Lookup-Table Delta-Sigma Modulator for Lower-Power RF Sampling
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Solution Overview
Problem
Conventional Delta-Sigma modulators for mobile radio applications face high implementation complexity and power consumption due to high sampling rates required for RF signals, which are challenging to achieve with existing bipolar semiconductor technologies.
Innovation Solution
A Delta-Sigma modulator design that uses pre-calculated digital output sequences stored in a look-up table, allowing for lower internal sampling rates by shifting baseband signals to a carrier frequency, reducing complexity and power consumption by operating primarily in the MHz domain instead of the GHz domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Delta-Sigma modulators are used with high sampling rates for RF signals, then the output signal quality is improved, but the implementation complexity and power consumption increase significantly
Solution Approach 1:
The patent pre-calculates and stores delta-sigma modulated sequences for various input values in a lookup table during a design phase. During operation, the modulator simply retrieves pre-computed sequences based on input samples, avoiding real-time high-rate modulation calculations and reducing implementation complexity while maintaining output signal quality
Solution Approach 2:
The patent creates a simplified copy of the delta-sigma modulation process by storing pre-computed output sequences in a lookup table. Instead of performing complex real-time modulation at high sampling rates, the system copies pre-calculated sequences and selects them based on input values, significantly reducing device complexity while preserving signal quality
2Speed
If conventional Delta-Sigma modulators operate at GHz sampling rates for mobile radio applications, then the RF signal processing capability is improved, but the power consumption becomes prohibitively high
Solution Approach 1:
The patent performs the computationally intensive delta-sigma modulation calculations in advance and stores the results in a lookup table. During actual operation, the system only performs simple table lookups and sequence selections at lower sampling rates, dramatically reducing power consumption while maintaining the ability to process RF signals for mobile radio applications
Solution Approach 2:
The patent replaces the power-intensive real-time high-speed modulation process with a low-power copy mechanism that retrieves pre-computed sequences from memory. This copying approach maintains RF signal processing capability while reducing power consumption to acceptable levels for mobile radio applications
3Ease of manufacture
If bipolar semiconductor technology is used for Delta-Sigma modulators, then the manufacturing process is established, but the power consumption and complexity constraints increase
Solution Approach 1:
The patent replaces the complex bipolar semiconductor implementation with a simplified lookup table-based system that can be implemented in lower-power technologies. The pre-computed sequences are stored in memory structures that can be realized in CMOS or other low-power semiconductor processes, reducing power consumption while maintaining ease of manufacture through established memory fabrication techniques
Data Source
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Figure 3
Figure 4a~5b
AI summary
One aspect of the invention relates to a Delta-Sigma-Modulator (1) for digitizing a baseband signal (X), comprising: an input stage (2) for generating input samples (yi) of the baseband signal (X) at an input sampling rate, a selecting stage (3) for selecting for each input sample (yi) a digital output sequence (SEQ) from a plurality of pre-calculated digital output sequences (SEQre, SEQim), and an output stage (4) for generating an output signal of digital output samples (zi) from the selected digital output sequences (SEQre_a, SEQim_a) at an output sampling rate being larger than the input sampling rate, wherein the pre-calculated digital output sequences (SEQre, SEQim) comprise delta-sigma modulated digital output samples of the baseband signal (X) shifted to a desired carrier frequency (fc), each digital output sequence (SEQre, SEQim) preferably having at least one property (IDre, IDim; N0nomre, N0nomim) which is related to at least one property of the input samples (yi). Other aspects of the invention relate to an active antenna element (5), to a base station (7), and to a corresponding method for digitizing a baseband signal (X).