SAR Preprocessing 
- An Examination on Speeding Complex Number Operation in NEDIPS - 
H. Nohmi, M. Murata, K. Nakada, N. Ito 
Guidance and Electro-optics Division 
NEC Corporation 
1-10, Nisshin-cho, Fuchu City, Tokyo, 183, JAPAN 
ABSTRACT 
Because a large number of complex number operations are required in carrying 
out SAR data processing, the adoption of complex number modules will be 
instrumental in effectively increasing SAR data processing speed. The 
authors believe that the use of complex number modules will produce a cost 
effective system which can satisfy the operational requirements for a 
Japanese ERS-1 SAR data processing system. 
In this paper, the hardware configurations and functions of complex modules 
are introduced and the effects of their use are described for complex number 
Fast Fourier Transformation (CFFT) which requires the lion's share of SAR 
data processing. 
1. INTRODUCTION 
  
At present, most SAR data processing systems consist of a host minicomputer 
and a high speed array processor. Although the NEDIPS SAR data processing 
system is similar in type, it is also a multiprocessor system because NEDIPS 
has parallel processing functions which derive from its data-flow archi- 
tecture. Figure 1 shows the block diagram of NEDIPS SAR data processing 
system. NEDIPS consists of a data-flow processor and a memory unit. Ring 
buses in the data-flow processor make up the arithmetic unit and the 
addressing unit, respectively. 
The arithmetic unit has modules for addition, subtraction and multiplication 
which are shown as "FLTOP" in Figure 1. 
The high efficiency operation of these modules in manipulating complex 
number data is of paramount important to achieve high speed SAR data 
processing because SAR data processing requires a large amount of complex 
number operations. Upon examination of various methods for high efficiency 
complex number operations, the authors believe that the use of complex 
number modules (i.e. the complex number addition and subtraction module 
CNASM and the complex number multiplication module CNMM) in NEDIPS is an 
outstanding method to realize a cost-effective system for high speed SAR 
data processing. This paper deals with the functions, the configurations 
and the effects of complex number modules. 
2. PROBLEMS IN COMPLEX NUMBER OPERATIONS 
For an example, consider the case of a complex number multiplication using 
several independent real number modules for addition, subtraction, and 
multiplication. 
In this case, four real number multiplication modules, one addition and one 
subtraction module are necessary in order to obtain the result shown in 
Figure 2. 
Technically, we could use one real number multiplication module four times 
instead of using four multiplication modules, however, the efficiency of the 
overall operation would be greatly reduced. The complex multiplication of 
two complex number (A, B) is represented in Figure 3. 
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