The existence of reverse radiation noise in the millimeter-wave (MMW) radiometric imaging system with a superheterodyne receiver seriously affects the imaging experiments carried out at short range, thus leading to the degradation of MMW radiometric images and difficulty in recognizing targets. Based on the generation mechanism of reverse radiation noise, the specific influence on imaging for relative radiometry is investigated in this paper, and some methods of eliminating or reducing this noise are proposed. Then, two series of comparative imaging experiments are conducted with a 3 mm band radiometric imaging system. Both theoretical analysis and experimental results are presented to validate the actual existence of interference-like stripes imposed by the reverse radiation noise. Moreover, it is proved that adopting an isolator in the MMW receiving front-end can effectively reduce the reverse radiation noise and significantly improve the imaging performance.
2. Boettcher, E. J., K. Krapels, R. Driggers, J. Garcia, C. Schuetz, J. Samluk, L. Stein, W. Kiser, A. Visnansky, J. Grata, D. Wikner, and R. Harris, "Modeling passive millimeter wave imaging sensor performance for discriminating small watercraft," Applied Optics, Vol. 49, No. 19, E58-E66, 2010.
3. Appleby, R. and R. N. Anderton, "Millimeter-wave and submillimeter-wave imaging for security and surveillance," Proceedings of IEEE, Vol. 95, No. 8, 1683-1690, 2007.
4. Oka, S., H. Togo, N. Kukusu, and T. Nagatsuma, "Latest trends in millimeter-wave imaging technology," Progress In Electromagnetics Research Letters, Vol. 1, 197-204, 2008.
5. Yeom, S., D.-S. Lee, H. Lee, J.-Y. Son, and V. P. Guschin, "Distance estimation of concealed objects with stereoscopic passive millimeter-wave imaging," Progress In Electromagnetics Research, Vol. 115, 399-407, 2011.
6. Hung, C. Y., M. H. Weng, R. Y. Yang, and H. W. Wu, "Design of a compact CMOS bandpass filter for passive millimeter-wave imaging system application," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 17-18, 2323-2330, 2009.
7. Thakur, J. P., W.-G. Kim, and Y.-H. Kim, "Large aperture low aberration aspheric dielectric lens antenna for W-band quasi-optics," Progress In Electromagnetics Research, Vol. 103, 57-65, 2010.
8. Ulaby, F. T., R. K. Moore, and A. K. Fung, Microwave Remote Sensing: Active and Passive, Volume I: Fundamentals and Ra-diometry, Addison-Wesley Publishing Company, Massachusetts, 1981.
9. Peng, S.-S., Z.-C. Xu, and X.-G. Li, "Effect of inverse radiation noise of microwave radiometer for remote sensing on antenna temperature calibration," Journal of Microwaves, Vol. 13, No. 2, 108-113, 1997.
10. Li, J. and J.-S. Jiang, "Reverse radiation in microwave radiometer," Journal of Remote Sensing, Vol. 2, No. 4, 241-244, 1998.
11. Li, Z.-P., D.-M. Zhao, and J.-G. Miao, "Simulation study of the effect on inverse radiation thermal noise of microwave radiometer on antenna calibration," Remote Sensing Technology and Application, Vol. 22, No. 2, 268-271, 2007.
12. Xiao, Z.-L., T.-Y. Hu, J.-Z. Xu, and L. Wu, "Millimetre- wave radiometric imaging for concealed contraband detection on personnel," IET Image Processing, Vol. 5, No. 5, 375-381, 2011.