FMCW Radar Interference Mitigation based on the Fractional Fourier Transform
Pith reviewed 2026-05-22 20:50 UTC · model grok-4.3
The pith
The discrete fractional Fourier transform compresses FMCW radar interference chirps into isolated peaks that can be zeroed out.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Interference chirps in FMCW radar are detected and mitigated by compression and zeroing in the fractional domain using the discrete fractional Fourier transform; an efficient multi-interferer implementation follows from generalizing the multi-angle centered discrete fractional Fourier transform and applying consecutive transforms via the angle-additivity property.
What carries the argument
The discrete fractional Fourier transform (DFrFT) with its angle-additivity property, which rotates signals so that linear chirps concentrate into removable peaks while the target signal stays distributed.
If this is right
- Hardware implementation becomes feasible because the algorithm relies on simple consecutive transforms and peak zeroing.
- Multiple simultaneous interferers can be suppressed by applying a sequence of DFrFTs whose angles are chosen to compress each chirp in turn.
- Performance gains appear in mean squared error, signal-to-interference-plus-noise ratio, error vector magnitude, true positive rate, false alarm rate and F1-score on synthetic I/Q data.
- The target echo remains usable after mitigation because only the compressed interference peaks are zeroed.
Where Pith is reading between the lines
- If rotation angles can be estimated directly from received data, the same compression step could support adaptive, real-time interference removal without prior knowledge of interferer parameters.
- The chirp-compression idea might transfer to other systems that transmit linear frequency sweeps, such as certain sonar or automotive sensing setups.
- Validation on recorded rather than purely synthetic waveforms would test whether the assumed peak compactness survives realistic propagation effects and receiver noise.
Load-bearing premise
Interference appears as distinct linear chirps that become compact peaks after a suitable fractional Fourier transform rotation, allowing clean separation from the desired signal by simple zeroing without distorting the target echo.
What would settle it
A measurement or simulation in which the interference does not form isolated compact peaks after the chosen DFrFT rotation or in which zeroing those peaks removes substantial energy from the target echo.
Figures
read the original abstract
In this paper, we propose a novel method for frequency modulated continuous wave (FMCW) radar mutual interference mitigation (IM) based on the discrete fractional Fourier transform (DFrFT). Interference chirps are detected and mitigated by compression and zeroing in the fractional domain. We provide an efficient implementation that can deal with multiple interferers, where we perform consecutive DFrFTs utilizing its angle-additivity property. For that purpose, we generalize and reduce the computational complexity of the multi-angle centered discrete fractional Fourier transform [1]. Our algorithm is designed to be simple and fast such that it can be implemented in hardware. We evaluate our algorithm on a synthetic I/Q-modulated dataset and outperform reference methods in terms of the mean squared error, signal-to-interference-plus-noise ratio, error vector magnitude, true positive rate, false alarm rate and F1-score.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes a method for FMCW radar mutual interference mitigation using the discrete fractional Fourier transform (DFrFT). Interference chirps are detected and mitigated via compression and zeroing in the fractional domain. An efficient implementation for multiple interferers is given by generalizing the multi-angle centered DFrFT and exploiting angle-additivity. The algorithm is evaluated on a synthetic I/Q-modulated dataset and reported to outperform reference methods on MSE, SINR, EVM, TPR, FAR, and F1-score.
Significance. If the separability assumption and generalization hold beyond the evaluated cases, the approach could yield a simple, low-complexity, hardware-suitable mitigation technique for radar systems. Credit is due for the explicit use of angle-additivity to handle multiple interferers and the claimed complexity reduction in the multi-angle DFrFT implementation. The exclusive reliance on synthetic data without parameter-selection details or hardware validation limits the assessed significance.
major comments (3)
- [§ on detection and mitigation by compression and zeroing] § on detection and mitigation by compression and zeroing: the central premise that interference chirps become compact, isolated peaks after DFrFT rotation (allowing clean zeroing without target distortion) is invoked without an analytic bound on required angle separation or ablation on chirp-rate mismatch; this assumption is load-bearing for the claimed mitigation performance.
- [§5 (Evaluation)] §5 (Evaluation): all reported gains in MSE, SINR, EVM, TPR, FAR, and F1-score are obtained exclusively on synthetic I/Q data; no description is given of how the fractional angle α is selected, nor any analysis of robustness to real-world noise, hardware impairments, or angle estimation errors.
