᫇Eᡔᴃҟඑ Edwin H. Armstrongࠡᣄᰃ᮴ඃᑓ᪁ᡔᴃՈথሩܜȥПϔˈҪথᯢ᮴ඃϹ᮴ඃ᫇ᡔᴃˈẝҪথሩՈݡᡔᴃᏆɴҷՈDŽ๒Ո᫇ᑓ᪁EˈEᆑDŽ᫇ˈݙˈএɴDŽᴀϔ༫ᡔᴃᡔᴃDŽᰃՈϔˈᅗӮ߽Ոˈẝᆑ᭄ᄫՈ᭄ᄫ᭄ˈẝDŽ᫇ᑓ᪁ỞˈԚ᭄ᄫ᮴ඃ᭄ˈ᮴ඃᑓ᪁᭄DŽ᫇Ո᳔ᰃབˈָDŽ>ᰃỞՈϹ@191819331940MPX191288-108MHz200kHz1960/ (stereo-mono blending) (soft mute) m(t) (RDS) (RBDS) (VCO)1 1 (VCO) ˖ՈˈṗᰃᅮՈˈṁˈ݊ᰃՈඃᗻ᭄DŽᔧ˗ᆩˈṗՈٰӮḍᓣ˖ₓDŽṗᰃय़ՈϹḰEˈ݊DŽᰃٰՈٰᓣˈՈࢳ˖ 1m(t) xFM(t) fc KVCO2 Hz/VKVCO× m(t) ˖ᅮՈℷˈẝᅮথɴDŽŊܜˈ᮴ˈՈᤃඃՈᗻˈ໐ȥࡼDŽ݊ˈ᫇ՈᏺᆑᯊӮˈඃᗻӮϬՈऩˈẝՈĽDŽ˖ɴ˖ᰃֵՈᤃˈᰃֵՈEDŽᇚᓣेথxFM(t) 1xFM(t) m(t) (single tone) Amfm ˈᏆˈՈᤃՈDŽПⒸՈ᳔ₓDŽₓˈᅗₓՈ↨᭄ˈỞDŽ᭄DŽẝˈṗՈ᭄ֲᰃ᭄᫇Ոߑϔ⓺᭄े˖ f = KVCO Amfmf (modulation index)f (significant sideband) nBessel [2, 3] ᓣẟˈेথɴ᫇ՈEˈϨ᭄བᓣՈߑ᭄˖ Ոᮕ᭄᭄ֲПՈ᭄ᜬDŽ 1Bessel 0 0.25 0.5 1.0 2.0 3.0 4.0 5.0 J0 1 0.98 0.94 0.77 0.22 -0.26 -0.40 -0.18 J1 J2 J3 J4 J5 J6 J7 J8 ᜬ˖ˈेՈ᫇DŽ0.02 0.05 0.12 0.24 0.44 0.58 0.34 -0.07 -0.33 0.03 0.11 0.35 0.49 0.36 0.05 0.02 0.13 0.31 0.43 0.36 0.03 0.13 0.28 0.39 0.04 0.13 0.26 0.01 0.05 0.13 0.02 1Bessel =1, =1, fm = 1kHzfc = 100kHz2 ˖ᆑDŽ᭄ϔ-˖ᅗ˗ԚՈ᳝ˈህ᭄ֲˈẝӮẟՈᏺDŽ᭄᫇ϔ˖ህₓϡˈᅗՈɴᕜࡼDŽϔˈ᭄ˈᮕ᭄ֲᏺᆑӮব˗Ԛ᭄ᰃEEՈ᭄ֵᙃֵোEɋˈ᫇EֵোᏺՈEɋDŽᇍDŽẝϾՈֵᙃֵোˈDŽḍˈϡՈᚙEֵোᏺˈ᫇EEՈ᳝EՈ᳔EEɋЎˈབEՈ᳔ֵᙃDŽEɋЎˈˈEᑓˈ᫇EֵোᏺˈᕜՈEDŽᆩDŽˈ᳔ՈEֵোৃϾEֵোˈDŽՈˈ᪂ᰃEֵᙃֵোߎˈẝϢᯊࣙEɋՈֵᙃֵো˗ߚֵোᯊˈᑨֵᙃֵোՈ᳔EɋЎՈDŽEֵোEɋˈᠡߎ᠔ՈֵᙃֵোDŽ᳔ՈEɋϾℸ 2=1,=1, fm = 1kHzfc = 100kHz = 0.251 = 58 ( (tone) =f / fm)fmBWFM » 2(+1)fm (Carson’s rule) 2(+1) [2, 3] (significant spectral tone) f75kHz75kHz/15kHz = 5200kHzBessel200kHz (-10dBc 15kHzBWFM = 2(5+1) × 15kHz = 180kHz (2 × 8 + 1)15kHz = 255kHz)fm E఼ˈᅗᰃϾᖂঞ݊ՈࣙDŽ (3) ˖ˈEֵোḰЎֵ᫇ো˖3 m(t) filter) Ͼࡃ˖ᅗߎֵᙃֵোDŽᰃ᫇EֵোՈˈEాˈֵᙃֵোՈֵো↨DŽЎњˈҹˈ᫇EᑓֵᙃֵোՈʌ᫇EEথDŽ᠔ՈEϾ8ՈϾЎDŽᰃ᫇Eথˈ߽ϢEాˈֵᙃֵোՈEɋˈҹঞ᫇EDŽ˖ՈʌḰࢿ˖ՈԢḰࢿ˖ (SNR) (pre-emphasis (de-emphasis filter)4Hde(f) Hpe(f) 4 (Pre-Emphasis) (De-Emphasis) ᯊⒸЎᰃDŽᯊⒸˈᅗ๒ঞϪЎˈ x50s/75s ϡՈᚙˈऩEֵোՈֵো↨Ў˖ BT (= BWFM)W (» fm)CNR (carrier-to-noise ratio) 200kHz (white noise) ↨Ў᫇EӴˈᅗˈЎֵᙃˈֵ݊োᏺˈᰃṁᰃՈEDŽˈẝϾֵো↨ֵᙃֵোᯬϢ᫇EӴՈEӴֵᙃֵোᏺˈ᫇EߎՈֵো↨ᑨE↨ṁ↨ߎDŽֵো↨ᮍˈ↨ᕜᯊᠡˈEℸE఼Ոṁ↨ˈᅗߎDŽՈߎɴEϾˈЎDŽ᫇EᰃᣛĽՈ᫇Eֵো↨ϟˈEֵোՈ᳔↨DŽབˈᰃ⍜EాˈҹEிֵো↨ՈᮍDŽՓՈ᫇Eˈṗߎֵো↨Ո˖ (SNR) 15kHz ( » 5.67) 27dB I (improvement factor) EɋЎᰃֵᙃֵোᏺЎՈՈᚙḰᢖˈEɋDŽḰՈᬍDŽؐՈᰃˈẝϾEℸE఼Ոṁ↨ᕜˈ᫇EӴǃֵᙃֵোᏺǃঞḰᢖEɋЎᯊˈ᫇EঞߎՈऩֵোˈᦤՈֵো↨ᬍDŽᰃˈᯊˈЎ᪩↨ᯊᕫֵো↨ՈՈ᫇Eֵো↨DŽˈЎEℸEˈẝЎ᮴DŽˈᇍߎՈֵো↨໐ˈএֵোՈֵো↨ᬍ↨ṁֵো↨ʌߎDŽϟЎ᫇E⚷EՈֵো↨ᬍ˖ fx = 1/2x2.1kHz3dB (corner frequency) 3dB15kHz13dB2.1kHz200kHz (x = 75s)27dB + 13dB = 40dB15kHz3dB40dB12dB17dB SNRMONO = 40 + CNR [dB] SNRSTEREO = 17 + CNR [dB] 0dBֵো↨DŽEᑓᑈҹᰃ᫇ǃEϹՈˈᔧᯊՈ᫇Eᑓˈᦤ݊ˈDŽࠄˈᅗᑈˈ๒ϢֵোՈϔᰃˈẝՈֵ᫇োՈᛇEՈѻDŽএEऩˈЎњϾֲˈֵোՈᯊֵࣙᙃˈDŽ┨ˈҹˈᅗDŽֵᙃֵোϾEՈՈֵোˈEএϢֵোDŽẝֵোՈ᫇EऩˈֵᙃEএোDŽɴՈߎDŽՈֵোEֵোϾˈᅗֵDŽ (CNR) —— 1961 (Subsidiary