In this paper, we proposed a method based on statistically homogeneous pixel (SHP) and coherence information for time series change detection of urban areas using synthetic aperture radar (SAR) images. The proposed framework was applied to KOMPSAT-5 SAR time series data to conduct time series change detection experiments on container yards in port areas. If the algorithm is verified with more SAR images in the future, the algorithm for detecting time series changes in areas of interest using domestic KOMPSAT SAR satellite images will become more generalized and reliable.

The Korea Aerospace Research Institute is responsible for supplying and supporting the utilization of imagery data from the Arirang satellite series for organizations affiliated with the Government Satellite Information Application Consultation. Most of them primarily utilize optical imagery, and there is a relative lack of utilization of Synthetic Aperture Radar (SAR) imagery. In this paper, as part of supporting the use of SAR images, we investigated SAR intensity-based change detection algorithms and their use cases that have been researched to determine SAR intensity-based change detection algorithms to be developed in the future. As a result of the research, we found that various algorithms utilizing intensity difference, correlation coefficients, histograms, or polarimetric information have been researched by numerous researchers to detect and analyze change pixels and the applications of change detection algorithms have been studied in various fields such as a city, flood, forest fire, and vegetation. This study will serve as a reference for the development of SAR change detection algorithms, intended for utilization in the Government Satellite Information Application Consultation.

Polarimetric SAR (PolSAR) data acquired using space-borne sensor perform excellently for forest biophysical parameters estimation. Among the forest biophysical parameters, forest aboveground biomass (AGB) is an important parameter describing all living biomass in the forest. In this research, AGB estimation is carried out by exploiting polarimetric parameters extracted from RADARSAT-2 quad-pol data in synergy with AGB inventory data. Six consecutive RADARSAT-2 quad-pol acquisitions under dry, humid and rainy weather were acquired from Canadian Space Agency (CSA). Polarimetric parameters (backscattering coefficient (σ o ), eigen decomposition parameters (entropy and α), Yamaguchi decomposition parameters (surface, volume scattering components) and parameters describing canopy structure) were extracted using acquired SAR data. Reference biomass data were extracted from referenced biomass map and field visit in study site. Regression analysis was carried out between the extracted polarimetric parameters and in - situ biomass data collected from reference biomass map. Significant regression models were inverted and biomass estimation was performed. Resultant biomass maps were validated using in - situ data collected through field visit.

In this paper, we propose a synthetic aperture radar (SAR) system called compact all time imaging sensor (CATIS) for small satellite. The weight of CATIS is less than 5 kg. including the controller board, signal transmission and reception board, RF modulator board, the high capacity data storage board. CATIS supports the multiple input and multiple output (MIMO) mode for the high resolution image acquisition, digital IQ modulation technique for high spectral purity, and The main features of the proposed SAR system are that the system supports multiple input and multiple output (MIMO) SAR mode for high resolution image acquisition, digital IQ modulation technique for high spectral purity. Also, this paper proposes the verification and validation result of the system by conducting the AutoSAR and airborne platform SAR test.

A synthetic aperture radar (SAR) is electromagnetic equipment which is composed of digital parts. It transmits and receives microwaves for observing long distance. In digital system, system clock is an important factor that determines waveform resolution. The SAR system is consist of FPGA, DAC, and other digital parts. In the SAR system, clock of FPGA and DAC are an upper limit for generation of chirp signal. However, digital parts are mostly expensive due to its specification. In this paper, we develop two types of digital waveform generator and propose a method for chirp waveform generation using relatively low cost parts. We test the chirp waveform generators. One used Virtex-5 and one DDS, and the other used Kintex-7 and four DDSs. In addition, we compare the waveform quality using impulse response function. As a results, peak to side-lobe ratio is -14.68 dB and -11.54 dB, and integrated side-lobe ratio is -21.78 dB and -15.48 dB, relatively.

In this paper, a soil moisture retrieval from full-polarimetric synthetic aperture radar (SAR) data is investigated for sparsely vegetated soil surfaces. An improved retrieval method adapting the variations in vegetation is proposed by incorporating the generalized volume model into the polarimetric two-scale two-component model (PTSTCM). The feasibility of the method, termed as the adaptive PTSTCM, has been tested for tropical peatland sites in Indonesia which exhibit a variety of sparse vegetation cover on soil after land clearing activities. The data were collected in March and August 2017 with the time domain reflectometry (TDR) probe for a total of 18 sample points over 11 regions. The method was applied to ALOS-2 L-band quad-pol SAR data that were acquired simultaneously with field measurements. We compared the results between the proposed adaptive PTSTCM and the original PTSTCM that utilizes specific types of volume model (i.e., randomly, horizontally, and vertically oriented volume models). Scatterplots of estimated versus measured results reveal that the adaptive PTSTCM yields a root-mean-square error (RMSE) of 5.1vol. and inversion rate of 35.0 and 58.5 for March and August data, respectively, which are found to be superior to those of the original PTSTCM.

