Tunable Microwave-Photonic Device for Antenna Backwave Suppression
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Solution Overview
Problem
Conventional super-thin frequency-independent antennas have narrow bandwidth coverage due to static lumped element technology, which restricts their frequency independence and antenna performance, particularly in volume-constrained applications like missiles, where deep cavities or narrow bands are required, leading to self-interference from backwaves that reduce antenna directivity.
Innovation Solution
A photonic approach is employed to suppress backwaves using a tunable microwave-photonic device with an electro-optically active material, laser light, and a photodiode to dynamically adjust the cavity impedance across a wide range of frequencies, effectively tuning the antenna to avoid unwanted frequencies and maintain well-behaved patterns within the desired bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep cavities are used to capture and remove backwaves, then antenna directivity is improved, but volume consumption increases significantly
Solution Approach 1:
The patent replaces the mechanical deep cavity structure with an electronically tunable filter system. Instead of using a physically deep cavity to capture and remove backwaves, the invention employs tunable filters that can be adjusted to resonate at specific frequencies, providing the same backwave suppression function with minimal volume consumption.
Solution Approach 2:
The patent changes the parameter of cavity depth from a fixed large value to a variable small value by introducing tunable filters. The filters can be adjusted to change their resonant frequency and impedance characteristics, effectively providing deep cavity functionality through parameter adjustment rather than physical depth.
2Device complexity
If static lumped element technology is used for tuning, then device complexity is reduced, but bandwidth coverage becomes narrow
Solution Approach 1:
The patent transitions from static lumped element tuning to dynamic tunable filtering. The system employs filters whose resonant frequencies and impedance characteristics can be changed in real-time, allowing the antenna to adapt to different frequency bands and maintain optimal performance across a wide bandwidth.
Solution Approach 2:
The patent creates a universal tuning system that can operate across multiple frequency bands (2-18 GHz) using a single tunable filter structure. Instead of requiring different fixed-element configurations for different bands, the same physical structure can be adjusted to serve multiple functions and frequency ranges.
3Reliability
If out-of-band attenuation is increased to reduce backwave interference, then antenna directivity is improved, but antenna mainbeam gain is reduced due to destructive interference
Solution Approach 1:
The patent employs a feedback mechanism where tunable filters are adjusted based on the detected backwave characteristics. By continuously monitoring and adjusting the filter parameters, the system can suppress backwaves while maintaining forward radiation patterns, avoiding the destructive interference that occurs with fixed attenuation approaches.
Solution Approach 2:
The patent uses dynamic filter tuning to selectively attenuate only the problematic backwave frequencies while leaving the forward radiation frequencies unaffected. This dynamic adjustment allows the system to achieve directivity improvement without the permanent power loss associated with fixed out-of-band attenuation.
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 solution provides full coverage of the 2-18 GHz band with high agility, avoiding unwanted frequencies and maintaining antenna performance without the need for multiple filters, thus overcoming the limitations of conventional technologies in terms of bandwidth and size.
Implementation Method 1
an electro-optically active material; means for communicating laser light to the electro-optically active material
Implementation Method 2
a photodiode; means for communicating electromagnetic products of interactions between radiation and laser light to a photodiode
Data Source
AI summary
A technique for suppressing backwaves employs a photonic approach. In one aspect, the technique includes an apparatus, including: a radiating element; and a microwave-photonic device for suppressing backwaves from the radiating element. In a second aspect, the technique includes a method for removing unwanted radiation from a radiating device, comprising: receiving unwanted radiation from the radiating device; communicating the received radiation to an electro-optically active material; communicating laser light to the electro-optically active material; communicating electromagnetic products of interactions between the radiation and the laser light to a photodiode; and communicating photodiode outputs to a termination.