Electronic Design

Single-Chip Radio Lets WiMAX Devices Switch Bandwidth On The Fly

Also known as 802.16-2004, WiMAX probably is the only wireless standard that allows for bandwidth changes to better match up with the available spectrum and the desired speed partitioning for different services. A 1.5-MHz bandwidth may be enough for a basic low-speed service, but higher rates may take 5 MHz or even more. The trick is to make a radio with adjustable bandwidth.

AsicAhead's AA1001 RF IC makes such radios a reality. It's designed for applications in WiMAX customer premise equipment (CPE) and pico cells. Because of its wide frequency range and on-the-fly bandwidth changes, this single chip can address many possible operating frequencies and data-rate offerings.

The AA1001 is a direct conversion transceiver with on-chip frequency synthesizers for transmit and receive (see the figure). Both use the on-chip digitally controlled crystal oscillator (DCXO). The input frequency ranges from 700 MHz to 6 GHz, making the chip usable in virtually any defined WiMAX spectrum.

The bandwidth of the on-chip tunable filters can be adjusted from 200 kHz to 20 MHz. This configuration eliminates the need for external surface acoustic wave (SAW) IF filters and a temperaturecompensated crystal oscillator (TCXO).

The radio uses external filters and switches on the front end. It provides both analog and digital IQ interfaces to the external baseband IC processor. It's compatible with the fixed 802.16-2004 standard and the newer 802.16e mobile WiMAX standard as well.

The AA1001 also offers a gain from 0 to 116 dB in 2-dB steps. The noise figure is 3 dB. Third-order intercept is ?8 to +15 dB. Adjacent channel rejection is 24 dB. The transmitter offers 0-dBm output with a ?35.2-dB error vector magnitude (EVM).

AsicAhead additionally offers the Black Mountain AA1001 reference platform. Fully 802.16e-compliant, it comes in a PCMCIA form factor for 3.4- to 3.6-GHz and 2.3- to 2.7-GHz designs. The chip is sampling now. Full production is expected in the late third quarter. Expected pricing is $18 in 10,000-unit lots.

AsicAhead NV
www.asicahead.com

TAGS: Mobile
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