5-6 MM ATTENUATION FOR THE CIRCULAR ELECTRIC WAVE 1119 



»» ' • " K>if 





.^^. .^W- -^P- .I^P. 



Fig. 2 — Waveguide portion of millimeter wave measuring set. 



MEASURING PROCEDURE 



With straight runs of round, TEoi waveguide lines whose length lies 

 in the 100-200 ft range, it is convenient to make attenuation measure- 

 ments on a round trip basis. This method has the advantage of conven- 

 ience in that the attenuation can be measured directly by using a wave- 

 guide switch but has the disadvantage of requiring a careful impedance 

 match of the measuring equipment to the line. Fig. 1 shows an overall 

 view of the lines; Fig. 2 shows the arrangement of the 5-6 mm measuring 

 set, and Fig. 3 shows a block diagram of the set-up employed. 



This measuring set makes use of two klystrons developed by these 

 laboratories.* The double detection receiver features a separate beating 

 oscillator klystron which is frequency modulated and a narrow band 

 (1.7 mc at 60 mc) IF ampHfier. The resulting IF pulses are detected 

 wuth a peak detector and then amphfied to provide the usual meter 

 indication. This method with its circuitry has been developed by W. C. 

 Jakes and D. H. Ring,^ and provides a greater amplitude stability than 

 is possible with a cw beating oscillator. 



In the waveguide schematic of Fig. 3 about a tenth of the power is 



^ E. D. Reed, A Tunable, Low Voltage Reflex Klystron for Operation in the 

 50-60 Kmc Band, B.S.T.J., 34, p. 563, May 1955. 

 * W. C. Jakes and D. H. Ring, unpublished work. 



