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THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1954 



has a six-peaked variation with angle Avhich indicates the presence 

 of TE31 . 



The transfer loss of the TMn transducer was derived by (1) calibrat- 

 ing the receiving probe on a known amount of power in the TEn wave, 

 (2) inserting this same amount of power in the rectangular waveguide 

 of the coupled wa^•e transducer and, with the probe at the transducer 

 output, observing the change in the receiver response, and (3) correcting 

 the observed loss using the theoretical difference in the rachal electric 

 field at the wall for the TEu versus TMu waves in the known wa^'eguide 

 diameter. (This technique is described in more detail by Aronoff.') The 

 result gave a transfer loss of about 25 db to the TMn wave. The insertion 

 loss for the rectangular guide of the transducer was less than 0.2 db. 



Coupled-wave devices of the type shown in Fig. 39 were built for 

 several of the modes in 2" round w^aveguide. The one built for the TE31 

 mode in 2" waveguide (mechanically similar to the TMu model of Fig. 

 39) has several characteristics worthy of mention. Fig. 41 shows the 



So 



a: J -60 



UJ(D 

 ?Q -64 



^ ^ , 



Zo 



RECEIVER 



80 120 160 200 240 280 



AZIMUTHAL ANGLE IN DEGREES 



Fig. 41 — Distribution of radial electric field at the guide wall for the forward 

 and V)ackward waves of TEiqCI to TE31O coupled wave transducer. 



