{"id":4318,"date":"2025-07-09T00:00:00","date_gmt":"2025-07-09T00:00:00","guid":{"rendered":"https:\/\/lp.szlogic.cn\/glossary\/clock-and-data-recovery-in-modern-communication-systems\/"},"modified":"2026-06-22T09:09:49","modified_gmt":"2026-06-22T09:09:49","slug":"clock-and-data-recovery-in-modern-communication-systems","status":"publish","type":"post","link":"https:\/\/resourceslp.szlogic.cn\/vi\/glossary\/clock-and-data-recovery-in-modern-communication-systems","title":{"rendered":"\u0110\u1ed3ng B\u1ed9 H\u00f3a \u0110\u1ed3ng H\u1ed3 v\u00e0 D\u1eef Li\u1ec7u l\u00e0 G\u00ec trong Truy\u1ec1n Th\u00f4ng Hi\u1ec7n \u0110\u1ea1i"},"content":{"rendered":"
\"What<\/figure>\n\n\n\n

Trong h\u00e0nh tr\u00ecnh kh\u00f4ng ng\u1eebng ngh\u1ec9 nh\u1eb1m \u0111\u1ea1t \u0111\u01b0\u1ee3c t\u1ed1c \u0111\u1ed9 truy\u1ec1n d\u1eef li\u1ec7u nhanh h\u01a1n, n\u01a1i h\u00e0ng terabit th\u00f4ng tin ch\u1ea3y qua c\u00e1p quang m\u1ed7i gi\u00e2y, vi\u1ec7c duy tr\u00ec t\u00ednh to\u00e0n v\u1eb9n c\u1ee7a t\u00edn hi\u1ec7u l\u00e0 y\u1ebfu t\u1ed1 then ch\u1ed1t. M\u1ed9t c\u00f4ng ngh\u1ec7 quan tr\u1ecdng ho\u1ea1t \u0111\u1ed9ng \u00e2m th\u1ea7m \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o \u0111\u1ed9 tin c\u1eady n\u00e0y l\u00e0 <\/span>CDR, hay Kh\u00f4i ph\u1ee5c \u0110\u1ed3ng h\u1ed3 v\u00e0 D\u1eef li\u1ec7u<\/strong><\/span>. B\u00e0i vi\u1ebft n\u00e0y \u0111i s\u00e2u v\u00e0o kh\u00e1i ni\u1ec7m CDR l\u00e0 g\u00ec, l\u00fd do v\u00ec sao n\u00f3 kh\u00f4ng th\u1ec3 thi\u1ebfu trong c\u00e1c h\u1ec7 th\u1ed1ng <\/span>quang h\u1ecdc<\/strong><\/span>, hi\u1ec7n \u0111\u1ea1i, <\/span>b\u1ed9 thu ph\u00e1t quang<\/strong><\/span><\/a> v\u00e0 c\u00e1ch th\u1ee9c n\u00f3 trao quy\u1ec1n cho c\u00e1c thi\u1ebft b\u1ecb nh\u01b0.<\/span><\/p>\n\n\n\n

\u2726 Hi\u1ec3u r\u00f5 v\u1ea5n \u0111\u1ec1 c\u1ed1t l\u00f5i: Suy gi\u1ea3m t\u00edn hi\u1ec7u<\/strong><\/h2>\n\n\n\n

H\u00e3y t\u01b0\u1edfng t\u01b0\u1ee3ng vi\u1ec7c g\u1eedi m\u1ed9t t\u00edn hi\u1ec7u s\u1ed1 ho\u00e0n h\u1ea3o v\u1ec1 m\u1eb7t th\u1eddi gian v\u00e0 s\u1eafc n\u00e9t qua h\u00e0ng kil\u00f4m\u00e9t s\u1ee3i quang. Trong su\u1ed1t h\u00e0nh tr\u00ecnh \u0111\u00f3, t\u00edn hi\u1ec7u n\u00e0y g\u1eb7p ph\u1ea3i nhi\u1ec1u th\u00e1ch th\u1ee9c:<\/p>\n\n\n\n

