Propai>ati()n Studies at Microwave 



Frequencies by Means of Very 



Short Pulses 



BY O. E. DE LAXGE 



(Maimscript roceived March 27, 1951) 



Microwave pulses with a duration of about 0.003 microseconds were trans- 

 mitted over a 22-mile path from Murray Hill, .V. ./., to Holmdel, iV. ./., 

 in order to deterrninc the effects of the transmission medium upon siich 

 puhes. During '\fading'' periods multi-path transmission effects with path 

 differences as great as 7 feet were observed, as well as some other effects. 

 A microwave frequency of 4000 megacycles was employed. 



INTRODUCTION 



This experiment was set up with two main purposes in \\e\\: First, 

 a.s a means of studying microwave propagation, especially with regard to 

 multi-path transmission effects and second, to determine the effect of 

 a transmission path upon the shapes of very short pulses, particularly 

 to learn what restrictions might be imposed upon minimum pulse length 

 or spacing between pulses by distortions produced in the transmission 

 medium. 



In regard to multi-path transmission the pulse method seems to be 

 the most straightforward way of studying such effects. For example, if 

 there is transmission by more than one path, and if the pulses are suffi- 

 ciently short in comparison to the path length differences involved, then 

 there will be received a separate pulse for each path. Under these condi- 

 tions the number of paths in\'olved, path length differences and other 

 information become directly evident. If pulse duration is too great with 

 respect to the path differences involved, the pulses received via the various 

 paths will o^'erlap in time and the resultant multi-path effect will be 

 pulse distortion rather than reception of indi\4dual pulses. This situa- 

 tion is much more difficult to anatyze. 



TRANSMISSION PATH 



The transmission path is the same as that used by A. B. Crawford fen* 

 microwave propagation studies by means of the frecjuency sweep method, 



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