FPGA DDS Phase Generation for Precise Distance Measurement
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Solution Overview
Problem
Existing distance measurement technologies, such as rangefinders, face challenges in achieving precise time-of-flight measurements due to the high cost and inflexibility of hard-wired ASICs and expensive digital components like DDS, which are not cost-effective for precise phase shift generation.
Innovation Solution
A device and method utilizing a programmable logic device for direct digital synthesis, where the phase precision is encoded in amplitude information, using a binarizer to convert signals into square waves, and a multiplexer to increase sampling rates, allowing for cost-effective and accurate phase shift generation without the need for separate expensive DDS components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a hard-wired ASIC is used for delay generation, then measurement precision is improved, but device cost and development complexity increase
Solution Approach 1:
The patent uses a Field-Programmable Gate Array (FPGA) to create a reconfigurable copy of the delay generation functionality that would otherwise require a custom ASIC. The FPGA allows the delay logic to be programmed and adjusted without requiring new hardware fabrication, thus achieving precise delay control while avoiding ASIC development complexity and cost.
Solution Approach 2:
The patent implements dynamically adjustable delay elements within the FPGA that can be reconfigured through programming. This allows the delay time to be changed flexibly by modifying the logic configuration rather than requiring physical hardware changes, enabling precise delay control while maintaining adaptability and reducing development complexity.
2Measurement precision
If a separate DDS component is used for phase generation, then signal precision is improved, but device cost increases
Solution Approach 1:
The patent merges the direct digital synthesis (DDS) functionality directly into the FPGA logic circuitry, eliminating the need for a separate DDS component. The phase-shifted clock signals are generated using the FPGA's internal logic resources, including phase shifters and frequency synthesizers, thereby reducing component count, cost, and overall system complexity while maintaining precise phase control.
Solution Approach 2:
The FPGA serves multiple functions simultaneously: it acts as the delay generator, phase shifter, frequency synthesizer, and logic controller all in one device. This multi-functional approach replaces what would traditionally require multiple separate components (DDS chip, delay lines, logic gates), reducing both cost and complexity while achieving the required precision.
3Adaptability or versatility
If programmable logic is used for signal generation, then adaptability is improved, but time resolution deteriorates
Solution Approach 1:
The patent segments the time delay into multiple fine-grained stages within the FPGA, using cascaded delay elements and phase-shifted clock signals. By dividing the total delay into many small, programmable steps, the system achieves both high adaptability (through programming) and fine time resolution (through the segmented structure), overcoming the limitation of coarse timing in traditional programmable logic.
Data Source
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AI summary
The device has a direct-digital-synthesis-device (2) with a memory (3) having truth table values for a periodic signal (8), and digitally outputting the signal with a sampling rate. The table values are selected, so that phase difference of the signal is smaller than integer and/or non-integer multiple of smallest time unit to provide the difference by the selection of appropriate table value independent of the rate and to enclose components in a programmable component (1) e.g. programmable logic device, except passive components of a digital-to-analog-converter (6) and filter (7). Independent claims are also included for the following: (1) a method for generating a periodic electrical signal (2) a method for determining distance of a reflected object.