1416 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1956 



version loss exceeding 20 db. We thus find that, for the greatest band- 

 width, the preferred nonhnear element for modulators is a nonlinear; 

 capacitor while the preferred nonlinear element for converters is a non- ■ 

 linear resistor. In modulators, the nonlinear capacitor device should ! 

 have as little resistance as possible, so that an external resistor could 

 be used to control the value of x. It could be connected across the non- 

 linear capacitor or across the input and output terminals. 



CONCLUSIONS 



The results given above show that the preferred nonlinear element 

 for use in modulators is a pure nonlinear capacitor while the preferred 

 nonlinear element for use in converters is a pure nonlinear resistor. By 

 shunting the nonlinear capacitor or the terminals of a nonlinear capacitor 

 modulator with an appropriate resistance, an impedance match, ade- 

 quate bandwidth, and a performance superior to that of a nonhnear 

 resistor modulator can be obtained. Nonlinear capacitance effects are 

 not useful in converters because of stability and bandwidth limitations 

 and also because there is no evidence that an improved noise figure would 

 result from a reduction in conversion loss. 



ACKNOWLEDGMENT 



The writer is indebted to H. E. Rowe for many helpful suggestions in 

 the mathematical analysis and to R. S. Ohl for supplying the bombarded 

 silicon rectifiers used in the experiments which lead to the ideas presented 

 here. 



REFERENCES 



1. H. C. Torrey and C. A. Whitmer, Crystal Rectifiers, 15, Radiation Laboratory 



Series, McGraw-Hill, New York, 1948, Chapter 13. 



2. L. C. Peterson and F. B. Llewellyn, The Performance and Measurement of 



Mixers in Terms of Linear Network Theory, Proc. I.R.E., 33, July, 1945. 



