Three optimizations of the antenna area and power for the spaceborne synthetic aperture radar (SAR) are presented in this thesis. Since the antenna area and power are the major factors in performance and budget of the spaceborne SAR, a lot of attention should be paid on the determination of the antenna area and power for different applications and/or purposes.
In chapter 3, a cost-effective antenna height and power determination procedure is proposed for the spaceborne small synthetic aperture radar in the stripmap mode(scheme I). In the conventional scheme, the antenna area is decided by the traditional minimum antenna area constraint and power by the required SNR. The proposed scheme I satisfies the requirements on the signal to noise ratio(SNR) and resolutions, given the SAR geometry (an altitude and incidence angles) and radar wavelength. The planar antenna length is fixed by the required azimuth resolution. The antenna height and average transmitted RF power of the SAR antenna are determined by minimizing the cost(defined as mass per swath width) of a stripmap small SAR satellite subject to the SNR constraint for the secure detection and the ambiguity constraint for avoiding ambiguities in range and Doppler. The proposed scheme I shows that the minimum cost of a stripmap small SAR satellite is much lower than the cost utilizing the minimum antenna height.
In chapter 4, a cost-effective antenna area and power determination procedure is proposed for the spaceborne small synthetic aperture radar in the spotlight mode(scheme Ⅱ). The antenna area and average transmitted RF power of the SAR antenna are determined by minimizing the cost(defined as mass per target area) of a spotlight small SAR satellite subject to the SNR constraint for the secure detection and the ambiguity constraint for avoiding ambiguities in range and Doppler. The proposed scheme Ⅱ shows that the minimum cost of a spotlight small SAR satellite is much lower than the cost utilizing the ambiguity-limited antenna area.
In chapter 5, an optimal antenna height and power determination over a wide range of incidence angles is proposed for in-orbit operations of the spaceborne stripmap synthetic aperture radar with variable antenna height and variable radiating element power(scheme Ⅲ). The conventional scheme claims for the incidence-angle-dependent operation of the spaceborne stripamp SAR by exploiting variable antenna height. In the proposed scheme Ⅲ, not only variable antenna height but also variable radiating element power is adopted. The antenna height and the average transmitted RF power of a radiating element for each incidence angle are determined so that mapping area can be maxzimized with the constraints on the SNR, ambiguities and swath width. The illustrative design example show that the mapping area of the proposed scheme Ⅲ is superior to that resulted from utilizing only the variable antenna height. The proposed optimization would have a more beneficial effect on applications that needl the high-incidence-angle operations.
The proposed three optimizations decide the antenna area and power giving the optimal performances in the stripmap cost (defined as mass per swath width) sense for a specific incidence angle, in the spotlight cost (defined as mass per target area) sense for a specific incidence angle, and in the stripmap mapping area sense over a wide range of incidence angles, respectively.
안테나 면적과 전송전력은 위성용 합성개구레이다의 성능과 예산의 중요 요인으로 작용하므로 다수의 응용들과 목적에 기인한 안테나 면적과 전송전력 결정에 많은 관심을 기울여야 한다. 본 논문에서는 위성용 합성개구레이다에 사용된 안테나 면적과 전송전력을 결정하는 세가지 최적화 방안을 제시한다.
본 논문에서 제시된 세가지 최적화 방안은 특정 입사각의 stripmap 모드 비용함수 (조사폭 대 위성질량) 관념으로, 특정 입사각의 spotlight 모드 비용함수 (조사영역 대 위성질량) 관념으로, 광역 입사각의 stripmap 모드 목적함수 (한 궤도주기 당 조사영역) 관념으로 각각 최적의 성능을 부여하는 안테나 면적과 전송전력을 결정한다.
