FMCW Radar Chirp Offsets for Higher Range Accuracy
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Solution Overview
Problem
The range resolution and accuracy in Frequency-Modulated Continuous-Wave (FMCW) radar systems are limited by the radar bandwidth, making it difficult to distinguish between targets at different ranges, especially when using conventional frequency modulation techniques.
Innovation Solution
The method involves transmitting a series of radar chirps with incremental frequency offsets, receiving return signals, constructing frequency transforms, and combining these transforms to detect a frequency peak in a composite transform, thereby improving range resolution and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional frequency modulation techniques are used in FMCW radar, then the system structure remains simple, but the range resolution and accuracy are limited by radar bandwidth
Solution Approach 1:
The patent applies parameter changes by modifying the frequency modulation parameters of the radar chirps. Specifically, it uses Frequency Shift Keying (FSK) to add frequency offsets to successive chirps, where the offset is a fraction of a range frequency bin. This changes the frequency domain characteristics of the transmitted signal, allowing the composite frequency transform to achieve finer range resolution without requiring increased bandwidth or complex hardware modifications.
2Measurement precision
If radar bandwidth is increased to improve range resolution, then range accuracy improves, but the system complexity and cost increase
Solution Approach 1:
The patent applies segmentation by dividing the frequency offset into fractional parts of a range frequency bin across multiple successive chirps. Instead of requiring a single large bandwidth, the system segments the range measurement process into multiple chirps with incremental frequency offsets (e.g., 0.1, 0.2, 0.3 of a frequency bin). The composite frequency transform combines these segmented measurements to achieve high range accuracy equivalent to much larger bandwidth systems.
3Measurement precision
If conventional FMCW processing is used, then the processing algorithm remains simple, but range-gate straddling loss occurs reducing measurement precision
Solution Approach 1:
The patent applies feedback by using the frequency offset information from successive chirps to correct for range-gate straddling effects. The FSK-modulated frequency offsets create a known pattern in the frequency domain that allows the processing algorithm to identify and compensate for targets that fall between range gates. This feedback mechanism improves range measurement precision by eliminating the straddling loss that occurs in conventional FMCW processing.
Data Source
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AI summary
A method for determining the range of an object includes transmitting successive radar chirps, adding a frequency offset to the successive radar chirps, the frequency offset being a fraction of a range frequency bin, receiving return signals, constructing frequency transforms from each of the return signals, adding each of the frequency transforms together to create a composite frequency transform, and interpolating the range of the object from a frequency peak detected in the composite frequency transform.