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.
Recently, there are many roundabouts installation works which are ordered to provide convenient transportation to road users as well as to eliminate traffic accidents and traffic delays. This study propose an approximate construction cost estimation model for early stages of roundabout construction. The model is designed considering the conditions of the early stage roundabout construction sites in Jeju. The regression equation of approximate construction cost was derived through regression analysis of 25 design data of roundabout construction in Jeju, and it was analyzed to have a high prediction accuracy. Finally, results verifies high prediction accuracy of the derived regression equation. Difference between the estimation cost and the design cost was only 2.3%, 3.7%, and 5.8% that verifies the high accuracy of the proposed approximate construction cost estimation model.
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