{"id":4654,"date":"2026-01-20T09:42:07","date_gmt":"2026-01-20T09:42:07","guid":{"rendered":"https:\/\/flj-pcb.com\/?p=4654"},"modified":"2026-01-20T09:47:45","modified_gmt":"2026-01-20T09:47:45","slug":"pcb-emi-analysis-maxwell-current-loops-flux-control","status":"publish","type":"post","link":"https:\/\/flj-pcb.com\/vi\/pcb-emi-analysis-maxwell-current-loops-flux-control\/","title":{"rendered":"Ph\u00e2n t\u00edch EMI tr\u00ean PCB: Maxwell, V\u00f2ng d\u00f2ng \u0111i\u1ec7n v\u00e0 Ki\u1ec3m so\u00e1t d\u00f2ng t\u1eeb"},"content":{"rendered":"<p>Trong m\u1ea1ch in (PCB), c\u00f3 nhi\u1ec1u y\u1ebfu t\u1ed1 c\u00f3 th\u1ec3 g\u00e2y ra nhi\u1ec5u \u0111i\u1ec7n t\u1eeb (EMI). V\u00ed d\u1ee5: <a href=\"https:\/\/flj-pcb.com\/vi\/pcb-manufacturer\/rf-pcb\/\" data-type=\"page\" data-id=\"2145\">t\u1ea7n s\u1ed1 v\u00f4 tuy\u1ebfn<\/a> D\u00f2ng \u0111i\u1ec7n, \u0111i\u1ec7n \u00e1p ch\u1ebf \u0111\u1ed9 chung, v\u00f2ng l\u1eb7p \u0111\u1ea5t, s\u1ef1 kh\u00f4ng kh\u1edbp tr\u1edf kh\u00e1ng v\u00e0 d\u00f2ng t\u1eeb. \u0110\u1ec3 ki\u1ec3m so\u00e1t EMI, ch\u00fang ta c\u1ea7n t\u00ecm hi\u1ec3u c\u00e1c nguy\u00ean nh\u00e2n n\u00e0y t\u1eebng b\u01b0\u1edbc m\u1ed9t v\u00e0 xem ch\u00fang \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn b\u1ea3ng m\u1ea1ch nh\u01b0 th\u1ebf n\u00e0o. Ch\u00fang ta c\u00f3 th\u1ec3 nghi\u00ean c\u1ee9u to\u00e1n h\u1ecdc t\u1eeb l\u00fd thuy\u1ebft \u0111i\u1ec7n t\u1eeb. Nh\u01b0ng con \u0111\u01b0\u1eddng \u0111\u00f3 d\u00e0i v\u00e0 kh\u00f3 kh\u0103n. \u0110\u1ed1i v\u1edbi \u0111a s\u1ed1 k\u1ef9 s\u01b0, nh\u1eefng l\u1eddi gi\u1ea3i th\u00edch r\u00f5 r\u00e0ng v\u00e0 \u0111\u01a1n gi\u1ea3n s\u1ebd h\u1eefu \u00edch h\u01a1n. B\u00e0i vi\u1ebft n\u00e0y s\u1ebd \u0111\u1ec1 c\u1eadp \u0111\u1ebfn: c\u00e1c \u201cngu\u1ed3n tr\u01b0\u1eddng \u0111i\u1ec7n\u201d tr\u00ean b\u1ea3ng m\u1ea1ch in (PCB), c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c ph\u01b0\u01a1ng tr\u00ecnh Maxwell, v\u00e0 \u00fd t\u01b0\u1edfng gi\u1ea3m thi\u1ec3u d\u00f2ng t\u1eeb.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">1. Ngu\u1ed3n c\u1ee7a tr\u01b0\u1eddng \u0111i\u1ec7n<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1.1 M\u00f4 h\u00ecnh \u0111i\u1ec7n c\u1ef1c \u0111i\u1ec7n (thay \u0111\u1ed5i theo th\u1eddi gian)<\/h3>\n\n\n\n<p>Ngu\u1ed3n c\u1ee7a tr\u01b0\u1eddng \u0111i\u1ec7n th\u01b0\u1eddng \u0111\u01b0\u1ee3c m\u00f4 h\u00ecnh