A Method of Generalized Orthogonal Complementary Codes Applying in Space Based Radars

The experience, obtained in the local military conflicts during the past twenty years, shows persuasively that the radioelectronic war has great importance for the combat success. Due to this reason, the radiocommunication systems, including radars, are high priority targets. After finding of their location they are attacked immediately. For their destroying special intelligent rockets are designed. With regard at present, the measures, providing high level of secrecy of the radiocommunication systems, are studied intensively. A promising method for increasing the radiocommunication and radar system secrecy is the applying of complex wideband radiosignals. They provide large performance range and high distance resolution. Simultaneously, due to the small spectral density of these signals, the discovering of radiosystem is very hard. With regard to the positive features of the complex wideband radiosignals, our paper is focused on a particular class of these signals, named generalized orthogonal complementary codes (GOCCs). Namely, we study a method for GOCC applying in the spacecraft based radars. INTRODUCTION The experience, obtained in the local military conflicts during the past twenty years, shows persuasively that the radioelectronic war has great importance for the combat success. Due to this reason, the radiocommunication systems, including radars, are high priority targets. After finding of their location they are attacked immediately. For their destroying special intelligent rockets are designed. This situation shows that providing high level of secrecy has great importance for some military applications [1], especially for the radars, including these based on spacecrafts. As known, military radars comprise two subsystems, named primary and secondary radar respectively. The primary radar is used for discovering of targets, measurement of their coordinates and for following of their trajectories (“tracking”). The most primary radars work as “active-passive” systems. The active operation is the sending by radar transmitter series of powerful electromagnetic pulses. The passive operation is scattering by targets the small part of power of the sent pulses, which returns to the radar receiver. The secondary radars are assigned for solving of a particular but very important military problem – dividing the observed objects in two main classes, named “friend” and “foe”. Due to the significance of the target identification, the secondary radars are “active-active” systems. It means that our (friend) targets have a transmitter, which is activated by the pulses, sent by observing radars. As a result the targets return the so-named “responses”, which are messages, containing special coded data. This data is verified in the secondary radar receivers and if it matches to a “pattern”, it is decided that target is “friend”.