An Investigation on Passive Inter-Modulation generated by antenna contact
Safieddin Safavi-Naeini and Nagula Sangary (Adjunct)
Non-linearity caused by passive sources can produce significant distortion for devices with high transmit power or low receive sensitivity requirement. In modern days' handheld cellular devices, low profile is a design target. However with the inclusion of 4G protocols, number of cellular bands has increased significantly. As a result, simultaneous transmission of multiple bands is more common than ever before. Because of the overlapping nature of numerous frequency bands, harmonics/ inter-modulation distortion is a big concern for receiver desensitize of the co-existing radios. This motivates us to investigate on non-linearity caused by the passive sources.
Metal-metal contact can generate a metal-insulator/semi-conductor junction because of non-ideal surface roughness. If the gap between the layers is significantly low it can generate a tunnel current through the gap. This tunnel current has a non-linear I-V characteristic. The aim of this research is to understand how to characterize and model an unknown non-linear behavior of a contact. Issues related to measure low level distortion has been investigated. A test setup has been developed to measure such low level distortion. Based on the measurement an approach to model the nonlinear relationship has been proposed.