402 



THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1957 



how much power in a forward traveling TEu^ wave is transferred to a 

 forward travehngTEio'"' wave. Figure 12 shows that the coupling polari- 

 zation transfer loss remains under 1.1 db in the three bands except for a 

 small region in the 11-kmc band, while the transfer loss for the non- 

 coupling polarization exceeds 20 db in the three regions as shown in 

 Fig. 13. The return loss at Port P exceeded 23 db o\'er the 4-kmc band. 

 This result included the total reflection of 4-kmc signals from Taper 

 J-K after attenuation by twice the coupler insertion loss, and also in- 

 cluded the reflections from the rectangular guide port A^ or L which 



1.5 



1.0 



0.5 



2.5 



2.0 



If) 



S 1.5 



1.0 



0.5 



10 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 5.8 5.9 



3.0 6.1 6.2 6.3 6. 



1 



10.6 10.7 10.8 10.9 11.0 11.1 11.2 11.3 11.4 11.5 11.6 



FREQUENCY IN KILOM EGACYCLES PER SECONO 



11.7 



11.8 



Fig. 12 — Transfer losses in the array for coupling polarization. 



are separated from P by only the small transfer loss. Return loss for the 

 6- and 11-kmc bands exceeded 23 db at Port P. Cross polarization is the 

 ratio of the energy in the coupling polarization waves to the orthogonal 

 non-coupling polarization waves emerging at Port P. Cross polarization 

 figures are no lower than 20, 32 and 22 db in the 4,-6- and 11-kmc bands. 



CONSTRUCTION OF COUPLERS 



The coupler design requires that the coupling aperture exist in a 

 narrow wall of the rectangular guide that is common to the round 

 guide. The 4-kmc coupler consists of machined rectangular and round 

 sections. A two-piece rectangular guide was milled from brass and 



