devices
- 2013
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Ingår i: [Host publication title missing]. - 1557-170X. ; , s. 3435-3438
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Konferensbidrag (refereegranskat)abstract
- Abstract—Rhythmic movement of the arms while walking is an important feature of human gait. In this paper, we present an approach to analyze the movements of the arms while walking by using three wearable wireless devices placed around the torso. One of the devices is transmitter placed at the back and the other two are symmetrically placed receivers that record the power variation due to movements of the arms while walking. We show that the power received by the receivers will have symmetrical variation if the arms’ swing is symmetrical. An analytical model has been used to calculate the position of the receivers. Full wave simulations on a walking phantom are done to confirm the results.
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| 6. |
- Chandra, Rohit, et al.
(författare)
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An elliptical analytic link loss model for wireless propagation around the human torso
- 2012
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Ingår i: 6th European Conference on Antennas and Propagation (EUCAP), 2012. - 9781457709180 ; , s. 3121-3124
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Konferensbidrag (refereegranskat)abstract
- A simple analytical model for the link loss between two very low profile wireless body area network transceivers located at the same level on the human torso is presented. The model is based on the attenuation of the creeping waves on an elliptical approximation of the human torso. A good agreement between the model and the FDTD simulations on realistic heterogeneous phantoms of different age and body-size is obtained.
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| 7. |
- Chandra, Rohit, et al.
(författare)
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Analytical On-Body Propagation Models for the Channel around the Body based on Attenuation of Creeping Waves over an Elliptical Surface
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Wireless wearable medical devices located on the opposite side of the body communicate through creeping waves. The creeping waves undergo exponential attenuation with distance. Hence, an analytical propagation model is useful to estimate the link loss for a reliable link. In this document, we have presented analytical link loss models for the wireless propagation channel between the devices located around the body such as: (a) around the torso and (b) in the ears for hearing aids. Initially, a model is developed based on attenuation of creeping waves over an elliptical approximation of the body. This model is then extended for the ear-to-ear propagation and around the torso propagation cases. The presented models are validated through full wave electromagnetic simulations done with numerical phantoms. A good agreement between the analytical models and the simulations is obtained showing the applicability of the models to estimate the link loss for around the torso and ear-to-ear propagation.
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| 8. |
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| 9. |
- Chandra, Rohit, et al.
(författare)
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Antennas and Propagation for In-Mouth Tongue Controlled Devices in Wireless Body Area Networks
- 2015
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757. ; 14, s. 1518-1521
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Tidskriftsartikel (refereegranskat)abstract
- Tetraplegic patients have to depend upon someone else for moving the wheelchair or typing on a computer. One of the ways to make them independent is by using tongue-controlled in-mouth wireless devices. This letter presents antennas and propagation for such devices in 2.45 GHz ISM band. A monopole and a loop antenna suitable in size and performance is presented for such devices. The propagation link between the in-mouth antenna and an external antenna is measured by mimicking the use-case scenarios of such devices by placing an external antenna on a laptop, and on a chair. The link loss is found to be in the range of 55-75 dB depending upon the antenna type and the scenario. Using these values of the link loss, a reliable link can be established between the in-mouth device and the external device either mounted on a wheelchair or a computer.
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| 10. |
- Chandra, Rohit, et al.
(författare)
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Antennas and Propagation for the Ear-to-Ear Propagation Channel for Binaural Hearing Aids
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We have investigated the possibility of using the 2.45 GHz ISM band for communication between binaural hearing aids. The preliminary investigations were done by FDTD simulations on a modified SAM phantom head, where we have included a simple model of the ear canal. Two different types of hearing aid placements have been investigated: in the outer ear and in the ear canal. Antennas which have been miniaturized by applying disc loads and high permittivity materials were used for estimating the ear-to-ear link loss. The outer ear placement gives a total link loss of 48 dB and the placement in the ear canal gives a total link loss of 92 dB. Since the preliminary investigation indicated that the loss in the outer ear placement is low enough to support low power communication at 2.45 GHz, this configuration was chosen for further investigation on realistic heterogeneous human phantoms with proper electrical properties of all the tissues in the head. It was found that the antenna detunes differently for the different realistic phantoms and different ears within the same phantom. It was also found that the ear-to-ear link loss was 30 dB higher in a realistic heterogeneous phantom (named Duke of a 34 year old male) than in the SAM phantom. This was mainly due to the presence of an outer lossy layer (skin) and outer ears (pinna) in the Duke phantom. Other factors which may affect the ear-to-ear propagation channel like shoulders, metallic glass frame and size of the head have also been investigated.
