Dual Frequency Tracking Loop for OFDMA Frequency Error Correction
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Solution Overview
Problem
Wireless communication systems face challenges in accurately correcting frequency errors between the carrier frequency of received signals and the local oscillator reference frequency, particularly in OFDMA systems, where existing solutions like VCTCXO are costly and power-intensive.
Innovation Solution
A dual frequency tracking loop (FTL) method that applies a portion of the estimated frequency error to both the RF phase-locked loop (PLL) and digital rotator, allowing for cost-effective and power-efficient correction of frequency errors using a standard crystal oscillator (XO), rather than a voltage-controlled temperature-controlled crystal oscillator (VCTCXO).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a VCTCXO is used to correct frequency errors, then frequency accuracy is improved, but cost and power consumption increase
Solution Approach 1:
The frequency correction is divided into two segments: a coarse correction applied to the RF PLL and a fine correction applied to the digital rotator. This segmentation allows the use of a lower-cost XO instead of a VCTCXO while still achieving the required frequency accuracy through the combined effect of both correction stages.
Solution Approach 2:
The digital rotator acts as an intermediary component that provides fine frequency adjustment without requiring a VCTCXO. By introducing this intermediate correction stage, the system achieves high frequency accuracy using a standard XO, thereby reducing power consumption and cost.
2Measurement precision
If a VCTCXO is used to correct frequency errors, then frequency accuracy is improved, but device cost increases
Solution Approach 1:
The frequency correction functionality is segmented between the RF PLL and digital rotator, allowing the use of a standard XO instead of an expensive VCTCXO. This segmentation enables cost-effective implementation while maintaining frequency accuracy requirements.
Solution Approach 2:
The patent replaces the expensive VCTCXO with a cheaper standard crystal oscillator (XO). Although the XO has lower inherent accuracy, the system compensates through digital correction mechanisms, achieving the required performance at lower cost.
3Device complexity
If only a digital rotator is used for frequency correction, then device complexity is reduced, but frequency correction accuracy is insufficient
Solution Approach 1:
The correction system is segmented into two stages: coarse correction via RF PLL and fine correction via digital rotator. This segmentation enables each component to operate within its optimal range, achieving high overall accuracy without excessive complexity.
Solution Approach 2:
The patent merges analog correction (RF PLL) with digital correction (digital rotator) to achieve superior frequency accuracy. By combining these two approaches, the system overcomes the limitations of using either method alone.
4Device complexity
If frequency correction is applied only to the RF PLL, then implementation is simplified, but sampling-time errors are not addressed
Solution Approach 1:
The correction is segmented such that the RF PLL handles frequency correction while the digital rotator handles sampling-time alignment. This segmentation ensures both frequency and timing accuracy, improving communication reliability without excessive complexity.
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 effectively corrects frequency errors while balancing cost, performance, and power consumption, ensuring reliable wireless communication by simultaneously addressing sampling-time and frequency errors.
Implementation Method 1
a radio frequency (RF) phase-locked loop (PLL)
Data Source
AI summary
Methods and apparatus for correcting frequency errors between a carrier frequency of a signal received by a wireless device and a reference frequency local to the device. For certain aspects, such a method generally includes receiving a signal in a receiver having an LO producing a reference frequency, a radio frequency (RF) phase-locked loop (PLL), and a digital rotator, estimating a frequency difference between a carrier frequency of the received signal and the LO reference frequency, and applying the estimated frequency difference to the RF PLL and the digital rotator.