Local Oscillator Frequency Control for Harmonic Interference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In communication systems, it is challenging to design receivers that effectively reduce interference from unwanted signals caused by harmonics of the local oscillator (LO) signal, especially when channels have wide bandwidths, as traditional filtering methods are difficult to implement and can be expensive or impractical.
Innovation Solution
The method involves determining the power level of interfering signals corresponding to harmonics of the LO signal and adjusting the LO frequency to minimize interference, allowing for adequate attenuation of these signals by selecting an LO frequency that shifts interfering signals out of the desired channel's range, thereby reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional filtering methods are used to reduce interference from LO harmonics, then interference attenuation is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the LO frequency parameter to a value that creates sufficient separation between the desired signal and interfering signals after mixing. By adjusting this single parameter, the system achieves effective interference rejection without requiring complex tunable filters, thus resolving the contradiction between interference attenuation and device complexity
Solution Approach 2:
The patent performs preliminary frequency selection of the LO signal before the mixing operation. By pre-selecting an LO frequency that avoids harmonic interference, the system eliminates the need for complex post-mixing filtering, thereby reducing device complexity while maintaining effective interference attenuation
2Adaptability or versatility
If tunable filters are used to receive all channels with wide bandwidths, then adaptability is improved, but device complexity and cost increase
Solution Approach 1:
The patent employs a fixed-frequency LO signal that can serve multiple channels across wide bandwidths. By carefully selecting the LO frequency, a single fixed LO can provide adequate interference rejection for multiple channels, eliminating the need for complex tunable filters and achieving universality without increased complexity
Solution Approach 2:
The system changes the LO frequency parameter based on the desired channel to maintain effective interference rejection across different channels. This parameter adjustment approach enables wide bandwidth coverage with simple fixed or selectively-tuned LO frequencies rather than requiring complex tunable filters for each channel
3Object-affected harmful factors
If LO frequency is adjusted to minimize harmonic interference, then interference reduction is improved, but control complexity increases
Solution Approach 1:
The patent implements a self-service mechanism where the system automatically selects or adjusts the LO frequency to minimize harmonic interference without requiring complex external control. The LO frequency control system serves itself by autonomously determining the optimal frequency setting, thereby reducing overall control complexity while achieving effective interference reduction
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 allows for reduced interference by adjusting the LO frequency to minimize the power of interfering signals, making it possible to use filters effectively after mixing, even in systems with wide bandwidths, thereby improving signal processing efficiency.
Implementation Method 1
the information signal is shifted to an intermediate frequency (IF) to generate an IF signal... The shifting of a signal to or from a carrier frequency may be accomplished by multiplying the signal by a sinusoid. This technique is often referred to as 'mixing' the signal with a local oscillator (LO)
Implementation Method 2
the resultant signal is filtered with a low-pass filter to remove unwanted high frequency components
Implementation Method 3
In the frequency domain, a square-wave signal is similar to a sinusoid, but with harmonics added (typically odd harmonics). Thus, when mixing with a square wave signal, unwanted interfering components corresponding to the harmonic frequencies of the square wave may be mixed down
Data Source
AI summary
In a method for setting a local oscillator (LO) frequency in a receiver, a power level of an interfering signal corresponding to a harmonic of an LO signal is determined. The LO frequency is set based on the determined power level of the interfering signal.