RF Front-End Module Bypassing T/R Switches for Low-Loss Linearity

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Solution Overview

Problem

Conventional RF front-end modules in wireless communication devices experience significant switching losses and linearity constraints due to the presence of T/R switches in the transmit path, particularly at high frequencies, leading to inefficient energy transmission and reception.

Innovation Solution

The implementation of a Single-Pole, Single-Throw (SPST) switching circuit that bypasses the switching circuit in the transmit path, allowing the power amplifier to directly provide RF signals to the antenna, thereby reducing switching losses and enhancing linearity by decoupling the low-noise amplifier during transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a T/R switch is placed in the transmit path to enable switching between transmit and receive modes, then the device can operate in both transmit and receive modes, but switching losses increase and linearity deteriorates at high frequencies

Engineering Contradiction:

Improvetransmit/receive mode switching capabilityVSAvoidswitching losses

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent divides the RF front end module into separate transmit path and receive path circuits. The transmit path includes a power amplifier and transmit filter, while the receive path includes a low noise amplifier and receive filter. This segmentation allows each path to be optimized independently, eliminating the need for a T/R switch in the transmit path and reducing switching losses.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extracts the T/R switch from the transmit path and places it only in the receive path. By removing the switch from the transmit path, the transmit signal can flow directly from the power amplifier through the transmit filter to the antenna without encountering switching losses, while the receive path retains switching capability for selecting between receive modes.

Inventive Principle:

Principle #2Taking out (Extraction)

2Adaptability or versatility

If a T/R switch is placed in the transmit path to enable mode switching, then the device can switch between transmit and receive modes, but linearity constraints worsen at high frequencies

Engineering Contradiction:

Improvetransmit/receive mode switching capabilityVSAvoidlinearity

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent segments the RF front end module into distinct transmit and receive paths with dedicated filters and amplifiers. This segmentation eliminates the need for the T/R switch to be in the transmit path, allowing high-power transmit signals to pass through without the non-linear distortion introduced by switching operations, thereby improving linearity at high frequencies.

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If a switching circuit is placed in the transmit path to enable mode switching, then the device can operate in both transmit and receive modes, but energy transmission efficiency decreases

Engineering Contradiction:

Improvetransmit/receive mode switching capabilityVSAvoidenergy transmission efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent divides the RF front end module into separate transmit and receive paths. The transmit path is designed as a direct signal path from the power amplifier through the transmit filter to the antenna, eliminating switching elements that would reduce energy transmission efficiency. The receive path contains the switching circuit for mode selection, but this does not affect transmit energy efficiency.

Inventive Principle:

Principle #1Segmentation

4Adaptability or versatility

If a T/R switch is placed in the transmit path to enable mode switching, then the device can switch between transmit and receive modes, but the complexity of the circuit increases

Engineering Contradiction:

Improvetransmit/receive mode switching capabilityVSAvoidcircuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the RF front end module into separate transmit and receive paths with dedicated components. By placing the T/R switch only in the receive path and designing the transmit path as a direct signal path, the overall circuit complexity is reduced compared to having the switch in both paths. The segmentation allows for simpler transmit path design while maintaining full transmit/receive switching capability through the receive path switch.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS11018714B2Radio front end module with reduced loss and increased linearity

Publication Date: 2021.05.25 SKYWORKS SOLUTIONS INC

AI summary

A Radio Frequency (RF) circuit including a receive path, a transmit path, a switching circuit, and an output configured to receive RF signals from an antenna in a receive mode of operation, and to provide RF signals to the antenna in a transmit mode of operation. The receive path is configured to be coupled between a low-noise amplifier and the output. The switching circuit is located in the receive path and is configured, in the receive mode, to selectively couple the low-noise amplifier to the output and to pass the received RF signals from the output to the low-noise amplifier. The transmit path is configured to be coupled between a power amplifier and the output, to provide, in the transmit mode, signals from the power amplifier to the output, bypassing the switching circuit, and to have, in receive mode of operation, an off-state impedance of at least 200+j*13 Ohm.