Characterization of Microstrip Meanders in PCB Interconnects

Meandering traces are often used to increase delay times in
printed circuit board (PCB) interconnects. An accurate
analysis of meanders in today’s high speed digital circuits
needs to take into account a number of different effects,
including near field coupling between the turns of the meander
and reflections at the line discontinuities. These effects have a
significant impact on the delay and waveshape of the
propagated signal. In this paper we analyze microstrip
meander structures using a finite difference time domain
(FDTD) based full wave method and a quasi-static technique.
Signal propagation through meanders with different trace
separations is examined. Shortcomings of the quasi-static
approach are pointed out. Simple design guidelines are given.
Introduction
In many analog and digital applications, printed circuit board
(PCB) interconnect delays need to be tightly controlled or
matched. This is typically done through the use of delay
routing. A number of structures that implement controlled
signal delays have been developed and analyzed through the
years (e.g., [1-3]). The meander line is one of these structures
(Fig. 1). It is an array of coupled parallel commensurate
conductors. The meander line is a special case in the general
set of planar structures that consist of coupled parallel
conductors between ground planes or on top of a ground plane.