Small UAVs and micro-drones are becoming more and more available to the general public for leisure activities and exploited in commercial applications. However, there is growing concern for accidental or even criminal misuses of these platforms. Radar systems can provide good capabilities, especially at long ranges and poor visibility conditions. Design considerations for distributed millimeter wave radar networks, particular suitable for high density populated urban areas, are given in the report. Special attention is given to: The choice of suitable working frequency bands; The use of antenna beam-forming networks, based on proposed by the author Random Phased Radial Line Slot Antennas and correlation signal processing; The radar signal waveforms in order to obtain un-ambiguity autocorrelation function and small radar resolution volume, as well as to the use of the external coherency principles of Doppler detection.