910 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1956 



qiiency of the transmitter, the bandwidth of the intermediate frequenc}^ 

 amplifier need be only wide enough to take care of non-linearity in the 

 sawtooth modulation. A signal-to-noiso advantage is obtained by the 

 use of the narrow-band amplifier. 



Table I gives the distances, heights and effective areas of the reflectors 

 as well as the sa^^iiooth repetition rates that were used in the experiment. 

 The frequency excursion of the sawtooth modulation was 5.8 mc. 



It will be noted that three reflectors were used; this was done to pro- 

 vide a long path (comparison of reflections from Rl and 7?3) for wave- 

 lengths at which the absorption was relatively low, and a short path 

 (comparison of Rl and R2) for wavelengths at which the absorption was 

 high. The small reflector, Rl, was one foot on a side; the large reflectors, 

 7?2 and i?3, were about 5.6 feet on a side. Fig. 3 is a set of side-by-side 

 measurements sho^^ing the reflecting properties of the large reflectors 

 relative to the small one for the wavelengths at which they were used. 



J 



APPARATUS 



A schematic diagram of the wa^•eguide and electronic apparatus is 

 shown in Fig. 4; Fig. 5 is a photograph of the waveguide eciuipment so 

 mounted that it moves as a unit with the horn antenna. The antenna is 

 adjusted in azimuth and elevation by means of the milling ^-ise at the 

 bottom of the photograph. The box at the left contains the transmitting 

 tube, a low voltage reflex klystron* which has an average power output 

 of about 12 milliwatts over its 5.1- to 6.1-mm tuning range. About 2 mil- 

 liwatts of the klystron output is fed through a 6-db directional coupler 

 to a balanced converter that contains two wafer-type millimeter rectifier 

 units, t The remainder of the power proceeds into a 3-db coupler which 



% 



NEAR REFLECTOR 



FAR REFLECTOR 



Fig. 2 — Transmitted and reflected frequency-modulated signals. 



* This klystron was developed by E. D. Reed, Electron Tube Development 

 Department, Murray Hill Laboratory. 



t These millimeter-wave rectifiers were developed by W. M. Sharpless, Radio 

 Research Department, at the Holmdel Laboratory. 



