be used to provide adequate transmitted power while preserving the resolu- 

 tion advantages of short pulses) are limited to compression ratios of ~ 100 

 to 1 and contribute significantly to system cost and complexity. More- 

 over, 15 m is already the order of the target's smallest dimensions so 

 that no increase in SCR is provided for smaller pulse lengths. It should 

 be noted that the above rationale is equally applicable to other indirect 

 methods of decreasing the effective range cell length such as pulse 

 compression or chirping techniques. Practical bounds on narrowing the 

 antenna beamwidth (and thus the azimuthal dimension of the clutter cell) 

 by increasing the antenna size are of the order of 1° beamwidths (corre- 

 sponding to a 17-ft diameter antenna at C band) for airborne radars be- 

 cause of aerodynamic drag problems. Note that a 1° beamwidth would sub- 

 tend a resolution cell dimension of over 5,000 ft at a slant range of 

 50 nrai, so that angular resolution remains the most significant contri- 

 bution to sea clutter susceptability of conventional microwave radars. 



An example of the state of the art in conventional 

 airborne radar is a proposed modification of an AN/APS-116 radar to 

 perform ocean surveillance from an aircraft flying at altitudes up to 

 70,000 ft. This proposal, by Texas Instruments, Inc. (TI), predicts 



the SCR performance shown in Figure 3. This performance would provide 



2 

 detection of our 500-m "design target" over an annular area underneath 



the aircraft with inner and outer radii of 15 and 320 nmi in sea state 

 3. The radar developed for the AWACS aircraft by Westinghouse Corpora- 

 tion is another example of a radar with at least comparable performance. 



A more sophisticated radar system, the SAR, with 

 complex signal processing techniques is available, which greatly reduces 

 the effective resolution cell size for airborne or satellite borne 

 radars. While providing the highest resolution (and sea clutter rejection) 

 capability of any radar technique, the SAR systems are comparatively 

 more complex and impose a significantly heavier data processing burden. 



40 



