Chap4 analog communication_system

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  • 1. pengtao@bupt.edu.cn

2. 4.1 M(t) 1 0 f W 2 PM f 0 m(t)1 2 0 3 3. 4.1 fc fc W c t Ac cos 2 f c t c Ac f c c c(t)m(t) m(t) A M m t Ac FM m t f c PM m t c 4. 4.1 FDM FMAM 5. 4.1 AMFMPM FDM 6. 4.2 m(t)Ac DSB-SC AM AM SSB AM VSB AM 7. 4.2.1DSB-SC AM s t m t c t m t Ac cos c t c 8. 4.2.1DSB-SC AM m(t)s(t)4.2.2 m ( t ) s ( t ) Ac cos c t c Ac cos c t c 9. 4.2.1DSB-SC AM s(t)s t m t c t S fM f *C f Ac M f * f fc f fc 2AcM f fc M f fc 2 10. 4.2.1DSB-SC AM s(t) 11. 4.2.1DSB-SC AM s(t) 2W2W 12. 4.2.1DSB-SC AM s(t) f f c f f c M f m t e j 2 ft dt j 2 f tM f m t e dt M f * 13. 4.2.1DSB-SC AM S(t)S t M t Ac cos 2 f c t M t 0 R M E S t E M t Ac cos 2 f c t 0 RS t, t Ac E M t M t cos 2 f c t cos 2 f c t 2 2AcR M cos 2 f c cos 2 f c 2 t 2 1 S t Tp 2 fc 14. 4.2.1DSB-SC AM S(t)Ac R M 21T /2R S T / 2 R S t , t dt cos 2 f cpTpp 2 2Ac1R S PS f PM f * f fc f fc 2 2 2Ac PM f f c PM f fc 4A RM 0 2RS 0 c 2 15. 4.2.1DSB-SC AM 2 / 16. 4.2.1DSB-SC AM 17. 4.2.1 DSB-SC AM r t Ac m t cos 2 f c t c c t cos 2 ft r t c t f c f t c cos 2 f c f t c 1 Ac m t cos 2 2 1y t Ac m t cos 2 f c f t c 2 18. 4.2.1DSB-SC AM 19. 4.2.1DSB-SC AM 4.2.7 COSTAS 20. 4.2.2 AM AM DSB SC-AM AM 21. 4.2.2 AM 4.2.8s t Ac 1 m t co s 2 f c t m t 1 a m ax m t 1 m t mn t m t m ax m t s t Ac 1 a m n t co s 2 f c t 22. 4.2.2 AM AMs t Ac 1 am n t cos 2 f c t Ac cos 2 f c t am n t Ac cos 2 f c t Ac AcS f f fc f f c aM n f *f fc f fc 22AcAc f fc f fc aM n f f c aM n f fc 2 2 DSB SC-AM 23. 4.2.2 AM AMM t 0 R M S t Ac 1 M t cos 2 f c t E S t Ac cos 2 f c t 2 R S t , t Ac E 1 M t 1 M t cos 2 f c t cos 2 f c t 2Ac1 R M cos 2 f c cos 2 f c 2 t 2 S t 24. 4.2.2 AMAM 2 AcR S 1 R M cos 2 f c 22 P AcPS fM f f c PM f f c f fc f fc 4 2 2 AcAcRS 0 1 R M 0 1 a 2 R M 0 22 n RM 0 a RM n 0 2 2 a PM n 1 RM 0 1 a RM n 0 1 a PM n2 2 25. 4.2.2 AM AM DSB SC-AM AM1/2 26. 4.2.2 AM AM 04.2.10 27. 4.2.3 SSB AM 28. 4.2.3 SSB AM SSB AM 1 f fc 1H f sgn f f c sgn f f c 0 2 1 f fc1H f 1 sgn f f c sgn f f c 0 2 29. 4.2.3 SSB AM c t 2 Ac cos 2 f c t 1S f Ac M f fc Mf fc sgn f f c sgn f f c 2AcM f f c sgn f f c M f f c sgn f f c 2AcM f f c sgn f f c M f f c sgn f f c 2AcM f fc M f fc 2 AA c M f sgn f * f fc c M f sgn f * f fc 2 2 30. 4.2.3 SSB AM jsgn f ts t Ac m t cos 2 f c t Ac j j 2 f c t Ac j j 2 fctm t *e m t *e 2 t 2 t Ac Ac m t cos 2 f c t j2 m t e j 2 fct ej 2 fct Ac m t cos 2 f c t Ac m t sin 2 f c t 31. 4.2.3 SSB AM SSB AMs t s D SB SC A M t s t Ac m t cos 2 f c t Ac m t sin 2 f c ts SSB t Ac m t cos 2 f c tAc m t sin 2 f c t SSB AM4.2.13 32. 4.2.3 SSB AM SSB AMs S S B t Ac R e m t j m t e j 2 fct m t j m t m t jm t s S S B t Ac R e m t jm t e j 2 fct 33. 4.2.3 SSB AM SSB AMS SSB t Ac M t cos 2 f c t Ac M t sin 2 f c tE S SSB t Ac E M t cos 2 f c t Ac E M t sin 2 f c t R S t , t Ac E { M t cos 2 f c tM t sin 2 f c t 2 M t cos 2 f t M t sin 2 f c t }c S SSB t R S Ac R M cos 2 f cR M sin 2 f c 2 34. 