AS the growth of wireless communications systems continues, the need t
o minimize interference between channels and systems operated in paral
lel is taking on greater importance. A significant part of this interf
erence is created by the mixing of multiple transmission frequencies i
n components with nonlinear characteristics-resulting in unwanted sign
als termed intermodulation (IM) products, Among the IM signals that mu
st be minimized are passive-IM (PIM) products, which are generated by
passive (or linear) components, such as high-frequency connectors. A t
est setup has been developed to evaluate the difference between variou
s surface-plating materials with respect to their PIM characteristics
at a point of contact. Unlike previous PIM investigations,(1-4) this t
est setup (Fig I) supports variation of the contact pressure (with the
aid of a piezo-electric crystal) with suitable precision to enable re
producible IM measurements with a defined force or strike range as a f
unction of the contact pressure.