Figure 18 - uploaded by Chen Wu
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The spectrum plot in one FFT window at 0.009 s of the simulation without the MTI. The spectrum plot in one FFT window at 0.009 s of the simulation without the MTI.
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In this paper, a high-performance antenna array system model is presented to analyze moving-object-skin-returns and track them in the presence of stationary objects using frequency modulated continuous wave (FMCW). The main features of the paper are bonding the aspects of antenna array and electromagnetic (EM) wave multi-skin-return modeling and si...
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... Therefore, the beamforming system requires precise control of the transmitted or received signal to have desired differences in time, amplitude, phase in all frequencies. To achieve this, many calibration methods have been proposed and implemented [8][9][10][11][12][13][14]. The PN gating method is a widely used technique for the calibration of the remote sensing radar system, which is based on the orthogonal code [15][16][17]. ...
This paper addresses the challenges of wideband signal beamforming in radar systems and proposes a new calibration method. Due to operating conditions, the frequency-dependent characteristics of the system can be changed, and the amplitude, phase, and time delay error can be generated. The proposed method is based on the concept of the sliding window algorithm for linear frequency modulated (LFM) signals. To calibrate the frequency-dependent errors from the transceiver and the time delay error from the true time delay elements, the proposed method utilizes the characteristic of the LFM signal. The LFM signal changes its frequency linearly with time, and the frequency domain characteristics of the hardware are presented in time. Therefore, by applying a matched filter to a part of the LFM signal, the frequency-dependent characteristics can be monitored and calibrated. The proposed method is compared with the conventional matched filter-based calibration results and verified by simulation results and beampatterns. Since the proposed method utilizes LFM signal as the calibration tone, the proposed method can be applied to any beamforming systems, not limited to LFM radars.
... Among them, CW radar cannot measure distance; pulse radar can measure distance, velocity, and angle, but the farther the distance, the lower the distance resolution; FMCW radar can measure distance, velocity, and angle, and its measured distance accuracy is only related to the modulated frequency bandwidth. Therefore, FMCW radar is widely used [5,6]. ...
Frequency-modulated continuous wave (FMCW) radar is widely used in automotive and consumer electronics because of its range, velocity, and angle measurement functionality. In an FMCW radar system, the isolation between transmitting (Tx) and receiving (Rx) subsystems affects the sensitivity of the FMCW system, which directly impacts the system’s overall performance in target detection. The factors that affect system performance include transmitter-to-receiver on-chip coupling and Tx-to-Rx antenna coupling. The on-chip isolation performance is basically fixed once a radar chip is given, but the antenna isolation performance depends on a designed antenna array. Usually, a targeted antenna requirement is first specified, and then the corresponding Tx and Rx antenna array is designed. However, there is no general principle or criteria for specifying a proper antenna isolation requirement in the existing research. In this paper, first, we reveal that the antenna isolation requirement should be set to be almost the same as the given on-chip isolation value, which is very significant as a general guideline in setting a targeted antenna isolation requirement. All current antenna isolation methods cannot reach the level of on-chip isolation in a compactly designed radar system. We further propose a teardrop-based method to provide high antenna isolation. The principle of an antenna isolation requirement and a novel antenna design using teardrops are both analyzed and demonstrated based on a representative 24 GHz FMCW radar. Our teardrop-shaped structure in the mouth of the conventional Vivaldi antenna achieved greater than 50 dB isolation, while the distance between the Tx and Rx antennas could be reduced to 2.1 mm.
... In some cases, the open loop tracking radar system performs the dual function of both searching and tracking. The closed loop tracking schemes, which are seen in [24][25][26][27], require initial input parameters, such as the initial range, the initial 2D angles and the initial Doppler of an intended target, to establish a track. After establishing the track, the closed loop tracking radar relies on its signal processing to track the target. ...
... After establishing the track, the closed loop tracking radar relies on its signal processing to track the target. In [27], an FMCW target-tracking radar is proposed and closed loop tracking of the target range and angles is applied to this system. This FMCW radar uses a constant false alarm rate (CFAR) detector [28,29] and 2D monopulse angle tracking [30,31]. ...
... In the FMCW context, PRI also refers to the period of the waveform. In [27], we also observe the blind speed phenomenon with the triangular FMCW waveform and MTI. ...
