30 BELL SYSTEM TECHNICAL JOURNAL 



megacycles, and the 1N23B unit which was of such great importance 

 in 10,000 megac3xle radars because of its exceptionally good performance. 

 From this stage in the development the diversification in types was quite 

 rapid. The evolution of the coded units, of increasing power handling 

 ability for a given performance level at a given frequency, and of better per- 

 formance at a given frequency is graphically illustrated in Fig. 17. The 

 large improvements in calculated receiver performance are again evident, 

 especially when it is considered that the receiver performances given are 

 for the poorest units which would pass the production test limits. 



Extent of Manufacture and Utilization 



An historical resume of the development of crystal rectifiers would be 

 incomplete if some description were not given of the extent of their manu- 

 facture and utilization. Commercial production of the rectifiers by Western 

 Electric Company started in the early part of 1942 and through the war years 

 increased very rapidly. Figure 18 shows the increase in annual production 

 over that of the first year. By the latter part of 1944 the production rate 

 was in excess of 50,000 units monthly. Production figures, however, reveal 

 only a small part of the overall story of the development. The increase in 

 production rate was achieved simultaneously with marked improvements in 

 sensitivity, the improvements in process techniques being reflected in manu- 

 facture by the ability to deliver the higher performance units in increasing 

 numbers. 



The recent experience with the silicon rectifiers has demonstrated their 

 utility as non-linear circuit elements at the microwave frequencies, that they 

 may be engineered to exacting requirements of both a mechanical and elec- 

 trical nature, and that they can be produced in large quantities. The defi- 

 ciencies of the detector of World War I, which limited its utility and contribu- 

 ted to its retrogression, have now been largely eliminated. It is a reasonable 

 expectation that the device will now find an extensive application in commu- 

 nications and other electrical equipment of a non-military character, at 

 microwave as well as lower frequencies, where its sensitivity, low capacitance, 

 freedom from aging effects, and its small size and low-power consumption 

 may be employed advantageously. 



Acknowledgements 



Tlie development of crystal rectifiers described in this paper required the 

 cooperative effort of a number of the members of the staff of Bell Telephone 

 Laboratories. The authors wish to acknowledge these contributions and in 

 j)articular the contributions made by members of the Metallurgical group 

 and the Holmdel Radio Laboratory with wliom they were associated in the 

 development. 



