. The Bell System technical journal . IN OUT ^^ (D=3 1 1 LU ) /^ ^ y \ \ v,^ TR/ ^NSF ER L OSS ^ X^ V FREQUENCY IN K ILOMEGACYLES Fig. 6 — Transfer loss of 6-kmc coupler. AN EXPERIMENTAL DUAL POLARIZATION ANTENNA FEED 399 the 11-kmc band; thereby low transfer loss is obtained in the 6-kmc bandand a high transfer loss in the 11-kmc band. Measurements have shownthat when the cut-off frequencies of higher modes occur in the band ofinterest an uncontrolled increase of coupling may result. Special precau-tions are recjuired in selecting the round guide size to av
. The Bell System technical journal . IN OUT ^^ (D=3 1 1 LU ) /^ ^ y \ \ v,^ TR/ ^NSF ER L OSS ^ X^ V FREQUENCY IN K ILOMEGACYLES Fig. 6 — Transfer loss of 6-kmc coupler. AN EXPERIMENTAL DUAL POLARIZATION ANTENNA FEED 399 the 11-kmc band; thereby low transfer loss is obtained in the 6-kmc bandand a high transfer loss in the 11-kmc band. Measurements have shownthat when the cut-off frequencies of higher modes occur in the band ofinterest an uncontrolled increase of coupling may result. Special precau-tions are recjuired in selecting the round guide size to avoid this condi-tion. The design process is shown in Appendix I. Figs. 6 and 7 show thetransfer and insertion losses in the G-kmc; band. 16 UJ mo UJ o 14 - 12 tnO zo I-cr UJ If) z 10 ROUND GUIDEINSERTION LOSS / -^ ^ ^ ^ / N V IN OUT ■— — 1 1 Fig. 7 FREQUENCY IN KILOMEGACYLES - Insertion loss of 6-kmc coupler. SLOT SIZE= X SPACING= POST DIA = GUIDE SIZE= X COUPLING ARRAY CONSISTSOF 38 FULL SIZE SLOTS REDUCED SIZE SLOTS Fig. 8 — 4-kmc coupler sketch. 400 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1957 56 48 _] UJ 5 40u UJ Q z 32 o - 24q: LUll_10 z 16< tr (4) L , (6) t 00 / ft V A ft , 1/ V II hi 1 IN 1 .{II 1 1 1 I / mouT v FREQUENCY IN Kl LOMEGACYCLES PER SECOND Fig. 9 — Transfer loss of 4-kmc coupler in 4-, 6- and 11-kmc bands. in _i - bU LUQ ? ^ in<n 3 3a: -2 < sr I- a^ TiT II iii 1 OUT 1 \ I V — 3500 3700 3900 4100 4300 FREQUENCY IN MEGACYCLES PER SECOND 4500 Fig. 10 — Transfer loss of 4-kmc coupler in 4-kmc band. 4-KMC DESIGN The use of periodic loading in the rectangular guide is not suitable foruse in a 4-kmc coupler design. When the phase constants are made equalin the 4-kmc band, the resulting difference of phase constants in theG-kmc band is too small to create a sufficiently high transfer loss in thatband. Perio
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