System and method for controlling electromagnetic interference in portable electronic devices having a radio frequency subsystem

摘要

A portable electronic device that has a radio frequency communication subsystem operationally connected switch-mode power supply subsystem. The switch-mode power supply subsystem generates a pulse-width modulation electrical signal that produces electromagnetic interference. The switch-mode power supply subsystem can reduce the slew rate of the pulse-width modulation electrical signal when the radio-frequency communication subsystem is active. This reduces the level of the electromagnetic interference signal only during radio frequency communication, which improves the efficiency of the radio frequency communication. Not having the reduced slew rate when there is no radio frequency communication allows for higher modulation efficiency.

主权项

1. A portable electronic device comprising:
a radio frequency (RF) communication subsystem configured to generate a RF activity status signal indicative of a RF activity status of the RF communication subsystem; and a switch-mode power supply subsystem configured to receive the RF activity status signal, the switch-mode power supply subsystem operable to output an output electrical signal as a function of the RF activity status signal, the output electrical signal being a first output electrical signal when the RF activity status signal indicates inactivity of the RF communication subsystem, the output electrical signal being a second output electrical signal when the RF activity status signal indicates activity of the RF communication subsystem, the first output electrical signal being a pulse-width modulated signal having an initial slew rate, the second output electrical signal being a modified pulse-width modulated signal having a modified slew rate, the modified slew rate being less than the initial slew rate, the portable electronic device producing an electromagnetic interference (EMI) signal as a function of the output electrical signal, the EMI signal being lower for the second output electrical signal than for the first output electrical signal.