h\u00f3a nh\u01b0 m\u1ed9t l\u01b0\u1ee1ng c\u1ef1c \u0111i\u1ec7n bi\u1ebfn \u0111\u1ed5i theo th\u1eddi gian. \u0110\u00e2y l\u00e0 kh\u00e1i ni\u1ec7m tr\u00e1i ng\u01b0\u1ee3c v\u1edbi ngu\u1ed3n t\u1eeb. L\u01b0\u1ee1ng c\u1ef1c \u0111i\u1ec7n c\u00f3 ngh\u0129a l\u00e0 hai \u0111i\u1ec7n t\u00edch \u0111i\u1ec3m \u0111\u1ed1i l\u1eadp, g\u1ea7n nhau v\u00e0 thay \u0111\u1ed5i theo th\u1eddi gian. Hai \u0111\u1ea7u c\u1ee7a l\u01b0\u1ee1ng c\u1ef1c th\u1ec3 hi\u1ec7n s\u1ef1 thay \u0111\u1ed5i v\u1ec1 \u0111i\u1ec7n t\u00edch. \u0110i\u1ec1u n\u00e0y x\u1ea3y ra v\u00ec d\u00f2ng \u0111i\u1ec7n ch\u1ea3y d\u1ecdc theo to\u00e0n b\u1ed9 chi\u1ec1u d\u00e0i c\u1ee7a l\u01b0\u1ee1ng c\u1ef1c. B\u1ea1n c\u00f3 th\u1ec3 m\u00f4 h\u00ecnh h\u00f3a m\u1ed9t ngu\u1ed3n \u0111i\u1ec7n b\u1eb1ng c\u00e1ch c\u1ea5p t\u00edn hi\u1ec7u dao \u0111\u1ed9ng cho m\u1ed9t \u0103ng-ten kh\u00f4ng c\u00f3 \u0111\u1ea7u cu\u1ed1i. M\u1ea1ch n\u00e0y cho th\u1ea5y c\u00e1ch m\u1ed9t ngu\u1ed3n \u0111i\u1ec7n ho\u1ea1t \u0111\u1ed9ng. Nh\u01b0ng b\u1ea1n kh\u00f4ng th\u1ec3 gi\u1ea3i th\u00edch \u0111i\u1ec1u n\u00e0y ch\u1ec9 b\u1eb1ng c\u00e1c kh\u00e1i ni\u1ec7m m\u1ea1ch t\u1ea7n s\u1ed1 th\u1ea5p.<\/p>\n\n\n\n<p>\u0110\u1eebng qu\u00ean r\u1eb1ng t\u1ed1c \u0111\u1ed9 truy\u1ec1n t\u00edn hi\u1ec7u kh\u00f4ng ph\u1ea3i l\u00e0 v\u00f4 h\u1ea1n. T\u1ed1c \u0111\u1ed9 n\u00e0y ph\u1ee5 thu\u1ed9c v\u00e0o h\u1eb1ng s\u1ed1 \u0111i\u1ec7n m\u00f4i c\u1ee7a c\u00e1c v\u1eadt li\u1ec7u kh\u00f4ng t\u1eeb t\u00ednh. V\u00ec t\u1ed1c \u0111\u1ed9 l\u00e0 h\u1eefu h\u1ea1n, d\u00f2ng \u0111i\u1ec7n RF s\u1ebd xu\u1ea5t hi\u1ec7n trong m\u1ea1ch. M\u1ed9t s\u1ed1 ng\u01b0\u1eddi cho r\u1eb1ng d\u00e2y d\u1eabn c\u00f3 c\u00f9ng \u0111i\u1ec7n \u00e1p t\u1ea1i m\u1ecdi \u0111i\u1ec3m v\u00e0 m\u1ea1ch lu\u00f4n \u1edf tr\u1ea1ng th\u00e1i c\u00e2n b\u1eb1ng t\u1ea1i m\u1ecdi th\u1eddi \u0111i\u1ec3m. \u0110i\u1ec1u n\u00e0y kh\u00f4ng \u0111\u00fang \u1edf t\u1ea7n s\u1ed1 RF.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1.2 C\u00e1c y\u1ebfu t\u1ed1 ch\u00ednh \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb<\/h3>\n\n\n\n<p>Tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb c\u1ee7a m\u1ed9t l\u01b0\u1ee1ng c\u1ef1c \u0111i\u1ec7n ph\u1ee5 thu\u1ed9c v\u00e0o b\u1ed1n y\u1ebfu t\u1ed1:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u0110\u1ed9 l\u1edbn d\u00f2ng \u0111i\u1ec7n trong v\u00f2ng l\u1eb7p: Tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb t\u1ef7 l\u1ec7 thu\u1eadn v\u1edbi d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua l\u01b0\u1ee1ng c\u1ef1c.