RF Multiplexer Phase Circuit Layout for Spurious Isolation
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Solution Overview
Problem
Multiplexers with multiple band pass filters face deterioration of bandpass characteristics due to spurious emissions generated by one filter affecting another, leading to unwanted wave transmission and phase changes.
Innovation Solution
Incorporating first and second phase circuits in a multiplexer to adjust impedance states, where the first phase circuit maintains an open state at the antenna terminal and the second phase circuit provides a short-circuited state at the connection node, preventing spurious emissions from being transmitted to filters with different passbands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple band pass filters are connected in parallel to an antenna terminal, then multi-band communication capability is improved, but spurious emissions from one filter can be transmitted to other filters causing deterioration of bandpass characteristics
Solution Approach 1:
Phase adjustment circuits are introduced as intermediary components between the filters and the antenna terminal. These circuits adjust the phase of signals passing through each filter to transform the impedance presented to other filters, thereby preventing spurious emissions from being transmitted while maintaining multi-band communication capability
Solution Approach 2:
The phase adjustment circuits change the electrical parameters (phase and impedance) of the signal paths between filters. By adjusting the phase to specific values, the impedance seen by other filters is transformed to minimize spurious emission transmission, thus resolving the contradiction between multi-band capability and spurious emission control
2Reliability
If phase adjustment circuits are added to prevent spurious emission transmission, then bandpass characteristics are improved, but device complexity increases
Solution Approach 1:
The phase adjustment circuits modify electrical parameters (phase and impedance) to prevent spurious emission transmission, thereby improving bandpass characteristics while adding only the necessary functional 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
This configuration effectively reduces or prevents the deterioration of bandpass characteristics by isolating spurious emissions, ensuring that they are not transmitted to filters with overlapping passbands, thereby maintaining the integrity of signal transmission.
Implementation Method 1
The first phase circuit adjusts a phase to provide an impedance in an open state in the first passband at the antenna terminal
Implementation Method 2
The second phase circuit adjusts the phase to provide the impedance in a short-circuited state in the first passband at the connection node
Implementation Method 3
a multiplexer with a plurality of band pass filters having different passbands
Data Source
AI summary
A multiplexer includes an antenna terminal, first to third filters with different passbands, and first and second phase circuits that adjust the phase of a passing signal. The first filter is connected to the antenna terminal. The second filter is connected to the antenna terminal with the first phase circuit provided between the second filter and the antenna terminal. The third filter is connected to a connection node between the first phase circuit and the second filter with the second phase circuit provided between the third filter and the connection node. In the second filter, an unwanted wave is generated in the first passband of the first filter. The first phase circuit adjusts the phase to provide an impedance in an open state in the first passband at the antenna terminal. The second phase circuit adjusts the phase to provide the impedance in a short-circuited state in the first passband at the connection node.