Orthogonal Polarization Matched Filter for Spread Spectrum Radar Detection
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Solution Overview
Problem
Modern spread spectrum radars are difficult to detect due to reduced transmit power and broad spectral modulation, requiring significant processing gain and challenging signal parameter estimation, especially at low signal-to-noise ratios.
Innovation Solution
The use of orthogonal polarization antenna feeds processed with matched filter techniques, including correlation and integration, allows for the detection and characterization of unknown signals by measuring channelizer bin frequency, coarse time of arrival, pulse width, and amplitude, with post-detection processing to determine frequency characteristics using a digital instantaneous frequency measurement algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional radar detection methods are used, then detection of high power radars is possible, but detection of modern spread spectrum radars with reduced transmit power and broad spectral modulation fails
Solution Approach 1:
The matched filter is designed to be signal-agnostic, capable of detecting multiple types of radar signals including conventional, spread spectrum, and modulated waveforms without requiring separate detection mechanisms for each signal type. The filter processes orthogonal polarization components and integrates them to provide universal detection capability across diverse radar signal formats.
2Object-affected harmful factors
If transmit power is reduced from 4000 watts to under 100 watts, then radar stealth and detection difficulty increase, but signal detection capability deteriorates
Solution Approach 1:
The system combines the outputs from two orthogonal polarization antenna feeds through coherent integration in the matched filter. By merging the signal energy from both polarization components and integrating over the pulse duration, the system achieves sufficient processing gain to detect low power signals that would be undetectable using a single polarization channel.
3Object-affected harmful factors
If spread spectrum modulation is used to broaden RF energy spectrum, then radar stealth improves, but signal parameter estimation accuracy deteriorates
Solution Approach 1:
The matched filter performs preliminary correlation processing with the known spread spectrum code before parameter estimation. This preliminary action despreads the signal, concentrating the broad spectral energy back into a narrow bandwidth, thereby improving the signal-to-noise ratio and enabling accurate subsequent measurement of parameters such as time of arrival and frequency characteristics.
4Reliability
If orthogonal polarization antenna feeds are processed with matched filter techniques, then detection of low power spread spectrum radars is enabled, but system complexity increases
Solution Approach 1:
The signal processing is segmented into distinct functional blocks: orthogonal polarization reception, channelization into frequency bins, matched filter correlation with spread spectrum code, coherent integration, and parameter estimation. This segmentation allows each function to be implemented efficiently and independently, managing overall system complexity while achieving low power signal detection.
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 enables the detection and characterization of spread spectrum radars at low signal-to-noise ratios, improving the accuracy of frequency and time of arrival measurements and allowing for the creation of a signal template for further estimation, effectively addressing the challenges of detecting modern radars.
Implementation Method 1
The multiplier logic multiplies the first RF input with a conjugate of the second RF input to produce a multiplied signal
Implementation Method 2
The integrator logic integrates the multiplied signal to product an integrated signal
Implementation Method 3
orthogonal polarization antenna feeds are processed using matched filter techniques
Data Source
AI summary
A system and method for detecting unknown signals that may be radar pulses is presented. The method includes conjugate multiplying a first signal with a second signal to produce a first multiplied signal and conjugate multiplying the second signal with a third signal to produce a second multiplied signal. The first and second signals are orthogonal and the second and third signals are orthogonal. The radar pulse is contained in all three signals but each signal has noise components. The first multiplied signal is integrated to produce a first integrated signal and the second multiplied signal is integrated to produce a second integrated signal. The first and second integrated signals are summed to produce a summed signal. A location of a peak power of the summed signal is then detected. A TOA of the of the radar pulse is then detected based on the location of the peak power.