TARGETS FOR MICROWAVE RADAR NAVIGATION 



855 



figure. For a reflector having the dimensions shown in the figure the 

 effective area for different angles of incidence 6 can be calculated by the for- 

 mula. 



A eff =2 ah sin (45° - 6) 



where d is always considered positive and less than 45°. 



Figure 3 shows the polarization of the reflected ray for differently polarized 

 incident rays. For our purpose, the incident rays may be assumed to enter 

 the left side of the reflector shown in the figure and the reflected rays may be 

 assumed to emerge from the right. It is apparent that if the incident ray 

 is polarized either parallel or perpendicular to the line of intersection of the 

 two surfaces the reflected ray will be polarized in the same plane as the inci- 



Fig. 3 — Polarization effect in a dihedral reflector. 



dent ray. If the incident ray is polarized at an angle of 45° to the line of 

 intersection, the reflected ray will be polarized perpendicularly to the 

 incident ray. In the latter case the signal received back at the radar will 

 not ordinarily be accepted by the same antenna which launched the incident 

 radiation. 



Trihedral Cornek Reflector 

 Assume that three reflecting surfaces AOB, AOC, and BOC are placed so 

 as to form the right-angled corner illustrated in Fig. 4. In general, electro- 

 magnetic waves, upon striking an interior surface of the device, will undergo 

 a reflection from each of the three planes and return in a direction parallel to 



