Rotman lenses are the beguiling devices used by the beamforming networks (BFNs). These lenses are generally used in the radar surveillance systems to see targets in multiple directions due to its multibeam capability without physically moving the antenna system. Now a days these lenses are being integrated into many radars and electronic warfare systems around the world. The antenna should be capable of producing multiple beams which can be steered without changing the orientation of the antenna. Microwave lenses are the one who support low-phase error, wideband, and wide-angle scanning. They are the true time delay (TTD) devices producing frequency independent beam steering. The emerging printed lenses in recent years have facilitated the advancement of designing high performance but low-profile, light-weight, and small-size and networks (BFNs). This paper will review and analyze various design concepts used over the years to improve the scanning capability of the lens developed by various researchers. 1. Introduction To appreciate the significance of the most popular constrained lens architecture, the Rotman lens antenna, it is necessary to provide a review of the constrained lens development. To fully understand the concept of these complicated and complex lenses, the basic concept of microwave beamforming network must be dealt with in detail. The Rotman lens antenna provides ideal performance for applications such as for satellite based direct radiating arrays, remote-piloted vehicles, collision-avoidance radars, ultra-wideband communications systems, and many more [1, 2]. Constrained lens arrays are special groups of beamforming networks. They share some similarities with dielectric lenses and reflector antennas on one hand and with antenna arrays on the other. Their function is to form beams in multiple directions which correspond to the position of the feed antennas at the focal surface. The name constrained comes from the fact that a wave incident on one face of the array does not necessarily obey Snell’s law when passing through the lens array [1]. It is instead constrained to follow the transmission line paths. Unlike dielectric lenses or reflector antennas, lens arrays do their collimation (transmission) and focusing (reception) discretely, using antenna arrays [2]. The frequency independent beam pointing angle characteristics of the lens due to its time delay nature makes it ideal for many broadband width electronics warfare. The paper is organized as follows. Section 2 represents various beamforming techniques and its development. Section 3
References
[1]
J. Kim and F. Barnes, “Scaling and focusing of the Rotman lens,” in Proceedings of the IEEE Antennas and Propagation Society International Symposium, vol. 2, pp. 773–776, July 2001.
[2]
R. C. Hansen, Phased Array Antennas, John Wiley Sons, New York, NY, USA, 1998.
[3]
S. S. D. Jones, H. Gent, and A. A. L. Browne, “Improvements in or relating to electromagnetic-wave lens and mirror systems,” British Provisional Patent Specification No. 25926/56, 1956.
[4]
K. Jaeheung, Developments of rotman lenses at micro/millimeter-wave frequencies [Ph.D. thesis in Electrical Engineering], University of Colorado, Boulder, Colo, USA, 2003.
[5]
M. Hawes and W. Liu, “Sparse array design for wideband beamforming with reduced complexity in tapped delay-lines,” IEEE/ACM Transactions on Audio, Speech, and Language Processing, vol. 22, no. 8, pp. 1236–1237, 2014.
[6]
D. H. Archer, “Fed multiple beam arrays,” Microwave Journal, vol. 27, no. 9, pp. 13–195, 1984.
[7]
H. Steyskal, C. Cox, and E. Ackerman, “Digital and optical beamforming techniques,” in Phased Array Systems and Technology International Symposium, p. 616, 2003.
[8]
C. W. Penney, R. J. Luebbers, and E. Lenzing, “Broad band Rotman Lens simulations in FDTD,” in Proceedings of the IEEE Antennas and Propagation Society International Symposium and USNC/URSI Meeting, pp. 51–54, Washington, DC, USA, July 2005.
[9]
G. L. Leonakis, “Correction to wide-angle microwave lens for line source applications,” IEEE Transactions on Antennas and Propagation, vol. 34, no. 8, p. 1067, 1986.
