1394 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1956 



Table I — Comparison of Low-Power Characteristics of 

 Cartridge-Type and Wafer-Type Rectifiers 



Test Conditions 



power 



Frequency 



Beating oscillator 



level 



Noise reference resistor 



Conversion loss 



Noise ratio 



Nominal IF impedance 



range 



JAN Specifications for Cartridge-Type 

 Rectifiers 



IN26 



23984 mc 



1.0 milliwatts 

 300 ohms 

 8.5 db (max) 

 2.5 (ma.x) 



300 to 600 ohms 



IN53 



34860 mc 



1 .0 milliwatts 

 300 ohms 

 8.5 db (max) 

 2.5 (max) 



400 to 800 ohms 



Performance of 



Wafer-Type 



Rectifiers 



55500 mc 



1.0 milliwatts 

 300 ohms 

 8.5 db (max)* 

 2.2 (average) t 



250 to 500 ohms 



* Limit arbitrarily set on basis of 100 per cent yield as explained in the text, 

 t Limit not set. Actually in more recent production A'^r has averaged 1.7 times. 



In practice, the beating oscillator noise sidebands can be eliminated 

 by the use of a matched pair of rectifiers in a balanced converter ar- 

 rangement described later. The resulting overall noise figure of 13 db 

 on an average compares quite favorably with the figures obtained at 

 longer wavelengths. 



In Table I it is seen that a high percentage of the group of one hundred 

 units would be able to pass low-power JAN specifications similar to those 

 set down for the commercially available IN26 and IN53 rectifiers used 

 at longer wavelengths. 



effect of VARYING THE BEATING OSCILLATOR POWER 



When the optimum over-all receiver noise figure is desired, it may 

 well turn out that a beating oscillator drive of one milliwatt (correspond- 

 ing to a dc rectified current for different wafers of from jq to Ij milli- 

 amperes) is too large. Fig. 11 shows the effect on the performance of a 

 typical unit as the beating oscillator drive is varied above and below the 

 one milliwatt level as indicated by the change in the dc rectified current. 

 It is seen that the value of N^. tends to increase rapidly for a beating 

 oscillator drive much in excess of one milliwatt; with reduced drive, the 

 over-all noise figure of the receiver, A^'rec for the example taken, im- 

 proves, reaching a minimum value near a rectified current of about ^u 

 m.illiampere corresponding to a drive of about f of a milliwatt. 



A BALANCED CONVERTER FOR WAFER UNITS 



A broad-band balanced first converter has been developed which makes 

 use of a pair of wafer- type millimeter-wave rectifiers. This converter 



