Composite Bandpass Filter Switching for Lower Insertion Loss
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Solution Overview
Problem
Existing composite filter devices with multiport ON-SW connections suffer from high insertion loss and degraded out-of-band reflection coefficients, leading to increased insertion loss in other bandpass filters sharing common connections.
Innovation Solution
The implementation of a composite filter device with bandpass filters connected in common, where at least one filter includes a switch and an impedance element with a value greater than the input impedance of another filter, allowing for switching between different connection states to reduce insertion loss, and utilizing elastic wave filters with complex impedances of the same polarity to enhance reflection coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multiport ON-SW is used to connect multiple bandpass filters to a common antenna terminal, then multiple frequency bands can be simultaneously used, but the circuit size becomes large and insertion loss increases
Solution Approach 1:
The invention divides the single multiport ON-SW into multiple independent single-port ON-SWs, with each bandpass filter having its own dedicated switch. This segmentation eliminates the need for a large multiport switch, reducing circuit size and insertion loss while maintaining the capability to selectively connect multiple frequency bands to the common antenna terminal.
2Adaptability or versatility
If a multiport ON-SW is used to connect multiple bandpass filters, then switching between frequency bands is enabled, but the out-of-band reflection coefficient deteriorates
Solution Approach 1:
By segmenting the multiport ON-SW into multiple single-port ON-SWs, each switch independently controls the connection state for its associated bandpass filter. This segmentation improves the out-of-band reflection coefficient by ensuring that when one filter is connected, others are properly disconnected, preventing signal leakage and maintaining better frequency selectivity.
3Adaptability or versatility
If one bandpass filter is electrically connected to the multiport ON-SW, then frequency band switching is achieved, but the insertion loss of other bandpass filters in their pass bands increases
Solution Approach 1:
The invention segments the connection control for each bandpass filter into independent single-port ON-SWs. This ensures that when one filter is connected to the antenna terminal, other filters are properly isolated, preventing their signals from being affected by the connected filter's out-of-band characteristics, thereby maintaining lower insertion loss for all filters.
Solution Approach 2:
The invention introduces individual single-port ON-SWs as intermediary elements between each bandpass filter and the common antenna terminal. These intermediary switches act as isolation mechanisms, preventing the out-of-band signals from one filter from affecting other filters, thus reducing insertion loss while maintaining the ability to connect multiple frequency bands.
Data Source
AI summary
A composite filter device includes bandpass filters whose respective one ends are electrically connected in common. A first bandpass filter of the bandpass filters includes a first filter, a switch, a second filter, and an impedance element that is electrically connected to the switch and having an impedance value larger than the input impedance value of the second filter. The switch is configured to be switched between a first state in which the first filter and the second filter are electrically connected and a second state in which the first filter and the impedance element are electrically connected.