Synthetic Aperture Radar Feed Network Phase Control
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Solution Overview
Problem
Current synthetic aperture radar systems with reflector antennas lack flexibility in configuring phase centers and antenna apertures, which limits their ability to adapt to varying requirements for interferometric measurements and resolution.
Innovation Solution
A method using a digital feed network to control the amplitude and phase of exciter elements in a satellite-based synthetic aperture radar system, allowing for flexible positioning and sizing of phase centers and apertures, both during transmission and reception, by varying the phase and amplitude assignments to generate beams with specific directions and illuminating sections of the reflector antenna.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple phase centers are used for interferometric measurements, then measurement capability is improved, but device complexity increases
Solution Approach 1:
A single reflector antenna system is designed to perform multiple functions: it can operate as a conventional SAR system and as an interferometric SAR system by dynamically reconfiguring the excitation elements. The same physical hardware achieves both single-aperture and multi-aperture operations through software-controlled phase and amplitude adjustments, eliminating the need for separate interferometric hardware.
Solution Approach 2:
The system dynamically reconfigures the excitation elements' phase and amplitude assignments to create virtual phase centers at different positions along the flight direction. This dynamic reconfiguration allows the system to adapt between different measurement modes (conventional SAR vs. interferometric SAR) and adjust the number and position of phase centers based on measurement requirements, rather than being fixed in hardware.
2Measurement precision
If phase centers are offset in the direction of flight for interferometric operation, then speed measurement capability is improved, but adaptability to different measurement scenarios is reduced
Solution Approach 1:
The system uses dynamic phase and amplitude assignment to excitation elements to reposition phase centers along the flight direction for speed measurements, rather than relying on fixed physical offsets. This allows the same hardware to adapt to different measurement scenarios by programmatically adjusting the phase center positions, providing both along-track interferometry capability and cross-track interferometry capability as needed.
Solution Approach 2:
The system changes the phase and amplitude parameters of the excitation elements to create virtual phase centers at different positions. By modifying these electromagnetic parameters, the system can achieve different interferometric configurations (along-track for speed, cross-track for altitude) without physical reconfiguration, enabling adaptability to various measurement requirements.
3Measurement precision
If phase centers are offset perpendicular to the direction of flight for altitude measurement, then altitude measurement capability is improved, but adaptability to other measurement types is reduced
Solution Approach 1:
The system dynamically adjusts the phase and amplitude of excitation elements to create virtual phase centers offset perpendicular to the flight direction for cross-track interferometry and altitude measurement. This dynamic reconfiguration allows the same system to switch between along-track and cross-track interferometric modes, providing multi-purpose measurement capability rather than being dedicated to a single measurement type.
4Manufacturing precision
If the size of the physical measurement aperture is increased to improve resolution, then azimuth resolution is improved, but the system's flexibility in parameter design is reduced
Solution Approach 1:
The system uses dynamic phase and amplitude assignment to excitation elements to create virtual apertures of different sizes and positions. Rather than being constrained by a fixed physical aperture size, the system can programmatically adjust the effective aperture by controlling which excitation elements are active and with what phase/amplitude weights, allowing flexible resolution optimization for different measurement scenarios.
Solution Approach 2:
The system creates virtual copies of phase centers and aperture configurations through digital signal processing and phase control. Instead of requiring multiple physical apertures or hardware configurations to achieve different resolution levels, the system generates virtual aperture copies by controlling the excitation elements, providing flexible parameter design without additional hardware.
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 flexible design of phase centers and apertures, improving interferometric capabilities and resolution, while allowing for simultaneous operation of multiple phase centers, reducing ambiguity and enhancing the system's adaptability to different measurement scenarios.
Implementation Method 1
During transmission, the digital feed network varies the amplitude and phase assignment of the excitation elements in a predetermined manner in order to control beams directed from the exciter towards the reflector antenna with respect to the reflector antenna's illumination area, thus generating beams of the same direction in the far field
Implementation Method 2
In the case of reception, the feed network combines the amplitudes and phases of the signals provided by the excitation elements in a predetermined manner in order to control rays directed from the reflector antenna towards the exciter with respect to their illumination areas of the reflector antenna, which result from rays with the same direction in the far field
Implementation Method 3
SAR (Synthetic Aperture Radar) systems enable remote sensing of the Earth's surface by detecting radar pulses reflected from the surface
Implementation Method 4
These pulses are emitted by the SAR system, which moves at a constant speed above the Earth's surface on a platform. Such a system utilizes the fact that, due to the moving platform, the same areas of the Earth are detected from different positions, thus providing amplitude and phase information
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The amplitude and/or phase distribution of energizing elements is varied in predetermined manner in the transmission case by the feed network. The radiation from exciter (3) directed toward reflector antenna (1) is controlled with respect to the direction and/or coverage area of the reflector antenna. An independent claim is included for radar system.