Misaligned Drive Coils for High Angular Resolution Low Frequency Radar
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Solution Overview
Problem
Low-frequency radar systems face poor angular resolution due to the use of long wavelengths, making it impractical to achieve high resolution with conventional antenna sizes, especially in applications like through-the-wall and ground-penetrating radar, and unmanned aerial vehicles (UAVs).
Innovation Solution
A low-frequency radar system employing two misaligned drive coils to produce separately modulated field patterns, with a composite sense coil to measure the magnitude and phase of the received modulations, allowing for improved angular resolution by inferring the target's angle and using a steering apparatus to direct the system towards the target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long wavelength radiation is used for penetration, then penetration capability is improved, but angular resolution deteriorates
Solution Approach 1:
The transmitting antenna is divided into two separate drive coils (first and second drive coils) that are misaligned with respect to each other. Each coil generates a separate field pattern with distinct modulation, allowing the system to resolve angular information that would otherwise be lost in a single long-wavelength beam.
Solution Approach 2:
The patent introduces a spatial dimension by misaligning the two drive coils at different positions and orientations. This creates two distinct far-field directions, adding angular dimensionality to the measurement process and enabling resolution beyond the diffraction limit of a single antenna.
2Measurement precision
If antenna size is increased to improve angular resolution, then angular resolution is improved, but device size and complexity worsen
Solution Approach 1:
Instead of using one large antenna, the system segments the antenna function into two smaller drive coils. The misalignment between these coils creates the necessary angular discrimination without requiring a single large aperture, thus reducing overall device complexity while maintaining resolution.
Solution Approach 2:
The patent uses periodic modulation of the two drive coils with different modulation schemes. This temporal periodicity allows the receiver to distinguish between the two spatial patterns through correlation processing, achieving angular resolution without increasing physical antenna dimensions.
3Measurement precision
If antenna size is increased to improve angular resolution, then angular resolution is improved, but ease of operation worsens
Solution Approach 1:
The antenna system is segmented into two independent but coordinated drive coils, each capable of being modulated separately. This segmentation allows the system to achieve high angular resolution with compact, maneuverable components suitable for UAV deployment, rather than requiring a single large fixed antenna.
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 sub-diffraction-limit angular resolution, enabling precise target localization with improved sensitivity and accuracy, even with small antenna sizes, significantly enhancing the detection capabilities of low-frequency radar systems.
Implementation Method 1
two drive coils, misaligned with respect to each other, that produce respective field patterns, each modulated with a respective modulation
Implementation Method 2
A radar receiver includes a composite sense coil that senses the effect a target has on the fields, and generates a corresponding signal that carries the two modulations
Implementation Method 3
An additional measurement of the angle may be made by comparing the phases of the carrier in the two received modulations
Data Source
AI summary
A ground-penetrating radar system or other low-frequency radar system that operates at a wavelength that is comparable to or larger than the dimensions of the transmitting and receiving antennas. In one embodiment, a radar transmitter includes two drive coils, misaligned with respect to each other, that produce respective field patterns, each modulated with a respective modulation. A radar receiver includes a composite sense coil that senses the effect a target has on the fields, and generates a corresponding signal that carries the two modulations. From the proportion of the two modulations in the received signal, which depends on the extent to which the target is in each of the two field patterns, the receiver estimates the angle (e.g., the azimuth angle) to the target. An additional measurement of the angle may be made by comparing the phases of the carrier in the two received modulations. The composite sense coil may consist of two coils wired in series and configured to generate no output when the only field incident on the composite sense coil is that of the two drive coils, in the absence of a target.