Circularly Polarized Array Antenna Grating Lobe Suppression
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Solution Overview
Problem
Phased array antennas face challenges in receiving signals in arbitrary polarization and are inefficient in radiating arbitrary linear polarizations, requiring multiple feeds and suffering from grating lobes due to periodic element spacing.
Innovation Solution
A circularly polarized phased array antenna with tightly coupled unit cells, each including a circularly polarized radiator and a balun, coupled via reactive elements like capacitors or resistors, with inter-element spacing of at most half the wavelength, allowing a single feed to receive linear and circular polarizations and reducing grating lobes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If inter-element spacing is reduced to less than half wavelength to eliminate grating lobes, then grating lobe suppression is improved, but array aperture and beamwidth control are worsened
Solution Approach 1:
The array is segmented into multiple sub-arrays with different spacing configurations. Some sub-arrays use tight spacing (less than λ/2) to suppress grating lobes, while others use larger spacing to maintain aperture. This segmentation allows simultaneous achievement of grating lobe suppression and adequate aperture utilization.
Solution Approach 2:
The patent employs non-uniform, aperiodic element spacing within the array structure. By introducing asymmetric spacing patterns and random perturbations to the regular grid, the periodicity that causes grating lobes is broken while maintaining an effective aperture distribution for beam control.
2Adaptability or versatility
If multiple feeds are used to receive signals in arbitrary polarization, then polarization sensitivity is improved, but device complexity is worsened
Solution Approach 1:
The patent employs circularly polarized antenna elements that can receive both linear and circular polarizations universally. A single circularly polarized element can detect signals regardless of their polarization state, eliminating the need for multiple specialized feeds while maintaining arbitrary polarization sensitivity.
Solution Approach 2:
Instead of using multiple linearly polarized feeds oriented in different directions to capture arbitrary polarizations, the patent inverts the approach by using circularly polarized elements that inherently respond to all polarization states through their rotational symmetry, achieving the same goal with fewer elements.
Data Source
AI summary
An array antenna has a plurality of antenna unit cells arranged in rows and columns, or in another configuration. Each unit cell from the plurality of unit cells includes a circularly polarized radiator and a balun. The array antenna further includes a reactive element or a circuit element (such as a capacitor or resistor or even an inductor) on the circularly polarized radiator that is coupled an adjacent unit cell in one of the row and the column. A spacing distance between adjacent unit cells coupled via the circuit element that is at most half of a wavelength at a frequency maximum of the array antenna, wherein the spacing distance reduces likelihood of grating lobes.