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  • 1.
    Alayón Glazunov, Andrés
    et al.
    Division of Electromagnetic Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Prasad, Sathyaveer
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Signal Processing Lab, KTH Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    ACCESS Linnaeus Centre; Signal Processing Lab, KTH Royal Institute of Technology, Stockholm, Sweden.
    Experimental Characterization of the Propagation Channel along aVery Large Virtual Array in a Reverberation Chamber2014Inngår i: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 59, s. 205-217Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We show that the combined use of radio frequency absorbers and directive antennas can produce significant changes of the radio propagation channel properties along the positions of a virtual array inside a reverberation chamber. A multidimensional characterization of the channel was performed at 40 antenna positions with spacing of 0:233λ at 1 GHz. The average power, the Ricean K-factor, the coherence bandwidth, the r.m.s. delay spread, the mean delay, the beamforming power angle spectrum and array antenna correlation have been studied for different arrangements in the reverberation chamber. The analysis shows that the joint average over time and frequency channel behavior is, as expected, rather homogeneous along the very large array. However, individual realizations of the channel present a pronounced selective behavior in space, time and frequency with parameters varying along the positions of the virtual array suggesting that a heterogeneous behavior of the radio channels can be emulated in reverberation chambers. An important application of the presented study comprises testing of antenna array designs and algorithms in multipath environments. Further development may lead to Over The Air testing of Multiple Input Multiple Output antenna systems of various sizes, i.e., from small to very large arrays.

  • 2.
    Ghahfarokhi, Sohil Shahabi
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Prasad, Sathyaveer
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Tayari, Danial
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Impact of Moisture Content on RFID Antenna Performance for Wood-Log Monitoring2011Inngår i: RFMTC11, Gävle, Sweden, 2011Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In recent years, the use of RFID technology has gained popularity in the timber industry for wood-log monitoring. Harvested wood-logs are stored for different time periods before being processed. As a result, the moisture content in the stored wood-logs varies compared to the freshly-cut wood and it must also be noted that the moisture content of freshly cut wood differs from one log to another. Apart from storage time period of wood-logs, the environmental factors such as temperature, rain, snow and sun also contributes to the variation in the moisture content of the wood-logs. This variation of the moisture content changes the dielectric constant of the wood and hence, influences the characteristics of the RFID antenna. In this paper the impact of variations in moisture content in wood and its effect on the performance of the RFID antenna are studied.

  • 3. Glazunov, Andres Alayon
    et al.
    Prasad, Sathyaveer
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH.
    Händel, Peter
    Bolin, Thomas
    Prytz, Kjell
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Fysik.
    Impact of Scattering Within a Multipath Simulator Antenna Array on the Ricean Fading Distribution Parameters in OTA Testing2014Inngår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 62, nr 6, s. 3257-3269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we investigate the unwanted scattering that exists within the multipath simulator (MPS) array antennas employed in over the air (OTA) testing of mobile terminals. The impact of scattering is evaluated in terms of the measurement uncertainty of the average received power and the Ricean K-factor. The maximum ratio combining diversity is investigated for a generic device under test comprising two half-wavelength dipole antennas. We provide closed-form expressions for the uncertainties of the average received power and the Ricean K-factor for a uniform circular array of MPS antennas and a 2-D uniformly distributed angle-of-arrival spectrum. We also derive the maximum number of MPS antennas and the minimum ring radius of the MPS system as a function of the separation between the most distant antenna elements if the device under test employs a uniform linear array. As a result, we provide design guidelines for MPS array in terms of the number antennas, the radius of the MPS array and the wavelength of the carrier frequency.

