Radio Unit Downlink Gain Compensation with Hybrid Analog-Digital Control
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Solution Overview
Problem
Existing downlink gain compensation methods in radio units are inefficient due to long gain estimation and compensation periods, errors in phase compensation, and instability caused by digital pre-distortion, leading to degraded performance.
Innovation Solution
A device and method incorporating a pre-distortion circuit, digital gain adjuster, gain determiner, and gain controllers to accurately determine and adjust gain differences between target and current downlink gains, using both digital and analog gain controllers to perform coarse and fine adjustments, respectively, for improved gain compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If software-based gain compensation is used, then gain adjustment capability is provided, but gain estimation period is long and instantaneous performance is degraded
Solution Approach 1:
The gain compensation function is segmented into two independent parts: a fast analog gain compensation path using VVA for immediate adjustments, and a digital gain compensation path using digital signal processing for precise long-term control. This segmentation allows the system to achieve both fast response and high precision without the limitations of a unified software-based approach.
2Manufacturing precision
If digital pre-distortion is applied, then nonlinearity compensation is achieved, but phase compensation errors and instability occur
Solution Approach 1:
An analog pre-distortion circuit is introduced as an intermediary component between the digital signal processor and the power amplifier. This analog circuit provides continuous nonlinearity compensation without the discretization and quantization effects of digital pre-distortion, thereby maintaining system stability while achieving precise compensation.
Solution Approach 2:
The patent replaces the digital pre-distortion system (based on discrete digital signal processing) with an analog pre-distortion system (based on continuous analog circuitry). This substitution eliminates the inherent instabilities and phase errors associated with digital implementation while preserving the nonlinearity compensation functionality.
3Measurement precision
If single gain controller is used, then control simplicity is maintained, but compensation accuracy is insufficient
Solution Approach 1:
The single gain controller is segmented into two specialized controllers: an analog gain controller (second gain controller) that handles coarse gain adjustments through the VVA, and a digital gain controller (first gain controller) that handles fine gain adjustments through digital signal processing. This segmentation enables high compensation accuracy while keeping each controller's structure relatively simple and focused.
Solution Approach 2:
The system dynamically switches between analog and digital gain control modes based on the operating conditions and required precision. The analog controller provides fast, continuous adjustment for large gain changes, while the digital controller provides precise, discrete adjustment for fine-tuning, creating a dynamic hybrid control system that adapts to different scenarios.
Data Source
AI summary
Device and method are disclosed for downlink gain compensation at a radio unit. According to an embodiment, the device comprises a pre-distortion circuit, a digital gain adjuster, a gain determiner and a first gain controller. The pre-distortion circuit is configured to generate and apply a pre-distortion to an input signal. The digital gain adjuster is configured to apply an adjustable gain to an output signal from the pre-distortion circuit. The gain determiner is configured to determine a gain difference between a target downlink gain and current downlink gain. The first gain controller is configured to control the digital gain adjuster based on the gain difference. A radio unit comprising the device is also disclosed.