Communications AuthorizationSCA) 1961 (FCC) (MPX) 38kHz0-15kHz (L) (L-R) (R) (L+R)23-53kHz19kHzMPX MPX557kHz RDSRBDS ˖োՈ᭄ֵᙃֵোᰃऩEℷֵোˈEᑓՈֵᙃֵᰃֵোˈᅗՈEϢDŽՈ᳔↨ЎՈٰEɋˈDŽՈᰃDŽֵᙃֵোՈֵোথ 5MPX m(t) MPX100% (75kHz110% [5]6level breakdown) 5100%FCC)SCAMPX (modulation ˖ϾֵোПˈֵোՈ᫇Ոˈẝ↨EɋDŽՈˈEɋֵᙃֵোᤃˈᯊˈֵᙃֵোݙՈ᠔ֵֵোᤃˈҹՈEɋDŽ 6MPX 6102.67%MPX77.0025kHzKVCOf = KVCO AmMPX KVCO˖ᰃϬֵোՈˈ݊ՈᯊˈֵোՈᯊDŽℸᯊৃֵᙃֵোᜬ˖ 7MPX 7MPXRDS(t) MPXRDS/RBDSL(t) R(t) MPX ֵোՈᤃǃˈҹᰃˈߚՈ᫇DŽC0C1C2 (L(t) ± R(t)) ֵোǃֵো19kHzRDS˖ᰃՈὖˈৃֵᙃֵোߎˈֵোDŽֵᙃֵোӮϾEɋЎǃঞՈᏺϔϾEߎЎՈԢDŽᰃϾˈ࿁ֵᙃֵোֵোDŽẝϾֵࠡোՈEɋסˈҹֵোՈᴀֵোDŽֵোּϢּˈህEˈϢEDŽϹֵোϢֵো⏋ֵোễߎDŽֵোễߎՈೄDŽŊˈᆩˈֵ߭োֵোǃֵোˈ᠔োDŽ݊DŽℸᯊˈՈߎᰃֵোˈẝֵˈѻֵোᯊˈЎໄˈẝDŽՈֵᙃˈˈ؛ֵᙃՈ 8MPX 8MPXMPX1938m(t) RDS15kHz19kHz19kHz (LO) RDS57kHzQ23 (L+R) (L-R) RDS57kHz 3dBMPX (L-R) RDS (stereo separation) (L-R) (L+R) RDSMPX ()815kHzˈЎˈЎDŽẝϾ՟ՈএϢֵোᲳՈᤃϢּˈẝՈDŽЎњEᑓՈ⚷ˈߎɴՈ᫇E᫇ϢऩঞḳˈՈǃDŽ1%-46dB NXPCCCAtomic/TigerHERO ˖ᰃՈ᫇EĽˈEֵোˈEṗߎּߎՈℷˈEṗߎֵোՈ᳔ߎDŽEǃেEǃऩˈẝֵোEՈᮍDŽẝϾ՟ˈEֵোṗˈՈএՈএֵো↨DŽབℸՈᏺˈˈऩ˗ֵּো↨ᇚDŽऩֵো↨ՈᰃЎᅗˈএֵোህDŽEֵোϢˈՈ⚷EህˈѻϢऩDŽϢऩˈẟEՈֵো↨DŽབˈএЎՈˈ⚷Eֵো↨ϢEߎɴՈ᫇DŽℸˈএՈˈᰃ≵ᯊՈDŽЎEֵো↨᠔Ո᳔EṗˈℸЎEֵো↨᠔ՈEֵোDŽˈᔧՈEṗᯊˈాˈϨEṗߎ 9 9X0dBY9RF330dB55dB15kHz60dBMPX53kHz RF2RF3RF0RF1“”1dB ՈϟDŽℸˈᔧEֵোᯊˈ⚷Eṗߎߎˈా⚷EṗߎDŽᔧߎɴᯊˈϡ⚷Eˈ໐↨᳔Eṗߎˈ᠔DŽᡅEֵোՈాˈϔϾᰃ߽ᯊEాDŽᰃࣙՈ᫇EĽˈℸᯊEాˈব↨᳔EṗߎˈẝᦤՈѻDŽ (RF0) 6dB6dB1014dB20dB 10˖