Effect of the Quadrature Component in Single 

 Sideband Transmission 



By H. NYQUIST and K. W. PFLEGER 



A PREVIOUS article ^ gives an analysis of single sideband trans- 

 mission. Since that article was written this subject, particularly 

 in its application to picture transmission and television, has assumed 

 considerable importance. For this reason it now seems desirable to 

 amplify the previous theoretical treatment and to indicate certain 

 experimental results which have been obtained in the meantime. The 

 present article gives experimental evidence that, for a given bandwidth, 

 single sideband transmission is distinctly superior to double sideband 

 in picture transmission. ^ It also gives a theoretical discussion which 

 indicates that this is not inconsistent with the observed fact that 

 oscillograms with single sideband transmission show considerable 

 distortion. 



As described in the previous article distortion to be considered in 

 single sideband transmission as compared with double sideband 

 transmission arises in three ways. 



1. There may be present a slowly varying in-phase component due 

 principally to the inaccurate location of the carrier frequency with 

 respect to the edge of the filter characteristic. 



2. The edge of the filter characteristic where the carrier is located 

 may be so designed that there is a net distortion due to failure of the 

 vestigial sideband to be accurately complementary to the principal 

 sideband. 



3. There is present a quadrature component which results in con- 

 siderable distortion of the envelope of the received wave under ordinary 

 conditions. 



By in-phase component is meant a component whose carrier is in 

 phase with the steady state carrier; by quadrature component is meant 

 a component whose carrier is in quadrature with the steady state 

 carrier. In some of the theoretical work in the present article, idealized 



1 rraH5. yl. /.£.£., Vol. 47, p. 617, April 1928. 



^ A paper by Goldman: "Television Detail and Selective-Sideband Transmission," 

 Proc. I. R. E., Vol. 27, pp. 725-732, Nov. 1939, dealing with the same subject, 

 has been published since our manuscript was sent to the printer. While the two 

 papers reach similar conclusions there is considerable difference in method between 

 them. 



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