Publications
Books and Monographs: | Weitzen, Jay, Raghothaman, Balagi and Srinivas, Annand , “Managing Coverage and Interference in UMTS Femtocell Deployments” in Deploying UMTS and LTE, March 2010, CRC press
Weitzen, J.A, Wallace M.S. Antenna Issues in the deployment of Next Generation Wireless Systems. Klewer Academic Publishers, Boston, Ma, 2000
Weitzen, J.A., Meteor Scatter Communication: A New Understanding, Chapter 1 of “Meteor Burst Communications Theory and Practice”, Edited by D.L. Schilling, John Wiley, New York, 1993, pages (9-58)
Weitzen, J.A., J.D. Larsen, and R.S. Mawery, “Network Contention Issues in the Design of very Large Meteor Scatter Networks for Vehicle Tracking and Communication”, Wireless Communications, Future Directions, ed J. Holtzman and D. Goodman, Klewer Academic Publishers, Boston, Ma, 1993
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US Patents: | Parl, S.A., Bussgang J.B.,Weitzen, J.A., and J.A. Zagami, A novel technique for position location using angle or arrival and time difference of arrival, US Patent 5,883,598, March 16, 1999
Parl, S.A., Bussgang, J.B, Weitzen, J.A and J.A. Zagami, “Position Location System and Method, US Patent 6,259,404, B1, July 10,2001
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Journal Papers: | Wang, Jiao, Jay Weitzen, Oguz Bayat, Volkan Sevindik, Mingzhe Li, “Joint Interference Coordination approach in femtocell networks for QoS performance optimization”, International Journal of Communication Systems, January 2017,
Weitzen, J.A. and Grosch T. “Measurements of Inter-Femtocell Reverse link interference”, Journal of Electrical Engineering, Vol 3, Number 4, April 2016
Jay Weitzen, Nathan Sutter, Rachel Wakim, and Ali Alkhatabih, “First Measurements of Cloud-RAN LTE Smallcells in an Indoor Stadium”, Journal of Selected Areas in Telecommunications, April 2016 Weitzen, J.A. and Wakim R.E, “Using Informatics to Manage and Measure Performance of Large Femtocell Networks”, Journal of Data Analysis and Information Processing (JDAIP) April 2015
Jay Weitzen, Erik Anderland, Mingzhe Li, Vedat Eyhlebu, “Deploying Large Femtocell Networks Approaching 1 Million Units”, Proceedings of the IEEE, November 2013
Volkan Sevindik, Oguz Bayat, Jay Weitzen, Scheduler design for traffic classification in CDMA2000 1xEVDO network. Wireless Networks 01/2011; 17:1731-1744.
Siva Sivananthan, Jay Weitzen, “Sub-optimality of Prefilter in Deeply Coupled Integration of GPS and INS,” Journal of the Institute of Navigation, Vol. 57, No. 3, Fall 2010
Siva Sivananthan, Jay Weitzen, “Improving Optimality of Deeply Coupled Integration of GPS and INS,” ION Technical Interchange Meeting, January 2009, pp 426 – 433
Weitzen, Jay A. and Grosch, Theodore, “Comparing Coverage Quality for Femtocell and Macrocell Broadband Data Services”, IEEE Communications Magazine, January 2010
Fagen, D, Vicharelli P.A. and Weitzen, J.A : “Automated Coverage Optimization in Wireless Networks”. IEEE Transactions on Vehicular technology, March 2009
Weitzen, J.A. and T. Lowe, “Spatial and Angular correlation properties of Log-Normal shadowing at 1980 MHz” IEEE Transactions on Vehicular Technology, Mar 2002, Vol 51, No 2, pp 265-273
Carroll, J.V., and J.A. Weitzen, GPS and Loran-C hybrid Approach Navaid for General Aviation,GPS Magazine, Summer 1997.
