Two new fully integrated RF CMOS direct conversion transceivers from Analog Devices Inc. are designed for WiMAX-certified terminals. Unlike conventional solutions, the AD9352 and AD9353 RF transceivers use smart-partitioning, a concept pioneered by ADI, to integrate all the analog signal processing technology—analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and RF functions—on a single chip. This allows the digital baseband chips to be manufactured on more cost-effective fine line processes, such as 90 nm or 65 nm, said ADI. The transceivers feature a direct connection to the digital modem via the ADI/Q digital I/Q interface, a simple parallel CMOS digital I/O interface that has been adopted by multiple digital modem partners.

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

Integrated on the transceivers are 12-bit, 160 Msps ADCs and DACs, along with smart system features such as self-calibration, automatic gain control, transmit power control, support for automatic frequency control, and auxiliary ADCs and DACs for system monitoring. The on-board converters and smart system features reduce the required level of real-time signal processing between modem and the transceiver, thus dramatically simplifying 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 path is achieved by integrating a fractional-N synthesizer. To reduce system cost, an on-chip crystal oscillator replaces the expensive voltage-controlled temperature compensated crystal oscillator (VCTCXO).

The devices offer a noise figure of 3.5 dB along with adjacent channel and alternate channel rejection capability that is 8 dB higher than the 802.16 standard requires. The devices’ highly linear transmit path has excellent spectral purity and offers error vector magnitude (EVM) of –37 dB at 0 dBm output power. The transmit power is detected by an accurate power detector and autonomously controlled with a range of 60 dB with step increments of 0.25 dB.