Reconfigurable Reflectarray Antenna for Compact Microwave Imaging
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Solution Overview
Problem
Current microwave single pixel radiometric systems have large apertures, which are not compatible with smaller platforms, and existing miniaturization techniques often compromise resolution or frequency, limiting their applicability in space, air, and ground/sea missions.
Innovation Solution
A reconfigurable reflectarray antenna system using a plurality of independently controllable reflector elements with modulated antenna patterns and corresponding temperatures, fed into a compressive sensing imaging algorithm to generate high-resolution images, allowing for smaller physical apertures while maintaining or improving resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large aperture is used to achieve desired beam directivity and angular resolution, then the imaging resolution is improved, but the system size becomes too large for smaller platforms
Solution Approach 1:
The reflectarray antenna is made reconfigurable with independently controllable reflector elements that can dynamically change their reflection coefficients. This dynamic capability allows the system to synthesize multiple different antenna patterns from a single physical aperture, effectively replacing the need for multiple fixed apertures or a mechanically movable antenna, thus achieving high angular resolution without requiring a large physical aperture
Solution Approach 2:
The system changes the electrical parameters (reflection coefficient magnitude and phase) of each reflector element to generate different antenna patterns. By varying these parameters across multiple measurement sequences, the system synthesizes diverse sampling basis functions that enable compressive sensing reconstruction with high angular resolution while maintaining a compact aperture size
2Area of stationary object
If the frequency of operation is increased to achieve smaller physical apertures, then the system size is reduced, but the sensitivity to environmental parameters degrades due to wavelength-dependent effects
Solution Approach 1:
The reconfigurable reflectarray allows the system to operate at lower microwave frequencies where environmental parameter sensitivity is higher, while still achieving compact aperture sizes through dynamic pattern synthesis. The ability to generate multiple antenna patterns electronically compensates for the longer wavelengths, maintaining imaging performance without requiring high frequencies that would reduce environmental sensitivity
3Area of stationary object
If traditional radiometer systems are miniaturized, then the system fits smaller platforms, but the aperture physical dimensions cannot be reduced without compromising resolution
Solution Approach 1:
The system uses a reconfigurable reflectarray with independently controllable elements that can dynamically synthesize multiple different antenna patterns. This dynamic capability allows a single compact aperture to perform the function of multiple larger apertures, achieving high imaging resolution without requiring a large physical aperture that would not fit on smaller platforms
Solution Approach 2:
The invention combines the functions of multiple antenna patterns and multiple measurement sequences into a single reconfigurable aperture system. By merging these functions into one dynamically controllable structure, the system achieves the resolution-equivalent performance of multiple separate systems while maintaining a compact size suitable for smaller platforms
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
The system achieves high accuracy and improved pixel angular resolution in a more constrained Size, Weight, and Power (SWaP) environment, enabling effective imaging with reduced physical aperture size.
Implementation Method 1
A reconfigurable reflectarray is used to generate the sampling bases. The reflectarray includes a plurality of independently controllable reflector elements, where each reflector element produces a corresponding independently controllable reflection coefficient.
Implementation Method 2
A radiometer is used to make the measurements of the targeted scene. A plurality of antenna temperatures respectively corresponding to the plurality of modulated antenna patterns is measured.
Data Source
AI summary
A microwave single pixel imager apparatus and method of using same. Sampling a targeted scene includes the following. A plurality of modulated antenna patterns is generated using a reflectarray. A plurality of antenna temperatures respectively corresponding to the plurality of modulated antenna patterns is measured. A retrieved scene corresponding to the sampled targeted scene is generated. Generating a retrieved scene corresponding to the sampled targeted scene includes the following. The plurality of modulated antenna patterns and the corresponding plurality of antenna temperatures are fed into a compressive sensing imaging algorithm.