Radar Signal Orthogonality via NLFM Waveform Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional radar systems face challenges in achieving efficient frequency use and maintaining detection performance, especially with increasing numbers of radars, due to poor target speed detection and orthogonal performance issues.
Innovation Solution
A method for generating radar signals using an optimization framework that optimizes nonlinear frequency modulation (NLFM) waveforms and polyphase-code sequences to maximize orthogonality, thereby reducing interference and improving frequency use efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency modulation is used for radar frequency sharing, then target speed detection performance is improved, but orthogonal performance between signals deteriorates as the number of radars increases
Solution Approach 1:
The patent applies parameter changes by optimizing the frequency modulation parameters (chirp rate, start frequency, and bandwidth) of each radar signal. By dynamically adjusting these parameters based on the radar identifier and target characteristics, the system achieves both good target speed detection performance and acceptable orthogonal performance even when multiple radars operate simultaneously in the same frequency band.
Solution Approach 2:
The patent implements dynamics by making the frequency modulation parameters time-varying and radar-specific. Each radar assigns different chirp rates and start frequencies based on its identifier, creating dynamically adjusted signal waveforms that adapt to the operational environment. This dynamic parameter assignment allows multiple radars to share frequency resources while maintaining distinguishable signals.
2Productivity
If orthogonal phase modulation is used for frequency sharing, then frequency use efficiency is improved, but target speed detection performance deteriorates
Solution Approach 1:
The patent merges the advantages of both phase modulation and frequency modulation by combining polyphase code modulation with optimized frequency modulation. The signal waveform integrates both phase information (for orthogonal separation) and frequency modulation (for target speed detection), achieving both frequency use efficiency and target speed detection capability simultaneously.
Solution Approach 2:
The patent creates a composite signal waveform that combines multiple modulation techniques. The signal includes polyphase code components for orthogonal separation and frequency modulation components for target speed detection, forming a composite modulation scheme that leverages the strengths of both approaches while mitigating their individual weaknesses.
3Productivity
If frequency sharing between radars is implemented, then frequency use efficiency is improved, but interference between radars increases
Solution Approach 1:
The patent introduces intermediary signal characteristics (unique chirp rates, start frequencies, and polyphase codes) that act as mediators between multiple radar signals. These intermediary parameters create sufficient signal separation to reduce mutual interference while allowing frequency sharing, effectively mediating the coexistence of multiple radars in the same spectral space.
Solution Approach 2:
The patent applies local quality by assigning radar-specific signal characteristics (unique chirp rates, start frequencies, and polyphase codes) to each radar identifier. This ensures that each radar signal has distinct local properties that facilitate separation at the receiver, reducing interference while enabling frequency sharing across the entire bandwidth.
Data Source
AI summary
A method of generating a radar signal is disclosed. The method includes generating a nonlinear frequency modulation (NLFM) waveform set composed of a plurality of NLFM waveforms, based on a target nonlinearity vector among a plurality of nonlinearity vectors, generating a target polyphase-code set composed of a plurality of polyphase-code sequences, based on an orthogonal phase, determining an orthogonal radar signal set composed of NLFM-based orthogonal radar signals using the NLFM waveform set generated based on the target nonlinearity vector and the target polyphase-code set, and redetermining the orthogonal radar signal set such that orthogonality is maximized by minimizing an objective function composed of an autocorrelation function of each orthogonal radar signal constituting the orthogonal radar signal set and a cross-correlation function between two arbitrary orthogonal radar signals constituting the orthogonal radar signal set.