RF Device Detection via Band-Edge Filter Response Analysis
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Solution Overview
Problem
Existing methods for detecting hidden radio-frequency devices are prone to false alarms from non-electronic nonlinear junctions and often fail to detect devices that are switched off or do not transmit RF signals, and they may also detect unwanted portable items.
Innovation Solution
A method involving the transmission of a complex RF stimulus with a first component at a fixed frequency and a second component swept across a range, generating third-order intermodulation products that are processed to compare with a pre-determined band-edge profile to detect the presence of radio devices with specific filter response characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nonlinear junction detection is used to detect hidden RF devices, then detection capability is improved, but false alarms increase due to non-electronic nonlinear junctions
Solution Approach 1:
The patent changes the detection parameter from general nonlinear junction response to specific band-edge filter response characteristics. By transmitting a swept frequency stimulus and analyzing the reflected signal's band-edge characteristics, the system distinguishes electronic devices with RF filters from non-electronic objects, reducing false alarms while maintaining detection capability.
Solution Approach 2:
The patent focuses detection on specific local characteristics of the frequency response, particularly the band-edge region. By analyzing the reflected signal's response at the band-edge frequency rather than the entire frequency spectrum, the system identifies unique signatures of electronic communication devices while ignoring non-electronic nonlinear junctions.
2Device complexity
If passive sensing of radiated signals is used, then device complexity is reduced, but detection fails when devices are switched off or do not transmit
Solution Approach 1:
The patent performs preliminary action by transmitting a swept frequency stimulus signal before detection. This active stimulation causes passive or switched-off devices to generate nonlinear junction responses and reveal their band-edge filter characteristics, enabling detection of devices that would otherwise remain undetectable to passive sensing methods.
Solution Approach 2:
The patent introduces an intermediary swept frequency stimulus signal that mediates between the detector and the target device. This stimulus signal activates the nonlinear junctions and filter responses in passive or switched-off devices, allowing the detection system to observe their characteristics without requiring the devices to be actively transmitting.
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
This approach effectively discriminates between electronic devices and non-electronic objects, reducing false alarms and ensuring detection of targeted electronic communications devices like cellular phones, even when they are not transmitting or switched off.
Implementation Method 1
Active techniques, on the other hand, typically rely on nonlinear junction detection, and may be used even when the target device does not transmit or leak any RF signals
Implementation Method 2
transmitting a complex radio frequency stimulus comprises transmitting a first component at a first frequency and sweeping a second component between a second and third frequency. The first, second, and third frequencies are selected so that third-order intermodulation products of the first and second components traverse a band-edge of a predicted device response.
Implementation Method 3
The response measurement is compared to a pre-determined filter response profile to detect the presence of a radio device having a corresponding filter response characteristic. In some embodiments, the pre-determined filter response profile comprises a pre-determined band-edge profile
Data Source
AI summary
Methods and apparatus for detecting the presence of electronic communications devices, such as cellular phones, are disclosed. In an exemplary method, a complex radio frequency stimulus is transmitted into a target area, and nonlinear reflection signals received from the target area are processed to obtain a response measurement. The response measurement is compared to a pre-determined filter response profile to detect the presence of a radio device having a corresponding filter response characteristic. In some embodiments, the pre-determined filter response profile comprises a pre-determined band-edge profile, so that comparing the response measurement to a pre-determined filter response profile comprises comparing the response measurement to the pre-determined band-edge profile to detect the presence of a radio device having a corresponding band-edge characteristic.