Abstract
Passive intermodulation (PIM) by metal contacts limits the bandwidth and
capacity of radio links used in mobile and satellite communications. In
this work, we investigate the effect of nonlinearities of metal-to-metal
contacts and their effects on PIM generation. An analytical expression
is obtained for the tunneling current density which has an error of
~1.6% in the case of a very thin insulator and low
voltages in MIM (Metal-InsulatorMetal) junctions. The presented
analytical model of the contact surfaces with the fractal geometry is
applied to simulate PIM products of third-order (PIM3) and fifth-order
(PIM5) versus the contact resistance and applied pressure. The
simulation results are validated experimentally by an open-ended
rectangular coaxial structure with a slotted enclosure. The measurement
results demonstrate that the presented model predicts the PIM with a
mean error of about 4.8 dB when the contact pressure varies from 0.5 MPa
to 1.7 MPa.
Â