Frequency-modulated Continuous-wave Systems Research Articles

Design and Optimization of a Fan-Out Wafer-Level Packaging- Based Integrated Passive Device Structure for FMCW Radar Applications.

This paper presents an integrated passive device (IPD) structure based on fan-out wafer-level packaging (FOWLP) for the front end of frequency-modulated continuous wave (FMCW) radar systems, focusing on enhancing the integration efficiency and performance of large passive components like antennas. Additionally, a new metric is introduced to assess this structure's effect on the average noise figure in FMCW systems. Using this metric as a loss function, we apply the support vector machine (SVM) for electromagnetic simulation and the genetic algorithm (GA) for optimization. The sample fitting variance is 2.42 dB, reducing computation time from 12 min to under 1 millisecond, with the entire optimization completed in less than 100 s. The optimized IPD structure is 0.7 × 0.9 × 0.014 λ03 in size and achieves over 35 dB isolation between the transmitter and receiver. Compared to the IPD model calculated by empirical formulas, the optimized device lowers the average noise figure by 15.2 dB and increases maximum gain by 4.19 dB.

Nondestructive testing and 3D imaging of PE pipes using terahertz frequency-modulated continuous wave.

Polyethylene (PE) pipes are widely used as the main carrier for the transportation of natural gas, so nondestructive testing techniques for PE pipes are essential for the safety of natural gas transportation. In order to compensate for the shortcomings of conventional inspection methods, a terahertz (THz) three-dimensional imaging system for nondestructive inspection of PE pipes is designed. The system is based on frequency-modulated continuous-wave (FMCW) technology, with a THz source bandwidth of 0.225-0.330THz and an output power of over 5mW, which can achieve submillimeter spatial resolution in three dimensions. The system is used to scan PE pipes in three dimensions in a laboratory environment, and the results show that the system could achieve nondestructive testing and three-dimensional imaging of different defects in PE pipes. In addition, combined with the deep-learning-based THz transformer network, the intelligent identification of different defects is realized, and the accuracy rate can reach up to 88%. The above results provide technical guidance for the application of THz FMCW systems in the actual detection of PE pipes, and provide supplements and improvements for traditional detection methods.

Low-Complexity Super-Resolution Detection for Range-Vital Doppler Estimation FMCW Radar

This paper proposes low-complexity super-resolution detection for range-vital Doppler estimation frequency-modulated continuous wave (FMCW) radar. In regards to vital radar, and in order to estimate joint range and vital Doppler information such as the human heartbeat and respiration, two-dimensional (2D) detection algorithms such as 2D-FFT (fast Fourier transform) and 2D-MUSIC (multiple signal classification) are required. However, due to the high complexity of 2D full-search algorithms, it is difficult to apply this process to low-cost vital FMCW systems. In this paper, we propose a method to estimate the range and vital Doppler parameters by using 1D-FFT and 1D-MUSIC algorithms, respectively. Among 1D-FFT outputs for range detection, we extract 1D-FFT results based solely on human target information with phase variation of respiration for each chirp; subsequently, the 1D-MUSIC algorithm is employed to obtain accurate vital Doppler results. By reducing the dimensions of the estimation algorithm from 2D to 1D, the computational burden is reduced. In order to verify the performance of the proposed algorithm, we compare the Monte Carlo simulation and root-mean-square error results. The simulation and experiment results show that the complexity of the proposed algorithm is significantly lower than that of an algorithm detecting signals in several regions.

Multilayer Thickness Measurements below the Rayleigh Limit Using FMCW Millimeter and Terahertz Waves

We present thickness measurements with millimeter and terahertz waves using frequency-modulated continuous-wave (FMCW) sensors. In contrast to terahertz time-domain spectroscopy (TDS), our FMCW systems provide a higher penetration depth and measurement rates of several kilohertz at frequency modulation bandwidths of up to 175 GHz. In order to resolve thicknesses below the Rayleigh resolution limit given by the modulation bandwidth, we employed a model-based signal processing technique. Within this contribution, we analyzed the influence of multiple reflections adapting a modified transfer matrix method. Based on a brute force optimization, we processed the models and compared them with the measured signal in parallel on a graphics processing unit, which allows fast calculations in less than 1 s. TDS measurements were used for the validation of our results on industrial samples. Finally, we present results obtained with reduced frequency modulation bandwidths, opening the window to future miniaturization based on monolithic microwave integrated circuit (MMIC) radar units.

