Frequency Modulated Continuous Wave Technology Research Articles

Blind Spot Detection Radar System Design for Safe Driving of Smart Vehicles

Recently, there has been extensive research and development in the field of smart cars, including technologies related to autonomous driving. Various industries are actively working towards creating efficient and safe self-driving cars. Sensor technologies are emerging to prevent traffic accidents and support safe driving in complex environments where human perception may be limited. One of the representative technologies being researched is the use of Frequency Modulated Continuous Wave (FMCW) radar. Automobile manufacturers are improving driving safety by equipping cars with Blind Spot Detection (BSD) radar systems that use FMCW technology. As the complexity of driving environments continues to grow, ongoing research is aimed at enhancing the accuracy and reliability of BSD radar technology for detecting blind spots in vehicles. This paper presents the signal processing and tracking algorithms that are the core technologies of the BSD radar, and the design for a BSD radar system. The designed radar system was installed on a vehicle to verify its performance in real-world road environments. The ultimate objective of this research is to design a BSD radar system with high accuracy and reliability in BSD detection using AI technology. In pursuit of this goal, this paper presents the hardware design of the BSD radar system, including antenna and modem designs.

Nonlinear error correction for Terahertz FMCW System by a new beat frequency estimation method.

Terahertz (THz) frequency modulated continuous wave (FMCW) technology is a means of nondestructive testing. The signal's nonlinearity is an unavoidable problem in the daily application of THz FMCW technology. The signal's nonlinearity will lead to the spectrum broadening of the FMCW's beat frequency (BF) signal, which degrades the range resolution and result in distance-measuring error. Traditional methods require additional hardware or require a lot of computation, which are not conducive to the miniaturization of the system and real-time measurement. A novel method for correcting the nonlinear error of THz FMCW technology has been proposed and demonstrated in this article. In the proposed method, the windowed Fourier transform (WFT) is introduced to estimate the BF corresponding to the measured target, according to the linearity distribution of voltage-controlled oscillator (VCO). In this way, the measured target's BF can be accurately estimated from the unprocessed BF signal with a poor linearity. From the estimated BF of the reference target, the non-linear compensation coefficients are calculated. With the non-linear compensation coefficients, the non-linearity of the output BF signal can be calibrated. The results of simulations and experiments show that the proposed method allows the range resolution of an FMCW system to reach the theoretical limit.

Application Research of Frequency-Modulated Continuous-Wave Displacement Sensor Based on Zero-Crossing Phase Detecting Algorithm

Frequency-modulated continuous-wave (FMCW) interference, as a new technology of laser interferometry, has the advantages of length traceability, large range, high accuracy, simple structure, and optical fiber transmission. Based on the formula of FMCW laser interference displacement, a zero-crossing phase detection algorithm is proposed, which can accurately calculate the initial phase of a cosine signal in a modulation period, and it is successfully applied to the contact laser interference displacement sensor. The experimental results show that the FMCW technology based on the zero-crossing phase detection algorithm can achieve the technical specifications of the contact displacement sensor with a measurement range greater than 15 mm and the standard deviation is less than 0.01 μm. The conversion of noncontact measurement to contact measurement can realize the direct measurement of workpieces with complex surface conditions on the production line, breaking through the limitation of optical measurement and expanding the application of optical fiber interferometry.

On the Capabilities of the Italian Airborne FMCW AXIS InSAR System

Airborne Synthetic Aperture Radar (SAR) systems are gaining increasing interest within the remote sensing community due to their operational flexibility and observation capabilities. Among these systems, those exploiting the Frequency-Modulated Continuous-Wave (FMCW) technology are compact, lightweight, and comparatively low cost. For these reasons, they are becoming very attractive, since they can be easily mounted onboard ever-smaller and highly flexible aerial platforms, like helicopters or unmanned aerial vehicles (UAVs). In this work, we present the imaging and topographic capabilities of a novel Italian airborne SAR system developed in the frame of cooperation between a public research institute (IREA-CNR) and a private company (Elettra Microwave S.r.l.). The system, which is named AXIS (standing for Airborne X-band Interferometric SAR), is based on FMCW technology and is equipped with a single-pass interferometric layout. In the work we first provide a description of the AXIS system. Then, we describe the acquisition campaign carried out in April 2018, just after the system completion. Finally, we perform an analysis of the radar data acquired during the campaign, by presenting a quantitative assessment of the quality of the SLC (Single Look Complex) SAR images and the interferometric products achievable through the system. The overall analysis aims at providing first reference values for future research and operational activities that will be conducted with this sensor.

