Modeling and Design for Reduced Cross Talk in Mixed Signal Analog/ Digital IC Packages for Wireless Applications

摘要

A critical requirement for the development of low cost, wide- bandwidth telecommunications equipment is the close integration of both digital and analog microelectronic components. The physical interface between an IC and its environment is the IC package, and its performance is severely tested by the high speed and high frequencies encountered in wide-bandwidth systems. Single chip mixed signal ICs that combine directly both high frequency analog and high speed digital sub-sections will require proper electromagnetic understanding of capacitive, inductive, and radiative coupling between components, and their impact on high sensitivity analog sub-circuits. The overall objective of this work is the development of techniques for the analysis and design of mixed signal packages, especially the impact of inductive cross talk between the digital and analog sections of the IC, and techniques to maintain appropriate RF to RF signal line isolation in low cost IC packages. In wireless personal communication services (PCS) units there are particularly severe constraints on package options, since these applications are typically very cost and form- factor sensitive. Some of the major problems induced by digital to analog and analog to analog cross talk are listed below: (1) high speed digital clocks cause severe interference with RF or IF front ends; (2) in digital portables, time-division-multiple-access (TDMA) may be used and power on / off cycles happen fairly frequently, causing additional transient noise on the power and ground planes; (3) in frequency division duplex systems, high-power transmit signals cause interference with weak receive signals since separation by filters is limited; (4) the leakage of the amplifier output to the input may cause the amplifier to oscillate.