Intermodulation Radar Signal Power Differential Detection
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Solution Overview
Problem
Conventional non-linear RADARs face difficulties in detecting small electronic devices due to their low RADAR Equivalent Area (SER) and non-linear response, leading to weak intermodulation signals that are challenging to detect and identify, especially when the second harmonic is outside the target device's bandwidth.
Innovation Solution
Transmitting two radiofrequency or microwave signals at different power levels, with a power difference of at least 10 dB, to enhance the generation efficiency of intermodulation signals, allowing for increased power levels of the received intermodulation products, which can be used to facilitate detection and identification of electronic devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If two electromagnetic signals of the same power level are transmitted (prior art), then the system maintains simplicity in signal transmission, but the power level of the received intermodulation signal remains very low, making detection and identification difficult
Solution Approach 1:
The patent changes the parameter of signal power levels by transmitting two electromagnetic signals at different power levels (with a difference of at least 10 dB) instead of equal power levels. This parameter change directly increases the power level of the received intermodulation signal, enabling effective detection and identification of electronic devices while maintaining reasonable system complexity
Solution Approach 2:
The patent introduces dynamic control of signal power levels by allowing the first and second electromagnetic signals to have variable power levels with a controlled difference. This dynamic approach enables optimization of intermodulation signal strength while managing system complexity through controlled power level variations
2Power
If very high power signals (exceeding 50 dBm) are transmitted to obtain a sufficiently intense second harmonic signal, then the second harmonic signal intensity is sufficient for detection, but the system requires extremely high transmission power which is inefficient and may cause interference
Solution Approach 1:
The patent changes the approach by using two signals with different power levels (difference of at least 10 dB) to generate intermodulation products, which naturally fall within the target device's operating bandwidth. This eliminates the need for extremely high transmission power (50 dBm+) required by conventional second harmonic methods, significantly reducing energy consumption while maintaining sufficient signal intensity for detection
Solution Approach 2:
The patent converts the target device's non-linear response, which was previously a source of weak signals outside the bandwidth, into a beneficial effect by using intermodulation products that naturally fall within the operating bandwidth. This transforms the previously harmful bandwidth mismatch into a useful feature that enables efficient detection at lower power levels
3Power
If the second harmonic frequency is outside the target device's bandwidth, then the harmonic can be generated, but the signal experiences high attenuation due to poor coupling through antenna gaps and PCB tracks
Solution Approach 1:
The patent changes the frequency generation mechanism from second harmonic (2f) to intermodulation products (2f1-f2 and 2f2-f1) where the frequencies can be controlled to fall within the target device's operating bandwidth. This parameter change ensures that the signals couple efficiently through the antenna and PCB tracks without experiencing high attenuation, as they operate within the device's designed frequency 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
This approach significantly increases the power level of intermodulation signals, improving detection and identification capabilities by maximizing the power difference between the transmitted signals, which serves as a signature for the detected electronic device.
Implementation Method 1
these targeted electronic devices are small, their RADAR Cross Section (RCS) makes them extremely difficult to detect. However, they inherently exhibit a non-linear response. It is therefore possible to illuminate such a target and then exploit the non-linear frequencies generated by it
Implementation Method 2
Intermodulation RADARs can partly overcome this difficulty by using two emitted signals of frequencies f1, f2 close together (frequency difference typically a few MHz) and by detecting the intermodulation products of order 3, at frequencies fIM3L = 2f1 -f2 and fIM3H = 2f2 -f1
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a method for detecting electronic devices comprising the steps of: a) simultaneously transmitting towards the same region of interest (RDI) a first electromagnetic signal (S1) at a first frequency f1 in the radio- or microwave range and a second electromagnetic signal (S2) at a second frequency f2, also in the radio- or microwave range and higher than the first frequency f1; and b) receiving an electromagnetic signal (SR) re-emitted by at least one electronic device (AEL) to be detected located in the region of interest, corresponding to an intermodulation product of the first and second electromagnetic signals; characterized in that the first and second electromagnetic signals have different power levels in the region of interest, exhibiting a difference (Δ) of at least 10 dB. The invention also relates to an apparatus for implementing such a method.