1386 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1956 



The wafer unit and holder were developed primarily for use as the 

 first converter in double detection receivers operating in the 4- to 7-mil- 

 limeter wavelength range. In order to check the practicability of the 

 design and to supply rectifiers for laboratory use, a pilot production 

 group of one hundred units was processed and measured. Performance 

 data obtained with this group are presented. A balanced converter using 

 wafer rectifiers is also described. 



Methods of estimating the values of the various circuit parameters of a 

 point-contact rectifier are outlined in an appendix. These calculations 

 proved useful in the design of the wafer unit and in predicting the broad- 

 band performance of the converter. 



DESCRIPTION OF WAFER UNIT AND HOLDER 



Fig. 1 is a drawing of the wafer type rectifier. The unit is made from 

 stock steel iV-inch thick and is gold plated after the milling, drilling and 

 soldering operations are completed. To allow for the transverse impe- 

 dance matching adjustment, the section of waveguide contained in the 

 wafer is made wider than the RG98U input guide to the holder. By 

 making the wafer thin {-^ inch), the short sections of unused guide on 

 either side will remain "cut-off" over the operating range of the recti- 

 fiers. The silicon end of the rectifier consists of a copper pin on which the 

 silicon is press mounted, the assembly held in place with Araldite ce- 

 ment which also serves as the insulating material for a quarter-wave- 

 length long high frequency bypass capacitor. The pin serving as the inter- 

 mediate frequency and direct current output lead is also cemented in 

 place with Araldite cement. A soft solder connection is made between this 

 pin and the pin holding the silicon wafer. A nickel pin with a conical end 

 on which a pointed tungsten contact spring is welded is pressed into 

 place from the opposite side of the guide at the time of final assembly. 



DC AND IF 

 OUTPUT 



0.031 "x 0.234^ 

 WAVEGUIDE 



0.063" "BRIGHT GOLD" 

 STEEL WAFER 



BORON- doped/ 

 SILICON 



-CONTACT SPRING 



Fig. 1 — Millimeter-wave wafer unit. 



