Interference Cancellation Repeater Stability Control
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Solution Overview
Problem
Interference cancellation repeaters face instability due to feedback oscillations when feedback signals are not adequately attenuated, leading to challenges in maintaining an acceptable desired/undesired (D/U) signal ratio.
Innovation Solution
An interference cancellation repeater system that includes a subtractor to cancel estimated signals, power calculators to determine signal power, and an attenuation controller to compare signal power differences and adjust attenuation values, using digital and analog attenuators to stabilize the repeater by adjusting the D/U ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If feedback signals are directly amplified without interference cancellation, then the repeater can maintain simple operation, but the repeater becomes unstable due to oscillation
Solution Approach 1:
The harmful feedback signal is extracted and separately processed from the main signal path. An interference cancellation unit is introduced that specifically targets and removes the feedback component before the signal is retransmitted, thereby eliminating oscillation while maintaining the overall simplicity of the repeater operation.
Solution Approach 2:
An intermediary interference cancellation unit is inserted between the amplifier and the antenna. This unit acts as a mediator that identifies feedback signals characteristic of the repeater itself and selectively cancels them, allowing the repeater to maintain signal amplification functionality while preventing harmful oscillations.
2Measurement precision
If strong attenuation is applied to feedback signals, then the D/U ratio improves, but the desired signal power is reduced
Solution Approach 1:
Instead of applying uniform attenuation to all signals, the system applies localized attenuation only to the harmful feedback component. The interference cancellation unit identifies and attenuates specifically the feedback signal characteristics while leaving the desired signal intact, thereby improving the D/U ratio without sacrificing overall signal power.
Solution Approach 2:
The attenuation level is dynamically adjusted based on the detected feedback signal characteristics. The system continuously monitors the signal and adapts the attenuation amount to match the actual feedback level, ensuring optimal D/U ratio improvement while maintaining sufficient signal power for communication.
Data Source
AI summary
An interference cancellation repeater including a subtractor configured to subtract an estimated signal from a digital reception signal and output an interference canceled signal; a first power calculator configured to calculate power of the digital reception signal; a second power calculator configured to calculate power of the interference canceled signal; and an attenuation controller configured to compare a power value of the calculated digital reception signal with a power value of the calculated interference canceled signal and determine an attenuation value of the interference canceled signal according to the comparison result.