Baseband-Controlled Local Oscillator Tuning to Reduce CIM3
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Solution Overview
Problem
Existing terminal devices generate counter 3rd-order intermodulation products (CIM3) that interfere with guard bands in LTE communications, leading to increased costs and power consumption due to complex circuitry or additional hardware like notch filters to mitigate this interference.
Innovation Solution
Adjust the center frequency of the local oscillation signal based on the offset of the RB signal relative to zero frequency, eliminating the need for complex circuitry or additional hardware by preventing the generation of CIM3 through controlled up-conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If complex circuitry or additional hardware like notch filters is used to mitigate CIM3 interference, then the interference of CIM3 to guard band is reduced, but the cost and power consumption of the device increase
Solution Approach 1:
The patent changes the operating parameters of the phase-locked loop system by adjusting the reference frequency and VCO tuning range to ensure that the third-order intermodulation products fall outside the guard band. This parameter optimization eliminates the need for additional filtering hardware while maintaining signal integrity and reducing device complexity
Solution Approach 2:
The patent applies preliminary frequency planning and offset selection to pre-position the RB signals such that potential CIM3 interference falls in guard band regions rather than in usable frequency bands. This proactive approach prevents interference before it occurs, eliminating the need for reactive filtering solutions
2Object-affected harmful factors
If complex circuitry or additional hardware like notch filters is used to mitigate CIM3 interference, then the interference of CIM3 to guard band is reduced, but the power consumption of the device increases
Solution Approach 1:
By optimizing the phase-locked loop parameters including reference frequency and VCO tuning characteristics, the system prevents CIM3 generation through proper frequency offset selection, eliminating the need for power-consuming notch filters and reducing overall power consumption
3Speed
If frequency offset is applied to shift center frequency of RB signal, then the RB signal can be transmitted at correct frequency, but CIM3 interference is generated in guard band
Solution Approach 1:
The patent carefully selects and optimizes the frequency offset parameters and reference frequency values so that when the RB signal is shifted to its correct transmission frequency, the resulting third-order intermodulation products fall into guard band regions rather than interfering with usable frequency bands
Solution Approach 2:
The patent converts the potential harmful effect of frequency offset-induced CIM3 into a beneficial outcome by strategically positioning the interference products in guard band regions where they do not affect signal transmission, effectively using the interference pattern to its advantage
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
Effectively eliminates CIM3 interference without increasing costs or power consumption, reducing the need for filtering or duty cycle adjustments, thereby simplifying the terminal device's design.
Implementation Method 1
an up-converter performs up-conversion on the RB signal whose center frequency is shifted to obtain a radio frequency signal
Data Source
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AI summary
A terminal device, a transmitter, a baseband chip, and a radio frequency signal generation method are provided, so as to reduce interference of CIM3 to a guard band without increasing costs and power consumption of a device that generates a radio frequency signal. The terminal device includes an application processor, a baseband processor, a local oscillator, and an up-converter. The application processor is configured to trigger the baseband processor to send a resource block RB signal. The baseband processor is configured to: determine an offset Δf of a center frequency of the RB signal relative to a zero frequency, and control the local oscillator to adjust a center frequency flo of a local oscillation signal generated by the local oscillator to flo+Δf. The local oscillator is configured to adjust, under control of the baseband processor, the center frequency flo of the local oscillation signal generated by the local oscillator to flo+Δf. The up-converter is configured to generate a radio frequency signal, where the radio frequency signal is obtained by performing, by the up-converter, up-conversion processing on the RB signal whose center frequency is zero by using the local oscillation signal whose center frequency is adjusted.