Effect of two tone transmit signal on nonlinear junction detection performance

Nonlinear junction detectors are developed to detect the nonlinear junctions which are used as security threats. Working principle of the detectors are based on harmonic radar but the detectors may sound the false alarm when the target junctions are too small or there are lots of nonlinear junctions which are not the security threats. In this study, the facts which effect the performance of nonlinear junction detectors are semtinized and depend on these facts, some of frequently used detectors that have different transmit signal frequencies and power options are compared. Additionally, two tone transmit signals simulated to detect the nonlinear junctions istead of single tone transmit signal which are generally used. Also, frequency domain max points of the signals reflected from the junctions and the characteristics of several junction types that effect the amplitude of the reflected signals are examined. Finally, an experimental set up prepared in an electromagnetically cleaned room and, the harmonic and mixed harmonic signals, which are created from the two tone transmit signals by the junction in the target area, are observed. In conclusion, it is seen that the detecting and distinguishing performance of classical detectors which use single tone transmit signal can be increased by the mixed harmonic signals which are generated from two tone transmit signals. The thesis propose to use mixed harmonic signals which are generated from the transmit signals to detect p-n type junctions and distinguish them from the other type of junctions.