Digital Quadrature Rate Converter with Oversampling Interpolation
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Solution Overview
Problem
Wireless RF transmitters face challenges in providing stable output power with minimal distortion under varying antenna loading and environmental conditions, particularly in systems requiring complex modulation schemes and rate conversion, such as WBCDMA, where distortion during interpolation and rate conversion processes is a concern.
Innovation Solution
A digital quadrature rate converter and oversampling interpolator are used to receive digital quadrature modulation data at one clock rate and provide oversampled data at a higher clock rate, with optional timing control and a fractional hold function to minimize distortion and simplify interpolation algorithms, potentially combined into a single digital circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rate conversion and interpolation are used to convert modulation data between different clock rates, then multiple clock frequencies can be accommodated, but distortion of modulation information occurs during the conversion process
Solution Approach 1:
An oversampling interpolator is introduced as an intermediary component between the rate converter and the modulation data path. This interpolator oversamples the converted data and applies interpolation filtering to reconstruct the modulation signal, thereby reducing distortion while maintaining compatibility with multiple clock rates
Solution Approach 2:
The system changes the sampling rate parameter by oversampling the modulation data at a higher rate during the rate conversion process. This parameter change allows for better preservation of modulation information by increasing the number of samples available for accurate interpolation and reconstruction
2Adaptability or versatility
If timing control is added to adjust reply transmission timing, then timing advance/delay can be achieved, but device complexity increases
Solution Approach 1:
The timing control function is merged with the existing oversampling interpolator and rate converter. By combining these functions into an integrated digital signal processing block, the patent achieves timing advance/delay capability without proportionally increasing device complexity, as the timing control leverages the same oversampled data path already required for rate conversion
3Manufacturing precision
If oversampling interpolation is used to reduce distortion, then modulation signal quality improves, but operating frequency and power consumption increase
Solution Approach 1:
The oversampling interpolation process is segmented into discrete processing stages that can be selectively applied. The system performs interpolation only on the necessary portions of the signal path and at specific rates, rather than continuously oversampling all signals at maximum rate, thereby reducing overall power consumption while maintaining signal quality where critical
Data Source
AI summary
The present invention includes a digital quadrature rate converter and an oversampling interpolator, which are used to receive digital quadrature modulation data at one clock rate and to provide oversampled digital quadrature modulation data at a higher clock rate. Rate conversion and oversampled interpolation are used to accommodate systems with multiple clock frequencies and to generate modulation signals with low distortion. Some embodiments of the present invention add timing control to the oversampled interpolation. Some embodiments of the present invention may combine the rate conversion, oversampled interpolation, and timing control operations into a single digital circuit.