Multiplexer Isolation Circuit for Wide-Band Signal Rejection
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Solution Overview
Problem
Existing multiplexers with filter circuits struggle to effectively minimize the entry of unwanted signals from one filter circuit into another, especially when their pass bands are far apart, leading to degradation in signal quality and reception sensitivity.
Innovation Solution
Incorporating an additional circuit with series-arm and parallel-arm components, including inductors and capacitors, between the filter circuits connected to a common terminal to reduce unwanted signal transmission by generating signals that cancel out unwanted frequencies, thereby preventing signal interference across different frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional circuit is added between filter circuits to reduce unwanted signal transmission, then isolation characteristics improve, but device complexity increases
Solution Approach 1:
An additional circuit is introduced as an intermediary element between the first and second filter circuits connected to the common terminal. This intermediate circuit specifically targets and reduces unwanted signal transmission between the filter circuits, improving isolation characteristics without requiring fundamental changes to the existing filter structure.
Solution Approach 2:
The additional circuit is divided into distinct functional segments: a series arm circuit connected in series with the signal path, and a parallel arm circuit connected in parallel to ground. This segmentation allows each sub-circuit to perform its specific function independently, achieving effective signal isolation while maintaining clear circuit design and ease of implementation.
2Measurement precision
If filter circuits with far apart pass bands are used, then frequency selectivity improves, but unwanted signal interference increases
Solution Approach 1:
The additional circuit is configured to preemptively counteract unwanted signal transmission between filter circuits with widely separated pass bands. By placing reactive elements (inductors and capacitors) in strategic positions, the circuit creates preliminary opposition to harmful signal paths before interference can occur, effectively reducing unwanted signal transmission.
Solution Approach 2:
The additional circuit utilizes reactive elements with specific impedance characteristics that change with frequency. By carefully selecting the values of inductors and capacitors, the circuit parameters are optimized to provide maximum attenuation of unwanted signals while maintaining minimal impact on the desired pass bands, thus resolving the interference issue.
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 reduces unwanted signal interference, maintaining high isolation characteristics and signal quality across a wide frequency range, even when the pass bands of the filter circuits are far apart, thus enhancing the overall performance of the multiplexer.
Implementation Method 1
The parallel-arm circuit includes only an inductor in series with the parallel-arm path, only a capacitor in series with the parallel-arm path, or only an LC parallel-arm resonant circuit being in series with the parallel-arm path and including an inductor and a capacitor connected in parallel
Data Source
AI summary
A multiplexer includes a first filter circuit including a pass band that is a first frequency band, a second filter circuit including a pass band that is a second frequency band, and an additional circuit. The first filter circuit includes a first terminal connected to a common terminal and a second terminal connected to a first input/output terminal. The second filter circuit includes a third terminal connected to the common terminal and a fourth terminal connected to a second input/output terminal. The additional circuit is connected to the fourth terminal and one of the first and second terminals and includes a series-arm circuit on a series-arm path connecting the fourth terminal to the one of the terminals and a parallel-arm circuit on a parallel-arm path connecting the series-arm path to the ground. The parallel-arm circuit includes only an inductor, a capacitor, or an LC parallel-arm resonant circuit in series with the parallel-arm path.