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Single-chip RF transceivers

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article image Phase angle of the local oscillator is held constant during transmit/receive operation.

MAXIM Integrated Products, represented in Australia by Arrow Electronics , has released two single-chip RF transceivers designed for single-band 802.11a and dual-band 802.11a/g WLAN applications.

The MAX2828 covers the world-band frequency spectrum from 4.9GHz to 5.9GHz while the MAX2829 covers both 2.4GHz to 2.5GHz and 4.9GHz to 5.9GHz bands. The ICs have a multiple-input-multiple-output (MIMO) mode in which the phase angle of the local oscillator is held constant during a transmit/receive operation, allowing multiple transceivers to be synchronised to the system reference oscillator. This feature is critical for 802.11n NxN MIMO radio and smart-antenna-based WLAN applications.

The MAX2828/MAX2829 transceivers are manufactured using Maxim's SiGe BiCMOS process. This results in up to 4dB better receiver sensitivity performance in both 11a and 11g 54Mbps mode. This performance improvement translates to 58% longer range for line-of-sight WLAN applications and 36% longer range for indoor applications.

The transceivers derive their receiver sensitivity from a combination of an RF-optimised IC process technology and circuit design. The result is a receiver noise figure of 3.5 dB, oscillator phase noise of -99dBc/Hz at 100kHz, 35ns group-delay variation in the channel filter passband, and I/Q quadrature sideband suppression of 40dBc. A digital AGC and dc-offset cancellation scheme allows antenna diversity selection within a packet header, further improving range. The transceivers are also designed with -10dBm receiver input IP3 at max gain, and 80dB filter channel selectivity, resulting in excellent immunity to 802.11a/g OFDM and 802.11b CCK jammers. On the transmitter side, the Tx output is highly linear, delivering -2.5dBm for 802.11g and -5dBm for 802.11a at <2% EVM. This allows the external PA to deliver its maximum power without added distortion from the transceiver, directly improving transmitter range.

The MAX2828/MAX2829 transceivers reduce the radio BOM cost and implementation size by integrating all RF transceiver function blocks between the RF switch and baseband processor I/Os. No external SAW filter is required. The transceivers integrate the full transmit path (from baseband IQ input to RF output) and full receive path (from LNA input to baseband IQ output), a low-noise VCO, a fractional-N PLL synthesizer, and baseband/control interface. Thy operate from a 2.7V-3.6V supply. A 1μA shutdown mode saves power during the system sleep mode. The ICs are available in an 8mm x 8mm, 56-pin, leadless QFN.

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