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| 11. |
- Chandra, Rohit
(författare)
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Antennas, Wave Propagation, and Localization in Wireless Body Area Networks
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A network of communicating wireless devices that are implantable, wearable or within close proximity of a human body is called wireless body area network (WBAN). The propagation channels for the devices in the WBAN are either through the body or over the body. This results in the attenuation and the absorption of electromagnetic waves radiated by the antenna of these devices due to the lossy tissues of the body. With a proper antenna and knowledge of the signal loss between the devices in the WBAN, a reliable wireless link can be designed. This thesis presents the investigations done for the antennas, wave propagation, and localization for various applications of these networks. The investigated applications are: (1) Binaural Hearing Aids (Paper I \& Paper II), (2) Sensor placed Around the Body (Paper III \& Paper IV), (3) Localization of Wireless Capsule Endoscope (Paper V), and (4) In-Mouth Devices. Binaural hearing aids communicate with each other for synchronization such as adjustment of volume or programing for the listening environment. In Paper I, antennas suitable in size and technical performance at 2.45 GHz for in-the-ear (ITE) and in-the-canal (ITC) placement of the hearing aids are presented. The ear-to-ear link loss found from the finite-difference-time-domain (FDTD) simulations for the ITE case was 48 dB and that for the ITC case was $92$~dB for the SAM head. The ITE case was further investigated on realistic heterogeneous phantoms of different age and head sizes. The link loss in the ITE case for an adult heterogeneous phantom was found to be $79$~dB. It was found that the absence of the pinna (outer ear) and the lossless shell under-estimates the link loss for the SAM phantom. Hence, a phantom with the lossy outer shell and the pinnas should be used for a proper estimation of the ear-to-ear link loss. In Paper II, an analytical model is presented for the ear-to-ear link loss based on the attenuation of the creeping wave over an elliptically modeled cross-section of the head. The model takes into account the dominant paths having most of the power of the creeping wave from the antenna in one ear to the antenna in the other ear and the effect of the pinnas. Simulations were done to validate the model using the ITE placement of the antenna at 2.45 GHz on heterogeneous phantoms of different age-groups and head sizes, showing a good agreement with the model. The effect of the pinnas was verified through measurements on a phantom where the pinnas fabricated by 3D-printing were included. In Paper III, an analytical model is developed for wireless propagation around the body based on the attenuation of creeping waves over an elliptical cross-section of the torso. The model includes the effect of the arms. It was verified through FDTD simulations on a numerical phantom with various arm positions. It was shown that it is critical to include the effect of the arms as their presence might result in extreme fading dips at some sensor positions. Further, a temporal variation in the power received by sensors placed around the torso was found when the arms moved while walking. This result is used in Paper IV to develop an approach to analyze the movements of the arms while walking using three wearable wireless devices. One of the devices is a transmitter placed at the back and the other two are symmetrically placed receivers at the side that record the power variation due to the arm movements. For such a placement of sensors, the variation in the receiver will be more or less symmetrical if the arm swing normally. However, a large degree of asymmetry in the arms swing will result in an asymmetrical variation in the received power by the two receivers. This was confirmed by simulations and measurements. Wireless capsule endoscopy (WCE) overcomes the problems of conventional endoscopy like not reaching the entire small-intestine. However, due to the lossy tissues, the localization of the capsule is a challenging task which is required in order to know the position of an abnormality captured in the endoscopy image. Paper V presents a method for the localization of an in-body RF source, as in WCE, based on microwave imaging. The electrical properties of the tissues and their distribution were found from microwave imaging at $403.5$~MHz. The method was applied on synthetic data obtained after addition of the white Gaussian noise to the simulated data of a simple circular phantom, and a realistic phantom for the 2D transverse magnetic polarization. The root-mean-square of the error distance between the various actual and estimated positions was found to be within $9$~mm for both the phantoms showing the capability of the algorithm to localize the capsule in the presence of noise with a good accuracy. An in-mouth device is a tongue controlled device used by the paraplegic or quadriplegic patients to control a wheelchair or type on a computer. Although the device is not surgically implanted but the performance of its antenna is influenced by the lossy tissues of the mouth or head in a similar way as that of an implant. In this work, antennas suitable in size and performance for such devices were investigated.
