RF Switch Topology With Dynamic Termination for Lower Insertion Loss
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Solution Overview
Problem
Conventional radio frequency switches suffer from increased insertion loss due to the RC component formed by the termination resistor and switching element, which is regarded as capacitance, leading to signal path deterioration.
Innovation Solution
A radio frequency switch design incorporating MOS transistors in parallel with termination resistors, controlled to be ON or OFF based on the selected transmission path, reduces insertion loss by minimizing the effective resistance and impedance mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a termination resistor is used to ground the off-port in the OFF state, then isolation between transmission paths is improved, but insertion loss increases due to the RC component formed by the termination resistor and switching element capacitance
Solution Approach 1:
The patent applies dynamics by making the termination resistor dynamically connectable and disconnectable from the off-port through a second switching element. When the first switch is ON, the second switch connects the termination resistor to ground to maintain isolation. When the first switch is OFF, the second switch disconnects the termination resistor to eliminate the RC component and reduce insertion loss. This dynamic configuration resolves the contradiction between maintaining isolation and reducing insertion loss across different operating states.
2Manufacturing precision
If the switch off-capacitance is optimized to function as input matching, then impedance matching is improved, but the resistance component cannot be eliminated during the ON state
Solution Approach 1:
The patent segments the switching function into two independent switching elements: the first switching element controls the main signal path between the input/output terminal and transmission terminal, while the second switching element independently controls the connection of the termination resistor to the off-port. This segmentation allows the off-capacitance of the first switch to be optimized for impedance matching without being compromised by the presence of the termination resistor, as the second switch can disconnect the resistor when not needed, thereby eliminating the RC component and reducing insertion loss.
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
The proposed design effectively reduces insertion loss and improves impedance matching, enabling high-quality signal transmission over longer distances and broader frequency bands.
Implementation Method 1
A radio frequency switch design incorporating MOS transistors in parallel with termination resistors, controlled to be ON or OFF based on the selected transmission path
Implementation Method 2
a radio frequency switch with a termination mode of the off-port (non-selected port) is grounded via a termination resistor (for example 50Ω)
Implementation Method 3
in the frequency band of radio frequencies as the object for signal transmission, the switching element is regarded as a capacitance, such that a signal path is formed by an RC component
Data Source
AI summary
According to one embodiment, a radio frequency switch of a Single-Pole-n-Throw (SPnT) type includes a first RF terminal, a second RF terminal, a single RF common terminal, first MOS transistors, termination resistors, and second MOS transistors. The first MOS transistors are respectively provided between the first RF terminal and the RF common terminal and between the second RF terminal and the RF common terminal. Each of the termination resistors is configured to be connected to the first RF terminal or the second RF terminal in a selected state where a corresponding one of the first MOS transistors is in an OFF state. The second MOS transistors are connected in parallel to the respective termination resistors, and each of the second MOS transistors is configured to be controlled in a same manner as a corresponding one of the first MOS transistors.