V.A. Kuznetsov¹, V.P. Likhachev², A.V. Unkovsky³

1-3 MESC AF «N.E. Zhukovsky and Y.A. Gagarin Air Force Academy»

Currently, it is known that the largest contribution to the phase sweep errors when shooting from an aircraft carrier is made by geometric errors caused by errors in measuring the length and angle of inclination of the base, coordinates of the carrier and the formation of two radar images when shooting from different angles. These problems lead to spatial de-correlation, leading to errors in measuring the phase difference when complex multiplication of two trajectory signals. One of the ways to eliminate phase measurement errors is the procedure for aligning two radar images. In turn, the alignment accuracy of radar images is associated with errors in the determination of reference objects, which leads to the destruction of the interferogram formed during a two-pass interferometric survey of a synthetic aperture radar station on a pilotless aircraft.

In accordance with this, the purpose of the work is to develop an algorithm for combining two-dimensional radar images of different altitude terrain, which ensures the efficiency of two-pass interferometric imaging of a radar station with a synthetic aperture of an antenna on an unmanned aerial vehicle.

The essence of the proposed algorithm is to use the function of local entropy in a complex radar image to determine reference objects by radar shadows and perform the procedure for aligning radar images in conditions of a low signal-to-noise ratio in order to form a three-dimensional radar terrain. stations with a synthetic aperture antenna on an unmanned aerial vehicle.

As the results of numerical studies have shown, in the absence of radio contrast objects, the coordination of two complex radar images with high accuracy is achieved by combining them with reference objects detected by their radar shadows by the local entropy function using affine transformations by the cross-correlation criterion. The presented results of numerical studies of the efficiency of searching for reference objects by local entropy by the modules of complex readouts of radar images indicate an advantage over the known detection algorithm in the range of 8-11 dB signal-to-noise ratio.

Kuznetsov V.A., Likhachev V.P., Unkovsky A.V. Matching radar images by the entropy of radar shadows of objects in the interests of twopass interferometric survey. Radioengineering. 2021. V. 85. № 1. P. 104−111. DOI: 10.18127/j00338486-202101-14. (in Russian)

1. Carrara W.G., Goodman R.S., Majewski R.M. Spotlight Synthetic Aperture Radar. Norwood, MA: Artech House. 1995. 554 p.
2. Kobernichenko V.G. Radioelektronnye sistemy distantsionnogo zondirovaniya Zemli. Ekaterinburg: Uralskii universitet. 2016. 220 s. (in Russian) 3. Shkolnyi L.A. Radiolokatsionnye sistemy vozdushnoi razvedki, deshifrirovanie radiolokatsionnykh izobrazhenii. M.: VVIA im. prof. N.E. Zhukovskogo. 2008. 531 s. (in Russian)  
3. Likhachev V.P. Unkovskii A.V. Problemnye voprosy navigatsionnogo obespecheniya dvukhprokhodnogo interferometricheskogo radiolokatora s sintezirovannoi aperturoi antenny na BLA. Sb. statei po materialam VII Mezhdunar. NPK «Akademicheskie Zhukovskie chteniya». Voronezh: VUNTs VVS «VVA». 2019. S. 162−166. (in Russian)
4. Zarubina V.S., Kanatnikov A.N., Krishchenko A.P. Analiticheskaya geometriya. M.: MGTU im. N.E. Baumana. 2000. 388 s. (in Russian)
5. Wojdała A., Gruszewski M., Olech R. Real-Time Shadow Casting in Virtual Studio. In Advanced Computer Systems. Eds Sołdek J., Pejaś J. The Springer International Series in Engineering and Computer Science. V. 664. 2002. Springer. Boston. MA.
6. Richards M.A., Scheer J.A., and Holm W.A. Principles of modern radar: basic principles. SciTech Publishing, Raleigh, NC. 2010. P. 202−208.
7. Likhachev V.P. Unkovskii A.V. Voronin A.A. Matematicheskaya model formirovaniya radiogologramm v rezhime dvukhprokhodnoi interferometricheskoi s'emki s bespilotnogo letatelnogo apparata. Sb. trudov XXVI MNTK. Voronezh: VGU. 2020. T. 3. S. 240−251. (in Russian)
8. Kupryashkin I.F., Likhachev V.P., Ryazantsev L.B. Malogabaritnye radiolokatsionnye stantsii s nepreryvnym chastotno-modulirovannym izlucheniem. M.: Radiotekhnika. 2019. 276 s. (in Russian)
9. Gonsales R., Vuds R. Tsifrovaya obrabotka izobrazhenii. M.: Tekhnosfera. 2012. 1104 s. (in Russian)