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RF transceiver chips target WiMAX terminal designers

Norwood, Mass.—Two direct-conversion transceiver ICs offer high integration for low-cost WiMAX (Worldwide Interoperability for Microwave Access) terminals that confer expanded coverage and improved QoS (quality of service). Shown for the first time at the WiMAX World Conference , Analog Devices Inc 's (ADI) ICs are the first two devices in a family of RF transceivers for WiMAX certified terminals.

Based on the IEEE-802.16 standard, WiMAX terminals provide wireless broadband connectivity and are low cost alternatives to wired approaches to connectivity, such as DSL and cable modems.

On-Chip Data Converters

ADI's transceivers integrate data converters on-chip. Unlike conventional devices that implement analog functions on separate devices, or include data converters on an ASIC , ADI's latest AD9352 and AD9353 RF transceiver chips use smart-partitioning, a concept pioneered by ADI to integrate all analog signal processing on a single die. So-called smart-partitioning integrates A/D (analog-to-digital) converters, DAC s (digital-to-analog converters), and other RF functions.

ADI's smart-partitioning permits the digital baseband chips to be manufactured on cost-effective fine-line processes, such as 90-nm or 65-nm fab processes. The transceivers feature a direct connection to a digital modem via ADI's ADI/Q digital I/Q (in-phase and quadrature) interface. ADI/Q is a simple parallel CMOS digital I/O interface.

ADI/Q has been adopted by multiple digital modem partners of ADI. Sequans Communications , for one, a supplier of WiMAX silicon and software has implements ADI/Q on its SQN1110 802.16e-compliant digital baseband device.

Two Versions

The dual-band AD9352 operates in the 2.3-GHz to 2.7-GHz, and 4.9-GHz to 5.9-GHz ranges. The single-band AD9353 operates in the 3.3-GHz to 3.8-GHz range. Together, the transceivers cover most licensed and unlicensed bands worldwide.

Integrated on the transceivers are 12-bit 160-Msample/s A/Ds and DACs. The devices also integrate smart system features such as self-calibration, AGC (automatic gain control), transmit power control, and support for AFC (automatic frequency control), as well as auxiliary A/Ds and DACs for system monitoring.

The on-board converters and smart system features reduce the required level of realtime signal processing between a modem and transceiver. ADI claims this will dramatically simplify RF driver development and support.

The transceivers also integrate a high sensitivity direct-conversion CMOS receiver, and channel-select filtering at baseband. A low phase-noise LO (local oscillator) path is achieved by integrating a fractional-N synthesizer.

To further reduce system cost, an on-chip crystal oscillator replaces expensive VCTCXO s (voltage-controlled temperature-compensated crystal oscillators).

RF Performance

The devices offer noise figure specs of 3.5-dB, along with adjacent-channel and alternate-channel rejection capability that's 8-dB higher than what the 802.16 standard requires. A highly linear transmit path also ensures spectral purity, offering an EVM (error vector magnitude) of -37-dB (at 0-dBm output power).

The IC's transmit power is detected by an accurate power detector and autonomously controlled. Control is exerted over a 60-dB range, in step increments of 0.25-dB.

Price And Availability

The AD9352 and AD9353 are sampling now with full production scheduled for December. Pricing starts at less than $15 per unit (in 1,000-piece quantities). The ICs are packaged in 9 x 9-mm 64-pin LFCSP s (lead-free chip-scale packages). They're spec'd for operation over a temperature range extending from -40°C to +85°C.

ADI also has an evaluation board available.

For more information, click here.

For further details contact Analog Devices, Inc., 804 Woburn St., Wilmington, Mass. 01887. Phone: 781-937-1710 or 1/800-ANALOGD. Fax: 781-937-1078.

Analog Devices 781-937-1710, www.analog.com

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