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| 12. |
- Chandra, Rohit, et al.
(författare)
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Directional Analysis of the On-Body Propagation Channels considering Human's Anatomical Variations
- 2012
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Ingår i: BodyNets '12 Proceedings of the 7th International Conference on Body Area Networks. - 9781936968602 ; , s. 120-123
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Konferensbidrag (refereegranskat)abstract
- This paper presents a directional analysis of the on-body propagation channels using the high resolution space alternating generalized expectation (SAGE) maximization algorithm. The analysis has been done on data obtained through FDTD simulations, on a male and a female numerical phantom. For estimating the angle of arrival (AoA) at a four element square array located at the chest, two different positions of the transmitter are considered. The presented results show that the anatomical variations between a male and a female results in different AoA for the same position of the transmitter-receiver pair. Directional analysis of the on-body channels could be used for increasing the reliability of the communication link between on-body devices.
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| 13. |
- Chandra, Rohit, et al.
(författare)
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Effect of Frequency, Body Parts and Surrounding on the On-Body Propagation Channel Around the Torso
- 2012
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Ingår i: 2012 Annual International Conference of the IEEE Engineering in Medicine and Biology Society. - 9781424441198
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Konferensbidrag (refereegranskat)abstract
- Wearable medical devices can be positioned around the torso for monitoring of critical health parameters. The signal transmission between them is through a wireless link over an on-body propagation channel. In this paper, the effect of some factors which could influence the propagation channel around the torso as: (a) frequency of operation (b) positions of the arms (c) material of a chair used, have been investigated. Moreover, a comparison between the link loss around the torso of a full body phantom and a truncated torso phantom has been done. It is found that the frequency of operation and the positions of the arms have a significant influence on the channel. The difference between the link loss of a full body phantom and a truncated phantom is found to be minimal, indicating a possibility of using a truncated torso for a faster simulation. The results presented in the paper gives an insight in to the influence of arms and the frequency of operation on the propagation channel around the torso and thus would be beneficial for designing a reliable wireless link.
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| 14. |
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| 15. |
- Chandra, Rohit, et al.
(författare)
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In-Mouth Antenna for Tongue Controlled Wireless Devices: Characteristics and Link-Loss
- 2011
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Ingår i: [Host publication title missing]. ; , s. 5598-5601
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Konferensbidrag (refereegranskat)abstract
- We have investigated the possibility of using a curved dipole antenna inside the mouth for the tongue controlled wireless devices in 2.45GHz ISM band. These devices can be interfaced with the wheelchair or the computer used by the paraplegic patients. Two antenna placement positions have been investigated: in front of the teeth and behind the teeth. The investigations were done through the FDTD simulations on a realistic heterogeneous phantom with the mouth closed and open. The link loss between the in-mouth dipole antenna and an external dipole antenna at 400mm from the center of the head was calculated. It was found that the radiation pattern changed according to the placement of the antennas inside the mouth and whether the mouth was open or closed. The link loss for the in front of the teeth placement was found to be 9dB-11dB lower than the behind the teeth placement depending on the open or the closed mouth. The variation in the link loss was 1dB-4dB for the open mouth when compared with the closed mouth depending on the antenna placement position. By using these results, a reliable wireless link for the in-mouth device can be designed.
