When range of the target estimated from the transmitter with transmitting subarrays, it is equivalent to estimating the phase difference in the transmitting steering vector and angle of the p-th target estimated from receiving steering vector before. Simulation results show that the estimation accuracy and resolution ability of the proposed AP-MLE algorithm are significantly superior over the classic MUSIC and ESPRIT algorithms. pt = Peak transmit Power Lm=Medium losses The estimation angle and range are mapped to the wrong target, which leads to a large error, so that the different targets cannot be distinguished correctly. In order to prevent the algorithm from falling into the local optimal value, a good initialization parameter value is very important. A. Tropp, I. S. Dhillon, R. W. Heath, and T. Strohmer, “Designing structured tight frames via an alternating projection method,”, I. Bekkerman and J. Tabrikian, “Target detection and localization using MIMO radars and sonars,”, I. Ziskind and M. Wax, “Maximum likelihood localization of multiple sources by alternating projection,”, C. Duofang, C. Baixiao, and Q. Guodong, “Angle estimation using ESPRIT in MIMO radar,”. Since the cost function of MLE requires high-dimensional search, the computation load is heavy. In many cases, once the system model is built, the next step could be adding more fidelity in different components. Abstract: Relationships between monostatic and bistatic radar images are reviewed and discussed, both from the point of view of identical receiver locations, and from the conventional point of view where the monostatic radar is located at the angular bisector between the bistatic transmitter and receiver. It is essentially equivalent to backprojection. In this paper, we utilize the method of transmitting subarrays to extend the maximum unambiguous range for monostatic FDA-MIMO radar. There are two types of FDA-MIMO radar, which are the bistatic FDA-MIMO radar and the monostatic FDA-MIMO radar. The main contributions of this paper are summarized as follows:(i)The method to extend the range ambiguity by transmitting subarrays is proposed in the monostatic FDA-MIMO radar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Firstly, the first group of angle and range initial values is obtained as follows: After that, the second group of angle and range is solved by. To further reduce the computational load, the AP-MLE is proposed. However, in FDA-MIMO radar, the angle-range of the target can be estimated jointly. When the number of targets is P, a global search will be conducted in the 2P-dimensional space. First, the log-likelihood function of angle and range estimation is derived. Lr=Receiver losses Figure 2 shows the MUSIC spectrum with ; in this case, the unambiguous range of nontransmitting subarrays (traditional FDA) is 150 km. Wang, “Frequency diverse array antenna: new opportunities,”, W.-Q. We are committed to sharing findings related to COVID-19 as quickly as possible. vice versa. Therefore, we mainly consider the effect of the frequency increment setting on the CRLB of range estimate in this simulation.where is the angle value of the p-th target estimated at the d-th time, is the range value of the p-th target estimated at the d-th time, and D is the number of Monte Carlo simulations. A monostatic radar is comprised of co-located radar transmitter and radar receiver. In order to verify the effectiveness of the proposed transmitting subarrays to extend the unambiguous range for monostatic FDA-MIMO radar, simulation 1 gives the unambiguous range of transmitting subarrays monostatic FDA-MIMO radar and nontransmitting subarrays monostatic FDA-MIMO radar by MUSIC spectrum. Figure 9 gives the resolution probability curves versus SNR. Taking equations (19) into (18) and simplifying, the maximum likelihood cost function for angle and range estimation can be described aswhere is the projection matrix and is the signal covariance matrix. NeXtRAD is a more capable version of NetRAD, a single-frequency, multistatic radar developed by UCT and UCL. Suppose a target is located at (20°, 50 km), under the conditions of signal-to-noise ratio (SNR) = 20 dB, and the number of snapshots L is 100, the following gives the monostatic FDA-MIMO MUSIC spectrum with frequency increment , , and , . The authors declare that there are no conflicts of interest regarding the publication of this paper. The angle of the target relative to the array is , and the two-way propagation range of the target is r. In this case, the transmitting steering vector of transmitting array is [10]where is the transmitting steering vector of the k-th subarray and can be expressed as [1–3]where and c is speed of light. The frequency diverse array (FDA) concept was first proposed at the 2006 IEEE Radar Conference and has received widespread attention because of its range-dependent beam pattern [1–3]. Obviously, the angle of p-th target can be estimated from the receiving steering vector without unambiguous. Advantages of RADAR. … Assuming the transmitting subarrays transmit KM orthogonal signals, the narrow-band complex signal transmitted by the m-th element in the k-th subarray can be expressed aswhere represents the km-th orthogonal signal. When SNR is greater than or equal to 20 dB, AP-MLE only needs about two iterations and the efficiency of the AP-MLE is significant. The estimation performance of the proposed AP-ML estimation algorithm is evaluated, which confirms the superiority of the proposed method in the monostatic FDA-MIMO radar with subarrays. Generally, the transmitter and receiver share a common antenna, which is called a monostatic radar system. 