WAFER TYPE MILLIMETER WAVE RECTIFIERS 



1401 



satisfy the relation, Zd tan 2-Ki/\g = — coLa . (See Fig. 14.) The imped- 

 ance of the guide as a function of d/a is given by, 



Zd = 2407r - 



'/RU 



sni 



xd 



a 



(3) 



As a compromise between electrical and mechanical requirements, a 

 waveguide height, 6, of -5^ inch was chosen for the wafer unit ; the width 

 of the guide was taken to be the same as RG9SU. For b = 7.88 X 10~*, 

 a = 3.76 X 10"', d/a = | and X = 5.4 X 10~', (3) gives a value of 113 

 ohms for Zd (and R2). The appropriate value for L then becomes 3.38 X 

 10"^" henries. 



An estimate of the size of a contact spring having the inductance 

 given above can be made from the formula below which gives the in- 

 ductance of a straight thin wire of length *S as a function of its sidewise 

 position in the waveguide.* (See Fig. 15.) 



2S log, 



. ird 

 2a sm — 

 a 



r2«d 



\-y 



X 10 henries 



(4) 



For d/a = I and 2r2 = 2.28 X 10 ^ (0.9 X 10 ' inches), the length, S, 

 is found to be about 3.38 X 10" meters or about 0.013 inches. 



Since the spring must be so very small, the circuit from the base of 

 the spring to the waveguide wall is completed with a large low induc- 

 tance conical post as shown in Fig. 2 of the text. 



Bandwidth Calculation 



Having assigned values to all the parameters of the equivalent cir- 

 cuit, it is now possible to calculate the mismatch loss of a fixed-tune 



Y- 



a 



i 



'/////////////////////////////7777. 



I fSTRAIGHTA 

 •"V WIRE ] 



-ZT2 



V///////////} //////////////77777yA 



U-d-J 



I 



s 



I 

 I 



JL 



Fig. 15 — Thin wire in waveguide. 



* Private communication from S. A. Schelkunoff. 



