High Throw-Count RF Switch Using State-Dependent Branch Isolation
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Solution Overview
Problem
Conventional multiple-pole FET-based RF switch architectures are limited by parasitic inductances and capacitances, which restrict the number of available transmit and receive paths, leading to suboptimal RF performance in terms of bandwidth, insertion loss, return loss, isolation, and power handling, especially at higher frequencies.
Innovation Solution
The introduction of additional common RF path branch isolation switches controlled by state-dependent logic, which reconfigure the switch architecture to reduce reactive loads and enhance bandwidth by isolating inactive branches, thereby improving RF performance across multiple ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of transmit and receive paths is increased in a multiple-pole FET-based RF switch, then the switch throw-count is increased, but parasitic inductances and capacitances increase leading to degraded RF performance
Solution Approach 1:
The common RF path is segmented into multiple sections with branch isolation switches inserted between sections. This segmentation allows inactive branches to be electrically isolated from the common path, preventing their parasitic capacitances from loading down active ports. The segmentation maintains low insertion loss for active paths while enabling high throw-count functionality.
Solution Approach 2:
Branch isolation switches serve as intermediary elements between the common RF path and individual signal path branches. These intermediary switches control the connection state of each branch, allowing the system to maintain good RF performance by isolating inactive branches while preserving connectivity for active paths.
2Reliability
If branch isolation switches are added to reduce reactive loads, then RF performance is improved, but device complexity increases
Solution Approach 1:
The branch isolation switches serve multiple functions: they isolate inactive branches from the common path, prevent parasitic loading, maintain impedance matching for active ports, and enable reconfiguration of the switch architecture. This multi-functionality justifies the added complexity by delivering comprehensive performance improvements across multiple RF parameters.
3Adaptability or versatility
If more signal paths are added to exceed 8 ports, then adaptability is improved, but insertion loss and bandwidth are degraded due to parasitic effects
Solution Approach 1:
The common RF path is divided into sections separated by branch isolation switches. This segmentation ensures that parasitic capacitances from inactive branches do not load down active ports, maintaining low insertion loss even as the number of ports increases beyond 8. Active paths experience minimal loss because inactive branches are electrically isolated.
Solution Approach 2:
Branch isolation switches are activated in advance to isolate inactive branches before signals are routed through active paths. This preliminary action prevents parasitic loading from degrading RF performance, ensuring that insertion loss remains low and bandwidth remains wide even in high throw-count configurations.
4Adaptability or versatility
If more signal paths are added to exceed 8 ports, then adaptability is improved, but operating bandwidth is reduced due to accumulated parasitic inductances
Solution Approach 1:
The common RF path is segmented into multiple sections with branch isolation switches. This segmentation prevents accumulated parasitic inductances from degrading bandwidth because inactive branches are isolated from the active signal path. Each section can be independently optimized, maintaining wide operating bandwidth even as the total number of ports increases.
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 approach enables high throw-count RF switches with improved RF performance at frequencies exceeding those of conventional circuits, maintaining low insertion loss and high isolation, even at higher frequencies, and supports more than 8 ports with extended operating bandwidth.
Implementation Method 1
radio frequency (RF) switch circuits utilizing field effect transistors (FETs)
Implementation Method 2
an 'OPEN' or 'OFF' (i.e., high impedance or blocking) FET behaves as a capacitor due to parasitic capacitances arising from the proximity of various semiconductor structures
Implementation Method 3
parasitic inductances caused by interconnections between FETs and by other circuit structures
Data Source
AI summary
A high throw-count multiple-pole FET-based RF switch architecture that provides good RF performance in terms of insertion loss, return loss, isolation, linearity, and power handling. A common port RFC is coupled along a common path to multiple ports RFn. Embodiments introduce additional common RF path branch isolation switches which are controlled by state dependent logic. The branch isolation switches help to isolate the unused branch ports RFn and the unused portion of the common path from the active portion of the common path, and thereby reduce the reactive load attributable to such branches that degrades RF performance of the ports RFn “closer” to the common port RFC. The branch isolation switches can also be used to reconfigure the switch architecture for a multiplex function as well as separate switch path banks for re-configurability of purpose, tuning, or varying switch throw counts and packaging options.