- [§ on efficient implementation] § on efficient implementation: while angle-additivity is used for consecutive DFrFTs on multiple interferers, the manuscript provides no quantitative verification that the generalized multi-angle centered DFrFT preserves the claimed complexity reduction when the optimal angles differ substantially.
minor comments (2)
- Clarify in the text how the fractional order is discretized and whether the same α is used for detection versus mitigation.
- [References] Add a reference or brief derivation for the claimed complexity reduction of the generalized multi-angle DFrFT relative to [1].
Simulated Author's Rebuttal
We thank the referee for the thorough and constructive review of our manuscript. We address each major comment point by point below, with clear indications of planned revisions to the manuscript.
read point-by-point responses
-
Referee: [§ on detection and mitigation by compression and zeroing] the central premise that interference chirps become compact, isolated peaks after DFrFT rotation (allowing clean zeroing without target distortion) is invoked without an analytic bound on required angle separation or ablation on chirp-rate mismatch; this assumption is load-bearing for the claimed mitigation performance.
Authors: We acknowledge that the separability assumption in the fractional domain is central to the method and would benefit from additional theoretical support. In the revised manuscript, we will add a derivation of an analytic bound on the minimum angle separation required for reliable isolation of interference peaks from target signals, drawing on the known concentration properties of linear chirps under DFrFT rotation. We will also include an ablation study that systematically varies chirp-rate mismatch between interferers and targets to quantify any resulting degradation in mitigation performance. revision: yes
-
Referee: [§5 (Evaluation)] all reported gains in MSE, SINR, EVM, TPR, FAR, and F1-score are obtained exclusively on synthetic I/Q data; no description is given of how the fractional angle α is selected, nor any analysis of robustness to real-world noise, hardware impairments, or angle estimation errors.
Authors: The current evaluation is performed exclusively on the synthetic dataset described in Section 5. In the revision, we will expand Section 5 to provide an explicit description of the α-selection procedure, which relies on a coarse estimate of the dominant interference chirp rate followed by a fine search around the estimated angle. We will further add Monte-Carlo simulations that inject additive white Gaussian noise at varying SNR levels and quantify performance sensitivity to errors in the estimated fractional angle. Hardware impairments and real-world validation lie outside the present scope and would require new experimental campaigns. revision: partial
-
Referee: [§ on efficient implementation] while angle-additivity is used for consecutive DFrFTs on multiple interferers, the manuscript provides no quantitative verification that the generalized multi-angle centered DFrFT preserves the claimed complexity reduction when the optimal angles differ substantially.
Authors: We will strengthen the complexity claims by adding both asymptotic analysis and empirical timing results for the generalized multi-angle centered DFrFT. These results will cover cases in which the optimal fractional angles for different interferers differ by up to 0.5 radians, demonstrating that the computational savings from angle-additivity remain intact and that the overhead of angle reordering is negligible. revision: yes
- Hardware validation and experimental results on physical FMCW radar systems subject to real hardware impairments.
Circularity Check
No significant circularity; method uses standard FrFT properties
full rationale
The paper proposes an FMCW radar interference mitigation algorithm that applies the discrete fractional Fourier transform (DFrFT) to compress interference chirps for detection and zeroing, then uses angle-additivity for multiple interferers. This relies on well-known mathematical properties of the FrFT rather than any derivation that reduces to its own inputs. The generalization of the multi-angle centered DFrFT is referenced to [1] as an implementation step but is not load-bearing for the core claims, which are supported by direct empirical evaluation (MSE, SINR, EVM, TPR, FAR, F1) on a synthetic I/Q dataset against reference methods. No equations define a quantity in terms of itself, no fitted parameters are relabeled as predictions, and no uniqueness theorem or ansatz is smuggled via self-citation. The approach is self-contained and externally falsifiable via the reported metrics.
Axiom & Free-Parameter Ledger
free parameters (1)
- fractional angle alpha
axioms (1)
- standard math The discrete fractional Fourier transform satisfies angle-additivity, allowing consecutive transforms to handle multiple distinct angles without recomputing the full operator each time.
Lean theorems connected to this paper
-
IndisputableMonolith/Foundation/AbsoluteFloorClosure.leanreality_from_one_distinction unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
Interference chirps are detected and mitigated by compression and zeroing in the fractional domain... utilizing its angle-additivity property.
