FIR DAC Architecture Using Delayed Inverter Groups for Spectral Purity
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Solution Overview
Problem
Existing digital-to-analog converters struggle to generate analog wideband calibration signals with high linearity and out-of-band rejection, which are essential for various applications.
Innovation Solution
A digital-to-analog converter (DAC) architecture that includes a delay circuit and multiple groups of inverter cells forming a Finite Impulse Response (FIR) filter, allowing for high spectral purity and high-speed operation by iteratively delaying digital input signals and inverting them to produce analog output signals, with optional capacitive and resistive elements for improved signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional DAC architectures are used, then device simplicity is maintained, but linearity and out-of-band rejection performance deteriorate
Solution Approach 1:
The DAC is segmented into multiple groups of inverter cells (first group, second group, etc.), each group processing different portions of the digital input signal. This segmentation allows independent optimization of each group's contribution to the analog output, improving overall linearity and spectral purity while maintaining manageable complexity through modular structure
Solution Approach 2:
Different groups of inverter cells are assigned different numbers of cells (e.g., first group has different count than second group) to create local variations in signal processing characteristics. This local quality differentiation enables precise control over the frequency response and spectral distribution, achieving high out-of-band rejection in specific frequency regions
2Manufacturing precision
If high spectral purity is achieved through multiple inverter groups, then linearity improves, but circuit complexity increases
Solution Approach 1:
The inverter cells are divided into multiple functional groups that process the digital input signal in parallel. Each group contributes a weighted portion to the final analog output, enabling spectral shaping and high out-of-band rejection through constructive and destructive interference of frequency components, while keeping individual group complexity low
Solution Approach 2:
Multiple groups of inverter cells are merged into a unified analog output structure where their individual outputs combine to form the final high-spectral-purity signal. The merging process leverages the complementary characteristics of each group to achieve superior linearity and spectral purity that would be difficult to obtain with a single complex circuit
3Productivity
If high-speed operation is implemented, then productivity increases, but signal quality may deteriorate
Solution Approach 1:
The inverter cells operate in periodic switching cycles synchronized with the clock signal, processing digital input bits at high speed. The periodic nature of the operation allows for predictable timing and phase relationships between different inverter groups, maintaining signal quality through consistent temporal patterns even at high operating frequencies
Data Source
AI summary
A digital-to-analog converter is provided. The digital-to-analog converter includes a delay circuit configured to iteratively delay a digital input signal based on a clock signal for generating a plurality of delayed digital input signals. Further, the digital-to-analog converter includes a plurality of groups of inverter cells. Each group of inverter cells is configured to generate a respective analog signal based on one of the plurality of delayed digital input signals. The inverter cells includes a respective inverter circuit configured to invert the respective delayed digital input signal. The plurality of groups of inverter cells include different numbers of inverter cells. The digital-to-analog converter additionally includes an output configured to output an analog output signal based on the analog signals of the plurality of groups of inverter cells.