AD6634

The AD6634 is a multimode 4-channel digital receive signal processor (RSP) capable of processing up to two WCDMA channels Each channel consists of four cascaded signal processing elements: a frequency translator, two fixed coefficient decimating filters, and a programmable coefficient decimating filter. Each input por has input level threshold detection circuitry and an AGC controller for accommodating large dynamic ranges or situations where gain ranging converters are used. Dual 16-bit parallel output ports accommodate high data rate WBCDMA applications. On-chip interpolating half-band can also be used to further increase the output rate. In addition, each parallel output port has a digital AGC for output data scaling. Link port outputs are provided to enable glueless interfaces to ADI's TigerSHARC^(R)  DSP core.

The AD6634 is part of Analog Devices' SoftCell^(R)  Multicarrier transceiver chipset designed for compatibility with Analog Devices' family of high sample rate IF sampling ADCs (AD9238/AD6645 12- and 14-bit). The SoftCell receiver comprises a digital receiver capable of digitizing an entire spectrum of carriers and digitally selecting the carrier of interest for tuning and channel selection. This architecture eliminates redundant radios in wireless base
station applications.
High dynamic range decimation filters offer a wide range of decimation rates. The RAM-based architecture allows easy reconfiguration for multimode applications.
The decimating filters remove unwanted signals and noise from the channel of interest. When the channel of interest occupies les bandwidth than the input signal, this rejection of out-of-band noise is called processing gain. By using large decimation factors, this processing gain can improve the SNR of the ADC by 30 dB or more. In addition, the programmable RAM coefficient filter allows antialiasing, matched filtering, and static equalization func-
tions to be combined in a single, cost-effective filter. Half-band interpolating filters at the output are used in WCDMA application to increase the output rate from 2* to 4* of the chip rate. The AD6634 is also equipped with two independent automatic gain control (AGC) loops for direct interface to a RAKE receiver.
The AD6634 is compatible with standard ADC converters such as the AD664x, AD923x, AD943x, and the AD922x families of data converters. The AD6634 is also compatible with the AD6600 diversity ADC, providing a cost and size reduction path.