Annular Antenna with Cylindrical Choke for Feed Isolation
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Solution Overview
Problem
There is a need for a compact, omnidirectional antenna with a horizontally oriented power distribution, resistant to physical impacts, and effective isolation of the radiation pattern from a coaxial feed line, even when the radiator is separated by a ground plane.
Innovation Solution
The antenna design features an annular radiator with a ground plane, radial microstrips connecting the radiator to the feed, and a cylindrical choke around the coaxial feed line, optimizing impedance matching and radiation patterns while providing structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a traditional dipole antenna is used to provide ideal power distribution pattern, then the radiation pattern is optimized, but the antenna becomes too large and fragile for compact applications
Solution Approach 1:
The antenna is segmented into multiple microstrip elements arranged in a circular configuration around the feed line. Each microstrip is approximately one-eighth wavelength long, and multiple segments work together to create an omnidirectional radiation pattern, achieving dipole-like performance in a compact form factor.
Solution Approach 2:
The antenna transitions from a linear dipole configuration to a circular planar arrangement. By distributing microstrip elements around the circumference of the feed line, the antenna achieves omnidirectional radiation in the horizontal plane while maintaining a compact vertical profile, effectively utilizing spatial arrangement in another dimension.
2Object-generated harmful factors
If the ground plane is used to isolate the radiator from the feed line, then isolation is provided, but the coaxial feed cable still interferes with radiation patterns
Solution Approach 1:
A choke balun is introduced as an intermediary component between the feed line and the microstrip elements. This choke balun provides additional isolation by creating an impedance discontinuity that prevents common-mode currents on the feed line, thereby eliminating feed line interference with the radiation pattern while maintaining the ground plane's isolation function.
3Volume of moving object
If a compact antenna design is used to reduce size, then space considerations are satisfied, but structural resistance to bumps and knocks is reduced
Solution Approach 1:
The antenna elements are merged with the feed line structure, with microstrips extending radially from the coaxial feed line. This integration creates a unified structure where the feed line serves as both the signal transmission medium and the structural support for the radiating elements, enhancing structural strength while maintaining compactness.
Solution Approach 2:
The choke balun is positioned at the feed point before the microstrip elements begin, providing preliminary structural reinforcement and current suppression. This preliminary action prevents structural weaknesses at the critical feed-point interface and prevents current leakage before it can affect the radiation pattern.
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 design achieves a compact, omnidirectional power distribution primarily horizontal in nature, resistant to physical stress, and significantly reduces the interference from coaxial feed lines, enhancing antenna performance and reliability in terrestrial applications.
Implementation Method 1
the ratio of the input impedance to the load impedance is a function of the ratio of the length of each microstrip from its first end to the feed, to the length of each microstrip from its first end to its second end
Implementation Method 2
a cylindrical choke approximately one-quarter wavelength in length is placed around the feed and connected to the underside of the ground plane
Implementation Method 3
The electrical signal of the input is converted to electromagnetic radiation that propagates from the radiator in accordance with its directivity
Data Source
AI summary
An antenna having a radiator comprising a conduct in a closed path driven by a plurality of microstrips connecting the radiator to a common, single feed and to a ground plane, with the radiator lying in a plane parallel to that of the ground plane. The radiator may be annular, with the feed located in its center. The relative location of the feed on the microstrips allows a lower input impedance to be leveraged to match a higher load impedance of the radiator. A single-ended input drives all points of the radiator substantially in phase. In another embodiment, the antenna comprises a cylindrical choke one-quarter wavelength in length placed around the coax feed and connected to the underside of the ground plane.