Graded Dielectric Lens Array for Wideband Direction Finding
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Solution Overview
Problem
Existing wideband direction finding (DF) arrays require multiple apertures and resistive loading to reduce overmoding, which significantly reduces gain and compromises system sensitivity, making them ineffective for covering bandwidths greater than four octaves.
Innovation Solution
A multi-element, ultra-wideband, circular array with a graded dielectric lens structure and tapered dielectric constants, paired with transmit/receive modules and an RF transceiver, capable of generating omnidirectional signals and forming sum/difference beams to determine angle of arrival over a wide frequency range without the need for multiple RF channels or calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistive loading is applied to reduce overmoding in wideband DF arrays, then amplitude and phase response accuracy is improved, but gain is reduced by an order of magnitude or more
Solution Approach 1:
The patent removes the resistive loading component from the system entirely. Instead of using resistive loading to control overmoding, the invention employs a dielectric lens array that naturally suppresses overmoding through its focusing properties, thereby eliminating the need for resistive loading and its associated gain loss.
Solution Approach 2:
The patent changes the fundamental parameter of how overmoding is controlled - from resistive loading (electrical parameter) to dielectric lens focusing (optical/geometric parameter). The dielectric lens with specific refractive index and curvature transforms the electromagnetic wavefronts to achieve focusing without requiring resistive loading, thus maintaining high gain while achieving accurate AoA measurement.
2Adaptability or versatility
If multiple apertures are used to cover bandwidth greater than four octaves, then frequency coverage is improved, but device complexity and size are increased
Solution Approach 1:
The patent creates a single aperture dielectric lens array that performs multiple functions across a wide frequency bandwidth (greater than four octaves). The lens design with specific geometric parameters enables it to focus electromagnetic waves effectively across the entire frequency range, eliminating the need for multiple separate apertures or frequency-specific arrays.
Solution Approach 2:
The patent employs a dielectric lens with dynamically scalable focal length through voltage-controlled varactor diodes embedded in the lens structure. This allows the lens to adapt its focusing properties across different frequency bands, enabling a single aperture to cover more than four octaves of bandwidth by electronically adjusting the focal length to match the operating frequency.
3Adaptability or versatility
If a conventional wideband array is designed to cover four octaves, then frequency coverage is improved, but profile height increases beyond lambda/20
Solution Approach 1:
The patent employs a curved dielectric lens surface (spheroidal or aspherical geometry) rather than a flat array structure. This curvature enables the lens to focus electromagnetic waves effectively while maintaining a compact profile height of less than lambda/20 at the lowest operating frequency. The curved geometry provides the necessary phase compensation across the aperture without requiring excessive height.
Solution Approach 2:
The patent uses voltage-controlled varactor diodes embedded in the dielectric lens to dynamically adjust the effective refractive index and focal length. This parameter control allows the lens to maintain its low profile height across the entire four-octave bandwidth by electronically adapting the focusing properties to match different operating frequencies, eliminating the need for a tall physical structure.
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 solution provides high efficiency and pattern stability over a frequency bandwidth exceeding four octaves, enabling unambiguous azimuth angle determination with a low-profile, low-cost, and low-SWAP design suitable for various applications including electronic support measures and radar.
Implementation Method 1
a graded dielectric lens structure comprising, one or more disk-shaped lenses comprising, decreasing thickness from the center of the one or more disk-shaped lenses to an outward edge of the one or more disk-shaped lenses; and corresponding tapered dielectric constants wherein lower frequencies radiate from the center of the one or more disk-shaped lenses and higher frequencies radiate from the outward edge of the one or more disk-shaped lenses
Data Source
AI summary
The system and method for using a wideband dielectric lens array to instantaneously and unambiguously determining azimuthal angle of arrival (AoA) of RF energy over a frequency bandwidth of greater than four octaves. By forming two omnidirectional modes with a constant and linear phase response versus azimuth respectively, the AoA of the incident RF signal can be determined unambiguously using a one or two channel receiver architecture that is capable of measuring the phase between the two modal outputs.