Bolovac application for HF and microwave power measurement and standardization
Myron C. Selby · Journal of Research of the National Bureau of Standards Section C Engineering and Instrumentation · 1970
Th e bolom e tric voltage a nd c urre nt (BOLOYAC) sta ndard fo r frequ e nc ies to 18 GHz and higher, recen tl y deve loped a t th e Nationa l Burea u of Sta ndard s (N BS), ca n a lso be used to meas ure power, offe rin g th e fo ll ow ing a dvantages ove r a n umbe r of other me th od s in use toda y:0) It e limina tes:(a) the un ce rta inty res ultin g from neglecting te rminati on mi s mat c h (b) meas ure me nt of re Aec tion coe ffi c ien ts and co mputa ti ons us in g co mp lex e qu a t ions (c) " Limits-o f-erro r" c ha rt s, thus rende rin g defInitive resu lts (d ) use of imp eda nce charts (e) d e or af cal ibra tio ns of power meters (f) need of co rrec tion s s uc h as "effective efficiency" and "calibrat ion fac tor." (2) It cove rs a wid e frequency ra nge (0.5 MHz to 18 GHz or wid e r) (3) It should res ult in s ub sta ntial reduc tion of cal ib ratio n ti me in ma n y in sta nces (4) It ca n be app li ed to ca librate fee d-t hrough powe r meas urement me thod s for powe r le ve ls ra ngin g into kil owa tt s.[n meas urin g power, th e Bolovac (1) measure s the volt age ac ross a kn ow n res is tance compo ne nt of a give n load, or (2) meas ures th e voltage in any plane of a coaxia l lin e of kn own c ha racte ri s ti c impeda nce and kn ow n voltage di st ribution along the line , or (3) ab so rb s th e rf power as any oth er absorptiontype powe r mount does.[n th e fir s t tw o cases res is ta nce a nd voltage distribution meas ure me nts ma y be mad e se para tely o r th ese meas ure me nt s ma y be co mbin ed with th e power measu re me nt procedure.In the third case the rf power is absorbed in a spec ial di s k-type bolome tric detector of th e B olova c and is eq ua l to the dc-(o r af) bias-power su bstituted in that de tec tor; thi s bi as power is meas ure d with co nv enti onal power s ub stituti on brid ges.Any app rec iab le un acco unted for power losses occ ur outside th e Bolovac and ca n be determined emp loy ing con ven tion a l tec hniqu es as well as th e Bolova c itse lf.The Bolovac needs no 1' 1' calibrati on.A Bolovac ma y have a powe r ra nge of 20 dB or hi ghe r, d epe nd ing on acc uracy d es ired, and a max imum power a pproac hin g it s safe powe r dissipation.e.g., 0.5 W or hi ghe r.Th is paper is limited to th e appl ica ti on of the Bolovac to power meas ure me nts only and presents .anal yti ca l a nd practical as pects of thi s ap plica t ion.Key W ord s : Bo lometric power standards; Bolovac power measure me nts; ca lib rati on of power me ters; RF an d mi crowave power meas uremen t s; standard of power th ro ugh 18 GHz.