Adaptive Mutual Coupling Cancellation for Antenna Proximity Detection
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Solution Overview
Problem
High-frequency wireless communications face challenges in balancing performance with Federal Communications Commission's Maximum Permitted Exposure (MPE) limits due to higher path loss and increased power densities, which can be exacerbated by mutual coupling between antennas, making it difficult to achieve optimal transmission ranges and comply with regulatory guidelines.
Innovation Solution
Implementing a mutual coupling cancellation module within a wireless transceiver to process receive signals from multiple feed ports, using zero-forcing or reciprocal cancellation techniques to suppress mutual coupling interference, enabling detection of weak reflections for proximity sensing and adjusting transmission parameters to meet MPE limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If transmit power levels are increased to compensate for higher path loss at high frequencies, then communication range is improved, but power density increases and may exceed MPE limits
Solution Approach 1:
The system dynamically adjusts transmit power levels based on real-time proximity detection of objects (such as user's hand or head) near the antenna. The transmit power is increased when no object is detected within a certain range, and decreased when an object is detected, thereby extending communication range when safe while preventing excessive power density exposure when objects are nearby.
Solution Approach 2:
The system uses a feedback mechanism where the antenna continuously monitors for reflected signals indicating the presence of nearby objects. Based on this feedback, the control system adjusts the transmit power levels accordingly, allowing the system to adapt to changing environmental conditions and maintain optimal performance within safety limits.
2Area of stationary object
If antennas are placed in close proximity to reduce device size, then device compactness is improved, but mutual coupling interference increases and degrades signal quality
Solution Approach 1:
The system extracts and separates the mutual coupling interference from the desired signal by detecting reflected components and using signal processing techniques to cancel out the interfering portion. This allows the antennas to maintain close proximity for device compactness while removing the harmful interference through active cancellation.
Solution Approach 2:
The system introduces an intermediate signal processing stage that acts as a mediator between the closely-spaced antennas. By detecting the mutual coupling interference and generating a compensating signal, the system eliminates the harmful interaction between antennas, allowing them to be placed in close proximity without degrading signal quality.
3Measurement precision
If multiple feed ports are used on a single antenna to enable proximity detection, then detection capability is improved, but device complexity increases
Solution Approach 1:
The system makes the antenna multi-functional by equipping it with multiple feed ports that serve dual purposes: the primary function of transmitting and receiving communication signals, and the secondary function of detecting proximity to objects through analysis of reflected signals. This eliminates the need for separate dedicated proximity sensors, thereby improving detection capability without significantly increasing device complexity.
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
Enables wireless devices to transmit with higher power levels while complying with MPE limits, allowing for extended communication ranges and adaptive adjustments to environmental changes, thus enhancing performance and safety compliance.
Implementation Method 1
the antennas are electromagnetically mutually coupled such that energy can leak between a transmitting antenna and a receiving antenna
Implementation Method 2
a reflected component corresponding to a reflection of the radar transmit signal via an object
Data Source
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AI summary
An apparatus is disclosed for proximity detection using adaptive mutual coupling cancellation. In an example aspect, the apparatus includes at least two antennas, a wireless transceiver connected to the at least two antennas, and a mutual coupling cancellation module. The at least two antennas include a first antenna and a second antenna, which are mutually coupled electromagnetically. The second antenna includes two feed ports. The wireless transceiver is configured to transmit a radar transmit signal via the first antenna and receive two versions of a radar receive signal respectively via the two feed ports of the second antenna. The wireless transceiver is also configured to adjust a transmission parameter based on a decoupled signal. The transmission parameter varies based on a range to the object. The mutual coupling cancellation module is configured to generate the decoupled signal based on the two versions of the radar receive signal.