  • 4.
    Händel, Peter
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Högskolan i Gävle, Radio Center Gävle. Royal Institute of Technology, Signal Processing Lab, ACCESS Linnaeus Centre, Stockholm, Sweden.
    Prasad, Sathyaveer
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Högskolan i Gävle, Radio Center Gävle. Royal Institute of Technology, Signal Processing Lab, ACCESS Linnaeus Centre, Stockholm, Sweden.
    Beckman, Claes
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Högskolan i Gävle, Radio Center Gävle.
    Maximum likelihood estimation of reverberation chamber direct-to-scattered ratio2009Inngår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 45, nr 25, s. 1285-1286Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The exact maximum likelihood estimator of the direct-to-scattered ratio of the Rician channel in a reverberation chamber is derived and its performance analysed. It is shown that the estimator obeys a non-central F-distribution, the mean value and variance of which are derived. For well stirred chambers, it is shown that the systematic error in the estimated ratio may be significant.

  • 5.
    Prasad, Sathyaveer
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH, Signalbehandling.
    Over-the-Air Performance Estimation of Wireless Device Antennas2013Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis work presents studies on the available measurement methods for estimating the over-the-air (OTA) performance of wireless device antennas. This thesis is divided into two parts. The first part is focused on studies of single-input single-output (SISO) OTA measurement methods and the second part is focused on studies of multiple-input multiple-output (MIMO) OTA measurement methods.

    In the first part, the three methods for estimating the up-link radio performance of mobile phone antennas are evaluated, including the “EMSCAN Lab Express” planar near-field system, the “Telia Scattered Field Measurement method (TSFM),” and the “Bluetest” reverberation chamber. These methods are compared to the standard reference anechoic chamber methods.

    Each method is experimentally evaluated by measuring the total radiated power from a number of commercially available mobile phones in addition to comparing the measurements to the results from a standard reference system. The comparison is performed statistically using simple regression analysis. For the reverberation chamber (RC), applying simple physical and statistical modeling extends the analysis. In particular, a maximum likelihood (ML) estimator for the Rician K−factor is derived, followed by both statistical and experimental evaluations.

    Based on the results of the first part of this thesis, it can be concluded that the EMSCAN Lab Express planar near-field method overestimates the uplink performance of mobile phones, consequently introducing an error. The up-link performance of mobile phones estimated using the TSFM method agrees with the reference method but suffers from problems such as extensive measurement time and poor repeatability. The Bluetest RC method estimates the uplink performance of mobile phones well. However, the Rician K−factor computed from the ML estimator is found to be greater than zero, indicating an inadequacy in the propagation environment inside the RC.

    In the second part, the anechoic chamber-multipath simulator (MPS) and the RC-very large MIMO (VLM) OTA testing methods are studied.

    In the MPS method, the impact of scattering within the MPS array antennas on the Rician fading statistics is addressed by performing simulations and measurements based on the proposed MPS scattering model and the derived far-field criteria. The results of the investigation suggest that to minimize the impact of scattering, a large MPS system must be designed, although it will result in higher costs. In turn, the costs can be lowered by miniaturizing the MPS system, which can be achieved by following the derived far-field (Fraunhofer distance) criteria. Thus, miniaturization will also allow the measurement uncertainties to be restricted at an acceptable level.

    In the VLM OTA testing method, the study is based on very large virtual uniform linear array measurements and focuses on the multidimensional characterization of the channel transfer function and the channel impulse response of the reverberation chamber. The results of this study suggest that the reverberation chamber can be used to emulate the more realistic channels for testing the VLM antenna systems.

  • 6.
    Prasad, Sathyaveer
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Studies of Three Different Methods to Estimate the Up-link Performance of Mobile Phone Antennas2011Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Antennas play an important role in determining the overall radio performance for wireless communications. If all other radio components perform according to their specifications, the performance of a mobile phone can be entirely determined by measuring the efficiency of its antenna. Poor performance of the mobile phone may result in reduced coverage, lower capacity and dissatisfied users. Hence, the ability to accurately and efficiently estimate the radio performance of the mobile phone antenna is of great importance to the telecommunications industry.

