3-Level PAM Transceiver Encoding for Higher Bandwidth and Signal Margin

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Solution Overview

Problem

Current pulse amplitude modulation (PAM) signaling techniques, such as PAM-2, PAM-4, and PAM-3, face challenges in increasing memory bandwidth for high-performance computing applications due to structural inefficiencies, sensitivity to noise, and high power consumption, which limits their effectiveness in maintaining impedance matching and data transmission quality.

Innovation Solution

A transmitter and receiver system that divides binary input bits into two groups, manipulating and encoding them differently to generate symbol groups with three voltage levels, allowing for parallel encoding and decoding to reduce occupied area and power consumption while maintaining data integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If PAM-2 signaling is used to simplify transceiver structure, then device complexity is reduced, but productivity (bandwidth) is limited because only one bit is transmitted per unit interval

Engineering Contradiction:

Improvetransceiver structureVSAvoidbandwidth

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The binary input bit stream is divided into two separate bit groups (first bit group and second bit group) that are processed independently through separate encoding paths. This segmentation allows parallel processing of multiple bits simultaneously, achieving 1.5 bits per UI transmission capacity while maintaining simplified individual encoder structures.

Inventive Principle:

Principle #1Segmentation

2Productivity

If PAM-4 signaling is used to transmit two bits per UI, then productivity (bandwidth) is improved, but reliability deteriorates due to small sensing margin and high sensitivity to noise

Engineering Contradiction:

Improvebits per unit intervalVSAvoidsensing margin

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Instead of using a single PAM-4 encoder with 4 voltage levels that has small sensing margins, the system segments the data into two separate PAM-3 encoding paths with 3 voltage levels each. This segmentation provides larger voltage margins for each encoding path, improving reliability while maintaining the ability to transmit 1.5 bits per UI through parallel processing.

Inventive Principle:

Principle #1Segmentation

3Productivity

If PAM-3 signaling is used to transmit 1.5849 bits per UI, then productivity is improved, but device complexity increases due to structural inefficiency and difficulty in maintaining impedance matching

Engineering Contradiction:

Improvebits per unit intervalVSAvoidencoder structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The input bit stream is divided into two groups that are encoded separately using identical PAM-3 encoder structures. This segmentation approach simplifies the overall design by using repeated, standardized encoder modules rather than a complex single encoder, making it easier to maintain impedance matching and reduce device complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The same PAM-3 encoder structure is used for both the first bit group and the second bit group, creating universal, interchangeable encoding modules. This multi-functionality allows the system to achieve 1.5 bits per UI transmission capacity while using identical, well-tested encoder designs that are easier to manufacture and maintain impedance matching.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Productivity

If clock frequency is increased to increase bandwidth in PAM-2 signaling, then productivity is improved, but reliability deteriorates due to channel attenuation and clock quality deterioration

Engineering Contradiction:

ImprovebandwidthVSAvoidclock quality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Instead of increasing clock frequency to achieve higher bandwidth, the system segments the data transmission into two parallel PAM-3 encoding paths. This approach achieves 1.5 bits per UI capacity without requiring higher clock frequencies, thereby avoiding channel attenuation and clock quality deterioration while maintaining reliable transmission.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS11942968B2Transmitter and receiver for 3-level pulse amplitude modulation signaling and system including the same

Publication Date: 2024.03.26 SAMSUNG ELECTRONICS CO LTD

AI summary

A transmitter includes an encoder configured to divide a first number of binary input bits of an input data signal into a first bit group and a second bit group, generate a first intermediate bit group and a second intermediate bit group by manipulating the first bit group and the second bit group differently based on a value of the first bit group, and generate a first symbol group and a second symbol group by encoding the first intermediate bit group and the second intermediate bit group, each of the first symbol group and the second symbol group including a plurality of symbols, and each of the plurality of symbols having three different voltage levels. The transmitter includes a driver configured to generate an output data signal by concatenating the first symbol group and the second symbol group.