Subject: [NEXTEL-1] RF predistorter shatters performance barriers

From: [email-masked]
Date: Sun, 28 Sep 2003 13:13:24 -0400

RF predistorter shatters performance barriers

MAXIM Integrated Products, represented by Arrow Electronics,
has introduced the MAX2009/MAX2010, the world's first
monolithic RF predistorter ICs. Each device provides AM-AM and
AM-PM distortion correction by introducing adjustable gain and
phase expansion into a power amplifier (PA) lineup.

These expansion
characteristics are
specifically designed to
counteract the gain and
phase compression
exhibited by today's
LDMOS (laterally diffused
metal oxide silicon) power
amplifiers.

A joint study conducted
by Maxim and Motorola
has shown that the
MAX2009/MAX2010
provide substantial improvements in both PA linearity and
efficiency.

"Many amplifier designers are using Motorola's RF Solutions for a
total LDMOS amplifier lineup," stated David Runton, RF Systems
Engineering Manager in Motorola's RF & DSP Infrastructure
Division.

"By combining Maxim's MAX2009 with Motorola's latest
MW4IC2230MB multistage driver IC and our 5th generation
discrete MRF5P21180, designers can expect up to 5.7dB of IM3
and 4dB of ACPR enhancement or, at an equivalent linearity, 5.5%
drain efficiency improvement. We are committed to offering our
customers solutions for simple designs and quick market
introductions."

The results described here are representative of a Class AB PA
supporting two WCDMA 3GPP modulated tones with 10MHz of
channel spacing. These basic linearization enhancements are
applicable, moreover, for virtually any signal format covering the
500MHz to 1100MHz (MAX2010) and 1200MHz to 2500MHz
(MAX2009) bands of operation (cdma2000(TM), GSM/EDGE,
iDEN(TM), WLAN, etc.).

For an input signal with a 10dB peak-to-average ratio, the AM-AM
correction can be set to yield 1dB to 6dB of total gain expansion.
Likewise, the AM-PM correction can be modified to provide 4
degrees to 19 degrees of phase expansion.

"Both expansion curves are precision-controlled by making simple
adjustments to the gain and phase breakpoints and slopes," Ahne
added.

With these settings in place, the linearisation circuit can either be
run in a static 'set and forget' mode, or employ a more
sophisticated closed-loop implementation with real-time
software-controlled distortion correction.

Hybrid correction modes are also possible using simple lookup
tables to compensate for factors such as PA temperature drift or
PA loading.

The MAX2009/MAX2010 are both available in a 28-pin TQFN-EP
(5mm x 5mm) package and are specified for the extended (-40ºC
to +85ºC) temperature range.

18 September 2003

http://www.ferret.com.au/articles/59/0c01a159.asp
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