-
IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We generalize and reduce the computational complexity of the multi-angle centered discrete fractional Fourier transform
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
On the multiangle centered discrete fractional Fourier transform,
J. G. Vargas-Rubio and B. Santhanam, “On the multiangle centered discrete fractional Fourier transform,” IEEE Signal Processing Letters , vol. 12, no. 4, pp. 273–276, 2005
work page 2005
-
[2]
Bats-inspired frequency hopping for mitigation of interference between automotive radars,
J. Bechter, C. Sippel, and C. Waldschmidt, “Bats-inspired frequency hopping for mitigation of interference between automotive radars,” in 2016 IEEE MTT-S International Conference on Microwaves for Intelligent Mobility (ICMIM) . IEEE, 2016, pp. 1–4
work page 2016
-
[3]
Fischer, Untersuchungen zum interferenzverhalten automobiler radarsensorik
C. Fischer, Untersuchungen zum interferenzverhalten automobiler radarsensorik. Cuvillier Verlag, 2016
work page 2016
-
[4]
Variational signal separation for automotive radar interference mitigation,
M. Toth, E. Leitinger, and K. Witrisal, “Variational signal separation for automotive radar interference mitigation,” IEEE Transactions on Radar Systems, vol. 2, pp. 1007–1026, 2024
work page 2024
-
[5]
Threshold-free interference cancellation method for automotive FMCW radar systems,
M. Wagner, F. Sulejmani, A. Melzer, P. Meissner, and M. Huemer, “Threshold-free interference cancellation method for automotive FMCW radar systems,” in 2018 IEEE International Symposium on Circuits and Systems (ISCAS). IEEE, 2018, pp. 1–4. 10 10 4 10 2 100 102 104 106 108 x (a) 0.0 0.2 0.4 0.6 0.8 1.0(MSE < x) 10 20 30 40 50 x (b) 0.0 0.2 0.4 0.6 0.8 1.0(...
work page 2018
-
[6]
Automotive radar interference mitigation using adaptive noise canceller,
F. Jin and S. Cao, “Automotive radar interference mitigation using adaptive noise canceller,” IEEE Transactions on Vehicular Technology , vol. 68, no. 4, pp. 3747–3754, 2019
work page 2019
-
[7]
Resource- efficient deep neural networks for automotive radar interference mitiga- tion,
J. Rock, W. Roth, M. Toth, P. Meissner, and F. Pernkopf, “Resource- efficient deep neural networks for automotive radar interference mitiga- tion,” IEEE Journal of Selected Topics in Signal Processing , vol. 15, no. 4, pp. 927–940, 2021
work page 2021
-
[8]
A. Fuchs, J. Rock, M. Toth, P. Meissner, and F. Pernkopf, “Complex- valued convolutional neural networks for enhanced radar signal de- noising and interference mitigation,” in 2021 IEEE Radar Conference 11 (RadarConf21). IEEE, 2021, pp. 1–6
work page 2021
-
[9]
——, “Multiantenna radar signal interference mitigation using complex- valued convolutional neural networks,” IEEE Transactions on Systems, Man, and Cybernetics: Systems , 2024
work page 2024
-
[10]
Angle-equivariant convolutional neural networks for interference mitigation in automotive radar,
C. Oswald, M. Toth, P. Meissner, and F. Pernkopf, “Angle-equivariant convolutional neural networks for interference mitigation in automotive radar,” in 2023 20th European Radar Conference (EuRAD) . EuMA, 2023
work page 2023
-
[11]
End-to-end training of neural networks for automotive radar interference mitigation,
——, “End-to-end training of neural networks for automotive radar interference mitigation,” in 2023 IEEE International Radar Conference (RADAR). IEEE, 2023, pp. 1–6
work page 2023
-
[12]
A novel GNSS anti-interference method using fractional Fourier transform and notch filtering,
K. Sun, B. Yu, L. Xu, M. Elhajj, and W. Y . Ochieng, “A novel GNSS anti-interference method using fractional Fourier transform and notch filtering,” IEEE Transactions on Instrumentation and Measurement , 2024
work page 2024
-
[13]
A. R. Nafchi, M. Esmaeili, A. Ghasempour, E. Hamke, B. Santhanam, and R. Jordan, “Mitigating the time-varying doppler shift in high- mobility wireless communications using multi-angle centered discrete fractional Fourier transform,” in 2021 IEEE 12th Annual Ubiquitous Computing, Electronics & Mobile Communication Conference (UEM- CON). IEEE, 2021, pp. 0607–0612
work page 2021
-
[14]
