650 



BELL SYSTEM TECHNICAL JOURNAL 



paper .^ This quantity will be called 7. These measurements were sufficient 

 for an evaluation of the four-pole parameters of the structure. All measure- 

 ments were made at a frequency of 4063 megacycles. 



The equivalent circuit of the passive triode structure is shown in ¥\g. 2. 

 The desired parameters are yn, yn, and y22. The following equations indi- 



INPUT V,| 



yi2 



yi.-yi2 



y22-y.2 



1^2 >62W 



Fig. 2 — Equivalent passive circuit of a triode. 



Fig 



PARALLEL-WIRE 

 GRID 



3 — Types of grids used in the measurements. 



CROSS-LATERAL 

 GRID 



cate the relation between these parameters and the measured quantities 

 Y and 7 : 



,„ = 1- + J>^^ « Y (1) 



62^22 + 1 



yi2 



y22 



7 



1 + 



1 



62 V. 



(2) 



where the number 62 represents the output terminating impedance. For 

 all cases to be described here the second term on the right side of Equation 1 

 is small in comparison with F. This is a result of the small values encountered 

 for yi2 . To a good approximation yn is equal to the measured input ad- 

 mittance F. This was verified by observing the variation m input admittance 

 as the output spacing was varied while keeping the input spacing fixed. 

 Only a slight variation in admittance was observed, which indicated that 

 the fractional term in Equation 1 was small in comparison with F. 



Suppose, then, that for a given input and output spacing Si and .S'2 , 



' "A Method of Measuring Phase at Microwave Frequencies," S. D. Robertson, Bell 

 System Technical Journal, Vol. XXVIII, No. 1, pp. 99-103, January 1949. 