4.2.3 SSB AM SSB AM R SSB PSSB f 0f fc P f 2 Ac PM f f c PM f fc f fc Ac2 PM f f c PM f fc f fc P f 0f fcP P Ac PM 2 c t 2 Ac cos 2 f c t 35. 4.2.3 SSB AM SSB AM4.2.15s t Ac m t cos 2 f c t Ac m t sin 2 f c t cos 2 f c t s t cos 2 f c t 1Ac m t cos m t sin 2 D SB A M 36. 4.2.3 SSB AM SSB AMs t A cos 2 f c t m t cos 2 f c t m t sin 2 f c t 2 a t cos 2 f c t t a t A m t m t 2 22m t t m t m t m t 2m t 2A m A 1 2 A 1A A Am t A 1 A m t A 37. 4.2.4 (VSB AM) VSB AM 38. 4.2.4 (VSB AM) m(t)=y(t)? 39. 4.2.4 (VSB AM)H(f) c t Ac cos 2 f c t r t s t AcS f Mf fc Mf fc Hf 2 c t cos 2 f c t r t s t 1r t c t s t Ac cos 2 f c t Sf fc S f fc 2AcAcM f 2 fc M f H f fc M f M f 2 fc H f fc 4 4AcY fM f H f fc H f fc 4 40. 4.2.4 (VSB AM) y(t)=m(t)H f fc H f fc f W 41. 4.3 m(t) s t Ac cos 2 f c t t t 1 d t 2 dt 42. 4.3.1 PMFMPM t K pm t K p 1 d t FM K f m t K f 2 dtPMFM d t dm t PM t K pm t Kp dt dt td t F M t 2 K m d 2 K f m t f dt 43. 4.3.1 PM m ax m ax t K p m ax m t p m ax K p m ax m t FM 1 d t f m ax m ax K f m ax m t 2dt f m ax m ax m t f K f WW W m t 44. 4.3.1 t 1 s t Ac cos 2 f c t t Ac cos 2 f c t Ac t sin 2 f c t AM 45. 4.3.2 46. 4.3.2 s t Ac cos 2 f c t sin 2 f m t J n s t Ac J n cos 2 f c nf m t n 98%99% 47. 4.3.2 Bc 2 1 f m Bc 2 1 WW 48. 4.3.2 49. 4.3.3 1. VCO 50. 4.3.3 2. s N B t Ac cos 2 f c t t y t Ac cos 2 nf c t n t s t Ac cos 2 nf f L o c t n t 51. 4.3.3 1. A.s t Ac cos 2 f t 2 K t m d f cds t Ac 2 f c 2 K f m t sin 2 f c t 2 Km d tdt f B. 4.3.7 52. 4.3.3 2. K f V C O K v K 11 tm t m t e t Ac Ao cos 2 f IF t 2 K m d ff1 Kv21 Kv Kv>>1e(t) 53. 4.3.3 3.G fG f K v 1 f W jf K v t m t f Kv G(f) 54. 4.4 N0nw t 2 B s t N0n t B 2n t n c t cos 2 f c t n s t sin 2 f c t Bnc t , ns t N0 2 55. 4.4.1 DSB-SC AM m t Ws t Ac m t cos 2 f c t c r t s t n t Ac m t cos 2 f c t c n c t cos 2 f c t n s t sin 2 f c t cos 2 f c t r t cos 2 f c t 11yo t Ac m t cos c n c t cos n s t sin 22 c c 0 11yo t Ac m t nc t 22 56. 4.4.1 DSB-SC AM 22 AcAc Po E m t 2 PM 4 4 1 1 N W Pn o E n c2 t N 0 2W 0 4 422 S Po Ac PM N o D SB Pn o 2 N 0W 2Ac PR PM 2 N Pni 2 0 2W 2 N 0W 2 2 S PR Ac PM N iD S B Pni 4 N 0W S PR S 2 N o D SB N 0W N iD SB 57. 4.4.2 SSB AM m t Ws SSB t Ac m t cos 2 f c t m t sin 2 f c t r t Ac m t n c t cos 2 f c t Ac m t n s t sin 2 f c t r t cos 2 f c t 11yo t Ac m t nc t 22 58. 4.4.2 SSB AM 2 Ac Po PM 4 1 1 Pn o E n c t N 0W24 42 S Po Ac PM N o SSB Pn o N 0W PR Ac PM2 Pni N 0W 2 S PRAc PM N iSS B Pni N 0W S PR S S N o SSB N 0W N iSS B N o D SB 59. 4.4.3 AM m t W m n t as A M t Ac 1 am n t cos 2 f c t r t Ac 1 am n t n c t cos 2 f c t n s t sin 2 f c t r t cos 2 f c t 1 1yo t Ac am t nc t 2 2 60. 4.4.3 AM1 PR Ac 1 a PM n2 2 22a PM n 1 a PM n21 2 2Ac a PM n 2 2 S Po 4 Ac a PM n PR N o AM Pn o1 Pn c 2 N 0W N 0W 4 DSB-SC AM 61. 4.4.3 AM r t Ac 1 am n t n c t cos 2 f c t n s t sin 2 f c t 2 Vr t Ac 1 am n t n c t ns t 2 1. y o t Ac am n t n c t 2. V n t n c t n s t 2 22 Ac n c t Vr t n t n t 1 2 1 am n t 2 2 nc t n s t c s2 Ac n c t Ac n c t V r t V n t 1 1 am n t V n t 1 am n t Vn t Vn t 2 62. 4.4.3 AM