Laser Ranging for Distributed Aperture Radar Positioning
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Solution Overview
Problem
Conventional distributed aperture radar systems face limitations in achieving precise beam control and position measurement due to the inherent limitations of GPS and pseudo target tracking methods, which result in inadequate angular measurement precision and costly laser ranging apparatus requirements.
Innovation Solution
A measuring apparatus using a laser ranging system with optical signal input/output units and multiple light sources and receiving units to measure the relative position of antennas through optical modulation wave reflecting units, enabling high-precision position and direction measurement by employing a three-point intersection method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If GPS is used to measure the relative position of antennas, then the measurement can be performed over long distances, but the measurement precision is only 10 to 100 meters in single point positioning and degrades depending on GPS satellite arrangement
Solution Approach 1:
The patent replaces GPS (radio wave-based positioning system) with a laser ranging system using light waves. The laser ranging apparatus transmits laser beams to retroreflectors mounted on antennas and measures the reflected beams to determine positions with millimeter-level precision, substituting the radio wave-based GPS system with an optical-based measurement system that achieves significantly higher precision while maintaining long-range capability
Solution Approach 2:
The patent changes the fundamental parameter of the measurement system by switching from radio wave frequency (GPS) to light wave frequency (laser). This parameter change enables precision improvement because the wavelength of light is much shorter than radio waves, allowing for more precise phase and time-of-flight measurements, thereby achieving millimeter-level position accuracy instead of meter-level accuracy
2Area of stationary object
If the antenna aperture is made small, then the distributed aperture radar can be compact, but the beam width spreads and angular measurement precision cannot be obtained
Solution Approach 1:
The patent replaces radar wave-based angular measurement with laser-based optical measurement. By mounting retroreflectors on antennas and using a laser ranging apparatus to measure the positions of these retroreflectors with high precision, the system achieves accurate angular measurement without requiring large antenna apertures. The optical measurement system compensates for the small aperture by providing external high-precision position reference
Solution Approach 2:
The patent introduces retroreflectors as intermediary objects mounted on the antennas. These retroreflectors serve as precise position markers that can be accurately located by the external laser ranging apparatus. The retroreflectors act as mediators between the small antenna aperture and the high-precision measurement requirement, enabling angular measurement precision without enlarging the antenna aperture
3Measurement precision
If the antennas are distributed in a large area to improve angular measurement precision, then the beam width narrows, but the system becomes complex and the relative position measurement is still limited to wavelength precision of radar waves
Solution Approach 1:
The patent introduces an external laser ranging apparatus and retroreflectors as intermediary measurement components. Instead of relying on the radar system itself to measure positions (which is limited by radar wavelength), the system uses the optical laser measurement system as an intermediary to provide high-precision position data. This separates the measurement function from the radar function, reducing system complexity while achieving superior measurement precision
Solution Approach 2:
The patent makes the laser ranging apparatus a universal positioning system that serves multiple antennas simultaneously. The single laser ranging apparatus can measure the positions of all antennas in the distributed array by sequentially or simultaneously targeting retroreflectors on each antenna, providing a multi-functional positioning solution that reduces overall system complexity compared to having dedicated measurement systems for each antenna
4Measurement precision
If a laser ranging apparatus is installed on each antenna to track with a laser beam, then enough distance and direction measurement precision can be attained, but it is disadvantageous in view of cost because the laser ranging apparatus is very expensive
Solution Approach 1:
The patent merges the laser ranging functionality into a single external apparatus rather than installing separate laser ranging apparatus on each antenna. The unified laser ranging system uses retroreflectors on antennas as passive targets, eliminating the need for active laser transmitters and receivers on each antenna. This consolidation dramatically reduces the number of expensive laser components from N (where N is the number of antennas) to just one shared system, thereby achieving high measurement precision at much lower cost
5Device complexity
If the measurement precision is about several cm using GPS or metal sphere, then the system is simple and low cost, but the beam formation is influenced when the wavelength of radar wave is in the range of several cm to several mm
Solution Approach 1:
The patent changes the measurement parameter from centimeter-level precision (GPS/metal sphere) to millimeter-level or sub-millimeter-level precision (laser ranging). This parameter improvement in measurement precision ensures that the position accuracy is sufficient for beam formation control when operating with radar wavelengths of several cm to several mm. The high-precision laser measurement provides the sub-wavelength accuracy needed for reliable phase and amplitude control across the distributed antenna array
Solution Approach 2:
The patent substitutes the low-precision GPS or metal sphere tracking system with a high-precision laser ranging system. This substitution replaces the inadequate measurement capability (several cm precision) with superior optical measurement capability (millimeter or sub-millimeter precision), enabling accurate beam formation control while maintaining the simplicity of using an external measurement system rather than complex on-antenna instruments
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 immediate, high-precision measurement of relative positions and directions of antennas in a distributed aperture radar system, overcoming the limitations of existing methods and reducing costs associated with laser ranging apparatuses.
Implementation Method 1
an optical signal input/output unit which applies a different optical modulation to an incident light beam and returns a modulated light beam
Implementation Method 2
returns a modulated light beam for reflection
Implementation Method 3
measuring a propagation distance of an optical signal from the light source to the light receiving unit through the optical signal input/output unit
Data Source
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AI summary
A ranging apparatus transmits an optical input signal to an optical signal input/output unit mounted on a measurement target. The optical signal input/output unit receives the optical signal and transmits an optical output signal applied with an optical change, to the ranging apparatus. The ranging apparatus receives the optical output signal, measures a propagation distance from a light source a the light receiving unit through the optical signal input/output unit, and measures a relative position of the optical signal input/output unit based on the propagation distance. Thus, a distributed aperture radar is realized from the ranging apparatus and the optical signal input/output unit.