Cannon, P.S., J. A. Weitzen, A preliminary study of the relative impact of meteor scatter and other long distance high latitude propagation modes on VHF communication systems, Radio Science, July 1996
Weitzen, J.A., J.V. Carroll, and H.J. Rome, RAIM Availability of GPS Augmented with Loran C and Barometric Altimeter for use in Nonprecision Approach, Navigation, J. Institute of Navigation, Summer 1996
Mawrey, R.S., and J. A. Weitzen, Use of Phased Array Antennas for High Performance Meteor Scatter Communication, IEEE Transactions on Communication, Vol 43, No.4, April 1995, pp 1467-1477
Ralston, W.T, and J. A. Weitzen, Spread Spectrum Multiple Access for Meteor Burst Communication , IEEE Transactions on Vehicular Technology, Vol 44, No 2., May 1995, pp 280-291
Weitzen, J. A., J. V. Carroll and B. T. Dao, “Use of Simulated Atmospheric Noise in the Calibration and Characterization of Loran-C receivers for airborne navigation”, Journal Institute on Navigation, vol. Vol. 40, 2, Summer, pp 1993. |
Weitzen, J.A., J.V. Carroll, B.T. Dao, Real Time Simulation of VLF Atmospheric Noise for use in the Calibration and Characterization of LORAN-C Receivers for Aircraft Navigation, Simulation Magazine, Society for Computer Simulation, May 1993
Ralston, W. T., J. A. Weitzen and J. C. Ostergaard, “Distribution of underdense meteor trail duration’s and duty cycles, and applications to meteor scatter communication system design”, Radio Science, vol. 28, No. 3, September-October, pp 747-759, 1993. |
Ralston, W. T., J. A. Weitzen and J. C. Ostergaard, “Distribution of underdense meteor trail duration’s and duty cycles, and applications to meteor scatter communication system design”, Radio Science, vol. 28, No. 3, September-October, pp 747-759, 1993. |
Weitzen, J. A., Performance of Short and Long Range Meteor Burst Communication With Different Antennas, IEEE Journal of Special Topics in Communication, JSAC-10, Vol. 3 April, 1992 pp. 491-497 |
Ostergaard, J.C., J.A. Weitzen, S.W. Li, P.M. Bench, A.D. Bailey, A.T. Coriaty, and J.A. Katan, Effect of High latitude Absorption on High Latitude Meteor Scatter Communication, Radio Science, July-August 1991, pp 931-943 |
Weitzen, J.A. S. Bourque, P.M. Bench, A.D. Bailey, J.C. Ostergaard, Distributions of Meteor Trail Amplitudes and Its Application to Meteor Scatter Communication System Design, Radio Science, March-April 1991 pp 451-458 |
Weitzen, J. A., A Study of Ground Illumination Pattern of Meteor Scatter Communication, IEEE Trans. on Comm., vol. Com-38, No 4., April 1990, pp 426-432 |
Sheridan, P. and J. A. Weitzen,. Evaluation of Network Planning and Design., IEEE Network Magazine. No, 11, November, 1989, PP 11-16 |
Weitzen, J. A., Effects of polarization Coupling Loss Mechanism on Design of Meteor Scatter Antennas for Short and Long Range Communication, Radio Science, Vol. 24, No 4, pp. 549-558, August 1989 |
Weitzen, J. A., Meteor Scatter Propagation: An Overview, Invited Paper, IEEE Transactions on Antennas and Propagation, Vol. 36, No 12, pp. 1813-1819, December 1988 |
Weitzen, J. A., Communicating Via Meteor Burst at Short Ranges, IEEE Transactions on Communications, IEEE Transactions on Communications, Vol. 35, No 11, November 1987, pp. 1213-1218 |
Weitzen, J. A., M.J. Sowa, J. Quinn, and R.A. Scofidio, Characterizing the Multipath Profile and Doppler Burst Communication Channel, IEEE Transactions on Communication, Vol. 35, No 10, October 1987, pp. 1050-1058
Weitzen, J. A., A Data Base Approach to Analysis of Meteor Burst Data, Radio Science, Vol. 22, Number 1, January 1987, pp. 133-140 |
Weitzen, J. A., Predicting the Arrival of Meteors Useful for Meteor Burst Communication, Radio Science, Vol. 21, Number 6, November 1986, pp. 1009-1020. |