Back-projection imaging algorithm of random noise frequency modulation continuous wave SAR

The combination of random noise frequency-modulation continuous wave technology and synthetic aperture radar (SAR) promises a cost-effective, low probability of intercept and high electromagnetic compatibility. This paper analyses the time-domain restricting algorithms for random noise frequency modulation continuous wave (RNFMCW) SAR. Two versions of the back-projection algorithm are proposed. At first, the radar antenna continuous motion in a pulse repetition period of RNFMCW SAR is analysed. Then the phase term which is caused by the continuous motion is described by a approximate expression with Taylor expansion. Meanwhile, both the start-stop approximate back-projection algorithm and the modified back-projection algorithm are proposed. In the end, with the help of numerical simulation, the limitations of the start-stop approximation back-projection algorithm and the validity of the modified back-projection algorithms are illustrated.

RANGE MIGRATION ALGORITHM IN THE PROCESSING CHAIN OF SIGNALS OF A GROUND-BASED SAR SENSOR

Abstract. Synthetic aperture radar (SAR) system based on frequency modulated continuous wave (FM-CW) transmission is a viable option for producing high-resolution ground-based imaging radars. Compared with pulsed SAR systems, the combination of FM-CW technology and SAR processing techniques have the advantages of small cubage, lightweight, cost-effectiveness, and high resolution in the SAR image. These characteristics make FM-CW SAR suitable to be deployed as payload on ground Based SARs (GB-SARs) for environmental and civilian applications. In this paper, the Range Migration Algorithm (RMA) is used in the processing chain of a Ground-Based SAR (GB-SAR) sensor. The mentioned sensor has been developed in Microwave Remote Sensing Laboratory (MReSL) at the School of Surveying and Geospatial Engineering, the University of Tehran for the generation of a complex image from the raw signal. The raw signal is acquired with that sensor working at S-band, frequency modulating from 2.26 GHz to 2.59 GHz.

Multichannel simultaneous dual-band fully polarimetric airborne synthetic aperture radar: system features and experimental results

This paper presents a frequency modulated continuous wave (FMCW) technology-based airborne synthetic aperture radar (SAR) system. This radar system operates on an eight-channel simultaneous dual band (X- and L-bands) in fully polarimetric mode. Compared with the traditional multiband airborne SAR, this radar system features a small size and low power consumption based on the FMCW technology. The antenna subsystem can be easily mounted behind the cargo door of a small aircraft platform without any modifications to the aircraft structure. A Cessna 208 is employed to mount this radar system in a left side looking installation. A single pass flight test is carried out in China, and preliminary imaging results are acquired and classified. The merged X–L band image provides the highest classification accuracy compared with the single X- and L-bands and optical images. The experimental results indicate that the proposed FMCW SAR is a powerful tool for terrain classification, especially for rural-urban region classification.

Signal Processing for a Multiple-Input, Multiple-Output (MIMO) Video Synthetic Aperture Radar (SAR) with Beat Frequency Division Frequency-Modulated Continuous Wave (FMCW)

In this paper, we present a novel signal processing method for video synthetic aperture radar (ViSAR) systems, which are suitable for operation in unmanned aerial vehicle (UAV) environments. The technique improves aspects of the system’s performance, such as the frame rate and image size of the synthetic aperture radar (SAR) video. The new ViSAR system is based on a frequency-modulated continuous wave (FMCW) SAR structure that is combined with multiple-input multiple-output (MIMO) technology, and multi-channel azimuth processing techniques. FMCW technology is advantageous for use in low cost, small size, and lightweight systems, like small UAVs. MIMO technology is utilized for increasing the equivalent number of receiving channels in the azimuthal direction, and reducing aperture size. This effective increase is achieved using a co-array concept by means of beat frequency division (BFD) FMCW. A multi-channel azimuth processing technique is used for improving the frame rate and image size of SAR video, by suppressing the azimuth ambiguities in the receiving channels. This paper also provides analyses of the frame rate and image size of SAR video of ViSAR systems. The performance of the proposed system is evaluated using an exemplary system. The results of analyses are presented, and their validity is verified using numerical simulations.