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| 16. |
- Chandra, Rohit, et al.
(författare)
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Influence on the ear-to-ear link loss from heterogeneous head phantom variations
- 2011
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Ingår i: [Host publication title missing]. - 9781457702501
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Konferensbidrag (refereegranskat)abstract
- We have investigated the detuning of the antennas and the ear-to-ear link loss for the in-the-ear (ITE) binaural hearing aids considering the different heterogeneous human phantoms through FDTD simulations. It was found that the resonance frequency shifts differently for different phantoms and between the ears within the same phantom. The ear-to-ear link loss between the antennas for the homogeneous SAM phantom has been compared with a heterogeneous phantom and was found to be 30 dB lower, indicating the presence of a lossless shell and the absence of a pinna in the SAM phantom underestimate the link loss as compared with a realistic phantom.
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| 17. |
- Chandra, Rohit, et al.
(författare)
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Localization of an RF source inside the Human body for Wireless Capsule Endoscopy
- 2013
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Ingår i: - : ACM. ; , s. 48-54
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Konferensbidrag (refereegranskat)abstract
- This paper presents a method based on the phase dierence of arrival and the non-linear least square estimation to lo- calize a radio-frequency (RF) source, e.g a wireless capsule endoscope, inside the human body. The phase dierence of arrival at multiple frequencies of a signal is used to estimate the distance of the source to a receiver. The linear least square estimation is used to estimate the initial position of the source followed by a non-linear least square method to improve the localization accuracy. The method is applied on noise free simulated data obtained from FDTD simulations in the 403.5 MHz MedRadio band of a simple homogeneous phantom and a more realistic heterogeneous phantom. The distance between the true position and the estimated po- sition is found to be within 1 cm for the simulated cases showing the possibility to use the proposed method for lo- calization of an RF source inside the human body, as long as the signal to noise ratio is high enough.
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| 18. |
- Chandra, Rohit, et al.
(författare)
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Miniaturized antennas for link between binaural hearing aids
- 2010
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Ingår i: Annual International Conference of the IEEE Engineering in Medicine and Biology Society.. - 1557-170X. ; 1, s. 688-691
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Konferensbidrag (refereegranskat)abstract
- We have investigated the possibility of using the 2.45 GHz ISM band for communication between binaural hearing aids. The small size of a modern hearing aid makes it necessary to miniaturize the antennas to make this feasible. Two different types of hearing aid placements have been investigated: in the outer ear and in the ear canal. Both put strict demands on the size of the antenna, which have been miniaturized by applying disc loads and high permittivity materials. The investigations have been done by FDTD simulation of a modified SAM phantom head, where we have included a simple model of the ear canal. Simulations show that the outer ear placement is better, as it gives a total link loss of 48 dB. The placement in the ear canal gives a total link loss of 92 dB.
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| 19. |
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| 20. |
- E. Lopez, Ernesto, et al.
(författare)
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3D Printed Miniaturized UWB Antenna for Wireless Body Area Network
- 2014
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Ingår i: 2014 8th European Conference on Antennas and Propagation (EuCAP). - 2164-3342. ; , s. 3090-3093
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Konferensbidrag (refereegranskat)abstract
- A wireless body area network (WBAN) is a network of compact low power devices that are either wearable or implantable. A compact antenna with suitable radiation pattern and polarization is useful for WBAN applications. Ultra-Wideband (UWB) technology can be used in WBAN applications that require high data rates. This paper present a small wearable (15x17x17 mm) UWB antenna designed and optimized in a FDTD full wave simulator. The simulated -10 dB impedance bandwidth is from 4.8 GHz to 29.8 GHz in free space. The lower -10 dB cut-off frequency shifts down to 3.5~GHz when placed on the body. The antenna is vertically polarized with respect to the body which makes it a suitable candidate for on-body to on-body UWB WBAN applications. The antenna was fabricated by 3D printing technology. The measured lower cut-off frequency for an on-body case was found to be 3.6 GHz and the antenna was well-matched in rest of the UWB band.