    The mobile phone was originally a simple device that only transmitted voice, but it has evolved into a complicated terminal for high data-rate services. This evolution poses many new challenges to mobile phone antenna manufacturers. Antennas must be tested during design and production phases to optimize the in-network radio performance. Standardization bodies, such as the Cellular Telecommunications and Internet Association (CTIA) and the Third Generation Partnership Project (3GPP), have specified procedures for comprehensive testing of the up-link and down-link radio performance of the mobile phone, characterized by the total radiated power (TRP) and total isotropic sensitivity (TIS), respectively.

    In this thesis, three methods for estimating the up-link radio performance of mobile phone antennas are evaluated: the "EMSCAN Lab Express" planar near field system; the "Telia Scattered Field Measurement method"; and the "Bluetest" reverberation chamber. These methods are compared to the reference CTIA- and 3GPP-approved anechoic chamber methods. Each method is experimentally evaluated by measuring the TRP from a number of commercially available mobile phones and comparing the measurements to the results from a standard reference system. The comparison is performed statistically using simple regression analysis. For the reverberation chamber, the analysis is extended by using simple physical and statistical modeling. In particular, a maximum likelihood (ML) estimator for the Rician K factor is derived, statistically and experimentally evaluated.

    Based on the results of this thesis, it can be concluded that the EMSCAN Lab Express planar near field method overestimates the up-link performance of mobile phones, thus, introducing an error. The up-link performance of mobile phones estimated by the Telia scattered field measurement method agrees with the reference method, but suffers from problems such as extensive measurement time and poor repeatability. The Bluetest reverberation chamber method estimates the uplink performance of mobile phones well. However, the computed Rician K factor from the ML estimator is found to be greater than zero, indicating an inadequacy in the propagation environment inside the reverberation chamber. 

  • 7.
    Prasad, Sathyaveer
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Beckman, Claes
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Comparison of Four Different Methods to Estimate the Radiated Power from Mobile Phones2010Inngår i: 2010 Loughborough Antennas and Propagation Conference, LAPC 2010, 2010, s. 425-428, artikkel-id 5666216Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this paper, the radiated power is estimated for various commercially available mobile phones using the Telia Scattered Field Measurement method (TSFM), In-Network performance estimation and the EMSCAN near field scanner: "Lab-Express". The results are then compared with the radiated power measured using the Satimo Star Gate 64/24 system. Our measurement results suggest that the radiated power measured in the TSFM method correlates to a great extent both with the Star Gate System and the In-network method suggesting that the TSFM method can be used an alternative tool to in-network measurements and also can be used for standard reference measurements provided accuracy and repeatability are accounted according to the standards. However, the results from the Star Gate system were weakly correlated to the results from the Lab-Express suggesting that Lab-Express cannot replace Star Gate System for standard reference measurements but can only serve as a good tool for testing antennas during design and development phases.

  • 8.
    Prasad, Sathyaveer
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Högskolan i Gävle, Radio Center Gävle.
    Halim, Humam
    Beckman, Claes
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Högskolan i Gävle, Radio Center Gävle.
    Evaluation of a Near Field Scanner for TRP and Radiation Pattern Measurements of GSM Mobile Phones2009Inngår i: 3RD EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION, IEEE conference proceedings, 2009, s. 2122-2126Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this paper a new tool for estimation of the radio performance of terminal antennas in terms of Total Radiated Power, TRP is tested and evaluated. The tool is known as Lab Express and is developed by the Canadian company EMSCAN.  The results from measurements performed with the Lab Express are compared with of the radiation patterns and total radiated power (TRP) estimates, measured with a CTIA approved Satimo SG24 chamber.

    The TRP and radiation pattern measurements are performed on 10 commercially available mobile phones at GSM 900 and GSM 1800 frequency bands. The dependency of the measured TRP on the positioning of the mobile phone on EMSCAN is also tested. Our results indicate that the TRP measured with Lab Express is well correlated with the results obtained from the Satimo SG24 chamber even though the Lab Express equipment seem to over estimate the TRP with on average about 4dB at 900MHz and about 1.3dB at 1800MHz.

