VGA Offset Control for Open Loop to Closed Loop Transition
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Solution Overview
Problem
Existing electronic systems face inaccuracies and cost issues due to the complexity of multiple detector diode circuitries, leading to errors during power transitions from open loop to closed loop modes, causing switching issues and spectrum widening in communication devices.
Innovation Solution
A circuit with two points of control for a variable gain amplifier (VGA), allowing for a smooth transition between open loop and closed loop modes by using an offset-controlled loop, where the error is multiplied with a reference value to adjust the gain, eliminating the need for baseband interaction and decision-making, and ensuring accurate power steps across mode transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple detector diodes are used to extend power measurement range, then the power measurement range is improved, but the circuit complexity increases leading to inaccuracies and higher cost
Solution Approach 1:
The power control system is segmented into two distinct operational modes: open-loop mode for high power levels and closed-loop mode for low power levels. This segmentation allows each mode to operate optimally within its range without requiring complex multi-diode circuitry to cover the entire range, thus resolving the contradiction between measurement range and circuit complexity.
Solution Approach 2:
The system dynamically transitions between open-loop and closed-loop control modes based on the current power level. This dynamic adaptation allows the system to maintain accurate power measurement and control across the full power range without requiring a fixed complex circuit structure, thereby improving measurement precision while avoiding excessive circuit complexity.
2Measurement precision
If standard power control loop is used in closed loop region, then accurate power control is achieved, but transition from open loop to closed loop mode causes power step errors
Solution Approach 1:
The transition from open-loop to closed-loop mode is initiated in advance when the power level approaches the transition threshold. This preliminary action allows the closed-loop feedback mechanism to be engaged before significant power step errors can occur, ensuring smooth and accurate power control during mode transitions while maintaining the accuracy benefits of closed-loop control.
3Reliability
If slot-to-slot transition between modes is used, then power step errors are minimized, but additional baseband processing and decision-making capabilities are required
Solution Approach 1:
The power control system performs self-service by automatically managing the transition between open-loop and closed-loop modes based on real-time power level monitoring. The transition logic is embedded in the power control circuitry itself, eliminating the need for external baseband processing and decision-making capabilities, thus achieving reliable power step accuracy without increasing baseband processing complexity.
Data Source
AI summary
This disclosure relates to a continuous open loop control to closed loop control transition.