Non-linear junction detectors (NLJD) are used for detecting objects which contain p-n junction or corrosive materials (m-m junction) in a target area. p-njunctions are mostly included in electronic circuits which may contain diodes, transistors, amplifiers etc. Typical NLJDs employ harmonic radar principels where the 2^nd and 3^rd harmonics created by the target area after illimunation by a sinusoidal signal are compared to distinguish whether a p-n or m-m junction or nothing at all exists in the area. In general, the p-n junctions create stronger 2^nd harmonics than the m-m junctions do. The performance of NLJD is measured over how well it can differentiate p-n and m-m junctions. In this paper, we investiagted the factors that effect the NLJD performance. It is observed that the single tone illuminater signal has inferior performance. Therefore, we investigated a 2-tone illuminator signal and analyzed the impact of additoal harmoncis created by the combination of sums and differences of the two illuminating tones.