  • 9.
    Prasad, Sathyaveer
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Medawar, Samer
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Händel, Peter
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Beckman, Claes
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Estimation of the Rician K-factor in Reverberation Chambers for Improved Repeatability in Terminal Antenna Measurements2008Inngår i: 30th Annual Symposium of the Antenna Measurement Techniques Association (AMTA), Boston, Mass.: AMTA-2008 , 2008, s. 6-Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The in-network performance of the mobile phone depends highly on the terminal antennas. Their performance may reduce the coverage and the capacity of the whole network. Hence, an antenna measurement method that accurately emulates the in-network radio environment is much desired.

    The reverberation, or mode-stirred, chamber is a cavity resonator with a high Q factor used for testing the performance of terminals and terminal antennas in a controlled field environment. In order to create a homogeneous field inside the chamber, emulating an isotropic multipath environment, mode stirrers are used.

    The Rician K-factor is a statistical parameter that describes the field distribution in the chamber and is defined as the ratio of the unstirred to stirred field components in the chamber. This K-factor varies from zero to infinity. In order to be able to accurately repeat a measurement performed in a reverberation chamber it is, hence, of greatest importance to accurately determine the Rician K-factor from said measurements.

    In this paper, a statistical model for the electromagnetic fields in reverberation chamber is reviewed for a Line of Sight (LOS) environment. An Estimator of the Rician K-factor is derived and its accuracy is verified.

  • 10.
    Prasad, Sathyaveer
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Ramachandran, Prasad
    Högskolan i Gävle, Radio Center Gävle.
    Mean Effective Gain Measurements of Mobile Phones using the Telia Scattered Field Measurement Method2007Inngår i: RFMTC07: The Conference on RF Measurement Technology for State of The Art Production and Design, Stockholm: KTH , 2007, s. 7-Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this paper, the measurement procedure for estimation of mobile phone antenna performance is presented. This is achieved by considering the Mean Effective Gain (MEG) relative to half-wavelength dipole antenna as the figure of merit. MEG of 13 commercially available mobile phones is measured using the Telia Scattered Field (TSFM) Method in one channel at each of the GSM900 and DCS1800 bands. The measurements of these handsets are carried out in Rayleigh fading environment, characterized by the XPR obtained from the propagation measurements. The statistics of the measured envelope distribution have been fitted to Rayleigh, Rice and Weibull distributions with corresponding goodness of fit analysis. Further, the investigation focuses on the variation of MEG with the surrounding environment of propagation and also with the position of the mobile phone.

  • 11.
    Prasad, Sathyaveer
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Högskolan i Gävle, Radio Center Gävle.
    Ramachandran, Prasadh
    Glazunov, Andres Alayon
    Beckman, Claes
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Högskolan i Gävle, Radio Center Gävle.
    EVALUATION OF THE TELIA SCATTERED FIELD MEASUREMENT METHOD FOR ESTIMATION OF IN-NETWORK PERFORMANCE OF MOBILE TERMINAL ANTENNAS2007Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this paper we present and evaluate a method for estimation of in-network performance of mobile terminal antennas developed by the Swedish telecom operator Telia.

    The Telia Scattered Field Measurement (TSFM) Method is intended to give a better estimate of the performance of the mobile terminal antenna as in an in-network fading scenario. The parameter measured from the TSFM method is referred to as the Scattered Field Measurement Gain, SFMG, i.e. the Mean Effective Gain, MEG, measured relative to a half wave dipole antenna. MEG includes the radiation pattern of the mobile terminal antenna as well as an estimate of polarization and directional losses that occur due to the propagation environment.

    In this study it is found that the TSFM method provides a good measure of the in-network performance of the mobile terminal antenna. Furthermore, it is shown that the SFMG measured with this method is found to be well correlated with the Total Radiated Power Gain, TRPG, or radiation efficiency. This suggests that the Total Radiated Power, TRP, may be a good measure of the in-network performance of mobile terminal antennas if measured with proper adjustment to the antenna and propagation channel mismatch.

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