RF Switch Bypass Topology for Low-Loss Paths and High Isolation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

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 the ability to isolate the bypass path from the target circuit, using a configuration of in-path, shunt, and bypass switches to minimize insertion loss and noise figure, and optionally incorporating a matching network integrated with the target circuit.

Engineering Contradictions & Design Principles

VSEngineering 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 if the matching network is isolated, then the bypass path insertion loss increases

Engineering Contradiction:

Improvebypass path insertion lossVSAvoidbypass path isolation

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent introduces an isolation switch as an intermediary component between the matching network and the bypass path. This switch acts as a mediator that can selectively connect or disconnect the matching network from the bypass path, allowing the system to achieve both low insertion loss and high isolation by controlling the switch state according to operational requirements

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If the matching network is connected to the bypass path, then the bypass path insertion loss is low, but the noise figure of the LNA is degraded

Engineering Contradiction:

Improvebypass path insertion lossVSAvoidnoise figure

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The isolation switch serves as a mediator that prevents the matching network from loading down the LNA input when the LNA is active. By controlling the isolation switch state, the system can maintain proper impedance matching for the LNA while keeping the bypass path available for low-loss operation when needed

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If standard isolation switches are added before the matching network, then bypass path isolation is improved, but the input insertion loss to the LNA increases

Engineering Contradiction:

Improvebypass path isolationVSAvoidinput insertion loss to LNA

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent applies isolation switching locally at the specific point where the bypass path connects to the LNA input, rather than adding isolation switches throughout the entire signal path. This localized approach provides the necessary isolation only where needed, minimizing the impact on the overall insertion loss to the LNA

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS10291223B2RF switch with bypass topology

Publication Date: 2019.05.14 PSEMI CORP

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.