    \n

  1. Su\u1ea5t suy hao:<\/strong> T\u00edn hi\u1ec7u suy y\u1ebfu theo kho\u1ea3ng c\u00e1ch.<\/p><\/li>

  2. T\u00e1n s\u1eafc:<\/strong> C\u00e1c b\u01b0\u1edbc s\u00f3ng (m\u00e0u s\u1eafc) kh\u00e1c nhau c\u1ee7a \u00e1nh s\u00e1ng di chuy\u1ec3n v\u1edbi t\u1ed1c \u0111\u1ed9 h\u01a1i kh\u00e1c nhau, khi\u1ebfn xung t\u00edn hi\u1ec7u lan r\u1ed9ng v\u00e0 m\u1edd \u0111i.<\/p><\/li>

  3. Nhi\u1ec5u:<\/strong> Can nhi\u1ec5u \u0111i\u1ec7n v\u00e0 khu\u1ebfch \u0111\u1ea1i quang th\u00eam c\u00e1c nhi\u1ec5u b\u1ea5t k\u1ef3 (jitter).<\/p><\/li>

  4. Bi\u1ebfn thi\u00ean v\u1ec1 th\u1eddi gian (Jitter):<\/strong> Th\u1eddi \u0111i\u1ec3m ch\u00ednh x\u00e1c c\u1ee7a c\u00e1c xung t\u00edn hi\u1ec7u c\u00f3 th\u1ec3 tr\u1edf n\u00ean kh\u00f4ng \u1ed5n \u0111\u1ecbnh do nhi\u1ec1u y\u1ebfu t\u1ed1 v\u1eadt l\u00fd kh\u00e1c nhau.<\/p><\/li>\n<\/ol>\n\n\n\n

    K\u1ebft qu\u1ea3? Khi t\u00edn hi\u1ec7u \u0111\u1ebfn \u0111\u00edch, n\u00f3 th\u01b0\u1eddng b\u1ecb b\u00f3p m\u00e9o, nhi\u1ec5u v\u00e0 th\u1eddi \u0111i\u1ec3m ch\u00ednh x\u00e1c (\u0111\u1ed3ng h\u1ed3 \u201cclock\u201d) c\u1ee7a n\u00f3 b\u1ecb che khu\u1ea5t. Ch\u1ec9 \u0111\u01a1n thu\u1ea7n khu\u1ebfch \u0111\u1ea1i t\u00edn hi\u1ec7u l\u00e0 ch\u01b0a \u0111\u1ee7; ch\u00fang ta c\u1ea7n t\u00e1i t\u1ea1o ch\u00ednh x\u00e1c g\u1ed1c<\/em> lu\u1ed3ng d\u1eef li\u1ec7u s\u1ed1 v\u00e0 th\u1eddi \u0111i\u1ec3m ch\u00ednh x\u00e1c<\/em> c\u1ee7a n\u00f3.<\/p>\n\n\n\n

    \u2726 Gi\u1edbi thi\u1ec7u CDR: B\u1ed9 l\u00e0m t\u01b0\u01a1i t\u00edn hi\u1ec7u<\/strong><\/h2>\n\n\n\n
    \"Clock<\/figure>\n\n\n\n

    \u0110\u00e2y l\u00e0 n\u01a1i m\u00e0 Kh\u00f4i ph\u1ee5c \u0110\u1ed3ng h\u1ed3 v\u00e0 D\u1eef li\u1ec7u<\/strong> (CDR) xu\u1ea5t hi\u1ec7n. H\u00e3y h\u00ecnh dung n\u00f3 nh\u01b0 m\u1ed9t b\u1ed9 \u0111i\u1ec1u khi\u1ec3n giao th\u00f4ng v\u00e0 l\u00e0m s\u1ea1ch t\u00edn hi\u1ec7u c\u1ef1c k\u1ef3 tinh vi \u0111\u01b0\u1ee3c t\u00edch h\u1ee3p trong m\u1ed9t thi\u1ebft b\u1ecb. Nhi\u1ec7m v\u1ee5 ch\u00ednh c\u1ee7a n\u00f3 g\u1ed3m hai ph\u1ea7n:<\/p>\n\n\n\n

