Optical Phased Array Row-Column Driver for Scalable Phase Shifting
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Solution Overview
Problem
Conventional methods for controlling large arrays of thermal optical phase shifters in optical phased arrays face challenges in scalability due to the need for numerous independent analog drive channels, leading to complex wiring and increased costs, as well as thermal crosstalk issues.
Innovation Solution
A driver system that employs a row-column driving scheme with a reduced number of digital-to-analog converters and multiplexed ground buses, allowing simultaneous operation of all phase shifters while minimizing thermal crosstalk and interface pin count, using diodes and thermal resistors to manage heat distribution efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If brute-forced control of each individual phase shifter with independent analog drive channels is used, then high resolution and large aperture are achieved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The phase shifter array is divided into multiple rows and columns, with each row having its own DAC but columns sharing common ground buses. This segmentation allows independent control of rows while grouping columns to reduce the total number of drive channels from N (for N phase shifters) to much fewer channels.
Solution Approach 2:
Multiple columns of phase shifters are merged to share common ground buses. Instead of providing independent ground connections for each phase shifter, the patent combines columns to share ground paths, thereby reducing the number of required drive channels and simplifying the overall control architecture.
2Ease of operation
If brute-forced control with independent analog drive channels is used, then each phase shifter can be controlled precisely, but the number of metal traces and wiring becomes unmanageable
Solution Approach 1:
The control architecture is segmented into row-specific DACs and column-shared ground buses. Each phase shifter at position (i,j) is controlled by the combination of row i's DAC output and column j's ground bus state, enabling individual control without requiring N independent wiring paths.
Solution Approach 2:
The common ground buses serve multiple columns simultaneously, making them multi-functional. A single ground bus can control the ground connection state for multiple phase shifters across different rows, thereby reducing the total number of wiring traces required on the chip.
3Adaptability or versatility
If more independent DAC channels are provided, then better control of large phase shifter arrays is achieved, but cost and system complexity increase
Solution Approach 1:
The DAC resources are segmented and allocated to rows rather than individual phase shifters. Each row has one DAC that controls all phase shifters in that row through the combination with column ground bus states, reducing the number of DACs from N to much fewer (equal to number of rows).
Solution Approach 2:
The control problem is transformed from a one-dimensional array of N independent controls to a two-dimensional row-column matrix. By adding the dimension of column grouping with shared ground buses, the system achieves control of N phase shifters using far fewer DAC channels.
4Ease of operation
If thermal phase shifters are used to control switching and modulation, then optical signal control is achieved, but thermal crosstalk between adjacent phase shifters occurs
Solution Approach 1:
The patent extracts and addresses the thermal crosstalk issue by implementing thermal isolation structures between adjacent phase shifters. Thermal barriers or spacing are introduced to prevent heat from one phase shifter from affecting its neighbors, thereby removing the harmful thermal coupling while preserving the optical control functionality.
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 approach enables efficient control of large arrays of phase shifters with reduced complexity and cost, while maintaining low thermal crosstalk and achieving precise phase shifting, allowing for scalable and cost-effective optical phased arrays.
Implementation Method 1
A thermal phase shifter, also referred to as a thermo-optic phase shifter, may be used to shift the phase of light in a waveguide by heating the waveguide, thereby changing the refractive index of the waveguide in a heated area via the thermo-optic effect
Implementation Method 2
a plurality of digital to analog converters (DACs), each one of the plurality of DACs configured to output an independent voltage or current onto one of the plurality of rows of optical phase shifters
Implementation Method 3
a multiplexer configured to selectively connect one of the plurality of ground buses to the common ground, while disconnecting others of the plurality of ground buses
Data Source
AI summary
An optical phased array comprising a row-column driving mechanism is disclosed that reduces the number of digital to analog converter (DAC) channels to the number of rows N and the total number of interface pin counts down to the number of columns plus the number of rows M+N. Disclosed herein are systems and architecture for thermal waveguide-based phase shifters which improve thermal efficiency by having multi-pass waveguides arranged proximate a heating element in a serpentine fashion, which enables an increase in phase shift without increasing the length or the power consumption of the heating element by increasing the total length of waveguide being heated by a singular heating element.