This paper proposes a novel phase error compensation algorithm for the direct digital synthesizer (DDS) chirp generator of high-resolution synthetic aperture radar (SAR). The proposed compensation algorithm adopts the curve fitting method to calculate the error of transmission SAR signal called chirp. In addition, this paper proposes the polynomial modeling method during chirp generation stage to improve spectrum characteristics. The mathematical equations proposed in this paper indicate that the phase shift of chirp in time domain can be eliminated clearly. Simulation results show that the proposed compensation algorithm enhances the peak-to-side lobe ratio (PSLR) and the integrated side ratio (ISLR) up to -0.2068 dB and -0.1091 dB respectively. In addition, spur components have been reduced when compared to the spectrum output of conventional DDS output.

Currently, most full-polarimetric synthetic aperture radar (SAR) systems adopt linear polarization (LP). On the other hand, circular polarization (CP) is also becoming popular due to its various benefits over LP. However, since CP-SAR is an emerging technique, there are not many imaging and polarimetric analysis results in the literature. As a fundamental study on CP-SAR, this paper presents the results of an investigation on the CP properties of ground-based SAR (GB-SAR) echoes from various canonical targets and a rice paddy sample. The C-band data acquired in a laboratory environment are analyzed and interpreted by means of several factors such as calibration performance, experimental verification of theoretical scattering matrices, imaging quality and accuracy of scattering decomposition results. The eigenvector-based decomposition of the coherency matrix is adopted, and the performance of CP in retrieving the targets’ dominant scattering mechanisms and physical parameters is evaluated from entropy-alpha (H -ᾱ) plane and orientation angle (β̄) value. Results demonstrate the effectiveness of CP in interpreting and discriminating the SAR image features mainly owing to its distinct advantage of highly reliable received signal strength.

This paper proposes the phase error compensation algorithm of the wide band chirp generator for the synthetic aperture radar (SAR) use. The proposed algorithm dynamically calculates the phase error of transmitting chirp to reduce spurious of signal. In addition, it uses the curve fitting method and feedback when the desired signal are set by user. Numerical results show that the proposed algorithm can enhance the impulse response function (IRF) results such as the peak to side-lobe ratio (PSLR) and the integrated side-lobe ratio (ISLR) up to −0.1561 dB and −0.0548 dB respectively. Furthermore, the spurious has been reduced by compared to the conventional direct digital frequency synthesizer (DDFS) chirp generators.

Synthetic aperture radar (SAR) is an imaging radar that uses the radio frequency (RF) signals. Conventional space-borne SAR employs linearly polarized (LP) RF signals and it is easily affected by Faraday rotation effect that distorts the signal amplitude as the signal traverses Ionosphere. This paper presents the development of SAR system that adopts circularly polarized (CP) antennas to compensate the Faraday rotation effect. The inverse SAR (ISAR) test using point target has been conducted in anechoic chamber to validate the performance of the proposed CP-SAR system. The peak to side-lobe ratio (PSLR) parameter from the point target image shows the characteristic of CP microwave. In case of surface scattering, the cross-polarization shows approximately -6 dB lowered PSLR than co-polarization. On the other hand, the double-scattering of co-polarization shows -7 dB lowered PSLR when compared to that of cross-polarization.

For L-band micro satellite on board SAR system, the suitable chirp signal generator for this system is needed. In this paper, the chirp signal generator with direct digital synthesizer (DDS) is considered instead of the memory map based chirp signal generator. Furthermore, to overcome the limitation of clock frequency of the space component, parallelized DDS (PDDS) method is used. However, phase error is one of the problem to implement DDS chirp signal generator. Therefore, we propose a novel method to compensate this error. As a result, the output performance of the signal is enhanced using the proposed phase error compensation method.

As an imaging radar, synthetic aperture radar (SAR) requires the images of high-resolution. To enhance the resolution of images, SAR adopts the chirp signal [1]. The chirp signal is often referred as a linear frequency modulated (LFM) signal because the instantaneous frequency of chirp signal increases or decreases linearly with the time. To realize the chirp signal in SAR system, the chirp signal generator adopts the direct digital synthesizer (DDS) type arbitrary waveform generator. However, the phase error due to the truncation in DDS degrades spectrum purity of output signal. This paper proposes the phase error compensation method for DDS chirp signal generator using polynomial model. To verify the performance of proposed method, the peak to side-lobe ratio (PSLR) and integrated side-lobe ratio (ISLR) are analyzed. In this paper, compared to the conventional DDS system, the PSLR is improved from -13.5536 dB to -13.6207 dB and ISLR is improved from -10.3263 dB to -10.3126 dB when the proposed method is applied.