Weitzen, J. A., W. P. Birkemeier, and M.D. Grossi, High Resolution Multipath Measurements on the Meteor Scatter Channel, Radio Science, Vol. 19, Number 1, January 1984, pp. 375-381 |
Weitzen, J. A., W.P. Birkemeier, and M.D. Grossi, An Estimate of the Capacity of the Meteor Burst Channel, IEEE Transactions on Communications, Vol. 32, Number 8 August 1984, pp. 972-976 |
Weitzen, J. A., and W. P. Birkemeier, The Skew Estimator Method for Aligning Troposcatter Antennas and Synchronization of Master Clocks, IEEE Transactions on Instrumentation and Measurement, Vol. 31, Number 1, Feb. 1982 |
Conference Papers | Weitzen, J.A. and Wakim, R.E, “Measuring and mapping multi-user cell-virtualization performance in a cloud-RAN small cell network”, Proceedings IEEE International Conference on Microwaves, Antennas, Communications and Electronics Systems, 6 Nov. 2017, Tel Aviv Israel
Wakim, R.E and Weitzen, J.A. “An autonomous system for high resolution mapping of indoor wireless coverage”, Proceedings IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications, (PIMRC) 1-5 October 2017, Montreal Canada
Jay Weitzen, Rachel Wakim and Erin Webster. Comparison of Coverage Quality RSRP,CQI, SINR for coordinated and uncoordinated LTE Small Cell Clusters, Proceedings IEEE COMCAS 2015 Conference, Tel Aviv Israel, November 2015
Jay Weitzen and Theodore Grosch, Measurements of Inter-Femtocell Reverse Link Interference, Proceedings 2015 International Conference on Wireless Networks, July 17-21, 2015, Las Vegas NV
Jay Weitzen, Dave Willis, Eric Maase, Steve Johnston, M. D. Rashid , Restructuring Our First-Year Introduction to Engineering Sequence at University of Massachusetts Lowell, Proceedings 2015 First Year Engineering Education Conference
Weitzen, J.A. Webster, E. and A. Rux, “Flipping ECE Laboratories using Laboratory in the Box”, Proceedings 2014 American Society of Engineering Education National Meeting, June 4-6, 2014, Indianapolis IN.
Weitzen, J.A, Webster, E. and A. Rux, “University of Massachusetts Lowell Laboratory in the Box for First Year ECE Students”, Proceedings First Year Engineering Conference, Aug 1-3, 2013, Pittsburgh PA
Jay Weitzen and Rachel Wakim, Managing Large Femtocell Networks with in excess of 1 Million Units, Proceedings IEEE COMCAS conference, Nov. 1-3, 2013, Tel Aviv Israel
Volkan Sevindik; Jiao Wang; Oguz Bayat; Jay Weitzen, “Performance Evaluation of a Real Long Term Evolution Network”, IEEE Conference on Local Computer Networks, 22-25, October, 2012, Clearwater Florida
Jay Weitzen and Rachel Wakim, Constraints of operating femtocells co-channel with macro networks, Proceedings of IEEE COMCAS 2011 Conference, Tel Aviv Israel, Nov 2011
Volkan Sevindik, Oguz Bayat, Jay Weitzen , Performance analysis and simulation of packet scheduling algorithms in a femtocell environment. Conference Proceeding: 01/2011; In proceeding of: 2011 Spring Simulation Multi-conference, SpringSim ’11, Boston, MA, USA, April 03-07, 2011. Volume 2: Proceedings of the 44th Annual Simulation Symposium (ANSS). Volkan Sevindik, Oguz Bayat and Jay Weitzen Traffic differentiation for BE users in CDMA 1xEVDO networks, Multi-media tools and networks, Springer Verlag, July 2010
Weitzen, Jay, “Advantages of Femtocells for Mobile Broadband Data Services”, Airvana White Paper, presented at 2009 Femto Forum, London United Kingdon, July 2009
Sevendik, Volkan, Bayat, Oguz, and Weitzen, J.A. Analysis of Inter-User Best Effort Class Users in CDMA 1xEVDO Network, Proceedings 2009 NetEval, Boston Ma, April 2009
Weitzen, J.A, and T. Grosch , “Measuring Coverage Quality for Femtocell and Macrocell Broadband Data Services”, Proceedings of IEEE COMCAS 2009 Conference, Tel Aviv, Israel November 2009
