Multistatic Radar Doppler Measurement Using Dual Carrier Waves
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Solution Overview
Problem
Bi-static radar systems face challenges in accurately measuring Doppler speed due to differential frequency drifts between transmitting and receiving oscillators, which can lead to significant speed errors, and existing solutions are either complex, costly, or vulnerable to jamming.
Innovation Solution
A method involving the generation of two carrier waves with a known frequency difference, where the Doppler speed is measured by dividing the difference in reception frequencies of these carriers, using a stable secondary frequency source to reduce errors, and partitioning the antenna for efficient signal emission and reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bi-static radar systems use separate local oscillators for transmitting and receiving radars, then system discretion and vulnerability are improved, but measurement precision of Doppler speed deteriorates due to differential frequency drifts
Solution Approach 1:
The patent introduces a stable secondary frequency source as an intermediary reference that both transmitting and receiving radars use to generate their carrier waves. This mediator allows the system to maintain the physical separation and discretion of bi-static configuration while eliminating differential frequency drift effects, since both oscillators are locked to the same stable reference frequency.
Solution Approach 2:
The patent changes the frequency parameter by using a stable secondary frequency source with a frequency lower than the radar transmission frequency. This frequency down-conversion allows for better frequency stability and drift compensation, as the secondary source can be more precisely controlled and measured, thereby improving Doppler speed measurement accuracy while maintaining system discretion.
2Measurement precision
If oscillators with better stability are used to reduce speed bias, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The stable secondary frequency source serves multiple functions: it acts as the reference for both the transmitting radar's local oscillator and the receiving radar's local oscillator, and also provides the reference for Doppler frequency measurement. This multi-functionality eliminates the need for separate high-stability oscillators at each site, reducing overall system complexity and cost while maintaining measurement precision.
3Measurement precision
If GNSS disciplined reference is used to control local oscillators, then measurement precision is improved, but reliability deteriorates due to vulnerability to jamming and signal distortion
Solution Approach 1:
The patent employs a stable secondary frequency source that does not rely on external GNSS signals, making it immune to jamming and distortion. While the patent text does not explicitly detail the implementation, the approach replaces vulnerable GNSS-dependent systems with a self-contained frequency reference that provides continuous, reliable operation regardless of external signal conditions.
4Measurement precision
If two carrier waves with known frequency difference are generated, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the signal generation process by using two distinct carrier waves with a known frequency difference, both derived from the stable secondary frequency source. This segmentation allows the receiving radar to measure the Doppler effect on each carrier separately and then compute the target velocity from the frequency difference, improving measurement precision while keeping the complexity manageable through systematic signal processing.
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 allows for accurate Doppler speed measurement with reduced errors and cost-effectiveness, while maintaining system discretion and resilience against jamming, by leveraging a stable frequency source and antenna partitioning for efficient signal processing.
Implementation Method 1
a first radar E emits a signal towards a target C, a second radar R receives and processes the signal backscattered by the target C
Implementation Method 2
If the target is affected by a 'Doppler velocity' producing a Doppler effect fD
Data Source
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AI summary
The invention relates to a Doppler measurement method for a multistatic radar device. The multistatic radar device comprises at least one first radar generating a transmission signal towards the target and a second radar receiving the signal backscattered by the target. According to the invention, two carrier waves are generated (23, 24, 25) on transmission having a given frequency gap (2Δƒ), the measurement of the Doppler velocity on reception being a function of the difference between the reception frequencies of the carrier waves divided by the frequency gap (2Δƒ).