Power Amplifier Back-Off for Wireless Transmitter Ramp-Down

Solution Overview

Problem

In wireless communication systems, particularly at higher power amplifier output levels, closed-loop power control systems struggle to track reference signals rapidly during ramp-down operations, leading to spectral degradation and failure to meet critical standards due to a 'dead-zone' in power amplifier performance, resulting in unfavourable interference and non-compliance with specifications like 3GPP/ETSI 05.05.

Innovation Solution

A power control method that initiates a slight negative perturbation before the ramp-down operation to bring the power amplifier out of its 'dead-zone', allowing it to react more smoothly and maintain bandwidth, thereby improving transient behaviour and switching transient performance by adjusting the back-off power and timing, specifically using a digital control signal to toggle bits and implement an improved back-off algorithm.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If closed-loop power control is used at higher power amplifier output levels, then power control functionality is provided, but the system cannot track reference signals rapidly enough due to control slope collapse

Engineering Contradiction:

Improvetracking speed of reference signalVSAvoidbandwidth sufficiency of closed-loop system

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent applies preliminary action by initiating a back-off period before the ramp-down operation begins. During this back-off period, the power control level is adjusted to a lower value in advance, allowing the power amplifier to exit its dead-zone and prepare for the upcoming power reduction. This preliminary adjustment ensures that when the actual ramp-down occurs, the system can track the reference signal more rapidly and accurately without suffering from the control slope collapse that would otherwise occur at higher power levels.

Inventive Principle:

Principle #10Preliminary action

2Power

If power amplifier operates at high output levels, then transmission power is sufficient, but spectral degradation occurs during ramp-down due to dead-zone effects

Engineering Contradiction:

Improveoutput power levelVSAvoidspectral degradation

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by initiating a back-off period before the ramp-down operation begins. During this back-off period, the power control level is adjusted to a lower value in advance, allowing the power amplifier to exit its dead-zone and prepare for the upcoming power reduction. This preliminary adjustment ensures that when the actual ramp-down occurs, the system can track the reference signal more rapidly and accurately without suffering from the control slope collapse that would otherwise occur at higher power levels.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies preliminary anti-action by preemptively reducing the power control level during the back-off period to counteract the impending spectral degradation. By adjusting the power control level before the ramp-down begins, the system prevents the control slope collapse and associated spectral degradation that would occur if the power amplifier remained at high output levels without preparation. This anticipatory counter-measurement eliminates the harmful spectral effects before they can manifest.

Inventive Principle:

Principle #9Preliminary anti-action

3Speed

If power control level is adjusted rapidly during ramp-down, then tracking performance improves, but switching transient hits are incurred causing spectral degradation

Engineering Contradiction:

Improveresponse speed to reference signalVSAvoidswitching transient interference

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by initiating a back-off period before the ramp-down operation begins. During this back-off period, the power control level is adjusted to a lower value in advance, allowing the power amplifier to exit its dead-zone and prepare for the upcoming power reduction. This preliminary adjustment ensures that when the actual ramp-down occurs, the system can track the reference signal more rapidly and accurately without suffering from the control slope collapse that would otherwise occur at higher power levels.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies beforehand cushioning by introducing a gradual back-off period that acts as a buffer before the main ramp-down operation. This back-off period allows the power amplifier to transition smoothly from its initial state, preventing abrupt changes that would cause switching transient hits. The cushioning effect of the back-off period absorbs the shock of the upcoming power reduction, enabling rapid tracking performance without generating harmful spectral degradation from transient interference.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS8265573B2Wireless subscriber communication unit and method of power control with back-off therefore

Publication Date: 2012.09.11 VELOCITY COMMUNICATION TECHNOLOGIES LLC

AI summary

A wireless subscriber communication unit comprises a transmitter having a power amplifier and a feedback power control loop having a power control function arranged to set an output power level of the power amplifier. The power control function is arranged to perform a back-off of the output power prior to completion of a transmission burst.