Weitzen, Jay, “Advantages of Femtocells for Mobile Broadband Data Services”, Airvana White Paper, presented at 2009 Femto Forum, London United Kingdon, July 2009
Sevendik, Volkan, Bayat, Oguz, and Weitzen, J.A. Analysis of Inter-User Best Effort Class Users in CDMA 1xEVDO Network, Proceedings 2009 NetEval, Boston Ma, April 2009
Karwedsky, K. Mills, D. Kotrlik, M. Weitzen, J ,“ Multicarrier CDMA with cross-system interference cancellation”, Wireless Communications and Networking Conference, 2004. WCNC. 2004 IEEE, Mar 2004, pp 1823-1827
Fagen, D, Vicharelli P.A. and Weitzen, J.A : “Automated Coverage Optimization in Wireless Networks”. Proceedings VTC Fall 2006: 1-5
Yang, S.M, J.Shankar,and J.A. Weitzen, On the use of unlicensed frequency spectrum, use rule evolution, and interference mitigation, Proceedings, Wireless Communication Association Conference, San Jose, 2001
Weitzen,J.A. and T. Lowe, Spatial and Angular correlation properties of Log-Normal shadowing and applications to design of CDMA systems, Proceedings IEEE Vehicular Technology Conference, Boston, Ma, Sept 2000
Weitzen, J.A., M.S. Wallace, Performance of Dual slant polarization relative to vertical polarization with horizontal space diversity in operational CDMA Personal Communication Networks, Proceedings, 1998 Personal Indoor mobile Radio Conference, Boston, Ma September 1998
Weitzen, J.A., J. Ketchum, and J. Musser, Performance Comparison of Polarization Diversity and Horizontal Space Diversity in an Operational AMPS Cellular Base Station Receiver, Proc. Mass Telecom, Research in Mass Conference, March 1996
Dao, B. and J. A. Weitzen, Analysis of a Vessel Traffic System using the DSC Protocol, Proc. Mass Telecom, Research in Mass Conference, March 1996
Cannon, P. A., J. A. Weitzen, J. C. Ostergaard and J. E. Rasmussen,”The relative importance of meteor burst and other long distance polar cap propagation modes in the low VHF band”, Proc AGARD, Electromagnetic Wage propagation Panel Symposium, Rotterdam, The Netherlands, 4-7 October, 1993, 1993
Weitzen, J. A., and W. P. Birkemeier, A New Method for Alignment of Troposcatter Antennas and Synchronization of Master Clocks, Proceedings IEEE MTIC Conference, Ottawa, Canada, September 22-24, 1982. |
Weitzen, J. A., High Speed Meteor Burst Communications for Military Applications, DCEC Symposium on Meteor Burst Communications, Reston, Va., October 18-19, 1983.
Weitzen, J. A., and W. Nelson, Predicting the Occurrence of Meteors in Meteor Burst Communication, IEEE MILCOM Conference, October 21-23, 1985. |
Weitzen, J. A., The Range Dependence of Meteor Burst Communication, Proceedings, MILCOM Communication Conference, October 1986. |
Weitzen, J. A., The Effect of Auroral Clutter on Meteor Communication, Proceedings TTCP/STC-8 Workshop on Meteor Communication for the 1990’s, Farnborough, U.K., June 1987. |
Weitzen, J.A., S.A. Parl, and A. Malaga’, Some Observations on the Performance of Meteor Scatter communication at short ranges. Proceedings NATO STC Symposium on Meteor Scatter Communication, Nov. 5,1987, The Hague Netherlands. |
Weitzen, J. A., D.L. Schilling, and E. Hibshoosh, Some observations on the distribution of Meteor Trail Amplitudes and Duration’s and Ramifications on the Design of Meteor Scatter Communication Protocols, Proceedings MILCOM Communication Conference, October 23-26, 1988, San Diego, Ca |
Scofidio, R.A. and J. A. Weitzen, A study of the ground interceptability of meteor scatter communication, Proceedings MILCOM Communication Conference, October 23-26, 1988, San Diego, Ca |
Hibshoosh, E., D.L. Schilling, and J.A. Weitzen, Optimum bit rate predictions for meteor communication, Proceedings MILCOM Communication Conference, October 23-26, 1988, San Diego, Ca |
