AN EXPERIMENTAL DUAL POLARIZATION ANTENNA FEED 405 



kmc band is due to an appreciable coupling of TEii° waves to TEso^ 

 waves in the 4 kmc couplers in the vicinity of the TEso^ cutoff. The TEso^ 

 cutoff might be moved above the 11 -kmc band by using ridged rectangu- 

 lar guide. 



SUMMARY 



A combination of three pairs of coupled-wa\'e transducers has suc- 

 cessfully permitted six distinct bands to be fed from individual TEio'"' 

 rectangular waveguides into the two orthogonal polarizations of TEn^ 

 waves in a multi-mode round waveguide. The resulting structure en- 

 abled low transfer loss values to be obtained simultaneously over two 

 500-mc wide bands and one band 1000-mc wide distributed over a 3-to-l 

 frequency interval. 



ACKNOWLEDGMENT 



A substantial portion of this work was carried out as a joint project 

 with H. E. Heskett and S. E. Miller. 



Appendix I 



DESIGN OF 6-KMC COUPLER 



A rectangular guide size is chosen and a reasonable value selected for 

 the phase constant such as /3° = I.Stt/Xo . The resulting round guide 

 size must prevent modes from cutting-off within the 6-kmc band and 

 preferably the cut-off frequencj^ should be above the 6-kmc band. The 

 thickness of the dielectric (polystyrene) strip is determined^ from (11), 

 (12), and (13) where Ki and K2 are transverse wave numbers of the air- 

 filled and of the dielectric sections of the guide. 



Cot K^ = -~ cot IU{a - d) (13) 



In the above equations Er is the relative dielectric constant and d is the 

 slab thickness. After soh-ing for d the equations are resolved for Ki and 

 Ki values at the 6-kmc band edges and also at the lower end of the 11-kmc 

 band. Resulting rectangular-guide phase constants should cause a very 



