Open-Circuit Spiral Antenna for Far-Field Wireless Sensing
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Solution Overview
Problem
Existing wireless sensing systems using open-circuit, electrically-conductive spiral trace sensors are limited to near-field applications due to their magnetic field being restricted to millimeters to tens of centimeters, which restricts their usage and read range.
Innovation Solution
An antenna design featuring an electrically unconnected, open-circuit spiral conductor and an overlapping loop portion, electrically isolated from the spiral, coupled with a radio frequency transceiver, which resonates to generate a harmonic electromagnetic field response, enabling far-field transceiving capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an open-circuit spiral trace sensor is used for wireless sensing, then the sensor can detect physical changes in the near field, but the read range is limited to millimeters to tens of centimeters
Solution Approach 1:
The patent implements a nested structure where a loop antenna is placed inside or around the spiral sensor. The loop antenna generates a time-varying magnetic field that induces current in the spiral sensor, enabling the sensor to operate at distances beyond its natural near-field range. This nested configuration allows the inner component (spiral sensor) to benefit from the field expansion provided by the outer component (loop antenna).
Solution Approach 2:
The loop antenna acts as an intermediary between the recording device and the spiral sensor. Instead of the recording device directly interacting with the spiral sensor at close range, the loop antenna mediates the interaction by generating a magnetic field that couples to the spiral sensor, thereby extending the effective read range while maintaining detection capability.
2Device complexity
If the sensor's magnetic field is limited to the near field, then the sensor can maintain simple structure, but the number of applications is limited
Solution Approach 1:
The system is segmented into functionally distinct components: the spiral sensor element that maintains simplicity for detection, and the loop antenna element that provides field extension. This segmentation allows each component to be optimized independently - the spiral remains simple for manufacturing while the loop provides the necessary field extension for broader applications.
3Measurement precision
If the loop antenna is placed in the sensor's near field to enable detection, then detection is possible, but the system remains limited to near-field applications
Solution Approach 1:
The system changes the magnetic field parameters through the loop antenna's oscillating current, creating a time-varying field that extends the effective detection range. By modifying the field's temporal characteristics (AC vs DC) and spatial distribution through the loop's geometry, the system achieves both detection capability and extended range.
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 antenna enhances the read range of wireless sensors from near-field to far-field distances, allowing for broader applications and increased detection capabilities beyond the previous limitations.
Implementation Method 1
In the presence of a time-varying electromagnetic field, the first electrical conductor so-shaped resonates to generate a harmonic electromagnetic field response having a frequency, amplitude and bandwidth
Implementation Method 2
A radio frequency transceiver capable of transmitting and receiving electromagnetic energy is electrically coupled to the second electrical conductor
Data Source
AI summary
An antenna includes a first electrical conductor that is shaped to form a spiral between its first and second ends that remain electrically unconnected such that the first electrical conductor so-shaped is maintained as an unconnected single-component open-circuit having inductance and capacitance. In the presence of a time-varying electromagnetic field, the first electrical conductor so-shaped resonates to generate a harmonic electromagnetic field response having a frequency, amplitude and bandwidth. A second electrical conductor includes a loop portion overlapping at least a portion of the spiral. The second electrical conductor is electrically isolated from the first electrical conductor. A radio frequency transceiver capable of transmitting and receiving electromagnetic energy is electrically coupled to the second electrical conductor.