Bistatic Radar Phase Compensation for Coherent Rough-Surface Imaging
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Solution Overview
Problem
Existing bi-static radar methods struggle to maintain phase coherence when surveying rough surfaces, such as oceans, due to changes in surface shape during the measurement period, leading to inaccurate signal comparisons and reduced signal-to-noise ratios.
Innovation Solution
Compensate for the relative movement of the transmitter, receiver, and reflection point by choosing a fixed reflection point on the surface, calculating the path length and runtime using a correction term, and integrating over longer periods to maintain phase coherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the measurement period is extended to improve signal-to-noise ratio, then the signal accumulation is improved, but the phase coherence is lost due to surface shape changes during measurement
Solution Approach 1:
The patent calculates and applies a compensation term before the actual signal evaluation to pre-correct for the expected phase changes during the measurement period. This preliminary compensation action allows the system to maintain phase coherence throughout the extended measurement period without requiring the surface to remain static.
Solution Approach 2:
The patent introduces a compensation term that dynamically adjusts the phase parameters of the measurement signal based on the relative motion between transmitter, receiver, and the defined reflection point. This parameter change allows the system to adapt to surface shape changes while maintaining coherent signal accumulation over extended periods.
2Adaptability or versatility
If the reflection point is allowed to move with surface changes, then the signal reflects from the actual current surface state, but the phase coherence of the accumulated signal is compromised
Solution Approach 1:
Instead of following the moving reflection point with the signal evaluation (which would maintain adaptability but lose phase coherence), the patent inverts the approach by fixing the reflection point definition and using a compensation term to account for the motion. This inversion allows phase coherence to be maintained while still adapting to surface changes through the compensation mechanism.
Solution Approach 2:
The compensation term acts as an intermediary that bridges the fixed reflection point definition and the actual moving reflection point on the changing surface. This intermediary element allows the system to maintain phase coherence by mathematically accounting for the discrepancies between the fixed reference and the actual dynamic surface state.
3Measurement precision
If compensation is applied to maintain phase coherence, then the signal accuracy is improved, but the computational complexity increases
Solution Approach 1:
The patent replaces complex real-time surface shape tracking and dynamic reflection point following with a simpler computational approach using a fixed reflection point definition and a compensation term. This substitution reduces the computational burden while maintaining phase coherence accuracy by using mathematical compensation rather than complex geometric tracking.
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
Enables accurate phase-coherent signal accumulation and improved signal-to-noise ratio for rough surfaces by maintaining consistent phase positions of reflected signals, allowing for precise location and surface property determination.
Implementation Method 1
one satellite serves as the transmitter and another satellite as the receiver, with the transmitter emitting an electromagnetic measurement signal that is reflected by the surface to be measured and subsequently received by the receiver
Implementation Method 2
the transmitter emitting an electromagnetic measurement signal that is reflected by the surface to be measured and subsequently received by the receiver
Implementation Method 3
the change in phase of the reflected signal with respect to the beginning of the measurement period is compensated by a compensation term
Data Source
AI summary
Method of locating a point P located on the earth's surface using bistatic radar with at least one transmitter and at least one receiver, wherein the point P has relative motion to the transmitter and/or receiver, the method comprising:a) emitting a measurement signal modulated onto a carrier wave from the transmitter to the surface,b) receiving the measurement signal reflected from the surface during a measurement period Δt in the receiver,c) during the measurement period Δt determining the runtime of the measurement signal along the signal path from the receiver via point P to the receiver,d) during the measurement period Δt determining the path length of the measurement signal along the signal path,e) compensating the runtime of the measurement signal changing due to the relative movement of the point P to the transmitter and/or receiver during the measurement period Δt using the path length changing during the measurement period Δt,f) calculating the distance of the point P from the transmitter and/or receiver based on the compensated runtime and the signal propagation speed of the measurement signal,wherein the point P is located at a defined point relative to, preferably between, end points A and B of a line L, one end point A being the reflection point of the measurement signal at which the angle of incidence at the beginning of the measurement period Δt is equal to the angle of reflection, and the other end point B being the reflection point of the measurement signal at which the angle of incidence at the end of the measurement period Δt is equal to the angle of reflection.