Booklet Security Document Antenna Detuning via LCR Resonant Circuit
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Solution Overview
Problem
Existing security documents with transponders face challenges in preventing data reading when the document is closed, as full-surface metal layers are only effective if positioned between the reader and transponder, and can be read if the reader is moved to the opposite side.
Innovation Solution
A security document with a booklet structure featuring a first sheet with an antenna structure and electronic circuit, and a second sheet with an LCR resonant circuit that overlaps with the antenna structure when closed, causing electromagnetic coupling and detuning of the antenna resonant circuit, making RF communication more difficult or impossible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a full-surface metal layer is used to absorb the read signal, then data reading is prevented when the document is closed, but the solution is only effective if the metal layer is positioned between the reader and transponder, allowing reading if the reader is moved to the opposite side
Solution Approach 1:
The shielding function is segmented into two parts: a full-surface metal layer for signal absorption and a pattern-shaped LCR resonant circuit for detuning. The LCR circuit is segmented with specific geometric patterns (lines, curves, or closed shapes) that create electromagnetic coupling with the antenna structure, providing position-independent protection while maintaining reading capability when needed.
Solution Approach 2:
Instead of using a full-surface metal layer uniformly across the entire document, the invention applies a pattern-shaped LCR resonant circuit only in specific areas where it can electromagnetically couple with the antenna structure. This localized approach provides effective shielding through detuning while minimizing material usage and preserving document properties.
2Reliability
If a full-surface metal layer is used to shield the transponder, then data reading is blocked from one side, but the document structure and tactile properties must be significantly altered
Solution Approach 1:
The invention changes the electromagnetic parameters of the antenna structure by introducing an LCR resonant circuit with specific inductance, capacitance, and resistance values. This detunes the antenna's resonant frequency, preventing RF communication when the document is closed, while maintaining the original document structure and tactile properties without requiring full-surface metal layers.
3Reliability
If active electrical components or switches are used to prevent data reading, then security is improved, but cost and error susceptibility increase
Solution Approach 1:
The invention replaces expensive and error-prone active electrical components with a passive pattern-shaped LCR resonant circuit made from simple conductive material patterns. This passive structure provides reliable shielding through electromagnetic detuning without requiring power sources, switches, or complex active components, significantly reducing manufacturing complexity and cost.
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
Effectively prevents data reading from the security document when closed, regardless of reader position, without requiring active components or significant material addition, and can be integrated into existing documents without altering their structure or tactile properties.
Implementation Method 1
the at least one LCR resonant circuit is electromagnetically coupled to the antenna structure. The electromagnetic coupling can in particular be an inductive or capacitive interaction between the antenna structure and the LCR resonant circuit.
Implementation Method 2
The electromagnetic coupling can in particular be an inductive or capacitive interaction between the antenna structure and the LCR resonant circuit.
Implementation Method 3
The electromagnetic coupling can in particular be an inductive or capacitive interaction between the antenna structure and the LCR resonant circuit.
Implementation Method 4
Studies have shown that the measure described above, in which a full-surface electrically conductive layer is used to absorb the read signal sent by the reading device, is only effective if this full-surface metal layer is arranged between the reading device and the transponder.
Data Source
Figure 1
Figure 2~4
Figure 5
AI summary
The invention relates to a security document (1) in the form of a booklet, comprising a plurality of sheets (11, 12, 13) bound together to form the booklet. A first sheet (11) of the security document has a carrier layer (20), an antenna structure (21) arranged in a first region (41) for RF communication, and an electronic circuit (22) connected to the antenna structure (21) with a storage device for storing data and a communication device connected to the antenna structure for transmitting data stored in the storage device via the antenna structure (21) to a reader via a radio interface. A second sheet (13) of the security document has a carrier layer (30) and one or more electrically conductive layers formed in a second region (43) to form at least one LCR resonant circuit (3).The antenna structure (21) and the at least one LCR resonant circuit (3) are arranged on the respective carrier layer such that, when the booklet is closed, the first area (41) of the first sheet (11) and the second area (43) of the second sheet (13) overlap at least partially and the at least one LCR resonant circuit (3) is electromagnetically coupled to the antenna structure (21).