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WiMAX transceiver with internal calibration debuts

Posted: 01 Oct 2007     Print Version  Bookmark and Share

Keywords:WiMAX transceivers  internal calibration algorithm  RF design 

AT86RF535B

Atmel Corp. has unveiled the third of its MAX-Link series of transceivers designed for WiMAX applications. AT86RF525B and its predecessor, the AT86RF535B, use a proprietary internal calibration algorithm, which eliminates the need for an external calibration circuit or calibration software.

The MAX-Link transceivers are the only WiMAX specific transceivers on the market today with internal calibration, according to Atmel. Initial startup calibration captures mismatch effects resulting in lower local oscillator leakage and improved image rejection. Changes in temperature, supply voltage or frequency during operation will cause RF performance degradation and hence, necessitate recalibration. The calibration routine is continuously performed between transmit and receive data frames, totally independent from the baseband and media access control (MAC) processor, to optimise the image rejection and LO leakage performance characteristics.

Along with enhanced WiMAX system functionality, the AT86RF525B enables one of the lowest component costs of any RF reference design on the market today. The frequency-agile, single-chip transceiver operates at 2.5GHz with multiple bandwidth options addressing the requirements of WiMAX base stations and subscriber equipment. Internal configuration and control registers can be programmed to integrate with new and existing baseband devices from different vendors. All of the MAX-Link transceivers provide excellent RF performance with low current consumption, low cost and a minimum of external components for RF design.

On-chip integration techniques combine a low-noise amplifier, power amplifier driver, receive/transmit mixer, receive/transmit filters, voltage-controlled oscillator, synthesizer, receive gain control and transmit power control all completely digitally controlled. The fully differential design of the transceiver can be configured for either low-IF or zero-IF applications and requires no external filters. The RF reference design incorporates a power amplifier including antenna diversity in a footprint of 40mm x 35mm on a four-layer PCB with components on only one side.

The fractional-N synthesizer in the AT86RF525B utilises a unique phase interpolation divider (PID) rather than the more conventional modulus divider architecture. The PID allows for very good frequency resolution and fast tuning speed. The calibrated voltage control oscillator can be tuned in less than 10µs to support 100MHz hybrid frequency division duplexing (HFDD) operations. The synthesiser has the speed and power advantages of an asynchronous divider and is fully programmable within the frequency range of the radio.

The AT86RF525B is available now. Pricing starts at Rs.586.50 ($14.50) in quantities of 10,000.




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