A novel F-RCNN based hand gesture detection approach for FMCW systems

With the rapid development of artificial intelligence, hand gesture detection has gradually become a research hotspot in human–computer interaction. However, the traditional hand gesture detection has low robustness and detection accuracy, and brings the problem of privacy protection. Therefore, this paper proposes a Faster Region-based Convolutional Neural Network (F-RCNN) hand gesture detection method based on Frequency Modulated Continuous Wave (FMCW) radar with 3-Dimensions deep convolutional Generative Adversarial Networks (3-DCGAN). In particular, the range Doppler and angle of the hand gestures are calculated by FMCW radar. Then, the semantic label maps of the Range-Time-Map, Doppler-Time-Map and Angle-Time-Map images are respectively sent to the 3-DCGAN to expand the datasets. After that, the original and the 3-DCGAN generated images are sent to F-RCNN for jointly training. The classifier function is designed, and a learning ranking based assessment called Rank based Quality Score (RQS) is applied to improve the detection performance. The experimental results show that the mean average precision reaches to 80.8%. Moreover, the RQS for hand gesture detection is as high as 96.3%, which is increased by 5.8% compared to the traditional F-RCNN.

MODIFIED CYLINDRICAL HOLOGRAPHIC ALGORITHM FOR THREE-DIMENSIONAL MILLIMETER-WAVE IMAGING

Millimeter-wave (MMW) imaging techniques have been developed for the detection of concealed weapons and plastic explosives carried on personnel at major transportation hubs and secure locations. The combination of frequency-modulated continuous-wave (FMCW) technology and MMW imaging techniques leads to wideband, compact, and cost-efiective systems which are especially suitable for security detection. Cylindrical three-dimensional (3-D) imaging technique, with the ability of viewing multiple sides, is an extension of rectilinear 3-D imaging technique only viewing a single side. Due to the relatively long signal sweep time, the conventional stop-and-go approximation of the pulsed systems is not suitable for FMCW systems. Therefore, a 3-D backscattered signal model including the efiects of the continuous motion within the signal duration time is developed for cylindrical imaging systems. Then, a holographic image reconstruction algorithm, with motion compensation, is presented and demonstrated by means of numerical simulations.

Multiple target detection for stepped multiple‐frequency interrupted CW radar

AbstractThis paper proposes a multiple target detection system using stepped multiple frequency ICW (Interrupted Continuous Wave) radar. The proposed system can obtain a short observation time compared to a conventional up/down sweep FMCW (Frequency‐Modulated Continuous Wave) system or a two‐frequency CW system with less computational complexity than a two‐dimensional super‐resolution system by using a new transmission frequency sequence intended for short‐range targets and a single‐dimension super‐resolution system that preprocesses a target velocity detection process through the use of an ordinary Fourier transformation. In addition, the proposed system can obtain a desired target range and velocity resolution with a transmission frequency bandwidth less than a pulse compression system or an FMCW system. The proposed system can also avoid pairing malfunctions which lead to problems with FMCW systems. Range separation of multiple equal‐velocity targets, a principal problem in two‐frequency CW systems, can also be obtained. Computer simulations show that as a radar system, the proposed system is expected to improve the above‐mentioned problems of conventional radar systems at practical input SN values. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(10): 49–59, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20388

An Overview of Synthetic-Aperture Image Reconstruction Algorithms for GPR Imaging with Pulse-Echo and Step-Frequency FMCW Systems

The ground-penetrating radar (GPR) systems currently deployed in field applications can be classified into two major types, pulse-echo and step-frequency frequency modulated continuous-wave (FMCW) devices, corresponding to the distinct features of the illumination waveforms. With the addition of synthetic-aperture scans, both versions can be directly applied to high-resolution tomographic imaging. This paper presents the tomographic image reconstruction algorithms for these two operating modalities based on one single framework of backward propagation image formation. In addition to the theoretical analysis and mathematical modeling, this paper presents the algorithm structures for both types of systems as well as results from full-scale field experiments.

Switching system for single antenna operation of an S-band FMCW radar

Increasing interest is being shown in frequency modulated continuous wave (FMCW) radars due to their advantages of compact size, low peak power requirement, good range resolution and low interference to other systems. A major disadvantage of FMCW systems is the need to use two separate, well shielded antennas for transmission and reception. Several schemes have been devised to enable FMCW radars to operate with a single antenna. The authors describe a ground based S-band ocean surface remote sensing FMCW radar that has been adapted for single antenna operation by alternately switching the single antenna between the transmitter and the receiver. Even though this frequency modulated interrupted continuous wave (FMICW) system is no longer a true continuous wave radar, the essential properties of the FMCW waveform are preserved, provided some conditions on the switching speed and FMCW parameters are met. The purpose of the radar is to deduce ocean wave and current parameters by measuring ocean surface velocities. The radar was tested operationally by comparing ocean surface data from both the single antenna (FMICW) and dual antenna (FMCW) systems recorded under similar conditions.