A multi frequency radar for detecting landmines: design aspects and electrical performance

A radar has been designed and built for application in the problem of anti-personnel landmine detection. The radar is based on the principle of a Stepped Frequency Continuous Wave (SFCW) transmission scheme. The novelty of the system is, that it transmits 8 frequencies at the same time through one antenna and that it repeats this procedure 16 times with shifted frequency offsets in order to collect a set of 128 frequency samples. The resolution in the synthesized range profile in air is just over 3cm, while the total frequency coverage is from 400MHz upto 4845 MHz, so ultra wide band. The architecture of the radar however is based on Commercial Off The Shelf narrow band technology. The acquisition time for collection of a full set of 128 frequencies covering the ultra wide band is less than 2 msec. This short time was achieved by simultaneously transmitting 8 frequencies and using Direct Digital Synthesis for signal generation. The concept of SFCW radar is prone to errors in phase. Therefore a calibration facility is built in. First results of the system while it is still in the setting-to-work phase are encouraging.