258 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1953 



Matching Coax Line to the Ground-Plane Antenna. R. T. DeCamp-. 

 QST, 36, pp. 18-19, 120, 122, September, 1952. 



This article describes a method for predetermining antenna and matching- 

 stub dimensions for matching an}^ selected transmission line. Although applied 

 particularly to the ground-plane antenna, the curves are useful for half-wave 

 dipoles if allowance is made, when necessary, for the effect of ground on the 

 antenna characteristics. 



The Telephone System in National Defense. C. M. Mapes^. Military 

 Engr., 44, pp. 375-377, September-October, 1952. 



Multi-Element Directional Couplers. S. E. Miller^ and W. W. Mum- 

 FORD^ I.R.E., Prcc, 40, pp. 1071-1078, September 1952. 



It is shown that the backward wave in a directional coupler is related to the 

 shape of the function describing the coupling between transmission lines by the 

 Fourier transform. This facilitates the design of directional couplers for arbitrary 

 directivities over any prescribed frequency band. Tightly coupled directional 

 couplers are analyzed in simple terms, and it is shown that any desired loss ratio, 

 including complete power transfer between lines, may be achieved. The theories 

 are verified using waveguide models operating at 4,000, 24,000, and 48,000 mc, 

 and it is indicated that the work is applicable to many types of electrical and 

 acoustic transmission lines. 



Segregation of Two Solutes, with Particular Reference to Semiconductors. 

 W. G. Pfann^. Jl. Metals, 4, pp. 861-865, August, 1952. (Monograph 

 2020). 



The simultaneous segregation of two solutes during the directional solidifica- 

 tion of an ingot is treated mathematically on the basis of simplifying assump- 

 tions. Expressions are derived for the difference in concentration of two solutes, 

 and for the location and concentration gradient of a pn barrier formed in a semi- 

 conductor by the segregation of a donor and an acceptor. 



Nonsynchronous Time Division with Holding and with Random Sam- 

 pling. J. R. Pierce^ and A. L. Hopper^. I.R.E., Proc, 40, pp. 1079-1088, 

 September, 1952. 



There is a general type of system in which an indefinitely large number of 

 transmitters can have access to any of an indefinitely large number of receivers 

 over a medium of limited band-width. In these systems, signal-to-noise ratio goes 

 down as more transmitters are used simultaneously. This paper describes a 

 particular system which sends samples by means of coded pulse groups sent at 

 random times. The signal-to-noise ratio is good in the absence of interference 

 and the effect of interference is minimized by holding the previous sample if a 

 sample is lost. An experimental system worked satisfactorily and gave close to 

 the predicted signal-to-noise ratio might be used to provide communication 

 and automatic switching in rural telephony, or for other applications. 



^ Bell Telephone Laboratories 



* American Telephone and Telegraph Company 