<\/li>\n\n\n\n<li>Polarity c\u1ee7a \u0103ng-ten l\u01b0\u1ee1ng c\u1ef1c v\u00e0 \u0103ng-ten \u0111o l\u01b0\u1eddng: Polarity c\u1ee7a \u0103ng-ten l\u01b0\u1ee1ng c\u1ef1c ph\u1ea3i tr\u00f9ng kh\u1edbp v\u1edbi polarity c\u1ee7a \u0103ng-ten \u0111o l\u01b0\u1eddng. \u0110i\u1ec1u n\u00e0y t\u01b0\u01a1ng t\u1ef1 nh\u01b0 m\u1ed9t ngu\u1ed3n t\u1eeb t\u00ednh.<\/li>\n\n\n\n<li>K\u00edch th\u01b0\u1edbc l\u01b0\u1ee1ng c\u1ef1c: Tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb t\u1ef7 l\u1ec7 thu\u1eadn v\u1edbi chi\u1ec1u d\u00e0i c\u1ee7a ph\u1ea7n t\u1eed d\u00f2ng \u0111i\u1ec7n. Tuy nhi\u00ean, chi\u1ec1u d\u00e0i c\u1ee7a d\u00e2y ph\u1ea3i ch\u1ec9 l\u00e0 m\u1ed9t ph\u1ea7n c\u1ee7a b\u01b0\u1edbc s\u00f3ng. L\u01b0\u1ee1ng c\u1ef1c c\u00e0ng l\u1edbn, t\u1ea7n s\u1ed1 \u0111o \u0111\u01b0\u1ee3c t\u1ea1i \u0103ng-ten c\u00e0ng th\u1ea5p. \u0110\u1ed1i v\u1edbi m\u1ed9t k\u00edch th\u01b0\u1edbc nh\u1ea5t \u0111\u1ecbnh, \u0103ng-ten s\u1ebd c\u1ed9ng h\u01b0\u1edfng \u1edf m\u1ed9t t\u1ea7n s\u1ed1 c\u1ee5 th\u1ec3.<\/li>\n\n\n\n<li>Kho\u1ea3ng c\u00e1ch: Tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb v\u00e0 t\u1eeb tr\u01b0\u1eddng c\u00f3 m\u1ed1i li\u00ean h\u1ec7 v\u1edbi nhau. \u0110\u1ed9 m\u1ea1nh c\u1ee7a ch\u00fang ph\u1ee5 thu\u1ed9c v\u00e0o kho\u1ea3ng c\u00e1ch. \u1ede v\u00f9ng xa, h\u00e0nh vi c\u1ee7a tr\u01b0\u1eddng gi\u1ed1ng nh\u01b0 m\u1ed9t ngu\u1ed3n t\u1eeb tr\u01b0\u1eddng d\u1ea1ng v\u00f2ng v\u00e0 b\u1ea1n quan s\u00e1t \u0111\u01b0\u1ee3c s\u00f3ng \u0111i\u1ec7n t\u1eeb ph\u1eb3ng. G\u1ea7n ngu\u1ed3n \u0111i\u1ec3m, s\u1ef1 ph\u1ee5 thu\u1ed9c c\u1ee7a tr\u01b0\u1eddng v\u00e0o kho\u1ea3ng c\u00e1ch tr\u1edf n\u00ean m\u1ea1nh h\u01a1n.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">1.3 M\u1ed1i quan h\u1ec7 gi\u1eefa v\u00f9ng g\u1ea7n v\u00e0 v\u00f9ng xa<\/h3>\n\n\n\n<p>V\u00f9ng g\u1ea7n v\u00e0 v\u00f9ng xa bao g\u1ed3m c\u1ea3 th\u00e0nh ph\u1ea7n t\u1eeb v\u00e0 \u0111i\u1ec7n. T\u1ea5t c\u1ea3 c\u00e1c s\u00f3ng \u0111\u1ec1u k\u1ebft h\u1ee3p c\u1ea3 th\u00e0nh ph\u1ea7n t\u1eeb v\u00e0 \u0111i\u1ec7n. S\u1ef1 k\u1ebft h\u1ee3p n\u00e0y \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 vect\u01a1 Poynting. Tr\u00ean th\u1ef1c