Full-Duplex Transceiver Echo Cancellation With a Shared DAC

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Solution Overview

Problem

Full duplex communication systems face challenges with echo cancellation, leading to increased physical form factor, heat dissipation requirements, and distortion, which degrade signal-to-noise ratio and increase system complexity due to uncorrelated distortion from TX and Echo DAC portions.

Innovation Solution

A transceiver design with a shared active circuit for both TX and Echo DAC portions, using a replica TX signal to subtract from the combined signal at the receiver, reducing distortion and noise, and employing a common switch to match the DAC circuits and minimize residual TX signal effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If separate TX and Echo DAC circuits are used for echo cancellation, then echo cancellation capability is achieved, but distortion increases and device complexity increases

Engineering Contradiction:

Improveecho cancellation capabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the TX DAC and Echo DAC circuits into a single shared DAC circuit. The control logic selectively configures the shared DAC to operate in TX mode or Echo mode based on operational requirements, eliminating the need for separate hardware circuits while maintaining full duplex echo cancellation capability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The shared DAC circuit is designed to perform multiple functions by being selectively configured through control logic. It can function as either a TX DAC or an Echo DAC depending on the operational state, making the circuit universal and eliminating the need for dedicated separate circuits.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If separate TX and Echo DAC circuits are used, then echo cancellation is implemented, but heat dissipation increases

Engineering Contradiction:

Improveecho cancellation capabilityVSAvoidheat dissipation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

By merging the TX and Echo DAC circuits into a single shared circuit, the total power consumption and heat generation are reduced compared to having two separate circuits operating simultaneously, while still achieving echo cancellation through selective configuration.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If separate TX and Echo DAC circuits are used, then echo cancellation is achieved, but signal-to-noise ratio deteriorates due to uncorrelated distortion

Engineering Contradiction:

Improveecho cancellation capabilityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The shared DAC circuit ensures that both TX and Echo signals originate from the same digital-to-analog conversion process, making their distortion characteristics correlated. This correlation allows the echo cancellation process to effectively remove the transmitted signal while preserving the received signal integrity, thereby improving signal-to-noise ratio.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11405044B2System for and method of cancelling a transmit signal echo in full duplex transceivers

Publication Date: 2022.08.02 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

The systems and methods discussed herein utilized a wireless or wired transceiver having a transmitter and a receiver. The transceiver is configured to reduce distortion contributions associated with echo cancelling. The transmitter provides a replica signal and a transmit signal. The replica signal and the transmit signal can be provided using a common switch.