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Description
The MAX2839 direct conversion, zero-IF, RF transceiver is designed specifically for 2GHz 802.16e MIMO mobile WiMAX systems. The device incorporates one transmitter and two receivers, with > 40dB isolation between each receiver. The MAX2839 completely integrates all circuitry required to implement the RF transceiver function, providing RF to baseband receive path, and baseband to RF transmit path, VCO, frequency synthesizer, crystal oscillator, and baseband/control interface. The device includes a fast-settling sigma-delta RF synthesizer with smaller than 40Hz frequency steps and a crystal oscillator that allows the use of a low-cost crystal in place of a TCXO. The transceiver IC also integrates circuits for on-chip DC-offset cancellation, I/Q error, and carrier leakage detection circuits. An internal transmit to receive loopback mode allows for receiver I/Q imbalance calibration. The local oscillator I/Q quadrature phase error can be digitally corrected in approximately 0.125° steps. Only an RF bandpass filter (BPF), crystal, RF switch, PA, and a small number of passive components are needed to form a complete wireless broadband RF radio solution.
The MAX2839 completely eliminates the need for an external SAW filter by implementing on-chip programmable monolithic filters for both the receiver and transmitter, for all 2GHz and 802.16e profiles and WIBRO. The baseband filters along with the Rx and Tx signal paths are optimized to meet the stringent noise figure and linearity specifications. The device supports up to 2048 FFT OFDM and implements programmable channel filters for 3.5MHz to 20MHz RF channel bandwidths. The transceiver requires only 2µs Tx-Rx switching time. The IC is available in a small 56-pin TQFN package measuring 8mm x 8mm x 0.8mm.
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