DAC Filtering with Delayed Signal Paths for Out-of-Band Noise

The patent replaces the mechanical analog filter system with a digital signal processing system. A delay element introduces a time delay to the digital signal, and digital-to-analog conversion circuitry converts both the original and delayed digital signals into analog signals that are then combined. This substitution of digital processing for analog filtering resolves the contradiction by achieving noise attenuation through digital means, thereby reducing device complexity and cost while maintaining effective out-of-band noise suppression.

The patent creates a universal filtering solution that works regardless of whether an analog base-band signal is available. The delay element and digital-to-analog conversion circuitry can process digital signals directly and produce filtered analog outputs suitable for various applications including WCDMA systems with direct digital up-conversion. This multi-functional approach resolves the contradiction by making the filtering technique adaptable to different system architectures while maintaining ease of implementation through a standardized digital processing approach.

The patent replaces bulky analog band-pass filters with compact digital processing circuitry. The delay element can be implemented using simple digital storage elements, and the digital-to-analog conversion circuitry integrates well with modern ASIC technology. This substitution resolves the contradiction by achieving effective out-of-band noise attenuation at high frequencies without requiring large, expensive analog filters, thereby significantly reducing the volume of the filtering component.