IMPLEMENTATION ON REDUCTION LUT MEMORY SIZE IN CHIRP SIGNAL GENERATION FOR SATELLITE ON-BOARD SAR

[ABSTRACT]The synthetic aperture radar(SAR) is an active sensor that is mounted on moving platform such as aircraft or satellite. It uses electromagnetic waves for the target detecting signal which can penetrate the Earth atmosphere. For that reason, it can obtain target images regardless of the weather condition. Generally, it obtains higher resolution images with the wide bandwidth reference signal. So it takes linearly frequency modulated (LFM) signal called chirp. The instantaneous frequency of chirp signal increases as time, so that this signal can enlarge the bandwidth. In this paper, we suggest the parallel direct digital synthesizer (PDDS) chirp signal generator to generate the wide bandwidth chirp signal. The proposed PDDS signal generator consists of 4-DDS in paralleled and 4 look-up tables (LUTs) those are cascaded to each DDS unit. By using the PDDS method, it takes an advantage on the clock frequency resource, but it occupies large memory resources. When implementing SAR system in satellite platform, the size of memory unit is a critical unit. To solve this problem, we suggest the LUT memory reduction method for using micro satellite use. Using the sinusoid, we divide one period of the sinusoid in quarter. We add an algorithm that represents a one period signal using the quarter signal of sinusoid, generate chirp signal and coded. The memory size of chirp signal generation algorithm is compared with conventional method through simulation. The memory that is used by generating chirp signal in entire system is confirmed by simulation that reduce about a quarter of conventional method. Because it applies the same algorithm in system generator, if it uses higher LUT output bit, ratio of the memory reduction will be increase. Therefore, it is considered that if it uses the same amount of memories, it would be able to design a chirp signal that has a better characteristic.

https://opac.ll.chiba-u.jp/da/curator/107932/

https://opac.ll.chiba-u.jp/da/curator/107932/ceresIntlSympo-24-P976.pdf

Chiba University. Center for Environmental Remote Sensing

千葉大学環境リモートセンシング研究センター

会議発表用資料

Proceedings of the CEReS international symposium = CEReS国際シンポジウム資料集

24

976

979

2016-11-21

publisher

環境リモートセンシング研究センター「CEReSシンポジウム資料集」