Q. Wang, Z. Chen, Q. Zhou, and X. Wu, “Mitigation of radio frequency interference in HFSWR using fractional fourier transform based filtering algorithms,” IEEE Geoscience and Remote Sensing Letters , vol. 18, no. 2, pp. 261–265, 2020
work page 2020
-
[15]
Q. Zhou, H. Zheng, X. Wu, X. Yue, Z. Chen, and Q. Wang, “Fractional Fourier transform-based radio frequency interference suppression for high-frequency surface wave radar,” Remote sensing , vol. 12, no. 1, p. 75, 2019
work page 2019
-
[16]
Y . Cui and J. Wang, “Wideband LFM interference suppression based on fractional Fourier transform and projection techniques,” Circuits, Systems, and Signal Processing , vol. 33, pp. 613–627, 2014
work page 2014
-
[17]
Sparse reconstruction of chirplets for automotive FMCW radar interference mitigation,
A. Correas-Serrano and M. A. Gonzalez-Huici, “Sparse reconstruction of chirplets for automotive FMCW radar interference mitigation,” in 2019 IEEE MTT-S International Conference on Microwaves for Intelligent Mobility (ICMIM). IEEE, 2019, pp. 1–4
work page 2019
-
[18]
FMCW interference suppression technique in OFDM automotive radar using grid dechirp- ing,
A. Maeda-Magalhaes, D. Delbecq, and G. Ferre, “FMCW interference suppression technique in OFDM automotive radar using grid dechirp- ing,” in 2023 IEEE International Radar Conference (RADAR) . IEEE, 2023, pp. 1–6
work page 2023
-
[19]
Interference compression and mitigation for automotive FMCW radar systems,
M. Rameez, M. I. Pettersson, and M. Dahl, “Interference compression and mitigation for automotive FMCW radar systems,” IEEE Sensors Journal, vol. 22, no. 20, pp. 19 739–19 749, 2022
work page 2022
-
[20]
Deep interference mitigation and denoising of real-world FMCW radar signals,
J. Rock, M. Toth, P. Meissner, and F. Pernkopf, “Deep interference mitigation and denoising of real-world FMCW radar signals,” in 2020 IEEE International Radar Conference (RADAR). IEEE, 2020, pp. 624– 629
work page 2020
-
[21]
A. G. Stove, “Linear FMCW radar techniques,” in IEE Proceedings F (Radar and Signal Processing), vol. 139, no. 5. IET, 1992, pp. 343–350
work page 1992
-
[22]
Analytical investiga- tion of non-coherent mutual FMCW radar interference,
M. Toth, P. Meissner, A. Melzer, and K. Witrisal, “Analytical investiga- tion of non-coherent mutual FMCW radar interference,” in 2018 15th European Radar Conference (EuRAD) . IEEE, 2018, pp. 71–74
work page 2018
-
[23]
Boashash, Time-frequency signal analysis and processing: a compre- hensive reference
B. Boashash, Time-frequency signal analysis and processing: a compre- hensive reference. Academic press, 2015
work page 2015
-
[24]
O. Aldimashki and A. Serbes, “Performance of chirp parameter estima- tion in the fractional Fourier domains and an algorithm for fast chirp-rate estimation,” IEEE Transactions on Aerospace and Electronic Systems , vol. 56, no. 5, pp. 3685–3700, 2020
work page 2020
-
[25]
Digital computation of the fractional Fourier transform,
H. M. Ozaktas, O. Arikan, M. A. Kutay, and G. Bozdagt, “Digital computation of the fractional Fourier transform,” IEEE Transactions on signal processing, vol. 44, no. 9, pp. 2141–2150, 1996
work page 1996
-
[26]
Closed-form discrete fractional and affine Fourier transforms,
S.-C. Pei and J.-J. Ding, “Closed-form discrete fractional and affine Fourier transforms,” IEEE transactions on signal processing , vol. 48, no. 5, pp. 1338–1353, 2000
work page 2000
-
[27]
The discrete fractional Fourier transform,
C. Candan, M. A. Kutay, and H. M. Ozaktas, “The discrete fractional Fourier transform,” IEEE Transactions on signal processing , vol. 48, no. 5, pp. 1329–1337, 2000
work page 2000
-
[28]
Discrete fractional Fourier transform based on orthogonal projections,
S.-C. Pei, M.-H. Yeh, and C.-C. Tseng, “Discrete fractional Fourier transform based on orthogonal projections,” IEEE Transactions on Signal Processing, vol. 47, no. 5, pp. 1335–1348, 1999
work page 1999
-
[29]
The discrete fractional Fourier transform based on the DFT matrix,
A. Serbes and L. Durak-Ata, “The discrete fractional Fourier transform based on the DFT matrix,” Signal Processing, vol. 91, no. 3, pp. 571– 581, 2011
work page 2011
-
[30]
