Passive Radar Reference Signal Extraction via Indirect Paths
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Solution Overview
Problem
Existing passive radar systems face limitations in sensitivity and detection performance due to the strong direct signal overpowering the target signal, leading to incomplete suppression of the direct signal and interference, which masks radar targets in the range-Doppler matrix.
Innovation Solution
The method involves positioning the passive radar to minimize the direct signal at the receiving device, obtaining the reference signal through indirect transmission paths, and using additional receiving units to tap the signal from the signal source before transmission, ensuring the reference signal is free from interference and modulation adjustments are made accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the direct signal is received by the receiving unit from the non-cooperative transmitter, then the reference signal is available for correlation processing, but the direct signal becomes orders of magnitude stronger than the target signal, masking radar targets and limiting detection performance
Solution Approach 1:
The patent divides the signal reception function into two separate receiving units: one dedicated to receiving the direct signal from the transmitter for reference signal extraction, and another for receiving the target signal reflected from objects. This segmentation allows each receiver to be optimized for its specific function and enables complete suppression of direct signal interference in the target signal channel.
Solution Approach 2:
The patent extracts the direct signal reception function into a separate receiving unit, removing the harmful direct signal from the target signal reception path. By taking out the direct signal component through a dedicated receiver, the target signal can be processed without contamination from the overpowering direct signal.
2Measurement precision
If the direct signal is strongly present at the receiving unit, then the reference signal can be obtained, but the dynamics of the receiving unit is limited and targets are masked in the range-Doppler matrix
Solution Approach 1:
The patent segments the correlation processing into two independent channels: one processing the direct signal from the first receiving unit and another processing the target signal from the second receiving unit. This segmentation simplifies the overall processing by allowing parallel independent correlation operations rather than attempting to separate mixed signals.
Solution Approach 2:
The patent introduces a signal separator that acts as an intermediary between the mixed received signal and the correlation processor. This intermediary component completely separates the direct signal from the target signal, providing clean inputs to the correlation process and eliminating the need for complex iterative interference cancellation algorithms.
3Reliability
If the receiving unit is positioned to minimize direct signal reception, then the target signal detection is improved, but the reference signal cannot be obtained through direct reception
Solution Approach 1:
The patent segments the signal acquisition system into two spatially separated receiving units with different functions: one positioned to receive the direct signal for reference signal extraction, and another positioned to receive the target signal with minimized direct signal contamination. This segmentation allows both signal types to be acquired in their optimal conditions simultaneously.
Solution Approach 2:
The patent creates a multi-functional radar system where the first receiving unit specializes in reference signal acquisition while the second receiving unit specializes in target signal detection. This division of labor allows each component to perform its function optimally, with the direct signal receiver ensuring reference signal quality and the target signal receiver ensuring detection sensitivity.
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 enhances the sensitivity and detection performance of the passive radar, increasing its range and improving the detection of air targets in higher airspace by eliminating the direct signal obstacle and allowing for better configuration options with multiple transmitters.
Implementation Method 1
The direct signal 103 travels directly from the transmitter 3 to the receiving unit 1 of the passive radar through wave propagation
Implementation Method 2
the target signal 102 arrives at the receiving unit 1 with a transit time and (if the target is moving) Doppler shifted compared to the direct signal 103
Data Source
Figure 1~2
Figure 3~4
AI summary
Method for operating a passive radar comprising a receiver (1) for receiving a signal (102) reflected from a radar target (4) and a processing unit (2), wherein the receiver (2) serves to process the reflected signal (102) including a reference signal for target detection which is correlated with the reflected signal (102), wherein the receiver (1) of the passive radar is spatially positioned with respect to a non-cooperative transmitter (3) used for target illumination such that the signal (103) of the non-cooperative transmitter (3) received directly by the receiver (1) is very weak, e.g.in the region of the thermal noise limit or is not present at all, - the reference signal is obtained by alternative transmission paths (107, 108, 109) than by transmission (103) directly from the non-cooperative transmitter (3) to the passive radar, and is made available to the processing unit (2), wherein the reference signal is obtained by tapping the signal of the signal source (13) assigned to the non-cooperative transmitter before transmission by the non-cooperative transmitter (3) and transmitting it to the passive radar via one of the following further transmission channels (107, 109, 108) - signal transmission (107) via the Internet (9), - signal transmission (109) via satellite (11) - signal transmission (108) via a line (10).