Receiver Protection Circuit for TDD Transmit Leakage Detection
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Solution Overview
Problem
Common return loss measurement systems fail to accurately measure low return losses, leading to false alarms or damage to receiver circuitry, and degrade RF system output power, while being costly and time-consuming in detecting reflections and protecting circuitry.
Innovation Solution
A communications device with a receiver protection circuit that includes a directional coupler, power detector, and comparator to measure and compare the power level of a transmit leakage signal, outputting an alarm signal when exceeding a threshold, and reducing transmit output power to prevent damage, without degrading RF system output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common return loss measurement systems are used to detect reflections, then receiver circuitry can be protected from damage, but the system degrades RF output power, increases cost, and consumes time
Solution Approach 1:
The patent extracts the essential protection function from complex return loss measurement systems by using a simplified approach: a directional coupler to sample the transmit signal, a power detector to measure signal level, and a comparator to trigger protection when thresholds are exceeded. This extracts only the necessary elements for protection without the complexity of full return loss measurement systems.
Solution Approach 2:
The patent replaces expensive, complex return loss measurement systems with a cost-effective solution using inexpensive components like directional couplers, power detectors, and comparators. This achieves the same protection function at lower cost and complexity.
2Reliability
If return loss measurement systems are used to detect reflections, then receiver circuitry can be protected, but the detection process is time-consuming
Solution Approach 1:
The patent implements preliminary action by continuously monitoring the transmit signal level during normal operation using the power detector and comparator. When a reflected signal exceeds the threshold, the system is already prepared to immediately activate protection circuitry, eliminating detection delays associated with traditional return loss measurement systems.
3Reliability
If return loss measurement systems are used to detect reflections, then receiver circuitry can be protected, but RF system output power is degraded
Solution Approach 1:
The patent uses a directional coupler as an intermediary element that samples a portion of the transmit signal without significantly affecting the main RF signal path. This allows monitoring and protection functionality to be added while maintaining minimal impact on RF output power, unlike direct return loss measurement systems that can load the signal path.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides faster and more accurate detection of potential damage, reducing the risk of circuitry harm and maintaining RF system power, while being cost-effective by eliminating the need for a processing unit.
Implementation Method 1
a coupler coupled to the receive signal path between the isolation device and an amplifier of the receive signal path
Implementation Method 2
a power detector coupled to the coupler and configured to measure a power level of a transmit leakage signal in the receive signal path
Data Source
AI summary
In an example, a receiver protection circuit includes a directional coupler configured to be coupled to a receive signal path of a communications device between an isolation device and an amplifier of the receive signal path. The receiver protection circuit further includes a power detector coupled to the directional coupler and configured to measure a power level of a transmit leakage signal in the receive signal path. The receiver protection circuit further includes a comparator configured to compare the measured power level of the transmit leakage signal in the receive signal path to a threshold value and output an alarm signal indicating that the measured power level of the transmit leakage signal exceeds the threshold value.