Transceiver Noise Canceler Using Split Amplifier Feedback

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Solution Overview

Problem

Conventional radio frequency (RF) front-ends in transceiver devices suffer from increased noise floor and power consumption due to the use of filters in both transmit and receive paths to mitigate out-of-band noise leakage, leading to higher parts count and inefficiency.

Innovation Solution

A noise canceler system utilizing split power amplifiers and feedback circuits to reduce out-of-band noise leakage by filtering and amplifying RF signals, with a controller adjusting amplification factors and filtering to minimize noise, thereby reducing noise floor and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If filters are used in both Tx and Rx paths to remove out-of-band noise, then noise rejection is improved, but insertion loss increases and noise floor rises

Engineering Contradiction:

Improveout-of-band noise leakageVSAvoidinsertion loss

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The harmful out-of-band noise is extracted and removed from the transmit signal path using a filter before amplification. This prevents the noise from being amplified and leaking into the receive path, thereby reducing noise floor penalty while maintaining energy efficiency.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of filtering the receive signal to remove transmit noise (conventional approach), this invention filters the transmit signal beforehand to prevent noise from entering the receive path in the first place. This inverted approach eliminates the need for high-gain LNAs and reduces overall system noise floor.

Inventive Principle:

Principle #13The other way round (Inversion)

2Object-affected harmful factors

If filters with strong rejection are used to support sharp rejection, then out-of-band noise removal is improved, but insertion loss increases

Engineering Contradiction:

Improveout-of-band noiseVSAvoidfilter insertion loss

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The filter is placed before the power amplifier in the transmit path to perform preliminary filtering of out-of-band noise. This preliminary action prevents the noise from being amplified, eliminating the need for high gain compensation and reducing overall energy loss.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If LNA with high gain is used to compensate filter insertion loss, then noise figure is improved, but noise floor increases

Engineering Contradiction:

Improvenoise figureVSAvoidnoise floor

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention converts the potential harm of transmit noise leaking into receive path into a benefit by filtering it out beforehand. This eliminates the need for high-gain LNAs that would otherwise be required to compensate for filter insertion loss, thereby achieving good noise figure without increasing noise floor.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Power

If high gain and power are used in Tx path to compensate filter insertion loss, then signal strength is improved, but power consumption increases

Engineering Contradiction:

Improvetransmitter powerVSAvoidpower consumption

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

Out-of-band noise is extracted and removed from the transmit signal before amplification. This prevents the noise from consuming additional power during amplification and transmission, thereby reducing overall power consumption while maintaining necessary signal strength.

Inventive Principle:

Principle #2Taking out (Extraction)

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

The noise canceler effectively reduces noise leakage by at least 20 dB in the receive band, lowering power consumption and parts count, while maintaining efficient signal transmission.

Implementation Method 1

a feedback circuit to filter and amplify the transmit signal to generate a detection signal

Methodology Applied

Scientific EffectFiltering: Filter (electronic)

Implementation Method 2

a feedback circuit to filter and amplify the transmit signal

Methodology Applied

Scientific EffectSignal amplification: Magnetic Amplifier

Implementation Method 3

a controller to adjust amplification factors and filtering to minimize noise

Methodology Applied

Scientific EffectGain control:

Implementation Method 4

The noise canceler effectively reduces noise leakage by at least 20 dB in the receive band

Methodology Applied

Scientific EffectSignal subtraction:

Data Source

PatentUS9450623B2Noise canceler for use in a transceiver

Publication Date: 2016.09.20 QUALCOMM INC

AI summary

A noise canceler for use in a transceiver is disclosed. In an exemplary embodiment, an apparatus includes a split amplifier to output an amplified transmit signal, the split amplifier providing a first noise attenuation factor in a receive band. The apparatus also includes a transmit antenna to transmit the amplified transmit signal, the transmit antenna being isolated from a receive antenna by an antenna isolation factor that provides a second noise attenuation factor in the receive band. The apparatus also includes a noise canceler configured to subtract a detection signal from a received signal to obtain an adjusted received signal, wherein subtraction of the detection signal provides a third noise attenuation factor in the receive band, and wherein the first, second, and third noise attenuation factors combine to provide a selected amount of noise attenuation in the receive band.