Time of Flight Distance De-aliasing via Phase Domain Computation
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Solution Overview
Problem
Existing ranging systems face complexity and resource-intensive calculations when extending the unambiguous range using multiple frequencies, leading to significant Integrated Circuit (IC) silicon area and processing time requirements for distance de-aliasing.
Innovation Solution
The implementation of phase domain computations in Time of Flight (ToF) systems, which project modulated electromagnetic radiation of at least two frequencies, calculate a weighted phase difference, and determine the actual distance using bit-wise operations, eliminating the need for division operations and reducing computational complexity to O(1).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple frequencies are used to extend unambiguous range, then measurement precision is improved, but device complexity increases due to complex calculations and significant IC silicon area requirements
Solution Approach 1:
The patent replaces complex division operations with bit-shift operations in the distance de-aliasing calculation. Instead of using traditional dividers that require significant IC silicon area and processing time, the invention uses bitwise right shift operations (>>) to achieve the same mathematical function with much lower computational complexity, reducing both hardware area and processing time while maintaining measurement precision
Solution Approach 2:
The patent changes the computational approach from O(n) time complexity or O(n) silicon area to O(1) time complexity by using bit-shift operations. The invention transforms the mathematical operation from division (which requires complex circuits) to bitwise operations (which use simple logic gates), fundamentally changing the parameter of computational complexity from linear to constant
2Measurement precision
If search algorithms are used to find best match between frequencies, then measurement precision is improved, but loss of time increases due to O(n) time complexity on serial processors
Solution Approach 1:
The patent substitutes iterative search algorithms with direct bit-shift based calculation. Instead of performing O(n) comparisons to find the best match between frequency measurements, the invention directly computes the de-aliased distance using weighted phase difference and bit-shift operations, reducing processing time from linear complexity to constant time complexity
3Productivity
If dividers are used to compute distance, then productivity is improved with O(1) time complexity, but device complexity increases due to expensive IC silicon area requirements
Solution Approach 1:
The patent replaces division operations with bit-shift operations. The bitwise right shift operator (>>) provides the same computational function as division by powers of two, eliminating the need for complex divider circuits while maintaining O(1) time complexity. This substitution dramatically reduces IC silicon area requirements while preserving computation speed
Data Source
AI summary
A system and method for determining a distance to a surface of interest, such as in a Time of Flight (ToF) system, includes projecting modulated electromagnetic radiation of at least two frequencies to a point on the surface of interest, receiving the electromagnetic radiation reflected from the point on the surface of interest and demodulating the received electromagnetic radiation. Whereupon, a weighted phase difference between the frequencies may be calculated, in accordance with the present systems and methods, and one bin for each of the reflected frequencies for an actual distance to the point on the surface of interest is calculated using the weighted phase difference. A final phase of the bin for the actual distance is calculated as a weighted average of the phases of the bins based on the reflected signal strengths, and the actual distance to the point on the surface of interest is then output.