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| 21. |
- Garcia Lopez, Aida, et al.
(författare)
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Optimization and Fabrication by 3D Printing of a Volcano Smoke Antenna for UWB Applications
- 2013
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Konferensbidrag (refereegranskat)abstract
- Abstract—Ultra-Wideband (UWB) technology is a low power and high data rate technology for applications like radar imaging, sensor data collection, position localization and medical imaging. In UWB systems, antennas plays a critical role as they are required to be compact and wideband with minimal pulse distortion. This paper present a small three-dimensional volcano smoke antenna, designed and optimized in a FDTD full-wave simulator and then fabricated by 3D printing. The antenna has a simulated 10 dB impedance bandwidth from 3.2 GHz to 12.6 GHz, suitable for the UWB band. The measured return-loss for the 3D printed antenna shows a good agreement with the simulations. Hence, 3D printing can be used as an alternative method for fabricating complex shaped three-dimensional antennas.
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| 22. |
- Sharma, Rohit, et al.
(författare)
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Analysis of Water Pollution Using Different Physicochemical Parameters : A Study of Yamuna River
- 2020
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Ingår i: Frontiers in Environmental Science. - USA : Frontiers Media S.A.. - 2296-665X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The Yamuna river has become one of the most polluted rivers in India as well as in the world because of the high-density population growth and speedy industrialization. The Yamuna river is severely polluted and needs urgent revival. The Yamuna river in Dehradun is polluted due to exceptional tourist activity, poor sewage facilities, and insufficient wastewater management amenities. The measurement of the quality can be done by water quality assessment. In this study, the water quality index has been calculated for the Yamuna river at Dehradun using monthly measurements of 12 physicochemical parameters. Trend forecasting for river water pollution has been performed using different parameters for the years 2020–2024 at Dehradun. The study shows that the values of four parameters namely, Temperature, Total Coliform, TDS, and Hardness are increasing yearly, whereas the values of pH and DO are not rising heavily. The considered physicochemical parameters for the study are TDS, Chlorides, Alkalinity, DO, Temperature, COD, BOD, pH, Magnesium, Hardness, Total Coliform, and Calcium. As per the results and trend analysis, the value of total coliform, temperature, and hardness are rising year by year, which is a matter of concern. The values of the considered physicochemical parameters have been monitored using various monitoring stations installed by the Central Pollution Control Board (CPCB), India.
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| 23. |
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| 24. |
- Sjöland, Henrik, et al.
(författare)
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Ultra low power transceivers for wireless sensors and body area networks
- 2014
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Ingår i: 2014 8th International Symposium on Medical Information and Communication Technology (ISMICT). - 2326-828X. - 9781479948567
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Konferensbidrag (refereegranskat)abstract
- A transceiver suitable for devices in wireless body area networks is presented. Stringent requirements are imposed by the high link loss between opposite sides of the body, about 85 dB in the 2.45 GHz ISM band. Despite this, minimum physical size and power consumption are required, and we target a transceiver with 1 mm2 chip area, 1 mW active power consumption, and data rate 250 kbit/s. The receiver is fully integrated., fabricated and measured in 65-nm CMOS, and size and power consumption are carefully considered at all levels of circuit and system design. The modulation is frequency shift keying, chosen because transmitters can be realized with high efficiency and low spurious emissions; a modulation index 2 creates a midchannel spectral notch. A direct-conversion receiver achieves minimum power consumption. A tailored demodulation structure makes the digital baseband compact and low power. The channel decoder has been implemented in both analog and digital domains to find the most power efficient solution. Antenna design and wave propagation are studied via simulations with phantoms. The 2.45 GHz ISM band was chosen as a good compromise between antenna size and link loss. An ultra-low power medium access scheme based on a duty-cycled wake-up receiver is designed.
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