OFDM Receiver Gain Control Using Threshold-Based Power Averaging
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Solution Overview
Problem
Conventional OFDM receivers require high-capacity calculations to determine average power, leading to increased complexity due to the need for square calculations and accumulation of instantaneous power over a symbol period, especially with wide-ranging digital values.
Innovation Solution
An OFDM receiver with a level control section comprising comparators, counters, and a moving average unit that compares signal levels with threshold values, counts exceedances, and calculates a moving average to generate a gain control signal for maintaining a predetermined signal level, replacing the complex power calculator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional power calculation method (square calculation and accumulation of instantaneous power) is used, then average power can be determined, but circuit complexity and calculation capacity requirements increase
Solution Approach 1:
The patent extracts only the essential information needed for average power measurement by comparing signal levels with threshold values, rather than calculating the complete instantaneous power. This selective extraction of information reduces the computational burden while maintaining measurement accuracy.
Solution Approach 2:
The patent replaces complex, high-capacity calculation circuits with simpler, lower-cost circuit elements (comparators and counters) that perform adequate function for the specific purpose of average power measurement in OFDM systems.
2Measurement precision
If square calculation and accumulation are performed on wide-ranging digital values, then accurate average power is obtained, but calculation speed requirements and circuit scale increase
Solution Approach 1:
The patent extracts only the necessary information for average power measurement by using threshold comparisons, avoiding the computationally intensive square calculation and accumulation operations while maintaining measurement accuracy.
Solution Approach 2:
The patent replaces complex arithmetic operations (multiplication and accumulation) with simpler logical operations (comparisons and counting), significantly reducing the computational resources and time required for average power calculation.
Data Source
AI summary
The present invention provides an OFDM receiver having a level control section comprising comparators which respectively compare a first signal outputted from an ADC with threshold values, counters which respectively count the frequencies with which the level of the first signal exceeds the threshold values, based on second and third signals corresponding to the results of comparison by the comparators, a moving average unit which calculates an average value of the level of the first signal lying in a predetermined period, based on fourth and fifth signals corresponding to the frequencies counted by the these counters, and a DAC which generates a gain control signal for controlling an AMP in such a manner that the average level of the first signal outputted from the ADC becomes a predetermined value, according to a sixth signal calculated by the moving average unit.