Phased Array Antenna Nulling for RFID Positioning
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Solution Overview
Problem
Current RFID antenna systems lack directivity, making it difficult to determine the precise location of radio-frequency transponders, such as RFID tags, in environments like warehousing, as they provide no information on the tag's position due to uniform radiation patterns.
Innovation Solution
A phased array antenna apparatus with a phase shifter that creates a minima in its radiation lobe, allowing the antenna to be moved to determine the transponder's position by minimizing the signal, enabling precise location indication through visual, auditory, haptic, or laser cues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a uniform radiation pattern antenna is used, then the detection range is large, but the position determination capability is lost
Solution Approach 1:
The antenna system is divided into multiple antenna elements arranged in a phased array configuration. By independently controlling the phase and amplitude of each element, the system can segment the radiation pattern to create directional lobes and nulls, enabling both wide detection coverage and precise position determination through signal nulling.
Solution Approach 2:
The system dynamically changes the phase parameters of individual antenna elements using phase shifters. By adjusting these phase parameters, the radiation pattern can be electronically steered and shaped to create nulls in specific directions, allowing the antenna to maintain large detection range while achieving precise position determination through null-based location.
2Measurement precision
If the phased array uses phase shifters to create minima, then the position determination accuracy is improved, but the device complexity increases
Solution Approach 1:
The system replaces mechanical antenna movement or physical reconfiguration with electronic phase shifting. Phase shifters electronically adjust the phase of signals at each antenna element, creating minima in the radiation pattern without any mechanical motion. This substitution of electronic control for mechanical systems reduces complexity while maintaining position determination accuracy.
3Measurement precision
If the antenna is moved to minimize signal, then the transponder position is accurately determined, but the time required for location increases
Solution Approach 1:
The system employs periodic scanning of the radiation pattern by sequentially adjusting phase shifters to create minima at different angular positions. This periodic action allows the system to systematically search for the transponder location by identifying where signal nulls occur, balancing position determination accuracy with reasonable time requirements through structured sequential measurement.
Solution Approach 2:
The system uses feedback from the received signal strength to determine when a minimum has been achieved. By continuously monitoring the signal from the transponder and adjusting phase shifters based on this feedback, the system can quickly converge on the correct position without exhaustive searching, reducing the time required for location while maintaining accuracy.
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 accurate positioning of RFID tags in two-dimensional space by creating a null in the radiation pattern, overcoming the ambiguity of uniform radiation patterns and improving operational efficiency in locating items.
Implementation Method 1
a phase shifter for providing a phase shift to at least one antenna of the phased array to provide a minima in a main radiated lobe of the phased array
Implementation Method 2
a phased array of antennas enabled to transmit and receive power at a given frequency for communicating with a radio frequency (RF) transponder
Data Source
AI summary
An antenna apparatus for determining the position of a radio-frequency transponder is provided, comprising a phased array of antennas enabled to transmit and receive power at a given frequency for communicating with a radio frequency (RF) transponder, the phased array being movable; and a phase shifter for providing a phase shift to at least one antenna of the phased array to provide a minima in a main radiated lobe of the phased array, such that when the phased array is moved from a first position, for detecting the RF transponder via the main radiated lobe, to a second position, where a signal from the RF transponder is minimized, a position of the RF transponder determined to be along an axis of the minima in the second position.