Diversity Receiver Chipset

The AD6600 mixed-signal receiver chip directly samples signals at analog input frequencies up to 250 MHz. The device includes two input channels, each with 1 GHz input amplifiers and 30 dB of automatic gain-ranging circuitry. Both channels are sampled with a 450 MHz track-and-hold followed by an 11-bit, 20 MSPS analog-to-digital converter. Digital RSSI outputs, an A/B channel indicator, a 2× Clock output, references, and control circuitry are all on-chip. Digital output signals are two’s complement, CMOS-compatible and interface directly to 3.3 V or 5 V digital processing chips.

The primary use for the dual analog input structure is sampling both antennas in a two-antenna diversity receiver. However, Channels A and B may also be used to sample two independent IF signals. Diversity, or dual-channel mode, is limited to 10 MSPS per channel. In single-channel mode, the full clock rate of 20 MSPS may be applied to a single carrier.

The AD6600 may be used as a stand-alone sampling chip, or it may be combined with the AD6620 Digital Receive Signal Processor. The AD6620 provides 10 dB–25 dB of additional processing gain before passing data to a fixed- or floating-point DSP.

Driving the AD6600 is simplified by using the AD6630 differential IF amplifier. The AD6630 is easily matched to inexpensive SAW filters from 70 MHz to 250 MHz.

Designed specifically for cellular/PCS receivers, the AD6600 supports GSM, IS-136, CDMA and Wireless LANs, as well as proprietary air interfaces used in WLL/fixed-access systems.

Units are available in plastic, surface-mount packages (44-lead LQFP) and specified over the industrial temperature range (–40°C to +85°C).

APPLICATIONS

* Communications Receivers

* PCS/Cellular Base Stations

GSM, CDMA, TDMA

* Wireless Local Loop, Fixed Access

* Dual IF Inputs, 70 MHz–250 MHz

Diversity or Two Independent IF Signals Separate Attenuation Paths

* Oversample RF Channels

20 MSPS on a Single Carrier

10 MSPS/Channel in Diversity Mode