The MAX2820/MAX2820A and MAX2821/MAX2821A single-chip zero-IF transceivers are designed for the 802.11b (11Mbps) applications operating in the 2.4GHz to 2.5GHz ISM band. The transceivers are nearly identical, except the MAX2821 and MAX2821A also provide a low-power shutdown mode and an analog voltage reference output. The MAX2820A/ MAX2821A are cost-reduced versions, virtually identical in pinout and performance to the MAX2820/ MAX2821. The transceivers include all the circuitry required to implement an 802.11b RF-to-baseband transceiver solution, providing a fully integrated receive path, transmit path, VCO, frequency synthesis, and baseband/control interface. Only a PA, RF switch, RF BPF, and a small number of passive components are needed to form the complete radio front-end solution. The ICs eliminate the need for external IF and baseband filters by utilizing a direct-conversion radio architecture and monolithic baseband filters for both receiver and transmitter. They are specifically optimized for 802.11b (11Mbps CCK) applications. The baseband filtering and Rx and Tx signal paths support the CCK modulation scheme for BER = 10-5 a t the required sensitivity levels.