Abstracts of Technical Articles from Bell System Sources 



Theorv of the Detection of Two Modulated Waves by a Linear Rectifier.^ 

 Charles B. Aiken. In this paper there is developed a mathematical 

 analysis of the detection, by a linear rectifier, of two modulated waves. 

 Solutions are obtained which are manageable over wide ranges of values 

 of carrier ratio and degrees of modulation. These solutions are of 

 greater applicability and are more convenient than those previously 

 obtained, and give a full treatment of the action of an ideal linear 

 rectifier under the action of two modulated waves. 



The development is first made in terms of the derivatives of zonal 

 harmonics of an angle which is directly related to the phase difference 

 between the carriers. As these derivatives are tabulated functions the 

 solution is convenient. 



The solutions are limited by the condition that K < (I - M)j 

 (1 + m), K being the carrier ratio, M the degree of modulation of the 

 stronger carrier, and m that of the weaker. Two methods of attack 

 are developed, one of which is applicable when K is small and M and m 

 large, and the other when M and m are small and K large. 



The cases of identical and of different programs are both considered 

 and a number of curves are given showing the magnitudes of various 

 output frequency components under typical operating conditions. 



In the latter part of the paper the phase angle between the carriers 

 is set equal to tit so that a beat note exists. There is then considered 

 the effect of a noise background on the reception of signals on shared 

 channels, and it is shown that much less "flutter" effect and much less 

 distortion of the desired signal will result from the use of a linear 

 rectifier than from the use of a square-law rectifier under the same 

 conditions. 



Finally, brief consideration is given to heterodyne detection and to 

 "masking" effects. 



Thermionic and Adsorption Characteristics of Thorium on Tungsten} 

 Walter H. Brattain and Joseph A. Becker. Variation of thermi- 

 onic emission of tungsten with surface density of adsorbed thorium. — 

 Thorium was deposited on a tungsten ribbon by evaporation from a 

 thorium wire. A study was made of the dependence of the thermionic 



1 Proc. I. R. E., April, 1933. 

 •^Phys. Rev., March 15. 1933. 



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