Weitzen, J.A., Effects of auroral multipath interference on meteor communication, 1989 Communication Theory Workshop, 9-12 April 1989, Hawks Cay Florida |
Weitzen, J.A., Performance predictions for several meteor scatter antenna configurations, Proceedings, International Communication Conference, June 12-14, 1989, Boston Ma |
Weitzen, J. A., “Effects of polarization Coupling Loss Mechanism on Design of Meteor Scatter Antennas for Short and Long Range Communication”, Radio Science, vol. 24, No 4, August, pp. 549-558, 1989. |
Weitzen, J. A., S. Bourque, M. Horton, P. M. Bench, A. D. Bailey and J. C. Ostergaard, “Distributions of meteor trail amplitudes and its application to meteor scatter communication system design”, Proceedings International Phoenix Conference on Computers and Communication, Phoenix, AZ, March 21-23, 1990 |
Ostergaard, J.C., J.A. Weitzen, S.W. Li, P.M. Bench, A.D. Bailey, A.T. Coriaty, and J.A. Katan, Effect of Polar Cap Absorption on High Latitude Meteor Scatter Communication, Proceedings, 1990 Ionospheric Effects Symposium, Washington DC, May 1-3, |
Kilpatrick, J.A., J.A. Weitzen, S.A. Parl, Meteor Scatter Network/Channel Simulator, Proceedings, 1990 MILCOM Military Communication Conference, September 1990 |
Krueger, P. and J. A. Weitzen, DPSK Signaling Rates That Maximize the Performance of 60 GHz Crosslinks in a Doubly Dispersive Channel, Proceedings, 1990 Military Communication Conference, September 1990 |
Ostergaard, J.C., J.A. Weitzen, S.W. Li, P.M. Bench, A.D. Bailey, A.T Coriaty, and J.A. Katan, New Results on Effect of Polar Cap Absorption on High Latitude Meteor Scatter Communication, U.S. Navy High Special Meeting on High Latitude Propagation, February 15, 1991, Monterey Ca |
Weitzen, J. A., P. S. Cannon, J. C. Ostergaard and A. D. Bailey, Seasonal Variations in Meteoric And Non-meteoric Duty Cycle in the Polar Cap and Auroral Regions, IEE International HF Conference, Edinborough, Scotland, 1991,July 1991 |
Smith, D. S., J. A. Weitzen, J. D. Larsen and D. Kocyba,”Improving the resistance of meteor scatter communication to interception”, Proc. 1991 MILCOM, Washington, DC., 1991 |
Ralston, W.T. and J.A. Weitzen, Performance of Large Meteor Scatter Networks using Code Division Multiple Access (CDMA), Proc. 1991 MILCOM, Washington DC., 1991 |
J.A. Weitzen, Mawrey, R.S., and J.D. Larsen, Probability of message contention in a very large meteor scatter communication network, Accepted, 1992 Vehicular Technology Conference, Denver Colorado, May 11-13, 1992 |
J.A. Weitzen, Mawrey, R.S., and J.D. Larsen, Feasibility of large meteor scatter networks for vehicle tracking, 1992 Wireless Information Laboratory Conference, Rutgers University, April 28-29, 1992 |
Weitzen, J. A., J. D. Larsen and R. S. Mawrey, “Design of a Meteor Scatter Communication Network for Vehicle Tracking”, Proc. IEEE Vehicle Technology Conference, Denver CO, May 11-14,1992 |
Larsen, J. D., R. S. Mawrey and J. A. Weitzen,”Use of Antenna Beam Steering to Improve the Performance of Meteor Burst Communication Systems”, Proc. IEEE Milcom-92, San Diego, Ca Oct. 11-14, 1992 |
Mawrey, R. S., J. D. Larsen and J. A. Weitzen, “Conversational voice communication over a high performance meteor burst channel”, Proc. IEEE Milcom-92, San Diego, Ca Oct. 11-14, 1992 |
Ralston, W. T. and J. A. Weitzen, “Network Waiting time for meteor-burst communication”, Proc. MILCOM, San Diego, CA., Oct. 11-14, 1992 |
Carroll, J.V., J.A. Weitzen, and B.T. Dao, Real time simulation of atmospheric noise for use in characterizing Loran-C receivers, Proceedings Wild Goose Association, International Symposium, Birmingham U.K., August 1992
Cannon, P. S., J. A. Weitzen, J. S. Ostergaard and J. E. Rasmussen,”The Relative Importance of Meteor Burst and Other Long Distance Polar Cap Propagation Modes in the Low VHF Band”, Proc. AGARD Advisory Group 244, Trieste, Italy, 1993 |
