532 



BELL SYSTEM TECHNICAL JOURNAL 



in detail and the performance as amplifier and modulator will be pre- 

 sented. Measurements of noise figure will be included with a discussion 

 of the performance of multistage amplifiers. 



Fig. 1. — Typical microwave repeater. 



INPUT 

 WAVEGUIDE. 



OUTPUT 

 WAVEGUIDE 



COAXIAL TO 

 - WAVEGUIDE 

 TRANSDUCER 



X/4 COAXIAL 

 TRANSFORMER 



PLATE CIRCUIT 

 RESONANT CAVITY 



INPUT CIRCUIT 

 RESONANT CAVITY 



Fig. 2. — Microwave circuit for 1553 triode. 



The Microwave Circuit 



The experimental circuit which has to date met with greatest favor 

 consists of cavities coupled to input and output waveguides, as shown in 

 Fig. 2. The grid, of course, is grounded directly to the cavity walls and 

 separates the input cavity from the output cavity. An iris with its orifice 



