Distributed Analog CTLE DAC for SerDes Bandwidth Extension

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Solution Overview

Problem

Existing methods for bandwidth extension in SerDes transmitters, such as using digital FIR for pre-emphasis or CTLE with spectral shaping, either consume additional power, reduce the dynamic range, or attenuate the wanted signal, and are hindered by large inductor components that increase size and power consumption.

Innovation Solution

Incorporating a distributed analog transmission continuous-time linear equalizer (CTLE) in a passive method within the transmitter, which includes a plurality of branches with amplifiers and filter circuits, allowing for voltage driver output stages and avoiding signal attenuation while reducing component size and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If digital FIR pre-emphasis is used for bandwidth extension, then transmission rate capability is improved, but power consumption increases

Engineering Contradiction:

Improvetransmission rate capabilityVSAvoidpower consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The patent replaces digital signal processing (FIR filtering) with an analog continuous-time linear equalizer (CTLE) implementation. This substitution moves the bandwidth extension function from the digital domain to the analog domain, eliminating the need for power-consuming digital filters while achieving the same bandwidth extension effect through analog circuitry with resistors and capacitors.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operational parameters by implementing the equalizer in the continuous-time analog domain rather than discrete-time digital domain. This parameter change allows the system to achieve bandwidth extension through analog RC time constants and transfer functions, which consume significantly less power than digital signal processing operations.

Inventive Principle:

Principle #35Parameter changes

2Speed

If CTLE with spectral shaping is used for bandwidth extension, then transmission rate capability is improved, but the wanted signal is attenuated

Engineering Contradiction:

Improvetransmission rate capabilityVSAvoidsignal strength

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent applies different RC time constants and filtering characteristics to different frequency ranges within the signal spectrum. The continuous-time linear equalizer uses multiple poles and zeros positioned at specific frequencies to provide selective amplification of high-frequency components while maintaining or boosting low-frequency signal levels, thus achieving spectral shaping without overall signal attenuation.

Inventive Principle:

Principle #3Local quality

3Speed

If large inductor components are used for bandwidth extension, then transmission rate capability is improved, but device size increases

Engineering Contradiction:

Improvetransmission rate capabilityVSAvoidcomponent size

Core Design Contradiction:

SpeedVSArea of stationary object

Solution Approach 1:

The patent substitutes inductor-based LC resonant circuits with resistor-capacitor (RC) based continuous-time linear equalizer circuits. This substitution eliminates the need for large physical inductor components, achieving the same bandwidth extension function through compact RC time constants and transfer function design, thereby dramatically reducing the device footprint.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Speed

If large inductor components are used for bandwidth extension, then transmission rate capability is improved, but power consumption increases

Engineering Contradiction:

Improvetransmission rate capabilityVSAvoidpower consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The patent replaces inductor-based resonant circuits with resistor-capacitor based continuous-time linear equalizer circuits. This substitution eliminates the power losses associated with large inductor components (including core losses and resistive losses in windings) while achieving the same bandwidth extension effect through RC time constants, thereby significantly reducing overall power consumption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11469768B2Systems, methods, and devices for digital-to-analog conversion in data transmission

Publication Date: 2022.10.11 MELLANOX TECHNOLOGIES LTD(IL)

AI summary

A digital to analog converter (DAC) includes a first amplifier configured to receive a first bit of a data block as an input and output a first signal based on a value of the first bit of the data block, a first filter circuit configured to filter the first signal, an output configured to output an analog signal based on a combination of the filtered first signal and a second signal that represents a value of a second bit of the data block.