128 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1956 



GLOSSARY OF SYMBOLS 



a Mean radius of inner helix 



h Mean radius of outer helix 



h Capacitive coupling coefficient 



Bio, 20 shunt susceptance of inner and outer helices, respectively 



Bi, 2 Shunt susceptance plus mutual susceptance of inner and outer 



helices, respectively, Bm + Bm , Boo + B^ 

 Bm Mutual susceptance of two coupled helices 

 c Velocity of light in free space 



d Radial separation between helices, h-a 



D Directivity of helix coupler 



E Electric field intensity 



F Maximum fraction of power transferable from one coupled helix 



to the other 

 F(ya) Impedance parameter 



7i, 2 RF current in inner and outer helix, respectively 

 K Impedance in terms of longitudinal electric field on helix axis 



and axial power flow 

 L ]\Iinimum axial distance required for maximum energy transfer 



from one coupled helix to the other, X6/2 



Axial power flow along helix circuit 



Radial coordinate 



Radius where longitudinal component of electric field is zero for 



transverse mode (about midway between a and b) 



Return loss 



Radial separation betw^een helix and adjacent conducting shield 



Time 



RF potential of inner and outer helices, respectively • 



Inductive coupling coefficient 



Series reactance of inner and outer helices, respectively 



Series reactance plus mutual reactance of inner and outer helices, 



respectively, Xio + Xm , X20 + Xm 



Mutual reactance of two coupled helices 



Axial coordinate 



Impedance of inner and outer helix, respectively 



Attenuation constant of inner and outer helices, respectively 



General circuit phase constant; or mean circuit phase constant. 



Free space phase constant 



Axial phase constant of inner and outer helices in absence of 



coupling, V^ioXio , VBioXio 



