L. B. Ryazantsev – Ph.D. (Eng.), Senior Lecturer, Air Force Academy n.a. Prof. N.E. Zhukovsky and Yu.A. Gagarin (Voronezh). E-mail: email@example.com
These days supplying a small-size synthetic-aperture radar on unmanned aerial vehicles (UAV) is an urgent problem. The quality of radar images provided by the synthetic-aperture radar (SAR) is, among other things, determined by the dynamic range of an output signal. One of the methods of its extension is to provide the invariable strength of the received signal, reflected from the ground re-gardless of the distance to it. This is possible through the cosecant antenna application or the use of the sensitive time control (STC) system. Cosecant antenna application is based on the special shape reflector antenna or phased arrays with corresponding aperture distributions in vertical plane. However, deployment of such antennae, C-band or L-band frequency in particular, on drones is technically challenging because of the existing limitations on aerodynamic characteristics of the external equipment and the maximum payload (max 4–5 kg). Unlike pulsed radar, STC system application in the FMCW radar, where the distance to the object is determined by frequency measurements, seems impossible.
The article contains the techniques of reflector antenna shape and the aperture distribution of phased array synthesis, which provides the arbitrarily assigned cosecant antenna shape. On the ground of these methods the reflector antenna and the phased array is estimated in MATLAB. The results provide the evidence for the choice of cosecant antenna design with regard to its size limitations and requirements to range and width of the swath which are characteristic to the FMCW SAR, deployed on drones.
Besides, the attainable antenna directivity values in the vertical plane that provide further justification of requirements to the average power transmitter and receiver sensitivity of the synthetic-aperture radar are estimated for the centimeter-waves antennae.