Digital Gain Control in RF/IF Receiver Amplifier Chains
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Solution Overview
Problem
Conventional digital broadcast receiving apparatuses require analog circuits for gain control, which increases costs and complexity, and struggle with temperature-related performance changes, especially when using silicon tuner ICs.
Innovation Solution
A receiving apparatus with a digital circuit that calculates power differences between pre- and post-filtered signals to control the gain ratio of high-frequency and intermediate-frequency amplifiers, eliminating the need for analog power detectors and gain controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If analog circuits (power detector and gain controller) are used for RF amp gain control, then gain control can be performed, but device complexity and cost increase
Solution Approach 1:
The patent replaces the analog power detection and gain control mechanism with a digital signal processing approach. The digital filter processes the signal to extract power information, and a digital controller adjusts the RF amplifier gain based on this processed information, eliminating the need for separate analog power detector and gain controller circuits.
Solution Approach 2:
The patent combines the power detection function with the existing digital filter and controller in the digital broadcast receiving apparatus. Instead of having a separate analog power detector, the power measurement is performed as part of the digital signal processing chain, merging multiple functions into existing circuit blocks.
2Device complexity
If analog circuits are integrated in silicon tuner IC, then device can be made compact and low cost, but temperature-related performance changes occur
Solution Approach 1:
The patent implements a feedback mechanism where the digital controller continuously monitors the signal power through digital filtering and adjusts the RF amplifier gain accordingly. This closed-loop control compensates for temperature-induced performance variations by dynamically adapting the gain to maintain stable reception across different operating conditions.
3Power
If RF amp gain is increased to amplify desired signal, then signal strength improves, but unnecessary signals become distorted
Solution Approach 1:
The patent employs dynamic gain control where the RF amplifier gain is continuously adjusted based on real-time power measurements of the desired signal. This dynamic adjustment ensures the gain is optimized for the current signal conditions, amplifying the desired signal adequately while preventing excessive gain that would cause distortion of adjacent channel signals.
Data Source
AI summary
Suitable gain control is achieved at low cost.In a receiving apparatus, an RF signal that is amplified by an RF amp is converted to an IF frequency by a frequency conversion unit and amplified by an IF amp, then the output signal from the IF amp that was converted to a digital signal by an ADC is inputted to a digital processing unit. The output from the ADC is then filtered to a desired frequency by a digital filter and inputted to the digital processing unit. In the digital processing unit the signal power before filtering by the digital filter and the signal power after filtering by the digital filter are measured, and the power difference is calculated. Based on the power difference, which indicates the ratio of unnecessary power, the digital processing unit controls the gain ratio of the RF amp and IF amp.