      \n

    1. Kh\u00f4i ph\u1ee5c \u0111\u1ed3ng h\u1ed3:<\/strong> Tr\u00edch xu\u1ea5t m\u1ed9t t\u00edn hi\u1ec7u \u0111\u1ed3ng h\u1ed3 \u1ed5n \u0111\u1ecbnh, ch\u00ednh x\u00e1c kh\u1edbp v\u1edbi trung b\u00ecnh<\/em> v\u1ec1 th\u1eddi gian (t\u1ed1c \u0111\u1ed9 bit) c\u1ee7a lu\u1ed3ng d\u1eef li\u1ec7u \u0111\u1ea7u v\u00e0o, ngay c\u1ea3 khi c\u00f3 nh\u1eefng bi\u1ebfn \u0111\u1ed9ng l\u1edbn v\u1ec1 th\u1eddi gian (jitter).<\/p><\/li>

    2. Kh\u00f4i ph\u1ee5c d\u1eef li\u1ec7u:<\/strong> S\u1eed d\u1ee5ng t\u00edn hi\u1ec7u \u0111\u1ed3ng h\u1ed3 \u0111\u00e3 kh\u00f4i ph\u1ee5c \u0111\u1ec3 l\u1ea5y m\u1eabu d\u1ea1ng s\u00f3ng d\u1eef li\u1ec7u \u0111\u1ea7u v\u00e0o b\u1ecb b\u00f3p m\u00e9o t\u1ea1i th\u1eddi \u0111i\u1ec3m t\u1ed1i \u01b0u<\/em> trong m\u1ed7i chu k\u1ef3 bit, t\u1eeb \u0111\u00f3 \u0111\u01b0a ra quy\u1ebft \u0111\u1ecbnh r\u00f5 r\u00e0ng v\u1ec1 vi\u1ec7c bit \u0111\u01b0\u1ee3c g\u1eedi l\u00e0 \u20181\u2019 hay \u20180\u2019, nh\u1edd \u0111\u00f3 t\u00e1i t\u1ea1o m\u1ed9t t\u00edn hi\u1ec7u s\u1ed1 \u0111\u1ea7u ra nguy\u00ean b\u1ea3n.<\/p><\/li>\n<\/ol>\n\n\n\n

      \u2726 CDR ho\u1ea1t \u0111\u1ed9ng nh\u01b0 th\u1ebf n\u00e0o? Nh\u1ecbp \u0111\u1eadp k\u1ef9 thu\u1eadt c\u1ed1t l\u00f5i<\/strong><\/h2>\n\n\n\n
      \"Clock<\/figure>\n\n\n\n

      M\u1ed9t m\u1ea1ch CDR \u0111i\u1ec3n h\u00ecnh s\u1eed d\u1ee5ng h\u1ec7 th\u1ed1ng ph\u1ea3n h\u1ed3i v\u00f2ng k\u00edn, th\u01b0\u1eddng t\u1eadp trung quanh m\u1ed9t V\u00f2ng kh\u00f3a pha (PLL)<\/strong> ho\u1eb7c m\u1ed9t ho\u1eb7c V\u00f2ng kh\u00f3a \u0111\u1ed9 tr\u1ec5 (DLL)<\/strong>. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 s\u01a1 \u0111\u1ed3 \u0111\u01a1n gi\u1ea3n h\u00f3a:<\/p>\n\n\n\n

        \n

      1. B\u1ed9 d\u00f2 pha (PD):<\/strong> So s\u00e1nh pha (m\u1ed1i quan h\u1ec7 th\u1eddi gian) gi\u1eefa c\u00e1c chuy\u1ec3n ti\u1ebfp (c\u1ea1nh) c\u1ee7a d\u1eef li\u1ec7u \u0111\u1ea7u v\u00e0o v\u00e0 t\u00edn hi\u1ec7u \u0111\u1ed3ng h\u1ed3 \u0111\u01b0\u1ee3c t\u1ea1o ra b\u00ean trong b\u1edfi Dao \u0111\u1ed9ng \u0111i\u1ec1u khi\u1ec3n \u0111i\u1ec7n \u00e1p (VCO) c\u1ee7a CDR.<\/p><\/li>

