Transmit Signal Squelching at Symbol Boundaries for SBET Bias Switching
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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.
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 adjusting gate voltage, crest factor reduction, and digital predistortion, to minimize spectral emissions and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If bias voltage transitions are implemented at symbol boundaries in SBET systems, then power amplifier efficiency is improved, but spurious spectral emissions increase
Solution Approach 1:
The transmit squelch block proactively zeros signal samples at symbol boundaries before the bias voltage transition occurs. This preliminary action prevents the generation of spurious emissions by ensuring the signal is already nulled when the voltage switch happens, while still allowing the efficient voltage transition to take place.
Solution Approach 2:
The system applies an opposing action by introducing zero-valued samples that counteract the potential harmful effect of bias voltage transitions. By pre-positioning these zero samples at symbol boundaries, the system neutralizes the spurious emissions that would otherwise be generated during voltage switching.
2Object-generated harmful factors
If signal power is reduced at symbol boundaries, then spurious emissions are decreased, but signal transmission efficiency deteriorates
Solution Approach 1:
The squelching operation is applied locally and selectively only at symbol boundary points rather than across the entire signal. This localized approach minimizes the impact on overall transmission efficiency by affecting only the minimal necessary portions of the signal where voltage transitions occur.
Solution Approach 2:
The system applies partial squelching by zeroing only specific samples at symbol boundaries rather than the entire symbol. This partial action is sufficient to eliminate spurious emissions while preserving the majority of the signal content and maintaining transmission efficiency.
3Object-generated harmful factors
If transmit signal is squelched at symbol boundaries, then spectral emissions are reduced, but signal integrity may be compromised
Solution Approach 1:
The cyclic prefix serves as a copy of the signal that can be used for synchronization and integrity verification. By preserving the cyclic prefix structure while squelching only the minimal boundary samples, the system maintains the copying mechanism that enables signal integrity checks.
Solution Approach 2:
The squelching is applied partially and minimally—only to the extent necessary at symbol boundaries—rather than excessively across entire symbols. This partial application preserves sufficient signal content for integrity verification while achieving emission reduction goals.
Data Source
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.