DESCRIPTION

The SA2400A is a fully integrated single IC RF transceiver designed for 2.45 GHz wireless LAN (WLAN) applications. It is a direct conversion radio architecture that is fabricated on an advanced

30 GHz fTBiCMOS process. The SA2400A combines a receiver, transmitter, and LO generation into a single IC.

FUNCTIONAL BLOCKS AND FEATURES

The block diagram of the SA2400A Direct Conversion transceiver is given in Figure 1. It consists of the following functional blocks:

•A 79 dB adjustable gain range direct conversion zero IF receiver with 3 µs (typical) Tx to Rx switching time, and comprising the following:

– Front-end LNA with two internal gain states

– A fast on-chip closed loop composite RF and IF AGC with zoomed analog RSSI output and 8 µs settling time

– Quadrature downconverters from 2.45 GHz RF directly to zero IF

– On-chip fast baseband DC cancellation with automatically stepped bandwidths of 10 MHz, 1 MHz, 100 kHz, and 10 kHz, settling within 8–13 µs for a DC error of 10% that decays to 1%.

– Fully integrated channel filters, appropriate for 11 Msymbols/s QPSK modulation RF bandwidth.

•An I/Q upconverter from baseband directly to 2.45 GHz, with +8 dBm output power, –40 dBc typical carrier leakage (calibrated) and 3 µs (typical) Rx to Tx switching time, and comprising the following:

– Wide band IQ modulator producing better than 14% EVM for 11 Msymbols/s QPSK modulation

– Integrated reconstruction and spectral shaping filters at I and Q modulation input that is driven by an external D/A. High common mode rejection to input ground bounce.

– FIR-DACs for digital I/Q input feeding the analog signal path and including additional filtering for spectral shaping.

– 2.45 GHz power amplifier driver with +8 dBm maximum output, 15 dB adjustable gain in 1 dB steps and a second switched output at –1.5 dBm power level with similar gain adjustments that are set by a separate register.

– Completely on-chip calibration for Carrier Leakage compensation.

– Internal power ramping with 2 µs delay and 0.5 µs ramp-up time.

•A fractional-N frequency synthesizer with on-chip VCO and XO

•A 3-wire bus for control of most blocks

•An additional high speed 3-wire bus for full control of Rx-Gain and DC-offset compensation parameters with 44Mbits/s.

•Fast Tx-Rx switching based on a single digital input pin.

•Reference currents and voltage for supply of Baseband Processor and PA-chip.

APPLICATIONS

•IEEE 802.11 and 802.11b radios

  – Supports DSSS and CCK modulation

  – Supports data rates: 1, 2, 5.5, and 11 Mbps

•2.45 GHz ISM band wireless communication devices