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RF predistorter shatters performance barriers

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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.

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