Most of the air surveillance and traffic control radars are working actively. These radars are able to detect and localize airplanes with continuously radiating radar signals. Typically these radar signals are high-energy impulses. The generation of such an impulses requires extremely expensive high power microwave amplifiers. Beside the significant cost of the manufacture and operation of the transmitter units, the radar can be detected from its emitted high energy impulses and thus it can jammed easily as well.
In contrast passive radars do not contain transmitter units hence it is almost impossible to detect them. Therefore these type of radars have great importance in military aspects. With eliminating the transmitter units from the radar, it needs to utilize external sources to detect targets. Since we cannot influence the properties of the illumination sources, we need to develop and apply such a methods that can handle the newly arising difficulties.
In my thesis I present the research and development process of a passive radar that is designed by myself. This radar uses the Digital Video Broadcasting - Terrestrial (DVB-T) signal as non-cooperative source of illuminator to detect and track targets. Due to the construction of the DVB-T signal it has excellent correlation properties, thus it is perfectly suitable to use as the illumination source of the radar. I have made simulations and experimental measurements to check the detection methods of the passive radars. Based on the theoretical operation and measurement results the further development paths have also been designated.
The most critical problem in the operation of the passive radars is to achieve high isolation between the reference signal and the signals coming from the observed area. The reference signal which travels on the direct path typically has reasonably high power relative to the reflected signals, hence the reference signal can mask the week target echoes. I realize the separation of the direct path signal with using antenna array and applying digital beamforming methods. In my thesis the examined beamforming techniques and their applicability in passive radars are investigated in detail. The operation of the system concept is verified with a simulation software implemented by myself. I have designed and realized a coherent multichannel receiver to expermentalize the practical operation of the phased array passive radars. The performance of the coherent multichannel receiver has been verified with measurements.