Automatic Frequency Control Using CORDIC Correlation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing automatic frequency control methods in WCDMA systems are inefficient and lack comprehensive frequency offset compensation, relying on hardware-intensive table lookup or triangular transformation methods, which are not accurate enough to handle the frequency offsets caused by local crystal oscillator inaccuracies and Doppler effects.
Innovation Solution
A method and apparatus that calculate correlation values of common pilot symbols to determine frequency offset adjustments for voltage-controlled oscillators, using a Coordinate Rotation Digital Computer (CORDIC) algorithm for precise frequency offset estimation and compensation, while saving hardware resources and improving calculation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional table lookup method or triangular transformation method is used for frequency offset compensation, then the implementation is simple, but hardware consumption is high
Solution Approach 1:
The patent replaces conventional table lookup and triangular transformation methods with a new frequency offset compensation algorithm that uses correlation calculation between pilot signals and received signals. This substitution reduces hardware consumption by avoiding large lookup tables and complex transformation circuits, while maintaining implementation simplicity through a streamlined computational approach.
2Ease of operation
If existing simple automatic frequency control method is used, then the system is easy to implement, but frequency offset compensation accuracy is insufficient
Solution Approach 1:
The patent implements a feedback mechanism where the frequency offset is continuously estimated by correlating pilot signals with received signals, and the compensation amount is adjusted based on the estimated offset. This feedback loop maintains ease of implementation while significantly improving frequency offset compensation accuracy compared to conventional open-loop methods.
Solution Approach 2:
The patent performs preliminary frequency offset estimation using correlation calculation between known pilot signals and received signals before applying compensation. This preliminary action enables accurate frequency offset measurement without complicating the overall system implementation, as the pilot signals are already available in the WCDMA system.
3Measurement precision
If comprehensive frequency offset compensation is implemented, then frequency offset control accuracy is improved, but system complexity increases
Solution Approach 1:
The patent achieves comprehensive frequency offset compensation by utilizing the existing pilot signals that are already transmitted in the WCDMA system for multiple purposes: channel estimation, synchronization, and frequency offset estimation. This multi-functionality approach improves frequency offset control accuracy without significantly increasing system complexity, as the same pilot signals serve multiple functions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy and stability of frequency offset control, reducing hardware consumption and enabling more precise radio frequency adjustments, thereby improving the overall system stability.
Implementation Method 1
determining, according to the combined frequency offset value, a frequency offset adjustment value for a voltage controlled oscillator
Data Source
Figure 1~2C
Figure 3~4
Figure 5~6
AI summary
The present invention discloses a method and apparatus for implementing automatic frequency control. The method comprises: calculating a correlation value of common pilot symbols in a reception signal of each path and a frequency offset value, calculating a combined frequency offset value according to the frequency offset value of the reception signal of each path, and determining, according to the combined frequency offset value, a frequency offset adjustment value for a voltage controlled oscillator, a frequency offset adjustment value for overall reception signals and a frequency offset adjustment value for the reception signal of each path. Compared with prior art, with the method and apparatus of the present invention, a new method of small-scope frequency offset estimation is selected, which makes frequency offset estimation more accurate; by using CORDIC, hardware resources are saved and calculation accuracy is improved; frequency offset adjustment and control policy enables radio frequency adjustment to be more gentle and the stability of system to be enhanced.