Inverted Conical Sinuous Antenna Fixed Phase Center
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Solution Overview
Problem
Traditional wideband antennas for radio telescopes face limitations in achieving simultaneous multi-frequency observations due to frequency-dependent phase centers and impedance variations, which restrict their ability to operate over a wide bandwidth without mechanical adjustments.
Innovation Solution
A wideband antenna design featuring an inverted cone with sinuous arms and a ground plane, integrated low noise amplifiers, and a specific taper angle to maintain a constant phase center and impedance, ensuring frequency independence and low cross-polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional feed horns are used for radio telescopes, then the antenna structure is simple and easy to excite, but the bandwidth is limited to less than an octave requiring multiple feed horns for wideband observations
Solution Approach 1:
The patent employs a log-periodic structure where the active resonant region dynamically shifts along the antenna elements as frequency changes. This dynamic behavior allows a single antenna structure to adapt to different frequency bands, achieving ultra-wideband operation (greater than one octave) without requiring mechanical switching between multiple feed horns.
Solution Approach 2:
The antenna is divided into multiple discrete elements of varying lengths and geometries arranged in a log-periodic sequence. Each element acts as an independent resonator that becomes active at specific frequency ranges, allowing the antenna to cover a broad spectrum through the coordinated operation of segmented elements rather than requiring a single broadband structure.
2Adaptability or versatility
If log periodic structures or pyramid-shaped elements are used to achieve wide bandwidth, then the bandwidth increases, but the phase center varies with frequency
Solution Approach 1:
The patent introduces a ground plane and positions the log-periodic antenna asymmetrically above it, creating an inverted conical radiation pattern. This asymmetric configuration with the ground plane reference establishes a stable phase center at the apex of the inverted cone, preventing phase center migration across the bandwidth while maintaining ultra-wideband operation.
Solution Approach 2:
The ground plane acts as an intermediary element that stabilizes the phase center position. By placing the log-periodic antenna above the ground plane and forming an inverted conical structure, the ground plane serves as a reference that anchors the phase center at the cone apex, eliminating the phase center variation problem inherent in conventional log-periodic antennas.
3Stability of the object's composition
If a ground plane is added to achieve fixed phase center, then the phase center stability improves, but the self-complementary nature is lost leading to frequency dependent impedance variations
Solution Approach 1:
The patent carefully controls the distance between the log-periodic antenna elements and the ground plane, maintaining it between 0.15λ-0.35λ across the operating bandwidth. This parameter optimization ensures that the antenna maintains near-constant impedance (within 1:2 VSWR) over the ultra-wideband range while preserving the fixed phase center benefit of the ground plane configuration.
Solution Approach 2:
The patent applies different geometries and orientations to specific elements within the log-periodic structure to optimize local electromagnetic characteristics. By varying element shapes and positions locally rather than using a uniform structure, the antenna maintains self-complementary properties and frequency-independent impedance across the broad bandwidth while working above the ground plane.
4Adaptability or versatility
If multiple feed horns are used to cover wide frequency ranges, then the frequency coverage increases, but mechanical movement is required which prevents instantaneous wide bandwidth observations
Solution Approach 1:
The patent designs a single log-periodic antenna structure that performs multiple functions across different frequency ranges simultaneously. The ultra-wideband capability (greater than one octave) allows one antenna to replace multiple frequency-specific feed horns, enabling instantaneous multi-frequency observations without mechanical switching or movement, thus achieving both wide frequency coverage and fast operation.
Data Source
AI summary
A wideband antenna is disclosed. The wideband antenna comprises an inverted cone, at least one sinuous arm coupled to the cone, and a ground plane behind the apex of the cone. The sinuous arm comprises at least two active resonators.