Sub-Nyquist HFM Radar for Unambiguous Range-Doppler Estimation
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Solution Overview
Problem
Existing radar systems, particularly FMCW and LFM chirp radars, face challenges with range ambiguity, range-Doppler coupling, high sampling rate requirements, and high costs due to expensive ADCs, which affect accuracy and efficiency in target detection and localization.
Innovation Solution
Employing hyperbolic frequency-modulated (HFM) chirp pulses sampled below the Nyquist rate to exploit unique aliasing phenomena, allowing for accurate range and Doppler estimation without additional filtering or stretch processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional FMCW or LFM chirp radars are used, then target detection capability is achieved, but range ambiguity and range-Doppler coupling occur
Solution Approach 1:
The patent changes the frequency modulation law from linear (LFM) or piecewise linear (FMCW) to hyperbolic frequency modulation. This parameter change in the signal waveform fundamentally alters the aliasing characteristics, enabling unambiguous range and Doppler estimation even when sampled below the Nyquist rate, thereby resolving the range ambiguity and range-Doppler coupling problems.
2Measurement precision
If high sampling rate is used to avoid range ambiguity, then measurement accuracy is improved, but device cost and complexity increase due to expensive ADCs
Solution Approach 1:
The patent converts the harmful aliasing effect that occurs at low sampling rates into a beneficial phenomenon. By using HFM chirp pulses, the aliasing components fold in a predictable manner that preserves range and Doppler information, transforming what is typically a source of ambiguity into a useful characteristic that enables accurate measurement with low-cost, low-rate ADCs.
3Measurement precision
If Nyquist rate sampling is used, then signal accuracy is maintained, but sampling cost and processing complexity increase
Solution Approach 1:
The patent changes the sampling rate parameter from Nyquist rate to sub-Nyquist rate by exploiting the unique properties of HFM chirp pulses. The hyperbolic frequency modulation ensures that even at reduced sampling rates, the aliased signal components contain sufficient information for accurate range and Doppler estimation, thereby improving sampling efficiency without sacrificing signal accuracy.
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
Enables precise target detection and localization with reduced sampling rates, overcoming range ambiguity and cost constraints, while maintaining high resolution and accuracy in single and multiple target scenarios.
Implementation Method 1
receiving a second signal, the second signal being a signal resulting from reflection of the first signal by at least one target
Implementation Method 2
exploiting unique aliasing phenomenon incurred by HFM pulses
Data Source
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Figure 5~6b
AI summary
Some embodiments in the present disclosure relate to transmitting and/or receiving of sensing. A waveform of a hyperbolic frequency modulated, HFM, chirp pulse in a frequency range is obtained. A first signal including a plurality of HFM chirp pulses is transmitted. A second signal is received, wherein the second signal is a signal resulting from reflection of the first signal by at least one target. A subsampled first signal is obtained by sampling the first signal at a sampling frequency fs below a Nyquist rate fnyq. A subsampled second signal is obtained by sampling the second signal at the sampling frequency fs. A range and/or a Doppler frequency is determined by processing of the subsampled first signal and the subsampled second signal.