50% Overlapped Subarray Antenna for Grating Lobe Suppression
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Solution Overview
Problem
Radar systems face challenges in achieving effective grating lobe suppression with sub-arrays, particularly for limited scan antennas, as existing solutions require costly phase control modules and receivers, and increasing radiating elements in each sub-array to mitigate grating lobes is inefficient.
Innovation Solution
A phased array antenna design with a substrate integrated waveguide (SIW) feed network that includes over-moded waveguide couplers, allowing half of the radiating elements of one sub-array to overlap with another, enabling energy distribution through multiple modes to achieve in-phase and out-of-phase paths, thereby reducing grating lobes and maintaining low side-lobes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If radiating elements are grouped into sub-arrays to reduce phase control modules and receivers, then cost is reduced, but grating lobes are generated
Solution Approach 1:
The antenna array is divided into multiple sub-arrays, each fed by a separate input port. This segmentation allows reduction of phase control modules and receivers while maintaining grating lobe suppression through the specific feeding structure of each sub-array element.
Solution Approach 2:
Radiating elements are shared between adjacent sub-arrays, with each element nested in multiple sub-array structures. This nesting allows a single radiating element to serve multiple sub-arrays simultaneously, reducing the total number of elements needed while maintaining pattern control.
Solution Approach 3:
The feeding network uses specific amplitude and phase parameters distributed to each radiating element through the substrate integrated waveguide. By controlling these parameters, the system achieves grating lobe suppression while using fewer phase control modules and receivers.
2Object-generated harmful factors
If the number of radiating elements in each sub-array is increased to narrow the sub-array pattern, then grating lobe suppression is improved, but the spacing between sub-arrays cannot be increased
Solution Approach 1:
Adjacent sub-arrays are merged by sharing common radiating elements between them. This merging allows the sub-arrays to be closely spaced while maintaining individual pattern control through the substrate integrated waveguide feeding network, achieving grating lobe suppression without increasing spacing.
Solution Approach 2:
Shared radiating elements serve multiple sub-arrays simultaneously, performing multiple functions. These universal elements contribute to the radiation pattern of each sub-array they belong to, allowing narrow beamwidth and grating lobe suppression without requiring large spacing between sub-arrays.
3Object-generated harmful factors
If sub-arrays are overlapped to achieve acceptable grating lobe suppression, then grating lobe suppression is improved, but implementation becomes difficult for limited scan antennas
Solution Approach 1:
The mechanical complexity of overlapping sub-arrays is replaced by an electromagnetic field-based substrate integrated waveguide feeding network. This substitution simplifies implementation by using planar waveguide structures and controlled electromagnetic coupling rather than complex mechanical or spatial arrangements.
Solution Approach 2:
The substrate integrated waveguide acts as an intermediary between the input ports and the radiating elements. It provides a structured method for distributing energy to overlapped sub-arrays, simplifying the implementation of grating lobe suppression by mediating the energy distribution through controlled coupling mechanisms.
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 antenna achieves significant grating lobe suppression with a 50% overlap of radiating elements, maintaining high gain and minimizing side-lobes, while reducing the number of phase control modules and receivers, thus lowering costs and improving performance.
Implementation Method 1
Each over-moded waveguide coupler includes an over-moded section defined by a width selected such that energy propagates through the over-moded section in multiple modes effective to establish a first path for energy from the left in-port and a second path for energy from the right in-port
Implementation Method 2
The multiple modes may include a TE10 mode and a TE20 mode
Implementation Method 3
The energy coupled from the over-moded section to left out-port may be in-phase with energy coupled from the over-moded section to right out-port... Energy from the two adjacent over-moded waveguide couplers of the sub-array that propagates to the four adjacent radiators that form the sub-group may be characterized as in-phase, and energy from the two adjacent over-moded waveguide couplers that propagates to a secondary radiator adjacent the sub-group may be characterized as out-of-phase with energy of the sub-group
Data Source
Figure 1A
Figure 1B~3
Figure 4~5
AI summary
An antenna (10) suitable for use as a phased array antenna of a radar system. The antenna (10) includes a plurality of radiating elements (12), and a substrate (14) integrated waveguide (SIW) configured to form a feed network (16) to couple energy from a plurality of inputs (18) to the radiating elements (12). The feed network (16) includes over-moded waveguide couplers configured so energy propagates through an over-moded section in multiple modes, TE10 and TE20 modes for example. The feed network (16) also defines sub-arrays configured such that half of the radiators of a sub-group (22A) are shared with an adjacent sub-group (22A) of an adjacent sub-array (20A), i.e. the sub-arrays are configured to have 50% overlap. Preferably, the feed-network is formed about a single layer of substrate (14) material.