Polarity-Switching Mixer for Flexible Intermediate Frequency
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Solution Overview
Problem
In typical mixers for receiving two different bands, the intermediate frequency is fixed halfway between the bands, limiting filter design freedom and resulting in poor filter performance due to high bandwidth and low attenuation in the stop band.
Innovation Solution
A mixer system that samples input signals at a predefined oscillator frequency and switches the polarity of the sampled signals at a predefined polarity switching frequency, allowing for flexible selection of intermediate frequencies and reducing the bandwidth of the low-pass filter, thereby improving filter performance by increasing attenuation in the stop band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the intermediate frequency is fixed halfway between two bands, then the mixer can simultaneously receive two different bands, but the filter bandwidth becomes too large resulting in poor filter performance with low attenuation in the stop band
Solution Approach 1:
The patent applies dynamics by making the intermediate frequency selectable and variable rather than fixed. The system allows dynamic selection of different intermediate frequencies based on the receiving requirements, enabling the filter bandwidth to be optimized for each specific case. This resolves the contradiction by providing both adaptability in frequency selection and improved filter performance through optimized bandwidth.
Solution Approach 2:
The patent changes the parameter of intermediate frequency from a fixed value to a variable parameter that can be selected from multiple options. By allowing the intermediate frequency to be changed according to different receiving scenarios, the system achieves both adaptability and improved filter performance with appropriate attenuation characteristics.
2Reliability
If a low-pass filter is used following the sampling mixer, then aliasing is prevented, but the filter bandwidth must be large enough to pass the intermediate frequency, reducing attenuation in the stop band
Solution Approach 1:
The patent makes the filter design dynamic by allowing selection of different intermediate frequencies that optimize the filter bandwidth. This enables the low-pass filter to maintain appropriate attenuation characteristics while still preventing aliasing, as the intermediate frequency can be chosen to match the filter's optimal performance range.
3Speed
If the oscillator frequency is increased to improve sampling rate, then the bandwidth of the low-pass filter increases, but this reduces the attenuation performance in the stop band
Solution Approach 1:
The patent changes the oscillator frequency from a fixed high value to a selectable parameter. By allowing the oscillator frequency to be adjusted, the system can optimize the balance between sampling rate and filter bandwidth, achieving both adequate sampling performance and improved stop band attenuation through appropriate parameter selection.
Data Source
AI summary
A mixer is configured to sample a received input signal at a predefined oscillator frequency to generate a sampled input signal, and to switch a polarity of the sampled input signal at a predefined polarity switching frequency to generate a polarity switched sampled input signal.