5.2 Characteristics of Multistatic Radar. Monostatic Radar equation is expressed as follows: From equation (9), we can conclude that the maximum unambiguous range of transmitting subarrays satisfieswhere is the maximum unambiguous range of transmitting subarrays. That means the maximum unambiguous detection range of monostatic FDA-MIMO radar is and the maximum unambiguous range is inversely proportional to the frequency increment. Kaikai Yang, Sheng Hong, Qi Zhu, Yanheng Ye, "Maximum Likelihood Angle-Range Estimation for Monostatic FDA-MIMO Radar with Extended Range Ambiguity Using Subarrays", International Journal of Antennas and Propagation, vol. The range of the p-th target can be retrieved from the equation , . In the ML algorithm, the joint angle-range estimation problem becomes a high-dimensional search problem; thus, it is computationally expensive. Similarly, we can conclude that there is a periodic ambiguity in the range estimated by k-the subarray and the periodic range is . Wang, and W. Wu, “Search-free DOD, DOA and range estimation for bistatic FDA-MIMO radar,”, J. Xu, G. Liao, S. Zhu, L. Huang, and H. C. So, “Joint range and angle estimation using MIMO radar with frequency diverse array,”, S. Qin, Y. D. Zhang, M. G. Amin, and F. Gini, “Frequency diverse coprime arrays with coprime frequency offsets for multitarget localization,”, Y. As the SNR increases, the number of iterations required decreases. For this purpose the monostatic radar uses duplexer. In iterative search, angle and range are automatically matched, and no additional angle and range matching algorithm is required. In a range. Consider the number of transmitting subarrays is K = 2, the number of subarrays elements is M = 6, and the frequency increment of the first subarray is 2 kHz. It simplifies the multidimensional searching into a series of one-dimensional searching and thus can greatly reduce the computational load. This Classification of Radar is based on the number of Radar antenna used. Weather Radar   That means targets are undetectable within the circle of Cτ/2 radius, where C is sound speed in water. The festivities started on … In , the angle and range estimation CRLB, MSE, and resolution of monostatic FDA-MIMO radar were analysed and compared with traditional MIMO radar, which illustrated the advantages of monostatic FDA-MIMO radar. In this paper, we consider a monostatic FDA-MIMO radar system with transmitting subarrays. monostatic, bistatic, and hybrid modes. Figure 6 gives the average number of iterations curves versus SNR of AP-ML angle and range estimation for transmitting subarrays monostatic FDA-MIMO radar. In the iterative process, perform a one-dimensional search for angle and range, respectively:where represents the P-1 pair angle and range from the j-th iteration, which can be described as. In monostatic systems, each antenna transmits and receives RF … In Bistatic radar two separate Antennas are used for transmission and reception purpose while in case of monostatic Radar only one antenna works as a transmitter and receiver antenna. Reconstruction algorithm based on compressed sensing always subject to the grid-mismatch effect and deteriorating the estimation performance [19]. Suppose three targets are located at (−5°, 11 km),(10°, 13 km), and (35°, 14 km), where the angle search step is 0.01° and the range search step is 1 m. The number of simulations D = 200 and other simulation conditions are the same as simulation 2. However, as a classic parameter estimation algorithm, maximum likelihood estimation (MLE) [21] has not been discussed for angle and range estimation in monostatic FDA-MIMO radar. In order to evaluate the estimation performance of the AP-MLE algorithm, the AP-MLE root mean square error (RMSE) of the angle and range against the SNR is compared with the MUSIC algorithm, ESPRIT algorithm (angle and range pairing algorithm in [25]), paper [13], and angle-range estimation CRLB. In this section, we explain the range ambiguity problem from the angle-range estimation principle. We will be providing unlimited waivers of publication charges for accepted research articles as well as case reports and case series related to COVID-19. Wang, “Physical-layer security for proximal legitimate user and eavesdropper: a frequency diverse array beamforming approach,”, D. W. Bliss and K. W. Forsythe, “Multiple-input multiple-output (MIMO) radar and imaging: degrees of freedom and resolution,” in, K. W. Forsythe, D. W. Bliss, and G. S. Fawcett, “Multiple-input multiple-output (MIMO) radar: performance issues,” in, C. Cui, J. Xu, R. Gui, W.-Q. Next, iteratively update the P groups of angle and range until the algorithm iteration stop condition is satisfied. The bistatic FDA-MIMO radar has the serious problem of angle-range coupling, which increases the difficulty of joint angle-range estimation [10]. and radar transmitting antenna To our best knowledge, there is only one work discussing how to extend the unambiguous range of monostatic FDA-MIMO radar at present. At this time, the array received signal obeys [23], and the joint probability density function (PDF) of can be represented aswhere . 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