Multiplexer Isolation Using Cross-Terminal Band-Stop Filtering
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Solution Overview
Problem
Existing multiplexers face challenges in improving isolation characteristics across wide bands, as signals in overlapping passbands tend to leak between terminals, degrading the isolation quality.
Innovation Solution
Incorporating a band-stop filter with specific attenuation poles within the passbands of bandpass filters to ensure signals in one passband have the same amplitude but opposite phases, thereby canceling each other out and enhancing isolation between terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional circuits are added to improve isolation characteristics, then isolation quality improves, but device complexity increases
Solution Approach 1:
The band-stop filter is integrated into the existing multiplexer structure by connecting it between two bandpass filter terminals, merging isolation functionality with the signal routing structure. This combination improves isolation characteristics without adding completely separate isolation circuits, thereby limiting the increase in device complexity.
2Reliability
If band-stop filter is added to cancel signals in overlapping passbands, then signal separation improves, but device complexity increases
Solution Approach 1:
The band-stop filter acts as an intermediary element connected between bandpass filter terminals, mediating the signal interaction between different passbands. By positioning the band-stop filter as an intermediary, signals in overlapping passbands are canceled through controlled interference, improving signal separation while maintaining a relatively simple overall structure.
3Reliability
If attenuation poles are positioned within passbands, then isolation characteristics improve, but manufacturing precision requirements increase
Solution Approach 1:
The band-stop filter is designed with specific local characteristics - attenuation poles positioned at predetermined frequencies within or near the passbands of bandpass filters. This local quality approach targets signal cancellation at specific frequency regions where overlap occurs, improving isolation characteristics while allowing broader tolerance in other frequency regions, thereby reducing overall manufacturing precision requirements.
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 configuration significantly improves the isolation characteristics between terminals by ensuring signals in overlapping passbands are effectively canceled, leading to better signal separation across the frequency range.
Implementation Method 1
a first band-stop filter having a first end coupled to the first terminal and a second end coupled to the second terminal, the first band-stop filter having a first stopband formed of a first attenuation pole and a second attenuation pole
Data Source
AI summary
A multiplexer includes: a first bandpass filter having a first end coupled to a common terminal and a second end coupled to a first terminal, the first bandpass filter having a first passband; a second bandpass filter having a first end coupled to the common terminal and a second end coupled to a second terminal, the second bandpass filter having a second passband that does not overlap with the first passband and is higher than the first passband; and a first band-stop filter having a first end coupled to the first terminal and a second end coupled to the second terminal, the first band-stop filter having a first stopband formed of a first attenuation pole and a second attenuation pole, the first attenuation pole being located within the first passband or near the first passband, the second attenuation pole being located within the second passband or near the second passband.