[10]
A. H. Jafari, W. Liu, and D. R. Morgan, “Study of sensor positions for broadband beamforming,” IEEE Signal Processing Letters, vol. 20, no. 8, pp. 779–782, 2013.
[11]
D. Archer, “Lens-fed multiple beam arrays,” Microwave Journal, vol. 18, pp. 37–42, 1975.
[12]
J. J. Lee and G. W. Valentine, “Multibeam array using Rotman lens and RF heterodyne,” in Proceedings of the AP-S International Symposium on Antennas and Propagation Society, vol. 3, pp. 1612–1615, Baltimore, Md, USA, July 1996.
[13]
A. Rahimian, “Microwave beamforming networks for intelligent transportation systems,” in Intelligent Transportation Systems, A. Abdel-Rahim, Ed., pp. 123–142, InTech, Rijeka, Croatia, 2012.
[14]
R. C. Hansen, “Design trades for Rotman lenses,” IEEE Transactions on Antennas and Propagation, vol. 39, no. 4, pp. 464–472, 1991.
[15]
W. Rotman and R. F. Turner, “Wide-angle microwave lens for line source applications,” IEEE Transactions on Antenna and Propagation, vol. 11, no. 6, pp. 623–632, 1963.
[16]
J. Ruze, “Wide-angle metal-plate optics,” Proceedings of the IRE, vol. 38, no. 1, pp. 53–59, 1950.
[17]
D. H. Archer and M. J. Maybell, “Rotman lens development history at raytheon electronic warfare systems 1967–1995,” in Proceedings of the IEEE Antennas and Propagation Society International Symposium, vol. 2, pp. 31–34, July 2005.
[18]
D. H. Archer, R. J. Prickett, and C. P. Hartwig, “Multi-beam array antenna,” U.S. Patent 3761936, 1973.
[19]
A. Al-Zayed, L. Schulwitz, and A. Mortazawi, “A dual polarized millimeter-wave multibeam phased array,” in Proceedings of the 2004 IEEE MITT-S International Microwave Symposium Digest, vol. 1, pp. 87–90, June 2004.
[20]
J. Rao, “Multifocal three-dimensional bootlace lenses,” IEEE Transactions on Antennas and Propagation, vol. 30, no. 6, pp. 1050–1056, 1982.
[21]
J. Rao, “Correction to “Multifocal three-dimensional bootlace lenses”,” IEEE Transactions on Antennas and Propagation, vol. 31, p. 541, 1983.
[22]
J. P. Shelton, “Focusing characteristics of symmetrically configured bootlace lenses,” IEEE Transactions on Antennas and Propagation, vol. 26, no. 4, pp. 513–518, 1978.
[23]
M. J. Maybell, “Ray structure method for coupling coefficient analysis of the two dimensional Rotman lens,” in Proceedings of the Antennas and Propagation Society International Symposium, pp. 144–147, Los Angeles, Calif, USA, June 1981.
[24]
G. S. Hardie, R. Hernandez, and M. J. Maybell, “Parallel plate lens antenna,” U.S. Patent 4490723, 1984.
[25]
T. Katagi, S. Mano, and S. Sato, “An improved design method of rotman lens antennas,” IEEE Transactions on Antennas and Propagation, vol. 32, no. 5, pp. 524–527, 1984.
[26]
L. Musa and M. Smith, “Microstrip rotman lens port design,” in Proceedings of the Antennas and Propagation Society International Symposium, vol. 24, pp. 899–902, 1986.
[27]
L. Musa and M. S. Smith, “Microstrip port design and sidewall absorption for printed Rotman lenses,” IEE Proceedings H: Microwaves, Antennas and Propagation, vol. 136, no. 1, pp. 53–58, 1989.
[28]
L. Hall, H. Hansen, and D. Abbott, “Rotman lens for mm-wavelengths,” in Smart Structures, Devices, and Systems, vol. 4935 of Proccedings of SPIE, pp. 215–221, 2002.
