FIGURE 5 - uploaded by Zhen Liu
Content may be subject to copyright.
Source publication
Localization of linear frequency modulation (LFM) source based on combination of time_ frequency analysis and spatial spectrum estimation technique has received extensive research. However, this scheme is always confined to far-field sources and suffers from high computational cost. In this letter, by performing the fractional Fourier transform (FR...
Context in source publication
Context 1
... and comparing the estimation mean with the upper bound of near-field source' range, our proposed algorithm could largely discern mixed sources and well achieve sources' localization. Further, under the same experimental parameters, we employ RMSE versus source's range to study the threshold of accurate range estimation. It can be seen from the Fig. 5 that the RMSE of estimation accelerates when the source's range is larger than the upper threshold of near-field source's range and the RMSE is too much to retain effectiveness of range estimation. ...
Similar publications
Acoustic emission (AE) is one of the most promising methods for structural health monitoring (SHM) of materials and structures. Because of its passive and non-invasive nature, it can be used during the operation of a structure and supply information that cannot be collected in real time through other techniques. It is based on the recording and stu...
Citations
... However, the ULA can only provide 1-D DOA and range parameter for nearfield signals, which is invalid for three-dimensional (3-D) parameter estimation of the near-field signals [29]. In contrast, the UCA can be utilized to estimate the 2-D DOA and range parameter for near-field signals [30]. ...
In this paper, we propose a beam space coversion (BSC)-based approach to achieve a single near-field signal localization under uniform circular array (UCA). By employing the centro-symmetric geometry of UCA, we apply BSC to extract the two-dimensional (2-D) angles of near-field signal in the Vandermonde form, which allows for azimuth and elevation angle estimation by utilizing the improved estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm. By substituting the calculated 2-D angles into the direction vector of near-field signal, the range parameter can be conse-quently obtained by the 1-D multiple signal classification (MUSIC) method. Simulations demonstrate that the proposed algorithm can achieve a single near-field signal localization, which can provide satisfactory performance and reduce computational complexity.
... In addition to the aforementioned methods, there are many other new localization approaches, such as time-frequency based method [26], learning based method [27,28], etc. ...
High-precision source localization depends on many factors, including a suitable location method. Beamforming-based methods, such as the steered response power (SRP), are a common type of acoustic localization methods. However, these methods have low spatial resolution. The SRP method with phase transform (SRP-PHAT) improves the spatial resolution of SRP and is one of the most effective and robust methods for source localization. However, the introduction of a phase transform to SRP might amplify the power of the noise and result in many local extrema in the SRP space, which has a negative impact on source localization. In this paper, a steered sample algorithm (SSA) based on the reciprocity of wave propagation for acoustic source localization is proposed. The SSA localization process is similar to the hyperbolic Radon transform, which is theoretically analyzed and is the most essential difference form the SRP/SRP-PHAT. Compared with the SRP-PHAT, the experimental results demonstrate that the SSA perform better when it comes to array signal positioning with limited array elements and narrow azimuth signal, where SSA can achieve high precision positioning with lower SNR.
... Uniform circular arrays (UCAs) which have been researched increasingly in recent years have the advantages over the other array geometries for providing 360° azimuth coverage, additional elevation angle information, and almost identical beamwidth [12,13]. Currently, by combining the geometry advantages of UCAs and the fast phase-based schemes introduced in [12,14,15], we have proposed an effective localisation algorithm for near-field LFM sources based on the fractional Fourier transform (FRFT) [16]. As both the divisions of frequency band and the signal subspace methods are not required, the computational complexity has been reduced, but the half-wavelength aperture restriction [17,18] is still existent. ...
... By referring to the previous literature [16], the unambiguous phase angle u m ′ can be reformulated as the formation of matrix multiplication, and the LS method is then employed to obtain the source's 3D parameter estimation. ...
Traditional localisation technologies for wideband linear frequency modulation (LFM) source are always confined to the far‐field situation and suffer from high computational cost for dealing with multiple sub‐narrowband components. In this study, by performing temporal delay‐and‐correlation to wideband LFM signals, a fast and closed‐form algorithm based on phase differences is proposed for three‐dimensional (3D) source localisation (azimuth angle, elevation angle, and range) under a uniform circular array. First, the cross‐correlation of the array outputs with their temporally delayed version is calculated to develop a new single‐frequency signal model. Then, the phase differences of adjacent sensors’ transformed outputs are exploited to construct indefinite equations. After that, the least‐square method is employed to estimate the source's 3D parameters simultaneously. Moreover, theoretical analysis and numerical examples show the aperture restriction in avoiding ambiguity can be relaxed under the new signal model. Finally, simulations demonstrate the effectiveness and advantages of the proposed algorithm.
... For the signal model of the LFM system which is commonly used in many fields [19][20][21], the radar transmitted signal is ...
