Single-Pole-Triple-Throw Switch Reduces LNA Bypass Insertion Loss

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Solution Overview

Problem

Conventional RF devices with low noise amplifier (LNA) bypass configurations using two single-pole-double-throw switches experience high insertion loss, typically over 3 dB, which affects RF receiver sensitivity.

Innovation Solution

Implementing a single-pole-triple-throw switch in the RF front end module (FEM) to reduce insertion loss by allowing the received RF signal to travel through only one RF signal switching device, with optional DC blocking capacitors and MOSFET configurations for improved performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If two single-pole-double-throw switches are used in series for LNA bypass configuration, then the LNA bypass function is achieved, but insertion loss increases to over 3 dB

Engineering Contradiction:

ImproveLNA bypass functionVSAvoidinsertion loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent combines two separate single-pole-double-throw switches into a single single-pole-triple-throw switch. This merging reduces the number of switching components from two to one, thereby reducing the cumulative insertion loss while maintaining the LNA bypass functionality. The SPTT switch integrates the functionality of both SPDT switches into a single device with a common terminal that can connect to transmitter input, receiver output, or LNA input.

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If two single-pole-double-throw switches are connected in series, then LNA bypass capability is provided, but the device complexity increases

Engineering Contradiction:

ImproveLNA bypass capabilityVSAvoidswitch configuration complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges two separate switch devices into one integrated single-pole-triple-throw switch. This reduces device complexity by eliminating the need for two separate switches and their associated control circuits, while maintaining all necessary LNA bypass capabilities through the unified SPTT switch architecture.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single-pole-triple-throw switch is designed to perform multiple functions: it can switch between transmitter input, receiver output, and LNA input connections. This multi-functionality replaces what previously required two separate switches, simplifying the overall device architecture while maintaining full operational versatility.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP2965436B1Reducing insertion loss in LNA bypass mode by using a single-pole-triple-throw switch in a RF front end module

Publication Date: 2018.10.31 MICROCHIP TECHNOLOGY INC

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AI summary

A microwave radio frequency (RF) front end module (FEM) having a low noise amplifier (LNA) with a bypass mode uses a single-pole-triple-throw RF switch that reduces insertion loss to about 1 dB and thereby improves RF receiver sensitivity over existing technology two series connected single-pole-double throw RF switches. The single-pole- triple-throw RF switch may be three metal oxide semiconductor field effect transistor (MOSFET) RF switches that may be arranged with a common source input and isolated independent drain outputs. The RF switches may be single, double or triple gate MOSFET RF switches. The MOSFET RF switches may also be configured as complementary metal oxide semiconductor (CMOS) field effect transistor (FET) RF switches.