[29]
D. R. Gagnon, “Procedure for correct refocusing of the Rotman lens according to Snell's law,” IEEE Transactions on Antennas and Propagation, vol. 37, no. 3, pp. 390–392, 1989.
[30]
P. K. Singhal, R. D. Gupta, and P. C. Sharma, “Design and analysis of modified Rotman type multiple beam forming lens,” in Proceedings of the IEEE Region 10 International Conference on 'Global Connectivity in Energy, Computer, Communication and Control (TENCON '98), vol. 2, pp. 257–260, December 1998.
[31]
M. J. Maybell, “Printed Rotman Lens fed array having wide bandwidth low side lobes, constant beam width and synthesized radiation pattern,” in Proceedings of the IEEE AP Symposium Digest, pp. 373–376, Houston, Tex, USA, 1983.
[32]
E. O. Rausch and A. F. Peterson, “Rotman lens design issues,” in Proceedings of the IEEE Antennas and Propagation Society International Symposium and USNC/URSI Meeting, vol. 2, pp. 35–38, July 2005.
[33]
P. K. Singhal, P. C. Sharma, and R. D. Gupta, “Rotman lens with equal height of array and feed contours,” IEEE Transactions on Antennas and Propagation, vol. 51, no. 8, pp. 2048–2056, 2003.
[34]
P. Simon, “Analysis and synthesis of Rotman lenses,” in Proceedings of the 22nd AIAA International Communications Satellite Systems Conference & Exhibit, Monterey, Calif, USA, May 2004.
[35]
J. Dong and R. Cheung, “A computer synthesized 2~8？GHz printed rotman Lens with 98 input-to-output configuration,” in Proceedings of the 2011 IEEE International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting (APSURSI '11), pp. 616–618, July 2011.
[36]
J. Dong, A. I. Zaghloul, R. Sun, and C. J. Reddy, “EHF rotman lens for electronic scanning antennas,” in Proceedings of the Asia Pacific Microwave Conference (APMC '08), December 2008.
[37]
J. Dong, A. I. Zaghloul, and R. Rotman, “Non-focal minimum-phase-error planar rotman lens,” in Proceedings of theUSNC /URSI National Radio Science Meeting, Boulder, Colo, USA, January 2008.
[38]
J. Dong, A. I. Zaghloul, and R. Rotman, “Non-focal minimum-phase-error planar rotman lens,” in Proceedings of the URSI National Radio Science Meeting, Boulder, Colo, USA, 2008.
[39]
J. Dong and A. I. Zaghloul, “Implementation of microwave lens for 360-degree scanning,” in Proceeding of the IEEE International Symposium on Antennas and Propagation (APSURSI '09), pp. 1–4, Charleston, SC, USA, June 2009.
[40]
A. I. Zaghloul and J. Dong, “A concept for a lens configuration for 360° scanning,” IEEE Antennas and Wireless Propagation Letters, vol. 8, pp. 985–988, 2009.
[41]
R. Uyguro？lu, A. Y. ？ztoprak, and C. Ergün, “Improved phase performance for rotman lens,” International Journal of RF and Microwave Computer-Aided Engineering, vol. 23, no. 6, pp. 634–638, 2012.
[42]
S. Christie, R. Cahill, N. B. Buchanan et al., “Rotman lens-based retrodirective array,” IEEE Transactions on Antennas and Propagation, vol. 60, no. 3, pp. 1343–1351, 2012.
[43]
Y. Zhang, S. Christie, V. Fusco, R. Cahill, G. Goussetis, and D. Linton, “Reconfigurable beam forming using phase-aligned Rotman lens,” IET Microwaves, Antennas and Propagation, vol. 6, no. 3, pp. 326–330, 2012.
[44]
W. Zongxin, X. Bo, and Y. Fei, “A multibeam antenna array based on printed rotman lens,” International Journal of Antennas and Propagation, vol. 2013, Article ID 179327, 6 pages, 2013.
