Electronically Scanned Antenna Waveguide Aperture Choke
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Solution Overview
Problem
Current aircraft radar systems face limitations in achieving rapid beam steering agility for various radar modes due to limitations in pulse repetition frequency and inability to discern targets within a 3 dB beamwidth, leading to restricted multi-mode operation and radar ground clutter issues.
Innovation Solution
The design incorporates a novel antenna aperture with a radio frequency choke and an array of waveguides with angled and depth-adjusted radiation slots, along with a feed manifold using hybrid couplers and coupling slots to enhance beam steering and reduce cross-polarization, enabling finer resolution and wider scan angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electronic antenna beam scanning is implemented to enhance radar functionality, then beam steering agility and multi-mode operation are improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The antenna aperture is divided into multiple discrete waveguide elements arranged in an array. Each waveguide can be independently controlled to steer the beam electronically, replacing mechanical scanning and enabling rapid beam steering agility while maintaining modular complexity
Solution Approach 2:
The antenna system is designed to support multiple radar modes (weather mapping, turbulence detection, wind shear detection, terrain mapping, collision avoidance) through a single electronically scanned aperture, allowing one system to perform multiple functions without requiring separate antenna systems for each mode
2Area of stationary object
If waveguides are placed in close proximity to reduce aperture size, then area is reduced, but cross-polarization interference between adjacent waveguides increases
Solution Approach 1:
A radio frequency choke is positioned between adjacent waveguides to act as an intermediary structure. The choke suppresses cross-polarization interference by preventing electromagnetic coupling between neighboring waveguide elements, allowing them to be placed in close proximity without harmful interference
Solution Approach 2:
The choke structure is strategically placed only at specific locations between adjacent waveguides where cross-polarization interference occurs. This localized intervention suppresses interference precisely where needed while maintaining the overall compact aperture design
3Ease of manufacture
If standard radiation slots are used in waveguides, then manufacturing is simplified, but feed coupling errors and aperture phase errors increase
Solution Approach 1:
The radiation slots are designed with specific non-standard parameters including angled orientations (5-25 degrees from the waveguide edge) and controlled depths (80-120 thousandths of an inch). These parameter adjustments compensate for feed coupling errors and aperture phase errors, improving phase accuracy while maintaining manufacturability through precise machining
4Device complexity
If pulse repetition frequency is limited to avoid radar ground clutter, then signal processing is simplified, but beam steering speed and target detection capability are reduced
Solution Approach 1:
The system replaces mechanical beam steering with electronic phase control through the waveguide array. This substitution enables rapid beam steering at electronic speeds without the mechanical inertia limitations, allowing high pulse repetition frequencies to be used for ground clutter suppression while maintaining fast steering capability
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 configuration allows for rapid beam scanning, improved target resolution, and concurrent multi-mode operation by eliminating radar ground clutter and enabling digital signal processing-based synthetic beam sharpening, enhancing the overall performance of aircraft radar systems.
Implementation Method 1
The first and third protrusions adjoin and the second and fourth protrusions adjoin to form a radio frequency choke. The radio frequency choke at least partially suppresses cross polarization of radio frequencies between the first and second waveguides.
Implementation Method 2
an array of waveguides, each waveguide comprising multiple radiation slots having an angle with respect to an edge of the waveguide and having a depth
Implementation Method 3
The coupling slot propagates a signal from the waveguide of the aperture to the junction, the propagated signal having the same mode in the junction as in the waveguide of the aperture.
Implementation Method 4
a feed manifold configured to split a received radio frequency signal into multiple outputs, the feed manifold comprising multiple hybrid couplers. Each hybrid coupler is configured to split a signal received at a single input port into two signals at two output ports.
Implementation Method 5
The ridge of the first waveguide comprises a step to match the impedance of the second waveguide with the impedance of the first waveguide.
Data Source
AI summary
An aperture of an antenna for a radar system comprises a first waveguide comprising a first protrusion and a second protrusion, each protrusion extending longitudinally along one side of the first waveguide. The aperture further comprises a second waveguide comprising a third protrusion and a fourth protrusion, each protrusion extending longitudinally along one side of the second waveguide. The first and third protrusions and second and fourth protrusions adjoin to form a radio frequency choke at least partially suppressing cross polarization of radio frequencies between the first and second waveguides.