LR-WPAN Preamble Detection Under Concurrent WLAN Interference
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Solution Overview
Problem
In compact electronic devices, the coexistence of WLAN and LR-WPAN radios in the 2.4 GHz band leads to interference due to insufficient spatial antenna isolation, reducing the operable range and reliability of LR-WPAN radios, especially Zigbee, as Wi-Fi transmissions desensitize Zigbee receivers.
Innovation Solution
Implementing a collocation adjustment circuit with an RF rectifier and dual paths to detect and respond to the presence or absence of WLAN signals, allowing the Zigbee receiver to switch between optimized sensitivity and blocker paths, maintaining receiver performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If WLAN and LR-WPAN radios are placed in close proximity in compact devices, then device size is reduced, but spatial antenna isolation becomes insufficient causing interference and desensitization of Zigbee receivers
Solution Approach 1:
The patent segments the receive signal path into two separate paths: a first path for when the transmit radio is not transmitting, and a second path for when the transmit radio is transmitting. This segmentation allows each path to be optimized for its specific operating condition, resolving the interference issue while maintaining compact device size.
Solution Approach 2:
The patent implements dynamic switching between two different receive signal paths based on the transmit radio's state. The system dynamically adjusts the receive path configuration by detecting whether the transmit radio is transmitting and selecting the appropriate path (first or second), thereby adapting to changing interference conditions in real-time.
2Reliability
If spatial separation between WLAN and LR-WPAN antennas is increased to reduce interference, then receiver sensitivity improves, but device compactness is compromised
Solution Approach 1:
The patent applies local quality by providing different signal path configurations for different operating conditions. The first path is optimized for normal operation while the second path is optimized for interference conditions, allowing each local segment of the signal path to have the specific properties needed for its operating context.
Solution Approach 2:
The patent introduces an intermediary switching mechanism that selects between two different signal paths based on transmit radio activity. This intermediary element (the switching circuitry) mediates between the conflicting requirements of compactness and receiver sensitivity by routing signals through the appropriate path.
3Device complexity
If a single receive signal path is used for both transmit and non-transmit states, then device complexity is reduced, but receiver performance deteriorates during transmit due to desensitization
Solution Approach 1:
The patent changes the configuration parameters of the receive signal path based on the transmit radio's state. By detecting whether the transmit radio is transmitting, the system changes parameters such as which signal path is active, thereby optimizing receiver performance for each operating condition without requiring permanently complex circuitry.
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
Enhances receiver sensitivity and reduces interference, enabling simultaneous operation of WLAN and LR-WPAN radios by achieving the required 38 dBm chip-to-chip isolation, even in reduced form factors.
Implementation Method 1
A collocation adjustment circuit with an RF rectifier and dual paths to detect and respond to the presence or absence of WLAN signals
Data Source
AI summary
Technologies directed to preamble detection in co-existence environments of WLAN and LR-WPAN signals are described. One wireless device has a first radio that sends a first RF signal to a second wireless device and a second radio that operates according to the IEEE 802.15.4 standard. The wireless device includes a circuit coupled between the first radio and the second radio. The circuit detects a presence of the first RF signal. The circuit receives a second RF signal from a third wireless device and attenuates the second RF signal to obtain a third RF signal in response to the presence of the first RF signal being detected. The second radio receives the third RF signal and decodes a preamble using the third RF signal.