This paper describes how information about the electromagnetic structure of targets can be obtained from direct detection radar techniques, where the relative phase of the transmitted and received signals is not measured. A comparison is made between the resolved structure of a simple test target from an ultra wide band, pulse synthesis direct detection radar system at 14-40 GHz and an equivalent heterodyne radar receiver where phase information is recorded. The test targets employed are wax sheet of thickness 20 mm and 80 mm which are illuminated alone and in contact with the human body. A vector network analyser is used as the radar system. The simplicity of constructing ultra wide band direct detection radar systems combined with their cost makes the use of such radar systems appealing for applications such as concealed threat detection and nondestructive testing, where absolute range to the target, if required, can be determined by other methods.
2. Robinson, L. A., W. B. Weir, and L. Young, "An RF time-domain reflectometer not in real time," IEEE Trans. Microwave Theory Tech., Vol. 20, 855-857, Dec. 1972.
3. Park, J. S. and C. Nguyen, "A new millimeter-wave step-frequency radar sensor for distance measurement," IEEE Microwave Wireless Compon. Lett., Vol. 12, No. 6, 221-222, Jun. 2002.
4. Boryssenko, A., O. Boryssenko, A. Lishchenko, and V. Prokhorenko, "Inspection of internal structure of walls by subsurface radar," IEEE Aerosp. Electron. Syst. Mag., Vol. 21, No. 10, 28-31, Oct. 2006.
5. Sheen, D., D. McMakin, and T. E. Hall, "Three-dimensional millimeter-wave imaging for concealed weapon detection," IEEE Trans. Microwave Theory Tech., Vol. 49, No. 9, 1581-1592, 2001.
6. Andrews, D. A., S. E. Smith, N. D. Rezgui, N. J. Bowring, M. Southgate, and S. W. Harmer, "A swept millimetre-wave technique for the detection of concealed weapons and thin layers of dielectric material with or without fragmentation," Proc. SPIE, Vol. 7309, 2009.
7. Andrews, D. A., N. Rezgui, S. E. Smith, N. J. Bowring, M. Southgate, and J. G. Baker, "Detection of concealed explosives at stando® distances using wide band swept millimetre waves," Proc. SPIE, Vol. 7117, 2008.
8. Bowring, N. J., J. G. Baker, N. Rezgui, M. Southgate, and J. F. Alder, "Active millimetre wave detection of concealed layers of dielectric material," Proc. SPIE, Vol. 6540, 2007.
9. Agurto, A., Y. Li, G. Y. Tian, N. Bowring, and S. Lockwood perspective, "A review of concealed weapon detection and research on," Proc. IEEE ICNSC, 443-448, 2007.
10. Bowring, N., D. Andrews, N. D. Rezgui, and S. W. Harmer, "Remote detection and measurement of objects,", U.K. Patent 2 458 764, Mar. 18, 2009.
11. Andrews, D. A., N. J. Bowring, N. D. Rezgui, M. Southgate, E. Guest, S. W. Harmer, and A. Atiah, "A multifaceted active swept millimetre-wave approach to the detection of concealed weapons," Proc. SPIE, Vol. 7117, 2008.
12. Bowring, N. J., J. G. Baker, N. D. Rezgui, and J. F. Alder, "A sensor for the detection and measurement of thin dielectric layers using re°ection of frequency scanned millimetric waves," Meas. Sci. Technol., Vol. 19, No. 2, 024004, Jan. 2008.
13. Bowring, N. J., J. G. Baker, and J. F. Alder, "Detection and measurement of thin dielectric layers using reflection of scanned millimetric waves," Proceedings of the IEEE International Conference on Networking, Sensing and Control, 437-442, Apr. 2007.
14. Harmer, S. W., N. J. Bowring, D. Andrews, and N. D. Rezgui, "A review of nonimaging stand-off concealed threat detection with millimeter-wave radar," IEEE Microwave Magazine, Vol. 13, No. 1, 160-167, Jan.-Feb. 2012.
15. Lamb, J. W., "Miscellaneous data on materials for millimetre and submillimetre optics," Int. J. Infrared Millim. Waves, Vol. 17, No. 12, 1997-2034, 1996.
16. Harmer, S. W. , P. D. Townsend, and N. J. Bowring, "Enhancement of photomultiplier sensitivity with anti-reflective layers," J. Phys. D: Appl. Phys., Vol. 45, No. 5, 055102, Feb. 2012.
17. Gashinova, M., V. Djigan, L. Y. Daniel, and M. Cherniakov, "Adaptive calibration in UWB radar," Proc. IEEE Radar Conference, 1161-1166, May 2008.
18. Buchner, R., G. T. Hefter, and P. M. May, "Dielectric relaxation of aqueous NaCl solutions," J. Phys. Chem. A, Vol. 103, No. 1, 1-9, Dec. 1998.