Tunable Sigma-Delta Modulator for Stable Multi-Band RF Conversion
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Solution Overview
Problem
Current Sigma-Delta modulators for RF receivers face complexity and high power consumption when adapting to various frequency bands, limiting their use in small, compact wireless communication devices.
Innovation Solution
A tunable Sigma-Delta modulator with constant noise shaping coefficients and a tunable delay element, allowing adjustment of the sampling frequency and loop delay to maintain stability across a wide range of frequencies without complex coefficient tuning, using a CMOS implementation to achieve low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Sigma-Delta modulator is tuned to various frequency bands, then the adaptability is improved, but the device complexity and power consumption increase
Solution Approach 1:
The patent applies parameter changes by making the delay element tunable to adjust the loop delay parameter according to the center frequency. This allows the modulator to adapt to different frequency bands by changing the delay parameter while keeping the noise shaping coefficients constant, thereby improving frequency band adaptability without increasing device complexity
Solution Approach 2:
The patent implements universality by designing a unified Sigma-Delta modulator architecture that can operate across multiple frequency bands (from baseband to 9 GHz) using the same noise shaping coefficients. The tunable delay element enables this single structure to serve multiple frequency band requirements, eliminating the need for different coefficient sets for different bands
2Measurement precision
If the sampling frequency is increased to maintain normalized center frequency, then the measurement precision is improved, but the power consumption increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the sampling frequency parameter based on the center frequency to maintain a constant normalized center frequency. This ensures optimal signal conversion precision across different frequency bands while the tunable delay element compensates to maintain stability, achieving good precision without excessively high power consumption
3Reliability
If the loop delay is adjusted for different frequencies, then the stability is improved, but the device complexity increases
Solution Approach 1:
The patent applies dynamics by implementing a tunable delay element that can dynamically adjust the loop delay according to the center frequency. This dynamic adjustment mechanism allows the modulator to maintain stability across different frequency bands by adapting the delay parameter in real-time, improving reliability while keeping the tuning mechanism relatively simple
Data Source
AI summary
A Sigma-Delta (ΣΔ) modulator for converting an analog input signal having a frequency bandwidth around a variable center frequency f0 to a digital output signal at a sampling frequency fs. The ΣΔ modulator comprises a quantizer (420) for generating the digital output signal and a loop filter for shaping the quantization noise. The loop filter comprises at least one subfilter (430, 410) centered around a frequency f0 and constant noise shaping coefficients (451, 452, 453). The ΣΔ modulator further comprises a tunable delay element (455), a frequency adjuster (480) for adjusting the sampling frequency fs such that the normalized center frequency f0/fs is constant, and a delay adjuster (490) for adjusting the loop delay td implemented by the quantizer and the tunable delay element (455), such that the normalized loop delay td/Ts falls in a predetermined range [tmin, tmax], where Ts=1/fs.