Local Oscillator Filtering to Suppress Intermodulation Distortion
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Solution Overview
Problem
Existing wireless communication devices face issues with intermodulation distortion due to noise signals entering the signal path between the multiplier and local oscillator, leading to unwanted noise spectra that can overlap with the communication signal band, disrupting data communication.
Innovation Solution
A wireless communication device is designed with a filter placed between the local oscillator and frequency multiplier to remove noise signals whose frequency difference with the local signal is within the bandwidth of the high frequency signal, preventing intermodulation distortion and ensuring the communication signal band does not overlap with noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a frequency multiplier is used to multiply the local signal in frequency, then the center frequency of the local signal can be made lower than that of the high frequency signal, but intermodulation distortion occurs when noise signals enter the signal path, generating unwanted noise spectra that overlap with the communication signal band
Solution Approach 1:
The patent applies preliminary action by placing a filter between the local oscillator and frequency multiplier to remove noise signals before they can cause intermodulation distortion. The filter proactively eliminates frequencies that would otherwise be multiplied and create harmful noise spectra, preventing the problem rather than solving it after occurrence.
Solution Approach 2:
The filter acts as an intermediary component between the local oscillator and frequency multiplier. It mediates the signal path by selectively removing unwanted noise frequencies while allowing the desired local signal to pass through to the frequency multiplier, thus protecting the system from intermodulation distortion.
2Reliability
If noise signals are removed from the signal path, then intermodulation distortion is suppressed, but the device complexity increases due to the additional filter component
Solution Approach 1:
The patent applies the taking out principle by extracting and removing the harmful noise signals from the signal path using a filter. By taking out the unwanted frequencies before they reach the frequency multiplier, the system maintains high signal quality and reliability while the filter itself is a relatively simple component that adds minimal complexity.
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
The implementation effectively suppresses intermodulation distortions and prevents noise from occurring, maintaining communication integrity by separating the communication signal band from noise bands, thus ensuring reliable data transfer.
Implementation Method 1
a filter is provided between the local oscillator and the frequency multiplier, allows the local signal to pass and removing a noise signal whose frequency is different from that of the local signal
Implementation Method 2
a frequency multiplier that multiplies the local signal in frequency, a center frequency of the signal output from the frequency multiplier being equal to the center frequency of the high frequency signal
Implementation Method 3
a mixer connected to the antenna and the frequency multiplier, the mixer mixing a signal from the frequency multiplier and a high frequency signal received from the antenna
Data Source
AI summary
A receiver device includes an antenna that receives a high frequency signal having a bandwidth, a mixer connected to the antenna and a frequency multiplier. A filter that removes a noise signal whose frequency is different from that of the local signal is provided between the local oscillator and the frequency multiplier. The filter removes the noise signal that satisfies the condition that the absolute value of the frequency difference between the center frequency of the local signal and the center frequency of the noise signal is less than the bandwidth of the high frequency signal.