FMCW LiDAR Frequency-Domain AGC for Dynamic Range Control
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Solution Overview
Problem
FMCW LIDAR systems face challenges in dynamic range limitations, leading to signal distortion and noise interference, which are not effectively addressed by increasing the number of bits in ADCs and digital datapaths, as this increases power, area, and cost without necessarily expanding the dynamic range if optical or analog components are the limiting factors.
Innovation Solution
Implementing automatic gain control (AGC) across optical, analog, or digital paths, or a combination thereof, to adjust the dynamic range of FMCW LIDAR systems by applying variable gain to signals, thereby reducing distortion and noise interference while maintaining power, area, and cost efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of bits in ADCs and digital datapaths is increased, then the dynamic range is improved, but the power consumption increases
Solution Approach 1:
The patent applies preliminary action by performing automatic gain control (AGC) before the ADC conversion stage. The AGC circuit adjusts the signal amplitude to an optimal level prior to digitization, ensuring that the ADC operates within its optimal dynamic range without requiring an excessive number of bits. This preliminary signal conditioning resolves the contradiction by preparing the signal in advance, allowing the use of lower-bit ADCs while maintaining adequate dynamic range performance.
2Measurement precision
If the number of bits in ADCs and digital datapaths is increased, then the dynamic range is improved, but the area occupied by components increases
Solution Approach 1:
The AGC circuit performs preliminary signal amplitude adjustment before the signal enters the ADC and digital datapath. By controlling the signal amplitude at this early stage, the system achieves the required dynamic range with fewer bits, thereby reducing the area occupied by ADCs and digital processing components. The AGC circuit itself occupies less area than the alternative of using high-bit ADCs and wide datapaths throughout the system.
3Measurement precision
If the number of bits in ADCs and digital datapaths is increased, then the dynamic range is improved, but the system cost increases
Solution Approach 1:
The patent implements preliminary gain control through the AGC circuit, which adjusts signal amplitude before ADC conversion. This approach allows the system to achieve the required dynamic range performance without investing in expensive high-bit ADCs and wide datapath implementations. The AGC circuit provides a cost-effective solution by managing dynamic range requirements through analog signal conditioning rather than through expensive digital infrastructure.
4Device complexity
If optical or analog components are used, then the system structure is simpler, but the dynamic range is limited
Solution Approach 1:
The AGC circuit serves as an intermediary component between the optical/analog front end and the digital processing stages. It mediates the dynamic range limitation by actively adjusting signal amplitudes to match the optimal input range of subsequent components. This intermediary function allows the system to maintain simplicity in its optical and analog architecture while overcoming dynamic range limitations through the AGC's real-time gain adjustment capability.
Solution Approach 2:
The AGC circuit introduces dynamic adaptability to the system by continuously monitoring signal levels and adjusting gain accordingly. This dynamic control mechanism allows the system to optimize its performance for varying signal conditions without requiring complex optical or analog component designs. The dynamic gain adjustment effectively extends the usable dynamic range while keeping the overall system structure relatively simple.
Data Source
AI summary
A light detection and ranging (LIDAR) system includes an automatic gain control (AGC) unit to reduce the dynamic range, reducing processing power and saving circuit area and cost. The system detects a return beam of a light signal transmitted to a target, having a first dynamic range in a time domain. An analog to digital converter (ADC) generates a digital signal based on the return beam. A processor can perform time domain processing on the digital signal, convert the digital signal from the time domain to a frequency domain, and perform frequency domain processing on the digital signal in the frequency domain. The AGC unit can measure a power of the return beam, and apply variable gain in the frequency domain to reduce a dynamic range of the return beam to a second dynamic range lower than the first dynamic range.