Mawrey, R. S., J. D. Larsen and J.A. Weitzen, “Meteor Burst System Design Using an Advanced Computer Based Prediction Model”, Proc. IEEE MILCOM-93, Boston, Ma, Oct. 12-15, 1993 |
Ralston, W. T. and J. A. Weitzen, “Direct sequence CDMA for Large Meteor Burst Networks”, Proc. IEEE MILCOM, Boston, Ma, Oct. 12-15, 1993 |
Weitzen, J. A., R. S. Mawrey and J. D. Larsen,”The use of meteor scatter and extended Range VHF for vehicle tracking and communication”, Proc. IVHS America 1993 Annual Meeting, Washington, DC. April 14-17, 1993 |
Weitzen, J. A., R. S. Mawrey and J. D. Larsen., “Design of a meteor scatter communication network for vehicle tracking”, Proc. IEEE Vehicle Technology Symposium, Secaucus NJ, May 18-21, 1993
Dao, B. and J.A. Weitzen, Simulation of a Vessel Tracking System using the DSC protocol, Mass Tech Conf on Research in Mass, Lowell Ma, March 1996
Weitzen, J.A., J. Ketchum, and J. Musser, Performance Comparison of Horizontal Space Diversity and Polarization Diversity in an Operational AMPS System, Mass Tech Conf on Research in Mass, Lowell Ma, March 1996 |
Published Technical Reports | Carroll, J.V., and J.A. Weitzen, Availability and RAIM Integrity Analysis of a Combination GPS and Loran-C Approach Navigation System, DOT-VNTSC-FA429-PM-94-9, August 1994
Kraemer, J.C., Weitzen, J.A., Nim, G., R. Boutette, Performance Monitoring of the GPS Standard Position Service, DOT-VNTSC-CD402-PM-94-6, September 1994
Carroll, J.V., J.A. Weitzen, F. Cassidy, B.Y. Dao, Digital Selective Calling For VTS, Functional Description, DOT-VNTSC-CD408-PM-94-3
Weitzen, J. A., A Data Base Approach to Analysis of Meteor Burst Data. RADC-TR-86-165, October 1986. |
Weitzen, J. A., The Multipath and Fading Profile of the High Latitude Meteor Burst Communication Channel. RADC-TR-86-166, October 1986. |
Weitzen, J. A., and S. Tolman, A technique for classification of meteor trails and identification of the Dominant propagation mechanism for the USAF High Latitude Meteor Burst Test Bed, RADC-TR-86-117, September 1986 |
Weitzen, J.A. Characterizing the multipath and Doppler profiles of the high latitude meteor scatter communication channel, RADC-TR-86-165, October 1986 |
Weitzen, J.A. Communicating via meteor scatter at high latitudes, Rome Air Development Center Technical Report, RADC-TR-89-172 |
Weitzen, J.A. Short range meteor scatter improvement study, Rome Air Development Center Technical Report, RADC-TR-89-173 |
Weitzen, J.A., S.W. Li, and M. Horton, A preliminary study of the effects of aurora on high latitude meteor communication, Air Force Geophysics Laboratory Technical report, AFGL-TR-89-0020 |
Weitzen, J. A. and M. Horton, “Meteor Scatter Data Analysis Software: A users guide”, Technical Report, Air Force Geophysics Laboratory, GL-TR-89-154, 1989 |
Weitzen, J. A. and J. A. Kilpatrick, “VHF MBC simulation for SICBM Phase III diversity comparisons”, Technical Report, Signatron, IC, Signatron-1100-013, 1989 |
Weitzen, J. A. and J. C. Ostergaard, Statistical Characterization of Fading on Meteor Scatter Communication Channels, GL-TR-90-0362, Geophysics Laboratory, Air Force Systems Command, December 1990 |
Weitzen, J. A. and J. C. Ostergaard, High resolution Characterization of Fading on Meteor Scatter Communication Channels, GL-TR-91-0320, Geophysics Laboratory, Air Force Systems Command, March 1991
Kilpatrick, J. A. and J. A. Weitzen, “Design of meteor burst link/network simulator”, Final Technical Report, Rome Air Development Center, RADC-TR-90-248, 1990 |
Kilpatrick, J.A., Weitzen, J.A, and S.A. Parl, Meteor Burst Adaptive Antenna Study, Rome Labs Technical Report RL-TR-91-234 |