Passive intermodulation in printed lines: effects of trace dimensions and substrate

Abstract

A comprehensive experimental study was performed to identify and discriminate mechanisms contributing to passive intermodulation (PIM) in microstrip transmission lines. The effects of strip length and width, and substrate materials on PIM performance of printed lines were investigated in the GSM900, DCS1800 and UMTS frequency bands. The major features of the experiment design, sample preparation and test setup are discussed in detail. The measurement results have demonstrated that the PIM level cumulatively grows on the longer microstrip lines and decreases on wider strips and, thus, indicated that the distributed resistive nonlinearity of the printed traces represents the dominant mechanism of intermodulation generation in the printed lines on PTFE-based substrates.

Methods of Low Passive Intermodulation Design

“…F. Suarez and others coated TiN on the flange by thermal evaporation. Their test results showed that TiN has good performance of resistance to the PIM [11]. Remarkably, permeability decreases with the increase of frequency.…”

“…It will reduce the current density flowing into the body of conductor and lower temperature, so that the resistance will be relatively stable. The reference [15] shows that the PIM level will cumulative grow with the increasing of the length of the microstrip line and strip width have no direct contact with the growth of the PIM .Thus in the design of microstrip line, we had better shorten the length and enlarging the width (but we should pay attention to try to use low permeability material as substrate). However, the increase in size is strictly limited in many practical conditions.…”

Experimental Studies of Passive Intermodulation in Metal-to-Metal Contacts

“…2 shows the return loss of the printed line connected to the 50 Ω cable through the brass block over a large bandwidth from 0.7 GHz to 1.2 GHz. The return loss for GSM band, from 910 MHz to 960 MHz, is less than −35 dB, by this way reducing the mismatching effect on PIM measurements as described in [12].…”

Effects of interface conditions and long-term stability of passive intermodulation response in printed lines

“…Recently, a series of investigations have been undertaken to identify the principal mechanisms and sources of PIM production in printed lines fabricated on commercial microwave laminates [9][10][11][12][13]. It has been shown that the weak distributed non-linearities inherent to the conductor cladding and material of the dielectric substrate are the major contributors to PIM generation in PCB [14].…”