Co-prime Optical Transceiver Array Grating Lobe Suppression
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Solution Overview
Problem
Optical phased arrays face limitations in achieving improved performance and a large field-of-view while minimizing grating lobes and side-lobes, particularly due to constraints in element spacing and the number of elements, which affects their efficiency in applications like 3D imaging and data communication.
Innovation Solution
A co-prime transceiver design where the spacing between transmitter and receiver array elements is defined by co-prime integer multiples of the wavelength, allowing for flexible optical routing and increased aperture size, thereby enhancing performance and controlling beam characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If element spacing is increased to reduce grating lobes, then side-lobe rejection is improved, but field-of-view is reduced
Solution Approach 1:
The patent divides the array into two separate co-prime arrays with different element spacings (d1 and d2 where gcd(d1,d2)=1). This segmentation allows each sub-array to contribute differently to the overall radiation pattern, enabling simultaneous achievement of large field-of-view (from the wider-spaced array) and good side-lobe rejection (from the narrower-spaced array), resolving the contradiction between these two parameters.
2Measurement precision
If number of elements is increased to improve resolution, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent changes the spacing parameters of the two arrays to be co-prime integers (d1 and d2). This parameter change creates a virtual aperture effect where the combined radiation pattern achieves resolution equivalent to a much larger uniform array, but with far fewer actual elements. The co-prime relationship ensures that the combined pattern fills in the gaps that would otherwise require many more elements to achieve.
3Adaptability or versatility
If element spacing is reduced to maintain large field-of-view, then adaptability is maintained, but grating lobes increase
Solution Approach 1:
The patent converts the harmful grating lobes generated by each individual co-prime array into beneficial main lobes of the combined system. The grating lobes of one array fall into the nulls of the other array's pattern, and vice versa, due to the co-prime spacing relationship. This transforms what would be harmful interference patterns into a constructive combined pattern with suppressed grating lobes and maintained wide field-of-view.
Data Source
AI summary
A co-prime transceiver attains higher fill factor, improved side-lobe rejection, and higher lateral resolution per given number of pixels. The co-prime transceiver includes in part, a transmitter array having a multitude of transmitting elements and a receiver array having a multitude of receiving elements. The distance between each pair of adjacent transmitting elements is a first integer multiple of the whole or fraction of the wavelength of the optical. The distance between each pair of adjacent receiving elements is a second integer multiple of the whole or fraction of the wavelength of the optical signal. The first and second integers are co-prime numbers with respect to one another. The transceiver is fully realizable in a standard planar photonics platform in which the spacing between the elements provides sufficient room for optical routing to inner elements.