OWC Receiver Photodiode Array for Large FoV and Bandwidth
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Solution Overview
Problem
Optical Wireless Communication (OWC) systems face challenges in achieving a large photodetector surface area and high bandwidth without reducing the field-of-view (FoV), as well as the need for complex alignment and high-frequency electronics, due to the limitations imposed by the Law of Etendue.
Innovation Solution
A novel OWC receiver design featuring a two-dimensional array of photodiodes positioned at or near the focal plane of a lens, where the photodiodes are arranged in a matrix configuration to increase the photodetector surface area while maintaining high bandwidth, by combining photocurrents from multiple photodiodes and using a transimpedance amplifier to convert the summed photocurrents into an output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large-diameter lens is used to collect much light, then the photodetector surface area is improved, but the field-of-view angle is reduced due to the large focal length
Solution Approach 1:
The photodetector is divided into multiple smaller photodiodes arranged in a two-dimensional array. Each photodiode has a small active area that maintains a short focal length, allowing for a large field-of-view angle. The array of photodiodes collectively provides a large photodetector surface area, resolving the contradiction between collecting much light and maintaining a wide field-of-view.
Solution Approach 2:
The invention transitions from a single large photodetector to a two-dimensional array of multiple photodiodes. This dimensional change allows the system to achieve a large effective photodetector surface area through the array configuration while each individual photodiode maintains a short focal length for wide field-of-view coverage.
2Area of stationary object
If a large-diameter lens with large focal length is used, then the light collection area is improved, but the alignment tolerance is reduced
Solution Approach 1:
The system uses multiple photodiodes in a two-dimensional array, each with a short focal length. This segmentation allows each photodiode to have relaxed alignment requirements while the array as a whole provides large light collection area. The short focal length of each photodiode maintains tolerance to angular offsets.
Solution Approach 2:
Multiple photodiodes are combined in a two-dimensional array configuration. The outputs of the photodiodes are combined through parallel columns of photodiodes with cascade connections, merging their signals to achieve both large light collection area and maintained alignment tolerance through the distributed architecture.
3Area of stationary object
If multiple photodiodes are connected in parallel to increase photodetector surface area, then the sensitivity is improved, but the bandwidth is reduced
Solution Approach 1:
The photodetector is segmented into multiple photodiodes arranged in a two-dimensional array with specific interconnection patterns. This segmentation allows the system to achieve large photodetector surface area while the distributed architecture and specific connection pattern maintain bandwidth performance.
Solution Approach 2:
The invention changes the interconnection parameters of the photodiodes by arranging them in parallel columns with cascade connections. This specific parameter configuration (M rows, K columns with K≥2 parallel columns) allows the system to achieve both increased sensitivity through area multiplication and maintained bandwidth through the specific interconnection topology.
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 design allows for a larger photodetector surface area and increased angular aperture, achieving a trade-off between sensitivity and bandwidth without requiring complex alignment or high-frequency electronics, thereby enhancing the receiver's ability to capture more light and maintain high data rates.
Implementation Method 1
a lens arranged to receive the incoming optical beam
Implementation Method 2
positioned at or closely to the focal plane of the lens
Implementation Method 3
each of the plurality of photodiodes being arranged to receive a fraction of the incoming optical beam and to generate a photocurrent in correspondence with photons received
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3~4
AI summary
An Optical Wireless Communication, OWC, receiver is presented for receiving an incoming optical beam modulated with data and outputting an output signal comprising the modulated data, the receiver comprising: a lens, arranged to receive the incoming optical beam; a plurality of photodiodes, positioned at a distance from the lens and positioned at or closely to (i.e. preferably before) the focal plane of the lens, each of the plurality of photodiodes being arranged to receive a fraction of the incoming optical beam and to generate a photocurrent in correspondence with photons received from the fraction of the incoming optical beam, wherein the plurality of photodiodes (N) are arranged in a two-dimensional array (N=MxK) comprising rows (1…M) and columns (1…K), and wherein outputs of the columns (1…K) are combined and their photocurrents are summed; an amplifier connected to the combined output of the columns (1…K) of the two-dimensional array and arranged to convert the summed photocurrents into the amplifier's output signal; wherein interconnections of the photodiodes of the two-dimensional array (MxK) are configured to form at least two parallel branches (1…K, wherein K≥2) of photodiodes, and wherein each of the parallel branches comprises a cascade (1…M, wherein M≥2) of at least two photodiodes forming a combined photodetector surface.