J. R. de Oliveira Neto and J. B. Lima, “Discrete fractional Fourier trans- forms based on closed-form Hermite–Gaussian-like dft eigenvectors,” IEEE Transactions on Signal Processing , vol. 65, no. 23, pp. 6171– 6184, 2017
work page 2017
-
[31]
Analysis and comparison of discrete fractional Fourier transforms,
X. Su, R. Tao, and X. Kang, “Analysis and comparison of discrete fractional Fourier transforms,” Signal Processing , vol. 160, pp. 284– 298, 2019
work page 2019
-
[32]
The fractional Fourier transform as a biomedical signal and image processing tool: A review,
A. G ´omez-Echavarr´ıa, J. P. Ugarte, and C. Tob ´on, “The fractional Fourier transform as a biomedical signal and image processing tool: A review,” Biocybernetics and Biomedical Engineering , vol. 40, no. 3, pp. 1081–1093, 2020
work page 2020
-
[33]
Comparison of centered discrete frac- tional Fourier transforms for chirp parameter estimation,
D. J. Peacock and B. Santhanam, “Comparison of centered discrete frac- tional Fourier transforms for chirp parameter estimation,” in 2013 IEEE Digital Signal Processing and Signal Processing Education Meeting (DSP/SPE). IEEE, 2013, pp. 65–68
work page 2013
-
[34]
Evaluation of probability of interference-related ghost targets in automotive radars,
K. Hahmann, S. Schneider, and T. Zwick, “Evaluation of probability of interference-related ghost targets in automotive radars,” in 2018 IEEE MTT-S International Conference on Microwaves for Intelligent Mobility (ICMIM). IEEE, 2018, pp. 1–4
work page 2018
-
[35]
T. Shimura, M. Umehira, Y . Watanabe, X. Wang, and S. Takeda, “An advanced wideband interference suppression technique using envelope detection and sorting for automotive FMCW radar,” in2022 IEEE Radar Conference (RadarConf22). IEEE, 2022, pp. 1–6
work page 2022
-
[36]
M. A. Richards et al. , Fundamentals of radar signal processing . Mcgraw-hill New York, 2005, vol. 1
work page 2005
-
[37]
A. V . Oppenheim, Discrete-time signal processing. Pearson Education India, 1999
work page 1999
-
[38]
J. R. de Oliveira Neto, J. B. Lima, G. J. da Silva Jr, and R. M. C. de Souza, “Computation of an eigendecomposition-based discrete frac- tional Fourier transform with reduced arithmetic complexity,” Signal Processing, vol. 165, pp. 72–82, 2019
work page 2019
-
[39]
A low-complexity approach to computation of the discrete fractional Fourier transform,
D. Majorkowska-Mech and A. Cariow, “A low-complexity approach to computation of the discrete fractional Fourier transform,” Circuits, Systems, and Signal Processing , vol. 36, pp. 4118–4144, 2017
work page 2017
-
[40]
B. C. Bispo, J. R. de Oliveira Neto, and J. B. Lima, “Hardware architectures for computing eigendecomposition-based discrete frac- tional Fourier transforms with reduced arithmetic complexity,” Circuits, Systems, and Signal Processing , vol. 43, no. 1, pp. 593–614, 2024
work page 2024
-
[41]
Efficient DFT architectures based upon symmetries,
T. Erseghe and G. Cariolaro, “Efficient DFT architectures based upon symmetries,” IEEE transactions on signal processing , vol. 54, no. 10, pp. 3829–3838, 2006
work page 2006
-
[42]
Real-time discrete fractional Fourier transform using metamaterial coupled lines network,
R. Keshavarz, N. Shariati, and M.-A. Miri, “Real-time discrete fractional Fourier transform using metamaterial coupled lines network,” IEEE Transactions on Microwave Theory and Techniques , vol. 71, no. 8, pp. 3414–3423, 2023
work page 2023
-
[43]
On discrete Gauss–Hermite functions and eigenvectors of the discrete Fourier transform,
B. Santhanam and T. S. Santhanam, “On discrete Gauss–Hermite functions and eigenvectors of the discrete Fourier transform,” Signal Processing, vol. 88, no. 11, pp. 2738–2746, 2008
work page 2008
-
[44]
Shifted Fourier matrices and their tridiag- onal commutors,
S. Clary and D. H. Mugler, “Shifted Fourier matrices and their tridiag- onal commutors,” SIAM Journal on Matrix Analysis and Applications , vol. 24, no. 3, pp. 809–821, 2003. Christian Oswald received his MSc (Dipl. Ing.) degree in Information and Computer Engineering at Graz University of Technology, Austria, in 2022. He is currently pursuing his PhD as ...
work page 2003
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.