| 1. |
- Jia, Wenkai, et al.
(författare)
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Coherent FDA Receiver and Joint Range-Space-Time Processing
- 2024
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 72:1, s. 745-755
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Tidskriftsartikel (refereegranskat)abstract
- When a target is masked by mainlobe clutter with the same Doppler frequency, it is difficult for conventional airborne radars to determine whether a target is present in a given observation using regular space-time adaptive processing techniques. Different from phased-array and multiple-input multiple-output (MIMO) arrays, frequency diverse arrays (FDAs) employ frequency offsets across the array elements, delivering additional range-controllable degrees of freedom, potentially enabling suppression for this kind of clutter. However, the reception of coherent FDA systems employing small frequency offsets and achieving high transmit gain can be further improved. To this end, this work proposes an coherent airborne FDA radar receiver that explores the orthogonality of echo signals in the Doppler domain, allowing a joint space-time processing module to be deployed to separate the aliased returns. The resulting range-space-time adaptive processing allows for a preferable detection performance for coherent airborne FDA radars as compared to current alternative techniques.
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| 2. |
- Jia, Wenkai, et al.
(författare)
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Designing FDA Radars Robust to Contaminated Shared Spectra
- 2023
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Ingår i: IEEE Transactions on Aerospace and Electronic Systems. - 0018-9251. ; 59:3, s. 2861-2873
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers the problem of jointly designing the transmit waveforms and weights for a frequency diverse array (FDA) in a spectrally congested environment in which unintentional spectral interferences exist. Exploiting the properties of the interference signal induced by the processing of the multi-channel mixing and low-pass filtering FDA receiver, the interference covariance matrix structure is derived. With this, the receive weights are formed using the minimum variance distortionless response (MVDR) method for interference cancellation. Owing to the fact that the resulting output signal-to-interference-plus-noise ratio (SINR) is a function of the transmit waveforms and weights, as well as due to the ever-greater competition for the finite available spectrum, a joint design scheme for the FDA transmit weights and the spectrally compatible waveforms is proposed to efficiently use the available spectrum while maintaining a sufficient receive SINR. The performance of the proposed technique is verified using numerical simulations in terms of the achievable SINR, spectral compatibility, as well as several aspects of the synthesized waveforms.
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| 3. |
- Jia, Wenkai, et al.
(författare)
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FDA antenna selection for localizing targets
- 2024
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Ingår i: Signal Processing. - 0165-1684. ; 216
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a joint transmit and receive antenna selection scheme for frequency diverse array (FDA) radar that aims at finding an optimal selection of employed FDA antennas, formed by minimizing the Cramér–Rao lower bound (CRLB) of the target localization problem given the available a priori knowledge of potential target locations. The resulting problem is a non-convex Boolean problem in which the objective function is a quadratic objective function with respect to the optimization variables. To allow for an efficient solution, an iterative relaxed algorithm is proposed, substantially simplifying the resulting minimization. Numerical simulations are provided to demonstrate the effectiveness of the proposed approach.
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| 4. |
- Jia, Wenkai, et al.
(författare)
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Time-range FDA beampattern characteristics
- 2024
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Ingår i: Signal Processing. - 0165-1684. ; 218
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Tidskriftsartikel (refereegranskat)abstract
- Current literature show that frequency diverse arrays (FDAs) are able of producing range–angle-dependent and time-variant transmit beampatterns, but the resulting time and range dependencies and their characteristics are still not well understood. This paper examines the FDA transmission model with an emphasis on analyzing the beam auto-scanning characteristics and the equivalence with the MIMO beampatterns taking into account their time-range relationship. We present the FDA instantaneous transmit beampattern, describing the auto-scanning capability of the FDA transmit beams. The scan speed, scan volume, and initial mainlobe direction of the beams are also analyzed. In addition, the equivalent conditions for the FDA integral transmit beampattern and the multiple-input multiple-output (MIMO) beampattern are investigated. Various numerical simulations illustrate the auto-scanning property of the FDA beampattern and the proposed equivalent relationship with the MIMO beampattern, providing a foundation for a better understanding and application of the FDA transmit beam.
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| 5. |
- Jia, Wenkai, et al.
(författare)
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Waveform optimization with SINR criteria for FDA radar in the presence of signal-dependent mainlobe interference
- 2023
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Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684. ; 204
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we focus on the design of the transmit waveforms of a frequency diverse array (FDA) in order to improve the output signal-to-interference-plus-noise ratio (SINR) in the presence of signal-dependent mainlobe interference. Since the classical multi-carrier matched filtering-based FDA receiver cannot effectively utilize the waveform diversity of FDA, a novel FDA receiver framework based on multi-channel mixing and low pass filtering is developed to keep the separation of the transmit waveform at the receiver side, while preserving the FDA range-controllable degrees of freedom. Furthermore, a range-angle minimum variance distortionless response beamforming technique is introduced to synthesize receiver filter weights with the ability to suppress a possible signal-dependent mainlobe interference. The resulting FDA transmit waveform design problem is initially formulated as an optimization problem consisting of a non-convex objective function and multiple non-convex constraints. To efficiently solve this, we introduce two algorithms, one based on a signal relaxation technique, and the other based on the majorization minimization technique. The preferable performance of the proposed multi-channel low pass filtering receiver and the optimized transmit waveforms is illustrated using numerical simulations, indicating that the resulting FDA system is not only able to effectively suppress mainlobe interference, but also to yield estimates with a higher SINR than the FDA system without waveform optimization.
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