In this paper, a novel signal processing algorithm for mitigating the radar blind speed problem of moving target indication (MTI) for frequency modulated continuous wave (FMCW) multi-target tracking radars is proposed. A two-phase staggered pulse repetition interval (PRI) solution is introduced to the FMCW radar system. It is implemented as a time-varying MTI filter using twice the hardware resources as compared to a uniform PRI MTI filter. The two-phase staggered PRI FMCW waveform is still periodic with a little more than twice the period of the uniform PRI radar. We also propose a slow time signal integration scheme for the radar detector using the post-fast Fourier transformation Doppler tracking loop. This scheme introduces 4.77 dB of extra signal processing gain to the signal before the radar detector compared with the original uniform PRI FMCW radar. The validation of the algorithm is done on the field programmable logic array in the loop test bed, which accurately models and emulates the target movement, line of sight propagation and radar signal processing. A simulation run of tracking 16 s of the target movement near or at the radar blind speed shows that the total degradation from the raw post-fast Fourier transformation received signal to noise ratio is about 2 dB. With a 20 dB post-processing signal to noise ratio of the proposed algorithm for the moving target at around a 20 km range and with about a −3.5 dB m2 radar cross section at a 1.5 GHz carrier frequency, the tracking errors of the two-dimensional angles with a 4×4 digital phased array are less than 0.2 degree. The range tracking error is about 28 m.
... Therefore, a target detection should be performed before applying the ESPRIT algorithm. In the frequency-modulated continuous wave (FMCW) radar system, a target is detected by searching the peak value in a range-Doppler map (R-D map), and the DOA for each target is estimated thereafter [24][25][26]. Therefore, the ESPRIT algorithm needs to perform DOA estimation only for one target. ...
... When the iteration process is repeated according to the number of antennas, the signal subspace is the output. The cyclic Jacobi method repeats the process in Equations (22)- (26), and the number of iterations to be repeated is M × (M − 1)/2. Thus, as the number of antennas increases, the computational complexity of the cyclic Jacobi method increases dramatically. ...
The estimation of signal parameters via rotational invariance techniques (ESPRIT) is an algorithm that uses the shift-invariant properties of the array antenna to estimate the direction-of-arrival (DOA) of signals received in the array antenna. Since the ESPRIT algorithm requires high-complexity operations such as covariance matrix and eigenvalue decomposition, a hardware processor must be implemented such that the DOA is estimated in real time. Additionally, the ESPRIT processor should support a scalable number of antenna configuration for DOA estimation in various applications because the performance of ESPRIT depends on the number of antennas. Therefore, we propose an ESPRIT processor that supports two to eight scalable antenna configuration. In addition, since the proposed ESPRIT processor is based on multiple invariances (MI) algorithm, it can achieve a much better performance than the existing ESPRIT processor. The execution time is reduced by simplifying the Jacobi method, which has the most significant computational complexity for calculating eigenvalue decomposition (EVD) in ESPRIT. Moreover, the ESPRIT processor was designed using hardware description language (HDL), and an FPGA-based verification was performed. The proposed ESPRIT processor was implemented with 10,088 slice registers, 18,207 LUTs, and 80 DSPs, and the slice register, LUT, and DSP were reduced by up to 71.45%, 54.5%, and 68.38%, respectively, compared to the existing structure.
Frequency Modulated Continuous Wave radar is nowadays considered as an important technology to monitor the health condition, fall condition and activities of elderly patients for their well-being and safety. Infrared Proximity (IP) and Passive Infrared (PIR) camera systems have traditionally been used for this purpose, but this system has crucial limitations, especially with regards to fast detection technique for such as preventing accident in the bathroom and indoor environment. The use of surveillance cameras not only struggles at nighttime detection but also can compromise patients' privacy, such as bathroom activities. FMCW radar technology can operate effectively in no-light conditions making them particularly suitable for nighttime monitoring by addressing privacy concerns. The principles of FMCW radar, signal processing algorithms and methods are discussed in this paper. Depending on the type of motion activity, a patient's returning radar signal will exhibit varying Doppler effect properties. This technology not only enhances patient care but also relieves healthcare providers and families from the need for constant in-room surveillance. FMCW radar technology bridges the gap between patient privacy concerns and the necessity for improving patient healthcare. This paper explores the utilization of FMCW radar for monitoring elderly patients and fall detection, with the goal of developing a privacy friendly app-based solution for real-time remote patient activity tracking.