Synthetic aperture radar (SAR) is an active sensor that is operated using the moving platforms such as satellite, aircraft, or unmanned aerial vehicle (UAV). As a kind of imaging radar, it uses microwave to detect the target in remote area. Due to the characteristics of microwave, the SAR can be operated regardless of the weather conditions. Also, it offers highresolution images of targets by utilizing the wide-bandwidth transmit signal. Due to the features of SAR, it is widely used in several area such as surveillance, land monitoring, urban managing, disaster monitoring etc. To conduct the continuous monitoring for some specific areas, the SAR payloads are loaded on UAV and operated recently. Several UAV-SARs exist already in research fields and practical uses (e.g. AirMOSS of NASA). These platforms usually perform its missions on 1-2 km above the ground. The specifications of the recent UAV-SARs and the conceptual design of the proposed UAV-SAR are listed in Table 1 [1]. To achieve the high-resolution, the SAR system uses a linear frequency modulated (LFM) signal called chirp. As the bandwidth of transmit signal is inverse proportional to the resolution, the SAR system requires wide-bandwidth signal to offer the better performance. There are several types of chirp signal generators: memory-map based type, signal generators using frequency multipliers, direct digital frequency synthesizer (DDFS) type, and parallel DDFS type. The memory-map based chirp signal generator stores the predefined chirp waveform in the PROM or other memory devices and loads the signal using the counter. It has the advantage of high-precision output. However, it requires the large sized ROM to store the wide-bandwidth signal and hard to update the predefined signal especially the SAR is operated in space mission. Compared to the previous one, the DDFS generates only the phase of the signal using registers and full-adders. Next, it combines the phase signal and the amplitude signal that is stored look-up table (LUT). When DDFS generates the desired signal, it controls the frequency control word (FCW). The fast switching speed, less memory dependency, simple structure, easy configurability, and etc. are the features of DDFS. However, as this system truncates the I/O bits between the phase signal generator and LUT, the signal characteristics are degraded due to the spurs. The signal generator using frequency multiplier is proposed to realize the wide-bandwidth signals. First, it generates the relatively narrow band signal. Next, using the frequency multiplier and band-pass filter (BPF), it expands the bandwidth of transmit signal. Using the frequency multiplier, SAR system can achieve the wide-bandwidth with simple structure. However, as the bandwidth of signal is multiplied with the hardware, also the residual noise of the signal gets larger. In this paper, the parallelized DDFS type chirp signal generator is presented. The signal generators are operated based on a digital circuit. Therefore, the baseband output bandwidth of the presented signal generation methods is limited due to the clock frequency of the devices. However, by using the multiple memory and the high-speed multiplexer, the parallelized DDFS can generate the wide-bandwidth chirp signal with relatively low clock frequency. As the recent SAR system requires the high-resolution images, the SAR system equipped with wideband signal generator is also needed. In this paper, the conceptual design for X-band UAV SAR and the parallelized DDFS chirp signal generator for the wideband chirp pulse (up to 800 MHz) have been proposed. Using the circular polarization, the proposed SAR system can be used to full-polarimetric SAR. Also, due to the wideband chirp pulse, the SAR system can offer the images of sub-meter resolution.

Synthetic aperture radar (SAR) is an active sensor that is widely used such as military purpose, land observation, and etc. The main characteristics of SAR system are as follow. First, as SAR uses microwave, it can be operated regardless of the weather and day-night conditions. SAR system uses the signal called chirp to acquire large bandwidth then it provides high-resolution images. The conventional analog type chirp generator of SAR system occupies large amount of space and weight. To implement chirp generator in small satellites, implementation of chirp generator on FPGA will be discussed in this paper.

Coastline is the boundary that discriminates the land and sea area. Originally, to utilize the coastline information, optical images from air-borne or space-borne systems are used. Due to manual interpretation from optical images, conventional coastline extraction method has several error. This paper proposes semi-automatic coastline extraction method using Synthetic Aperture Radar (SAR) images to reduce these errors. SAR is a platform on-board active sensor which can observe Earth day and night regardless of the weather condition. SAR provides high-resolution images for variety of applications in remote sensing field such as climate change research, surveillance imaging, geoscience, and etc. Using the phase information in SAR image data, we detect and measure the coherence between land and sea area, finally get the coastline information.

Synthetic aperture radar (SAR) is an active sensor using microwave to acquire the images of target in interest. To be operated, an SAR platform usually loaded on moving platform such as aerial vehicle or satellite then transmits and receives microwave signal for its own illumination sources. Space-borne SAR that is operated on space orbit uses ionosphere and air as a propagation medium. When linearly polarized microwave which conventional SAR system uses traverses thorough ionosphere, the reference plane of polarization rotates eventually causes polarization mismatch. To reduce the polarization mismatch, this paper proposes circular polarization on SAR sensor.