RF Switch Bypass Topology With Shunt Isolation for Low Insertion Loss
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Solution Overview
Problem
Existing RF signal switching circuits face challenges in achieving low input insertion loss (IL) and noise figure (NF) while maintaining high isolation, especially when the low noise amplifier (LNA) is bypassed, and they lack flexibility for tunable gain states and signal function modes.
Innovation Solution
The RF signal switch circuit design allows connection of RF input terminals to a Switch Output port in low loss or bypass modes, with a single switch in the series input path and isolation of the bypass path from the target circuit, incorporating a matching network that can be integrated or external, and includes a signal function mode for altering RF signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the LNA is bypassed to reduce insertion loss, then the bypass path isolation from the matching network is degraded, but the patent achieves high isolation through a shunt switch configuration
Solution Approach 1:
The bypass path is segmented into multiple sections with independent switching control. The shunt switch is positioned to selectively connect or disconnect the matching network from the bypass path, allowing independent optimization of insertion loss and isolation performance without requiring the entire bypass path to be isolated when LNA is bypassed.
Solution Approach 2:
The shunt switch acts as an intermediary element between the matching network and the bypass path. When activated, it provides a ground connection that isolates the matching network from the bypass path, enabling high isolation performance while maintaining low insertion loss through the bypass path when the LNA is bypassed.
2Reliability
If multiple series switches are added to improve isolation, then the insertion loss increases, but the patent maintains low insertion loss with a single series switch
Solution Approach 1:
The patent employs dynamic switching configurations where the shunt switch can be activated or deactivated based on operational mode. This dynamic control allows the system to achieve high isolation when needed while maintaining low insertion loss during normal operation, eliminating the need for multiple series switches that would continuously increase loss.
Solution Approach 2:
The switching state of the shunt switch changes the electrical parameters of the circuit configuration. When the shunt switch is closed, it changes the impedance configuration to provide isolation; when open, it allows low-loss signal transmission. This parameter change approach enables high isolation performance without adding multiple series switches that would increase insertion loss.
3Loss of energy
If the matching network is isolated from the bypass path, then the bypass path insertion loss is reduced, but the circuit complexity increases
Solution Approach 1:
The isolation function is extracted as a separate, dedicated shunt switch component rather than being integrated into the main signal path switches. This extraction allows the bypass path to maintain low insertion loss while the isolated shunt switch provides the necessary isolation functionality, minimizing the impact on overall circuit complexity.
Solution Approach 2:
The shunt switch serves multiple functions: it provides isolation between the matching network and bypass path, enables ground connections for RF signals, and works in conjunction with series switches to define different operational modes. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in circuit complexity while achieving the desired isolation performance.
Data Source
AI summary
An RF signal switch circuit that allows connection of any of N radio frequency (RF) input terminals to a switch output port, either in a low loss mode, in a bypass mode, or, optionally, in a signal function mode. Embodiments of the invention allow for both a single switch in the series input path to a target circuit while still having the ability to isolate the bypass path from the target circuit. In the low loss and bypass mode, the circuit simultaneously exhibits low input insertion loss (and thus a low noise factor) and high bypass mode isolation.