In the WiMAX market, some of the first transceivers were largely based on the ones used for wireless LAN or WiFi applications. Recognizing this, the RF design team at Atmel Duisburg committed themselves early on in the process to tailor a new line of transceivers just for WiMAX. Although early design was challenging because the actual WiMAX specification had yet to solidify, the team leveraged its depth of experience in WiFi to keep pace with the specification and tailor a solution just for WiMAX. And, when the WiMAX spec was ready, so was Atmel.
After getting the AT86RF535A design to meet the required performance specifications, the number one consideration for the design team was integration. They knew that their potential customers would be looking to streamline their designs and would want to avoid external filters as well as the need for two or three different radio components. "We wanted a device with the highest integration possible, that still met the performance, cost, size, and bandwidth requirements for our customers," explains Reiner Franke, RF Design Engineer, Atmel Duisburg. The resulting AT86RF535A integrates LNA, PA driver, Rx/Tx mixer, Rx/Tx filters, VCO, synthesizer, Rx gain control, and Tx power control in a single 8x8mm QFN56 package.
In order to integrate the different filter bandwidths of 1.75, 3.5, and 7MHz, the team selected a highly integrated low-IF conversion architecture. Because then the image frequency is part of the TX mask spec, the team had to use higher performance calibration techniques to achieve the necessary image rejection. "We choose a SiGe BiCMOS process," says Michael Livingston, Product Manager, Atmel Colorado Springs, "because it met the performance needs and offered advantages as compared to CMOS. Because Atmel's fab in Colorado Springs is one of the most cost effective fabs in the world for 6-in wafers, we are able to get both a technology and cost advantage."
What design trade-offs had to be made? "We focused on the performance and functionality, and, because this part is specifically designed for the fixed market, we did not optimize power consumption," explains Franke.
The RF design team at Atmel is by no means finished with WiMAX. The group is already working on a WiMAX roadmap that includes a miniPCI version that will be developed in partnership with WaveSat. There is another version of the AT86RF535 on the horizon that will have improved performance features and will be compatible with industry-standard basebands (the AT86RF535A is designed to work with WaveSat's baseband ICs). Small metallization changes on this upcoming IC (sampling planned for Q3 2006) will enable designers to change radio frequencies and achieve additional Wibro bandwidths.
Key specs:
Single-chip WiMAX Transceiver at 3.5GHz
Self Calibration Mode for RX / TX Filters
Modulation up to 64QAM
Sensitivity < -68dBm at 64-QAM, CR=3/4, 7MHz BW
Phase noise (synthesizer): 0.8deg (-37dBc)
Supply Voltage: +2.7VDC
Tx output power: -12 dBm
Rx/Tx operating current: 200/320mA Typical
Power off Current: < 20μA Typical
The AT86RF535A is available now. Production volumes will be available early in the second quarter of 2006. Pricing is $18.00 in quantities of 10,000. Click here for the data sheet.
Atmel Corporation, +1 (408) 441-0311, www.atmel.com .
