Parallel DAC Phase Alignment for Destructive Image Cancellation
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Solution Overview
Problem
Conventional digital-to-analog converters (DACs) face challenges in effectively suppressing unwanted signal images, leading to increased complexity and cost in analog bandpass filtering, especially when dealing with wideband signals or signals with large frequency separations, as they struggle to maintain filter selectivity and avoid phase distortion.
Innovation Solution
The use of multiple parallel DACs with gain/phase adjusters and phase shift elements, where the digital signal is split and adjusted before conversion, allowing undesired signal images to combine destructively, thereby reducing the need for complex analog filtering and minimizing phase errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional single DAC with analog bandpass filter is used, then analog filtering can remove unwanted images, but filter complexity and cost increase due to wideband signals and large frequency separations
Solution Approach 1:
The invention divides the single DAC system into multiple parallel DACs, each processing a portion of the digital signal. By segmenting the signal processing across multiple converters, the system can suppress unwanted images through controlled interference patterns rather than relying on complex analog filtering. Each DAC output is combined with appropriate phase and gain adjustments to achieve image suppression at the combiner output.
Solution Approach 2:
The invention converts the harmful effect of multiple DAC outputs (which could create additional images and interference) into a beneficial mechanism for image suppression. By deliberately controlling the phase and gain of each DAC output, the system causes unwanted images to combine destructively while desired signals combine constructively. This transforms what would be harmful interference into a useful suppression mechanism, eliminating the need for complex analog filters.
2Object-affected harmful factors
If complex analog bandpass filtering is applied to suppress images, then unwanted signal images are attenuated, but phase distortion increases
Solution Approach 1:
The invention replaces the mechanical/analog filtering system with a digital control system. Instead of using analog bandpass filters that inherently introduce phase distortion, the system uses digital gain and phase adjustment of individual DAC outputs. This substitution of digital signal processing for analog filtering eliminates the phase distortion problem while maintaining image suppression capability through controlled destructive interference of unwanted images.
3Object-affected harmful factors
If multiple parallel DACs with gain/phase adjusters are used, then unwanted signal images are suppressed through destructive combination, but device complexity increases
Solution Approach 1:
The invention makes each DAC channel multi-functional by incorporating gain adjustment and phase shifting capabilities within each parallel path. These adjustment mechanisms serve dual purposes: they enable precise control over individual channel contributions for image suppression, while also allowing optimization of signal quality and compensation for component variations. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in overall system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively attenuates undesired signal images, reducing the complexity and cost of analog bandpass filters by allowing for relaxed filtering requirements and maintaining the integrity of desired signal images within the Nyquist zone of interest.
Implementation Method 1
a plurality of phase shift elements coupled to respective ones of the plurality of digital to analog converters and configured to shift the phases of the analog signals generated by the digital to analog converters to form phase-shifted analog signals
Implementation Method 2
Transfer functions of the plurality of gain/phase adjusters may be selected based on phase shifts of the plurality of phase shift elements to cause undesired signal images in the analog signals output by the digital to analog converters to combine destructively in the combiner
Data Source
AI summary
A digital to analog conversion apparatus includes a plurality of gain/phase adjusters configured to receive a digital signal and to output a plurality of adjusted digital input signals, a plurality of digital to analog converters coupled to respective ones of the plurality of gain/phase adjusters and configured to receive the adjusted digital input signals and to generate respective analog signals representative of the adjusted digital input signals, a plurality of phase shift elements coupled to respective ones of the plurality of digital to analog converters and configured to shift the phases of the analog signals generated by the digital to analog converters, and a combiner coupled to the outputs of the plurality of digital to analog converters and configured to combine the respective phase-shifted analog signals to form an analog output signal.