Focused arrays are attracting increased interest because of their wide range of applications. Focusing the antenna's radiation in the near field requires proper phase distribution of the array elements that must be fed through many phase shifters. This work presents a design idea for a focused circular array antenna, whose focal distance can be varied by only a single variable phase shifter. The idea is implemented on a dual-ring circular array having a six-wavelength diameter and focused at five wavelengths by using a single fixed phase shifter. Theoretical analysis and computer simulations of a sample design using MATLAB and CST Microwave Studio show that a phase change of 0.9π leads to a four-wavelength change in the focal distance. A formula for the estimation of the depth of field DOF is derived. The proposed array offers a simple method to vary the focal length continuously by a single variable phase shifter. This idea can be utilized in hyperthermia, RFID, and imaging applications, where the position of the focal spot needs to be moved along the normal to the array.
Mohammed Z. Mohammed Fwzi,
"A Focused Circular Array with Variable Focal Length," Progress In Electromagnetics Research M,
Vol. 121, 63-72, 2023. doi:10.2528/PIERM23071404
1. Nepa, P. and A. Buffi, "Near-field focused microwave antennas near-field shaping and implementation," IEEE Antennas & Propagation Magazine, Vol. 59, No. 3, 42-53, 2017. doi:10.1109/MAP.2017.2686118
2. Nepa, P., A. Buffi, A. Michel, and G. Manara, "Technologies for near-field focused microwave antennas," International Journal of Antennas and Propagation, Vol. 2017, 17, 2017.
3. Bogosanovic, M. and A. G. Williamson, "Microstrip antenna array with a beam focused in the near-field zone for application in noncontact microwave industrial inspection," IEEE Transactions on Instrumentation and Measurement, Vol. 56, No. 6, 2186-2195, 2007. doi:10.1109/TIM.2007.907954
4. Daniels, D. J., Ground Penetrating Radar, IET, London, United Kingdom, 2004. doi:10.1049/PBRA015E
5. Guo, T. C., W. W. Guo, and L. E. Larsen, "A local field study of a water-immersed microwave antenna array for medical imagery and therapy," IEEE Transactions on Microwave Theory and Techniques, Vol. 32, 844-854, 1984. doi:10.1109/TMTT.1984.1132781
6. He, X., W. Geyi, and S. Wang, "Optimal design of focused arrays for microwave-induced hyperthermia," IET Microwaves, Antennas, and Propagation, Vol. 9, No. 14, 1605-1611, 2015. doi:10.1049/iet-map.2014.0696
7. Lee, K., J.-Y. Kim, and S.-H. Son, "Experimental phantom test of 925 MHz microwave energy focusing for non-invasive local thermotherapy," Results in Physics, Vol. 38, 105585, 2022. doi:10.1016/j.rinp.2022.105585
8. Omrani, A., G. Link, and J. Jelonnek, "A near-field focused phased-array antenna design using the time-reversal concept for weed control purpose,", arXiv:2302.01012v1 [eess.SY], Feb. 2, 2023.
9. Ismail, M. S. and K. H. Sayidmarie, "Investigation of three array geometries for focused array hyperthermia," The International Symposium on Antennas and Propagation, Sapporo, Japan, 1992.
10. Sayidmarie, K. and A. M. Abdulkhaleq, "Investigation of six array geometries for focused array hyperthermia applications," Progress In Electromagnetics Research M, Vol. 23, 181-194, 2012. doi:10.2528/PIERM12010605
11. Tomás, J. J., M. Arrebola, G. León, and F. Las-Heras, "Near-field focussed array with two simultaneous and independent spots," Proceedings of the 2012 IEEE International Symposium on Antennas and Propagation, Chicago, IL, USA, 2012.
12. Yi, X., X. Chen, L. Zhou, and S. Hao, "A high-efficiency nearfield focused transmitting antenna based on the equal power divisions," AIP Advances, Vol. 10, No. 11, 115111, 2020. doi:10.1063/5.0029673
13. Sayidmarie, K. H. and E. U. Taha, "Development of a semicircle phased array for local hyperthermia," 2005 IEEE International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications Proceedings, 1430-1434, 2005. doi:10.1109/MAPE.2005.1618193
14. He, X., W. Geyi, and S. Wang, "A hexagonal focused array for microwave hyperthermia: Optimal design and experiment," IEEE Antennas and Wireless Propagation Letters, Vol. 15, 56-59, 2016. doi:10.1109/LAWP.2015.2429596
15. Lyu, C., W. Li, Si Li, Y. Mao, and B. Yang, "Design of ultra-wideband phased array applicator for breast cancer hyperthermia therapy," Sensors, Vol. 23, 1051, 2023, https://doi.org/10.3390/s23031051. doi:10.3390/s23031051
16. Yildiz, G., I. Farhat, L. Farrugia, J. Bonello, K. Zarb-Adami, C. V. Sammut, T. Yilmaz, and I. Akduman, "Comparison of microwave hyperthermia applicator designs with fora dipole and connected array," Sensors, Vol. 23, 6592, 2023, https://doi.org/10.3390/s23146592. doi:10.3390/s23146592
17. Siragusa, R., P. Lemaitre-Auger, and S. Tedjini, "Near field focusing circular microstrip antenna array for RFID applications," IEEE Antennas and Propagation Society International Symposium, 1-4, 2009.
18. Siragusa, R., P. Lemaitre-Auger, and S. Tedjini, "Tunable nearfield focused circular phase-array antenna for 5.8-GHz RFID applications," IEEE Antennas and Wireless Propagation Letters, Vol. 10, 33-36, 2011. doi:10.1109/LAWP.2011.2108632
19. Huang, R., B. Liu, and Q. Tan, "A near-field focused circular array based on dielectric resonator antenna," IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (APS/URSI), Dec. 4–10, 2021.
20. Fwzi, M. Z. M. and K. Sayidmarie, "A circular array with improved focusing properties," Progress In Electromagnetics Research C, Vol. 126, 13-22, 2022. doi:10.2528/PIERC22080806
21. Cheng, Y. J. and F. Xue, "Ka-band near-field-focused array antenna with variable focal point," IEEE Transactions on Antennas and Propagation, Vol. 64, No. 5, 1725-1732, May 2016. doi:10.1109/TAP.2016.2540646
22. Graham, W. J., "Analysis and synthesis of axial field patterns of focused apertures," IEEE Transaction on Antennas and Propagation, Vol. 31, No. 4, Jul. 1983.
23. Smith, D., V. Gowda, O. Yurduseven, S. Larouche, G. Lipworth, Y. Urzhumov, and M. Reynolds, "An analysis of beamed wireless power transfer in the fresnel zone using a dynamic, metasurface aperture," Journal of Applied Physics, Vol. 121, 014901, 2017, http://dx.doi.org/10.1063/1.4973345. doi:10.1063/1.4973345
24. Shan, L. and W. Geyi, "Optimal design of focused antenna arrays," IEEE Transactions on Antennas and Propagation, Vol. 62, No. 11, 5565-5571, Nov. 2014. doi:10.1109/TAP.2014.2357421
25. Zainud-Deen, S. H., H. A. Malhat, and K. H. Awadalla, "Dielectric resonator antenna phased array for fixed RFID reader in near field region," Proceedings of the Japan-Egypt Conference on Electronics, Communications and Computers Conference (JEC-ECC’12), 102-107, Alexandria, Egypt, Mar. 2012.