Transmit Signal Squelching at Symbol Boundaries for Spurious Emissions

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing radio systems face challenges in reducing spurious emissions and power consumption at symbol boundaries in radio frequency power amplifiers, particularly in symbol-based envelope tracking (SBET) systems, where transitions in bias voltage lead to significant spectral emissions and inefficiencies.

Innovation Solution

Implementing transmit squelching at symbol boundaries by zeroing or significantly reducing the power of a portion of the transmit signal, combined with other techniques like gate voltage adjustment and digital predistortion, to minimize spectral emissions and improve power efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If bias voltage transitions are implemented at symbol boundaries in SBET systems, then power efficiency is improved, but spurious spectral emissions increase

Engineering Contradiction:

Improvepower efficiencyVSAvoidspurious spectral emissions

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The transmit signal is squelched (reduced or zeroed) at symbol boundaries before the bias voltage transition occurs. This preliminary action prevents the interaction between full-power signal and voltage transition that causes spurious emissions, while still allowing the SBET power efficiency benefits to be realized during normal symbol periods.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The squelching is applied locally only at symbol boundaries rather than throughout the entire signal. This localized treatment addresses the specific problem area (symbol transitions) without affecting the overall power efficiency improvements gained from SBET operation during regular symbol periods.

Inventive Principle:

Principle #3Local quality

2Object-generated harmful factors

If transmit signal power is reduced at symbol boundaries, then spurious emissions are decreased, but signal integrity may be compromised

Engineering Contradiction:

Improvespurious emissionsVSAvoidsignal integrity

Core Design Contradiction:

Object-generated harmful factorsVSReliability

Solution Approach 1:

The signal power is temporarily changed (reduced or zeroed) only at symbol boundaries where it is necessary to prevent spurious emissions. The signal returns to normal power levels during data-bearing portions of symbols, maintaining signal integrity for information transmission while eliminating harmful emissions at transition points.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP4708676A1Transmit signal squelch at symbol boundaries

Publication Date: 2026.03.11 ANALOG DEVICES INT UNLTD CO

Figure 1A~1C
Figure 2
Figure 3

AI summary

Aspects of this disclosure relate to squelching a symbol at a symbol boundary. A transmit squelch block can squelch a portion of a symbol at a symbol boundary. The transmit squelch block can be included in a symbol based envelope tracking system. Transmit squelching can reduce spurious emissions associated a symbol based envelope tracking voltage toggling on a symbol boundary.