LO Frequency Shifting for Higher Wi-Fi RU Transmit Power
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Solution Overview
Problem
In wireless communication devices using Wi-Fi networks, especially under OFDMA transmission protocols like 802.11ax, increasing the transmit (TX) power level in resource units (RUs) is limited by unwanted CIM3 emissions, which violate regulatory emission requirements.
Innovation Solution
The method involves shifting or changing the local oscillator (LO) frequencies during TX operations to reduce unwanted CIM3 emissions. This is achieved by using a fast-locking phase-locked loop (PLL) with adjustable bandwidth, which allows for rapid locking to new LO frequencies, and configuring different LO frequency shift amounts for various RUs within a frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmit power level is increased in resource units, then transmission efficiency and range are improved, but unwanted CIM3 emissions increase and violate regulatory requirements
Solution Approach 1:
The patent changes the LO frequency parameter dynamically based on the RU index. By adjusting the LO frequency offset from the nominal value, the system shifts the spectral position of transmitted signals to avoid generating harmful CIM3 emissions while maintaining adequate transmit power for efficient communication.
Solution Approach 2:
The patent applies different LO frequency offsets to different resource units within the frequency band. Each RU receives a customized LO frequency adjustment tailored to its specific position and requirements, allowing optimal emission control and power transmission for each local frequency region rather than using a uniform approach.
2Object-generated harmful factors
If LO frequency is changed during TX operation, then CIM3 emissions are reduced, but frequency switching time increases
Solution Approach 1:
The patent pre-calculates and stores the optimal LO frequency offset values for different RU indices before transmission begins. This preliminary preparation allows the system to quickly switch between predetermined frequency offsets during TX operation without requiring complex real-time calculations, thereby minimizing frequency switching time while maintaining emission control.
3Productivity
If multiple RUs are allocated within a frequency band, then data throughput is improved, but interference between RUs increases
Solution Approach 1:
The patent assigns different LO frequency offsets to different RUs based on their indices. This parameter differentiation creates frequency separation between signals transmitted on different RUs, reducing mutual interference while allowing multiple RUs to operate simultaneously and maintain high data throughput.
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 enables an increase in TX power level without exceeding emission requirements, leading to higher transmission efficiency, accuracy, and range in wireless communication devices.
Implementation Method 1
using a fast-locking phase-locked loop (PLL) with adjustable bandwidth, which allows for rapid locking to new LO frequencies
Implementation Method 2
the RF input signal may be an intermedia frequency (IF) signal having frequency F IF , which is mixed with a local oscillator (LO) signal having frequency F LO in a mixer to generate the RF radio signal having a carrier frequency F RF for transmission
Data Source
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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.