Envelope tracking signal generator incorporating trim cell

摘要

A novel and useful radio frequency (RF) front end module (FEM) circuit that provides high linearity and power efficiency and meets the requirements of modern wireless communication standards such as 802.11 WLAN, 3G and 4G cellular standards, Bluetooth, ZigBee, etc. The configuration of the FEM circuit permits the use of common, relatively low cost semiconductor fabrication techniques such as standard CMOS processes. The FEM circuit includes a power amplifier made up of one or more sub-amplifiers having high and low power circuits and whose outputs are combined to yield the total desired power gain. An integrated multi-tap transformer having primary and secondary windings arranged in a novel configuration provide efficient power combining and transfer to the antenna of the power generated by the individual sub-amplifiers.

主权项

1. An envelope tracking system, comprising:
an envelope detector operative to extract an envelope from an input RF signal; an analog to digital converter operative to generate a trim command based on said envelope; and a DC-DC converter operative to generate a power amplifier (PA) supply voltage in response to said trim command, said DC-DC converter comprising:
a switching circuit coupled to a DC voltage source and operative to convert an input voltage into said PA supply voltage across an output capacitor in accordance with a reference voltage;a feedback circuit coupled to said switching circuit and operative to generate a drive signal for said switching circuit; anda plurality of trim cells, each trim cell incorporating a trim capacitor adapted to be charged to a predetermined trim voltage and connected in series with said output capacitor in accordance with a trim command thereby increasing said PA supply voltage substantially instantaneously.