Digital Linear Transmitter Using Split DAC and Oversampled RF Conversion
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Solution Overview
Problem
Existing wireless transmitter core architectures rely heavily on analog circuit elements, leading to increased circuit area consumption, performance variations, and scalability issues, while introducing signal distortion and noise due to the use of voltage-to-current converters and high-order analog filters.
Innovation Solution
The implementation of a wireless transmitter core that reduces analog components by utilizing a delta sigma digital-to-analog converter (DAC) with oversampling and weighted transistor conversion, integrating first-order filtering and mixing, and eliminating the voltage-to-current converter and high-order analog filters, thereby increasing digital domain circuits and minimizing noise and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analog circuit elements (voltage-to-current converters, high-order analog filters) are used in the transmitter core, then signal conversion and filtering functions are achieved, but circuit area increases and performance variations occur
Solution Approach 1:
The patent replaces analog circuit elements (voltage-to-current converters, high-order analog filters) with digital signal processing techniques. Specifically, digital filtering and digital-to-analog conversion are used instead of analog filtering and analog conversion circuits, thereby reducing circuit area while maintaining signal quality.
Solution Approach 2:
The patent changes the operating parameters by using oversampling in the digital-to-analog conversion process. By increasing the sampling rate beyond the Nyquist rate, the filtering requirements are relaxed, allowing first-order filters to achieve the same performance as high-order analog filters would provide at lower sampling rates.
2Reliability
If voltage-to-current converters and high-order analog filters are implemented, then signal conversion and noise filtering are achieved, but quantization noise and signal distortion increase
Solution Approach 1:
The patent substitutes digital signal processing for analog signal processing. By performing filtering operations in the digital domain before digital-to-analog conversion, the system avoids introducing quantization noise and distortion that occur in analog circuits. The digital filters can precisely implement the desired frequency response without the non-linearities inherent in analog filter components.
Solution Approach 2:
The patent performs filtering operations in advance, in the digital domain, before the signal undergoes digital-to-analog conversion. This preliminary digital filtering removes unwanted frequency components before conversion, preventing the introduction of quantization noise and distortion that would occur if filtering were performed after conversion in the analog domain.
3Ease of manufacture
If analog circuit elements are used in the transmitter core, then signal processing functions are achieved, but manufacturing precision and scalability are reduced
Solution Approach 1:
The patent replaces analog circuitry with digital circuitry and digital signal processing. Digital circuits are inherently more robust to manufacturing variations and process deviations compared to analog circuits. Digital filters implemented in software or programmable logic can be precisely replicated across manufacturing batches, ensuring consistent performance without the sensitivity to component tolerances that plagues analog designs.
Data Source
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AI summary
A digital linear transmitter for digital to analog conversion of a radio frequency signal. The transmitter includes a delta sigma (?S) digital to analog converter (DAC) and a weighted signal digital to analog converter in the transmit path of a wireless device to reduce reliance on relatively large analog components. The ?S DAC converts the lowest significant bits of the oversampled signal while the weighted signal digital to analog converter converts the highest significant bits of the oversampled signal. The transmitter core includes components for providing an oversampled modulated digital signal which is then subjected to first order filtering of the oversampled signal prior to generating a corresponding analog signal. The apparatus and method reduces analog components and increases digital components in transmitter core architecture of wireless RF devices.