Digital-to-RF Modulation Control for DAC Image Suppression
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Solution Overview
Problem
Digital-to-RF transmitter architectures face challenges with DAC images at clock frequencies and harmonics, violating regulatory and co-existence requirements, particularly in wide-bandwidth systems, where conventional solutions like sinc functions and analogue filtering are inefficient or costly.
Innovation Solution
A method to dynamically configure digital control modules within digital-to-RF converters by determining a desired digital control word switching frequency based on RF signal bandwidth, channel frequency, and power level, allowing for modulation that reduces DAC images within sensitive frequency bands or shifts them outside, thereby meeting regulatory requirements without additional analogue filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If additional analogue band-pass filtering is used to suppress DAC images, then DAC images are attenuated and regulatory requirements are met, but extra cost and pass-band loss are introduced
Solution Approach 1:
The patent replaces the mechanical analogue filtering system with a digital signal processing approach. A digital filter processes the output of the digital-to-analogue converter to suppress DAC images, eliminating the need for additional analogue band-pass filters. This substitution reduces device complexity and cost while maintaining effectiveness in attenuating DAC images to meet regulatory requirements.
2Object-affected harmful factors
If sinc function is applied to DAC sample-and-hold to suppress DAC images, then DAC images are notched out, but the solution is only appropriate for narrow band systems
Solution Approach 1:
The patent implements a dynamic filtering approach where the digital filter's characteristics can be adjusted based on the system's bandwidth requirements. Unlike the static sinc function approach limited to narrow band systems, this digital filter can be configured to suppress DAC images effectively across both narrow band and wide band applications, enhancing adaptability and versatility.
3Productivity
If digital-to-RF transmitter architecture is used for high efficiency, then transmission efficiency is improved, but DAC images at clock frequency and harmonics violate regulatory requirements
Solution Approach 1:
The patent introduces a digital filter as an intermediary component between the digital-to-analogue converter and the RF output stage. This digital filter acts as a mediator that suppresses DAC images generated by the efficient digital-to-RF transmitter architecture, allowing the system to maintain high transmission efficiency while meeting regulatory requirements by eliminating harmful DAC images at clock frequency and harmonics.
Data Source
AI summary
A method and apparatus for performing modulation of a radio frequency, RF, signal within a digital-to-RF converter. The method includes determining a desired digital control word switching frequency value based at least partly on at least one parameter corresponding to a bandwidth of the RF signal to be modulated and at least one from a group including: at least one parameter corresponding to an RF channel frequency of the RF signal to be modulated; and at least one parameter corresponding to a power level of the RF signal to be modulated. The method further includes dynamically configuring at least one digital control module to output at least one digital control word signal in accordance with the desired digital control word switching frequency value, and performing modulation of the RF signal in accordance with the at least one digital control word signal output by the at least one digital control module.