INDUSTRY TRENDS nents incrementally lower the high-frequency analog or RF wireless signals (currently about 900 MHz for cellular phones) to the lower frequencies used in digital signal processing (typically about 1 KHz). Brodersen said this process requires noise filtering. However, implementing analog filtering on digital chips can be difficult and expensive. Digital components. To avoid these problems, newer mixed-signal designs (particularly those with RF functionality) rely heavily on digital signal processors (DSPs) for filtering and may not even include analog filters. Because DSPs work with digital information rather than analog signals, they can filter noise better than analog filters. In some cases, Brodersen said, waveshaping by DSPs is the only practical way to handle particularly complex filtering. Improved DSP technology has helped this process. Today’s DSPs have smaller feature sizes and more transistors. In addition, they are faster and more efficient, and some can be programmed on-chip, permitting one DSP engine to perform several signal-modifying functions. DSPs have also become less expensive than in the past, said Tony Grewe, director of strategy and business development at Lucent Technologies. In some cases, though, they are still more expensive to include in a handheld device than comparable analog circuitry, so designers must balance cost considerations against functionality when deciding whether to use either DSPs or analog circuitry. Therefore, some applications will still require separate analog chipsets to meet price/performance specifications, Brodersen said.