      2. B\u1ed9 b\u01a1m \u0111i\u1ec7n t\u00edch (CP) & B\u1ed9 l\u1ecdc v\u00f2ng (LF):<\/strong> PD t\u1ea1o ra c\u00e1c t\u00edn hi\u1ec7u l\u1ed7i. CP chuy\u1ec3n \u0111\u1ed5i c\u00e1c t\u00edn hi\u1ec7u n\u00e0y th\u00e0nh c\u00e1c xung d\u00f2ng \u0111i\u1ec7n, c\u00f2n LF l\u00e0m m\u01b0\u1ee3t ch\u00fang th\u00e0nh m\u1ed9t \u0111i\u1ec7n \u00e1p \u0111i\u1ec1u khi\u1ec3n \u1ed5n \u0111\u1ecbnh. B\u1ed9 l\u1ecdc n\u00e0y r\u1ea5t quan tr\u1ecdng \u0111\u1ec3 thi\u1ebft l\u1eadp d\u1ea3i th\u00f4ng c\u1ee7a CDR \u2014 kh\u1ea3 n\u0103ng theo d\u00f5i jitter.<\/p><\/li>

      3. Dao \u0111\u1ed9ng \u0111i\u1ec1u khi\u1ec3n \u0111i\u1ec7n \u00e1p (VCO):<\/strong> T\u1ea1o t\u00edn hi\u1ec7u \u0111\u1ed3ng h\u1ed3. \u0110i\u1ec7n \u00e1p \u0111i\u1ec1u khi\u1ec3n t\u1eeb LF \u0111i\u1ec1u ch\u1ec9nh t\u1ea7n s\u1ed1\/ph\u00e2n pha c\u1ee7a VCO \u0111\u1ec3 \u0111\u1ed3ng b\u1ed9 ho\u00e0n h\u1ea3o v\u1edbi th\u1eddi \u0111i\u1ec3m c\u1ee7a d\u1eef li\u1ec7u \u0111\u1ea7u v\u00e0o.<\/p><\/li>

      4. B\u1ed9 l\u1ea5y m\u1eabu d\u1eef li\u1ec7u (M\u1ea1ch quy\u1ebft \u0111\u1ecbnh):<\/strong> Khi \u0111\u1ed3ng h\u1ed3 \u0111\u00e3 kh\u00f3a, n\u00f3 k\u00edch ho\u1ea1t m\u1ed9t b\u1ed9 l\u1ea5y m\u1eabu (v\u00ed d\u1ee5 nh\u01b0 flip-flop) \u0111\u1ec3 \u0111\u1ecdc t\u00edn hi\u1ec7u d\u1eef li\u1ec7u t\u1ea1i th\u1eddi \u0111i\u1ec3m ch\u00ednh x\u00e1c nh\u1ea5t khi m\u1ee9c t\u00edn hi\u1ec7u \u1ed5n \u0111\u1ecbnh nh\u1ea5t (th\u01b0\u1eddng l\u00e0 \u1edf gi\u1eefa chu k\u1ef3 bit). Vi\u1ec7c n\u00e0y t\u00e1i t\u1ea1o d\u1eef li\u1ec7u s\u1ed1 s\u1ea1ch.<\/p><\/li>\n<\/ol>\n\n\n\n

        \u2726 C\u00e1c th\u00f4ng s\u1ed1 k\u1ef9 thu\u1eadt CDR quan tr\u1ecdng c\u1ea7n hi\u1ec3u<\/strong><\/h2>\n\n\n\n

        Khi \u0111\u00e1nh gi\u00e1 c\u00e1c module quang ho\u1eb7c hi\u1ec7u su\u1ea5t CDR, c\u00e1c th\u00f4ng s\u1ed1 sau \u0111\u00e2y r\u1ea5t quan tr\u1ecdng:<\/p>\n\n\n\n