MIMO FMCW Reader Concept for Locating Backscatter Transponders

This paper presents a multiple-input multiple-output (MIMO) frequency-modulated continuous-wave (FMCW) reader concept for locating backscatter radio-frequency identification (RFID) transponders. The proposed MIMO concept enables transmitter sided digital beamforming after a measurement has been executed. An algorithm is presented to decompose the MIMO response to match a digital beamforming input matrix. A 2.4-GHz experimental reconfigurable localization system based on FMCW technology was set up to demonstrate the concept. Multichannels are implemented to allow the possibility of testing the MIMO concept. A frequency-division multiplexing was implemented into an MIMO FMCW RFID reader and successful tested. Moreover, the system is able to locate multiple transponders simultaneously. Measurements confirm the functionality of the concept. The implementation of a digital beamforming algorithm shows the possibility of transmitting and receiving sided spatial filtering. Angle and distance precision were determined in an antenna chamber as well as in a harsh multipath environment. To help readers to compare the system with others, the mean absolute error of the position shows the system accuracy in a laboratory environment. Finally, an error analysis of the decomposition algorithm verified its robustness.

Development of Coastal Radar Network at Sunda Strait

In this paper, d evelopment on a coastal surveillance Radar network , which is called ISRA (Indonesian Sea Radar), is presented. This Radar network was developed for surveillance at the Sunda Strait . The radar network monitors the sea traffics and activities at the Sunda Strait, which an international shipping route. There were three Radars installed for this network. All these Radars in this research use FM-CW (Frequency Modulated Continuous Wave) technology. This FM-CW has an advantage of low power consumption, low cost of operational, longer life time and high reliability. Another important feature of this Radar is the LPI (Low Probability of Intercept) capability, where the signal transmission of this Radar cannot be easily detected by a Radar detector (electronic support measure) so that this Radar can be used for a covert operation. Detected targets by Radars are shown on the display and on the web based display for the Radar network. These three Radars on the remote sites can be monitored and controlled via an internet connection from the control room in our Bandung office, which is 300 KMs away. The results of this research and development show the Indonesian capability to build a complex system such as a chain of coastal surveillance Radar network. The knowledge obtained from this research will be used to develop more advanced Radars for different applications.

Transmitter and receiver design at L-band and X-band for FM-CW radar altimeter

In recent years, there has been a growing interest in FM-CW (frequency modulated continuous wave) technology for military and civilian applications. FM-CW radar altimeters find applications to detect ground proximity during automatic landing in low-visibility condition, collision avoidance systems in vehicles, and ground penetrating radars for buried object detections such as landmines, pipelines, etc. The development of a low-power L-band and X-band FM-CW radar hardware and design of a third order loop filter for the phase locked loop (PLL) is the main focus of this paper. Results of laboratory trial for the calibration of FMCW radar hardware are presented to demonstrate the feasibility of operation at X band

A frequency-modulated continuous wave birefringent fibre-optic strain sensor based on a Sagnac ring configuration

Two-mode fibre interferometers have been shown to be well suited as optical fibre strain sensors because (i) they have a higher resolution than do intensity modulation-based strain sensors and (ii) they have a simple geometry since the reference and signal light beams propagate along a single fibre core. This paper discusses a Sagnac ring configuration of polarization-maintaining fibre strain sensor based on frequency-modulation continuous wave technology wherein the basic sensor layout consists of a frequency-modulated single-mode laser, a 100 metre ring of single-mode birefringent fibre and a PIN photodiode detector. By launching light into both ends of the fibre, propagating and counter-propagating beams may be employed to sense the variations in length due to strain. The sensor exhibits good characteristics including temperature insensitivity over a limited temperature range (C), high resolution ( microstrain), large dynamic measurement range ( microstrain), large signal intensity and good signal contrast.

A distributed frequency modulation continuous wave fiber stress sensor based on a birefringent sagnac ring configuration

A new distributed stress sensor, based on a birefringent fiber Sagnac ring configuration and frequency modulation continuous wave technology, has been investigated. The two forward-coupled mode beams in the Sagnac ring, induced by an applied stress at any given point along the fiber length, produce a beat frequency which can be analysed to determine, simultaneously, the magnitude and position of the stress. The system has a reasonable spatial resolution of 1 m in a dynamic sensing range of 50 m.