High Throw-Count RF Switch With Branch Isolation for Low Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional multiple-pole FET-based RF switch architectures are limited to about 8 ports due to design complications such as parasitic inductances and capacitances, which degrade RF performance, especially at higher frequencies, leading to trade-offs with bandwidth and insertion loss.
Innovation Solution
The introduction of additional common RF path branch isolation switches controlled by state-dependent logic, which are normally OFF and only activated when necessary to couple 'far side' ports to the common port, reducing reactive load and enhancing RF performance by isolating inactive branches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of ports in a multiple-pole FET-based RF switch is increased beyond 8 ports, then the throw-count and versatility of the switch is improved, but parasitic inductances and capacitances increase, degrading RF performance
Solution Approach 1:
The common RF path is segmented into multiple sections with isolation switches placed between them. This divides the continuous path into isolated segments, reducing the cumulative parasitic effects across the entire path while maintaining the ability to connect multiple ports.
Solution Approach 2:
Isolation switches are introduced as intermediary elements between different sections of the common RF path. These intermediary switches actively manage signal flow and isolate inactive branches, preventing parasitic capacitances from affecting active signal paths.
2Adaptability or versatility
If additional branches are added to increase throw-count, then the switch can support more transmit and receive paths, but insertion loss increases due to accumulated parasitic effects
Solution Approach 1:
The common RF path is divided into isolated segments using isolation switches. This segmentation ensures that parasitic effects are localized to individual segments rather than accumulating across the entire path, thereby reducing overall insertion loss.
Solution Approach 2:
Inactive branches are extracted or isolated from the active signal path using isolation switches. This removes the harmful parasitic effects of inactive branches from the signal path, reducing insertion loss for active connections.
3Adaptability or versatility
If more ports are added to the switch, then the switch architecture becomes more complex with additional interconnections, but device complexity increases making design and fabrication more difficult
Solution Approach 1:
The switch architecture is segmented into modular sections with isolation switches. This modular approach organizes the complexity into manageable units, making design and fabrication more systematic even as the 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 allows for high throw-count RF switches with improved insertion loss, return loss, isolation, linearity, and power handling, extending operating bandwidth beyond conventional limits, supporting frequencies exceeding 6 GHz with better performance across multiple ports.
Implementation Method 1
A multiple-pole FET-based RF switch architecture utilizes field effect transistors (FETs) as switching elements that can be fabricated in various technologies (e.g., standard bulk silicon, silicon-on-insulator, silicon-on-sapphire, GaN HEMT, GaAs pHEMT, and MESFET processes)
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
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.