MEASUREMENT OF IMPEDANCE MISMATCHES 



447 



calibrated detector and indicator, a termination Z', a piece of waveguide 

 EF (the flange E of which is to be part of the couphng BE to be measured) 

 and a termination Z inserted into the waveguide piece EF so that the 

 reflection coefl&cient of the couphng BE alone will be measured. In addi- 

 tion a fixed shorting plate should be available for attachment to flange B. 

 Four cases are considered : 



I. Termination Z and Z' perfect, only one coupling on hybrid junction. 

 II. Termination Z imperfect, termination Z' perfect, only one coupling 

 on hybrid junction. 



III. Termination Z perfect, four couplings on hybrid junction. 



IV. Termination Z imperfect, four couplings on hybrid junction. 



TERMINATION Z 



\AA/ 



rr 



Fig. 1 — Block schematic for cases I and II. 



It is assumed in all cases that: 



1. The hybrid junction has the properties as defined in the discussion of 



case I. 



2. The signal oscillator absorbs all the power reflected through arm A of 



the hybrid junction. 



3. The calibrated detector and indicator absorb all the power transmitted 



through arm C of the hybrid jimction. 



4. The oscillator output and frequency are not changed when the hybrid 



junction arm B is short-circuited. 



5. The attenuation of waveguide may be neglected. 



I. Termination Z and Z' Perfect, Only One Coupling on 

 Hybrid Junction 



In this case the hybrid junction, termination Z' and termination Z, 

 as shown in Fig. 1, are all considered to be perfect. This means for the 

 hybrid junction that its electrical properties are such that the energy from 