Radar plays an increasingly important role in target detection because of its all-weather detection capability. Furthermore, to detect weak and flexible target, effectively coherent integration method is required in radar signal processing to enhance the target signal intensity. Based on the Radon-Fourier transform (RFT) algorithm, which is widely used to solve the problem of weak target detection, range migration and Doppler ambiguity in low signal-to-noise ratio (SNR) environment, an improved multiple pulse repetition intervals (PRIs) RFT (MRFT) coherent integration method is presented in this paper. The method adopts the Linear frequency modulated (LFM) signal with three different PRIs as the transmitted signal, then combines with the RFT outputs of three RPIs to enhance the target energy and suppress the blind speed side lobe (BSSL) caused by RFT. Meanwhile, the design rules and constraints of this method are also discussed in detail. The experiments with simulation data and real measured data are provided to demonstrate that the designed method can get better BSSL suppression capability and higher detection rate than conventional methods.
... The digital computation of the FRFT was published by Ozaktas et al. [15]. The FRFT was a widely used tool in radar [16]- [20], image processing [21], [22], communications [23], [24], in which the signal is formed with linear frequency modulation (LFM), and it is still currently a powerful tool for different applications [25]- [28]. ...
... Equations (23), (24), (25), and (30) can be used to construct an accurate estimator of the Doppler rate. Again, proposed κ µ 2 Cα obtained from (30), which can almost match with the original expression as given in the left side of (29), (31), or (32), will make a significant difference for the subsequent Doppler rate estimator under high dynamics. ...
When the fractional Fourier transform (FRFT) is introduced into the weak and high-dynamic global navigation satellite system (GNSS) signal acquisition, the two-dimensional search cell will be transferred to a three-dimensional one with respect to the code chip, the Doppler shift, and the Doppler rate. The proper determinations of the code bin and Doppler shift bin in the acquisition process have already been covered in the previous researches. The aim of this work is to provide an exhaustive analysis of the approach to specify an optimal FRFT order bin, in terms of the Doppler shift rate. The lower and upper bound of FRFT order ranges are determined by the incoming signal dynamics. Then, we propose a precise model to yield an optimal FRFT order bin. Besides, a novel and fast Doppler estimator based on the non-linear least square (NLS) method is presented to improve the performance of the digital FRFT implementation. Finally, an alternate search procedure is proposed to reduce the singular estimations of the NLS method. Simulating examples demonstrate the performance of the proposed algorithms. It has been verified that the computation efficiency and the estimation accuracy have been significantly improved by proposed techniques.
Estimating the location parameters of moving target is an important part of intelligent surveillance for Internet of Vehicles (IoV). Satellite has the potential to play a key role in many applications of space-air-ground integrated networks (SAGIN). In this paper, a novel passive location parameter estimator using multiple satellites for moving aerial target is proposed. In this estimator, the direct wave signals in reference channels are first filtered by a band-pass filter, followed by a sequence cancellation algorithm to suppress the direct-path interference and multi-path interference. Then, the fourth-order cyclic cumulant cross ambiguity function (FOCCCAF) of the signals in the reference channels and the four-weighted fractional Fourier transform fourth-order cyclic cumulant cross-ambiguity function (FWFRFT-FOCCCAF) of signals in the surveillance channels are derived. Using them, the time difference of arrival (TDOA) and the frequency difference of arrival (FDOA) are estimated and the distance between the target and the receiver and the velocity of the moving aerial target are estimated by using multiple satellites. Finally, the Cramer-Rao Lower Bounds of the proposed location parameter estimators are derived to benchmark the estimator. Simulation results show that the proposed method can effectively and precisely estimate the location parameters of the moving aerial target.
In underwater applications, linear chirp signal with linearly instantaneous frequency over the signal bandwidth also known as a linear frequency modulated (LFM) signal is often used in active sonar to realize direction of arrival (DOA) estimation of targets. For this kind of wideband signal, traditional array signal processing method firstly transforms the time domain signal into frequency domain using fast Fourier transform (FFT) and then does beamforming for each sub-band. Different from FFT based signal processing method, this paper uses fractional Fourier transform (FRFT) for preprocessing of wideband LFM signals. By FRFT preprocessing, the wideband LFM signals are transformed into narrowband signals in the fractional Fourier domain, avoiding the influence of cross-interference terms. This paper compares the performance of FRFT based DOA estimation using conventional beamforming (CBF), minimum variance distortionless response (MVDR) and robust Capon beamforming (RCB) respectively. Then the revised RCB (RRCB) algorithm is proposed to solve the DOA estimation problem with a small number of snapshots. Simulations are carried out for single target and multi-targets DOA estimation using FFT based and FRFT based array signal processing method respectively. Simulation results show that FRFT based array signal processing method can achieve much narrower main lobe and higher main-to-side lobe ratio in low signal-to–noise ratio conditions. Besides, it can realize accurate DOA estimation of two adjacent targets while FFT based array signal processing method fails.
