LO Frequency Shifting With Fast-Locking PLL for CIM3 Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication devices, especially those using Wi-Fi networks with OFDMA transmission, unwanted CIM3 emissions limit the transmit power level, restricting transmission efficiency and range due to regulatory emission requirements.
Innovation Solution
Implementing a fast-locking phase-locked loop (PLL) with adjustable bandwidth to rapidly change the local oscillator (LO) frequency during transitions between receive and transmit operations, allowing for increased transmit power without exceeding emission limits by configuring different LO frequency shifts for various resource units within a frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmit power level is increased to improve transmission efficiency and range, then transmission performance is improved, but unwanted CIM3 emissions exceed regulatory requirements
Solution Approach 1:
The system performs preliminary frequency offset compensation before transmit signal generation by estimating the frequency offset between the local oscillator and the assigned RU center frequency, then adjusting the LO frequency in advance to minimize CIM3 emissions before high-power transmission begins
Solution Approach 2:
The system dynamically changes the LO frequency parameter based on the assigned RU location and estimated frequency offset, adjusting the frequency by an amount equal to the estimated offset to align the LO with the RU center frequency, thereby reducing unwanted emissions while maintaining transmission efficiency
2Object-generated harmful factors
If LO frequency is changed rapidly during RX to TX transition to reduce emissions, then emission compliance is improved, but frequency transition disruption increases
Solution Approach 1:
The frequency offset estimation and LO frequency adjustment are performed in advance during the RX to TX transition period before high-power transmission begins, ensuring that the correct frequency is locked before data transmission starts, thus minimizing both emission violations and transmission disruption
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 reduces unwanted CIM3 emissions, enabling higher transmission efficiency, accuracy, and range while adhering to regulatory standards by minimizing disruption during frequency transitions and optimizing LO frequency shifts for different RUs.
Implementation Method 1
a phase-locked loop (PLL) configured to generate an oscillator (LO) signal; and a controller coupled to the PLL and configured to change a frequency of the LO signal during a transition between the RX period and the TX period
Data Source
AI summary
Disclosed herein are devices and methods to reduce unwanted CIM3 emission in a wireless communication device, such that the transmit (TX) power level applied in a RU can be increased without exceeding a regulatory emission requirement. In some aspects, unwanted emission may be reduced by shifting or changing local oscillator (LO) frequencies during TX operation. Some embodiments are directed to a fast-locking PLL with adjustable bandwidth that can be controlled to increase the PLL bandwidth during the RX to TX transition to provide a fast locking to a new LO frequency. Some aspects are directed to configuring an LO frequency shift amount for different RUs when multiple RUs are allocated within a frequency band.