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An inverse synthetic aperture radar (ISAR) is a radar system capable of forming high-resolution images regardless of weather conditions or light levels. The frequency-modulated continuous wave (FMCW) technique overcomes the system size limitations of pulse-based radars by significantly reducing the analog-to-digital conversion (ADC) sampling rate, consequently increasing the versatility of radar systems, leading to their widespread application in various fields. By separating the transmitter and receiver, bistatic radar can exploit the diverse scattering characteristics of targets and offers advantages such as improved resolution compared with monostatic radar. However, the operation of a bistatic FMCW radar must solve the problem of signal synchronization. This study presents the challenges of bistatic FMCW radar systems, proposes a master–slave structure to address synchronization issues, and demonstrates the formation of ISAR images in real-world scenarios. [ABSTRACT FROM AUTHOR]

A static frequency-modulated continuous-wave (FMCW) radar imaging system uses different local oscillator (LO) and clock signals owing to the spatial separation of the transmitter and receiver, resulting in asynchronization problems of various factors that can deteriorate the quality of radar images. In this study, we defined signal models for bistatic FMCW asynchronization factors:1) the time difference between reference signals in the transmitter and receiver, 2) LO phase noise difference, 3) pulse repetition frequency mismatch, and 4) center frequency difference. We generated ISAR images of the point scatterer for each asynchronization factor to analyze the influence of asynchronization through the ISAR image in terms of quality parameters. [ABSTRACT FROM AUTHOR]

This paper presents an active decoy algorithm using digital radio frequency memory for synthetic aperture radar (SAR) image jamming. First, we analyzed a geometric method for deceptive target generation according to parameters such as SAR velocity, pulse repetition frequency, and slant range. We developed a simple and easy-to-use SAR jamming algorithm using linear approximation. Additionally, we validated the SAR jamming algorithm using a range doppler algorithm with various slant range parameters. As a result, the position of the deceptive target for the azimuth direction was moved in proportion to the slant range, and a deceptive target for the range direction was generated at the same position regardless of the slant range. [ABSTRACT FROM AUTHOR]

In this study, a method was proposed to develop a compact antenna for a drone-borne synthetic aperture radar(SAR). The compact antenna structure was designed as a microstrip patch antenna, and a parasitic patch was stacked on the radiation patch to improve the bandwidth and gain of the antenna. The size and interval between patches were iteratively adjusted based on the simulation in order to satisfy the requirements of the antenna. Additionally, HH-, VV-, HV-, and VH-polarimetric antennas were fabricated to acquire fully polarimetric SAR data. As a result, the compact antenna could be successfully developed with a small weight of less than 100 grams. [ABSTRACT FROM AUTHOR]

Although the back-projection algorithm(BPA) is the best method for image reconstruction of air-borne synthetic-aperture radar(SAR), it requires a long processing time. In this study, a real-time processing method of BPA was proposed to reconstruct the image of a compact drone-borne SAR in real time. To achieve this, the raw data of the SAR was acquired by a test flight with SAR based on frequency-modulated continuous wave(FMCW) radar. The performance of the BPA was confirmed by using raw data and a modified BPA processing kernel based on graphics processing unit(GPU) technology. The results confirmed the possibility of real-time image reconstruction of SAR. [ABSTRACT FROM AUTHOR]

The accuracy of extracting the azimuth angle of a target is significantly affected by the error in the mono-pulse ratio of the air-borne antenna hybrid mono-pulse Radar system. This error is strongly induced by the phase imbalance between the channels of the system. In this paper, a method is proposed for effectively calibrating the phase imbalance caused by physical differences between the RF channels from the antenna to the 180° hybrid. Through a flight test, it was confirmed that the accuracy of the azimuth angle of the target is improved by using the proposed method. [ABSTRACT FROM AUTHOR]

Simplified factorizing-technique to improve the efficiency on computational procedure and the complexity of the conventional back-projection algorithm, which is used to reconstruct airborne FMCW-SAR image, is suggested, and the reconstruction process of SAR image by this simplified factorizing-technique are presented in this paper. This technique can be efficiently applied to airborne FMCW-SAR having a relatively narrow beamwidth and long synthetic aperture length, and its basic rationale is to exclude the data that has low level of contribution during computational procedure. Using the raw data of practical airborne FMCW-SAR system, performances of this proposed technique such as SAR image quality and processing time were compared and analyzed. [ABSTRACT FROM AUTHOR]