DVB-H Receiver AGC Using RF Blocker Detection at the LNA
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Solution Overview
Problem
Conventional wireless receivers face challenges in quickly detecting blocker signal levels at the LNA and applying gain steps without affecting data transmission, leading to degraded front-end linearity and signal-to-noise ratio due to soft switching non-linearity and lack of integration of digital RFAGC with baseband AGC logic.
Innovation Solution
A method and system for digital autonomous AGC in DVB-H receivers that utilize a RF servo loop integrated with baseband AGC to differentiate between desired and undesired signals by varying the differential gain of current through the LNA, employing a RF wideband detector and programmable comparators to step down gain in approximately 6 dB decrements, with operational timing during a DVB-H data burst cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If soft switching is used in the LNA signal path to control gain, then gain adjustment is achieved, but the third-order intercept point (IP3) is degraded due to non-linearity
Solution Approach 1:
The patent replaces the mechanical soft-switching approach with a digital control system that uses a detector to measure LNA output power and a digital processor to calculate appropriate gain adjustments. This substitution eliminates the non-linear soft-switching mechanism while preserving gain control functionality, thereby maintaining IP3 and front-end linearity performance.
Solution Approach 2:
The patent introduces a detector as an intermediary element that measures the LNA output power and provides feedback to a digital processor. This intermediary enables precise measurement and digital calculation of gain adjustments without requiring direct manipulation of the LNA signal path, thus avoiding the introduction of non-linearity while achieving accurate gain control.
2Measurement precision
If the demodulator takes time to correct the tuner's baseband gain, then proper correction is achieved, but the response time is slow (hundreds of Hz)
Solution Approach 1:
The patent implements preliminary action by having the detector continuously monitor LNA output power and the digital processor continuously calculate appropriate gain adjustments in advance. This preparation allows the system to respond immediately when gain changes are needed, eliminating the slow response time of conventional systems that wait for demodulator processing while maintaining accurate correction.
Solution Approach 2:
The patent extracts the gain control function from the slow demodulator processing chain and places it in a separate digital processor that operates independently and continuously. This extraction allows the gain control to respond quickly to signal conditions without being constrained by the demodulator's processing speed, achieving both accuracy and fast response.
3Reliability
If RFAGC and baseband AGC are implemented separately, then each loop can be optimized, but integration of digital RFAGC with baseband AGC logic is lacking
Solution Approach 1:
The patent merges the RFAGC detector and baseband AGC logic into a single integrated digital control system. The detector measures LNA output power and feeds this information to a digital processor that also receives baseband AGC information. This integration allows both loops to work together efficiently, sharing processing resources and coordinating their actions, thereby reducing overall system complexity while maintaining the ability to optimize each loop's performance.
Data Source
AI summary
Digital autonomous AGC for a DVB-H receiver comprises detecting a plurality of RF signals entering a LNA in the DVB-H receiver; detecting a RF transmitter blocker signal occurring at the LNA; and differentiating between a desired RF signal and an undesired RF transmitter blocker signal by varying a differential gain of current through the LNA. A RF servo loop is used for detecting the RF transmitter blocker signal. Logic circuitry of the RF servo loop is integrated with a baseband AGC loop to step control the differential gain of current through the LNA. A RF wideband detector is used for detecting the plurality of RF signals entering the LNA; and sending a voltage output corresponding to voltage levels of the RF signals to a plurality of comparators, wherein each of the plurality of comparators are set at a different programmable voltage threshold level compared with one another.