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, DACs (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 VCTCXOs (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 LFCSPs (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 Devices781-937-1710, www.analog.com