Multi-Phase Local Oscillator Switching to Suppress Frequency Pulling
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Solution Overview
Problem
In communication systems, the non-linearity of circuits at the transmission and reception ends causes multiple-frequency harmonic oscillation signals, which interfere with the oscillator, leading to a frequency pulling effect that degrades signal quality, particularly in 2G/3G/4G mobile communication networks and WLAN.
Innovation Solution
A local oscillation generator using a multi-phase circuit and multiplexer to generate a local oscillation signal with a frequency that is a non-integral multiple of the fundamental frequency, preventing the integral-multiple harmonics from coinciding with the oscillator's fundamental frequency, thus suppressing the frequency pulling effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the oscillator operates at a frequency that is an integral multiple of the local oscillation frequency, then the local oscillation signal can be generated by frequency division, but the multiple-frequency harmonic oscillation signals from the power amplifier cause a frequency pulling effect on the oscillator, degrading signal quality
Solution Approach 1:
The patent changes the frequency relationship parameter between the oscillator and local oscillation signal. Instead of using an integral multiple relationship (e.g., 2.4 GHz and 4.8 GHz), the oscillator operates at a frequency that is a non-integral multiple (e.g., 2.3 GHz for 2.4 GHz local oscillation). This parameter change eliminates the frequency pulling effect while maintaining frequency division capability, thus resolving the contradiction between generation efficiency and signal quality
Solution Approach 2:
The patent converts the potentially harmful frequency pulling effect into a beneficial arrangement by deliberately designing the oscillator frequency to be a non-integral multiple of the local oscillation frequency. This ensures that the harmonic frequencies from the power amplifier do not coincide with the oscillator frequency, transforming what would be a harmful interference into a design feature that protects against frequency pulling while maintaining system functionality
2Power
If the power amplifier operates at high power to amplify the RF signal, then the transmission power is sufficient for communication, but the non-linearity of the power amplifier generates high-power multiple-frequency harmonic oscillation signals that interfere with the oscillator
Solution Approach 1:
The patent introduces an intermediary frequency relationship between the oscillator and local oscillation signal. By making the oscillator frequency a non-integral multiple of the local oscillation frequency, it creates a frequency buffer that prevents direct interference from the power amplifier's harmonic signals. This intermediary frequency arrangement allows high power operation while blocking the harmful harmonic interference from reaching the oscillator
Solution Approach 2:
The patent applies local quality by creating a specific frequency relationship in the oscillation generation path that is different from the standard integral multiple relationship. This localized frequency arrangement (non-integral multiple) is applied specifically to the oscillator frequency to protect it from harmonic interference, while the rest of the system continues to operate with standard frequency relationships
Data Source
AI summary
A local oscillation generator includes a multi-phase circuit and a multiplexer. The multi-phase oscillator provides a plurality of multi-phase oscillation signals of a same frequency and different phases. The multiplexer conducts one of the multi-phase oscillation signals to an output end in different time slots to provide an output oscillation signal. The frequency of the multi-phase oscillation signals is the same as a fundamental frequency, and the frequency of the output oscillation signal is different from the fundamental frequency. Thus, the local oscillation generator provides a local oscillation signal according to the output oscillation signal such that the fundamental frequency is different from the frequency of the local oscillation signal.