Question

5. An O- type travelling wave tube (TWT) operates at 10 GHz. The slow –wave structure has a pitch angle of 0.8o. Determine the propagation constant of the travelling wave in the tube. Assume that the tube is lossless

Answer 1

As we are given tube is losless so =0

the propogation constant is given by

=+j=j -----------as =0 in this case----------------------------------------(a)

now we need to find only which is given as

=-------------------------------------------------------------------------------------------------------(1)

where =wavelength of wave=

but we are given pitch=0.8 so effective wavelength becomes e=0.03*0.08=0.0024--------(2)

so from (1) and (2)

=e==2617.99

so from equation (a) we get propogation constant as

=+j=j=j2617.99

------------------------------------------------------------

Method 2

if we ignore pitch angle then =0.03

then ===209.44

=+j=j=j209.44