A programmable DSP engine for high-rate modems

The authors discuss a general adaptive FIR (finite impulse response) filter (GAFF) which provides the signal-processing functions required for high data rates and supports a simple frequency-multiplexed core for ADSL (asymmetric digital subscriber line) operations, or a full-duplex full-feature unit that includes echo cancellation, decision feedback equalizer, and Tomlinson precoding. In addition to FIR operations, the device incorporates binary functions to complete all real-time modem operations, providing a complete system solution and eliminating external support circuitry. For low rate and low complexity, a single device can implement all the modem functions, while at the high end, a few devices are needed to share the load.<>