t\u1ebf, kh\u00f4ng c\u00f3 s\u00f3ng \u0111i\u1ec7n thu\u1ea7n t\u00fay hay s\u00f3ng t\u1eeb thu\u1ea7n t\u00fay. Ch\u00fang ta c\u00f3 th\u1ec3 \u0111o \u0111\u01b0\u1ee3c s\u00f3ng ph\u1eb3ng v\u00ec, \u0111\u1ed1i v\u1edbi m\u1ed9t \u0103ng-ten nh\u1ecf c\u00e1ch xa v\u00e0i b\u01b0\u1edbc s\u00f3ng, m\u1eb7t s\u00f3ng tr\u00f4ng gi\u1ed1ng nh\u01b0 m\u1ed9t m\u1eb7t ph\u1eb3ng.<\/p>\n\n\n\n<p>M\u1ed9t b\u1ea3n v\u1ebd nh\u1ecf c\u00f3 th\u1ec3 h\u1eefu \u00edch. N\u00f3 s\u1ebd th\u1ec3 hi\u1ec7n tr\u1edf kh\u00e1ng s\u00f3ng v\u00e0 kho\u1ea3ng c\u00e1ch. C\u00e1c nh\u00e3n s\u1ebd ghi: tr\u1edf kh\u00e1ng s\u00f3ng; v\u00f9ng \u01b0u th\u1ebf tr\u01b0\u1eddng \u0111i\u1ec7n v\u1edbi E = 1\/r v\u00e0 H = 1\/r\u00b2; s\u00f3ng ph\u1eb3ng v\u1edbi Z = 377 \u03a9; \u0111\u01b0\u1eddng ti\u1ec7m c\u1eadn; h\u00ecnh d\u1ea1ng th\u1ef1c; v\u00f9ng \u01b0u th\u1ebf tr\u01b0\u1eddng t\u1eeb; khu v\u1ef1c chuy\u1ec3n ti\u1ebfp; v\u00f9ng g\u1ea7n tr\u01b0\u1eddng H = 1\/r\u00b3, E = 1\/r\u00b2; v\u00f9ng xa tr\u01b0\u1eddng; tr\u1ee5c ngang 0.1, 0.5, 1.0, 5.0.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img fetchpriority=\"high\" decoding=\"async\" width=\"800\" height=\"533\" src=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Relationship-Between-Wave-Impedance-and-Distance.webp\" alt=\"Relationship Between Wave Impedance and Distance\" class=\"wp-image-4660\" srcset=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Relationship-Between-Wave-Impedance-and-Distance.webp 800w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Relationship-Between-Wave-Impedance-and-Distance-300x200.webp 300w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Relationship-Between-Wave-Impedance-and-Distance-768x512.webp 768w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Relationship-Between-Wave-Impedance-and-Distance-18x12.webp 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><\/figure>\n\n\n\n\n\n<p>\u0110\u00e2y l\u00e0 \u201ch\u00ecnh d\u1ea1ng\u201d v\u1eadt l\u00fd m\u00e0 \u0103ng-ten quan s\u00e1t \u0111\u01b0\u1ee3c. H\u00e3y t\u01b0\u1edfng t\u01b0\u1ee3ng vi\u1ec7c n\u00e9m m\u1ed9t h\u00f2n \u0111\u00e1 v\u00e0o s\u00f4ng v\u00e0 quan s\u00e1t nh\u1eefng g\u1ee3n s\u00f3ng. Tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb ph\u00e1t ra t\u1eeb m\u1ed9t ngu\u1ed3n \u0111i\u1ec3m v\u1edbi t\u1ed1c \u0111\u1ed9 \u00e1nh s\u00e1ng. T\u1ed1c \u0111\u1ed9 n\u00e0y ph\u1ee5 thu\u1ed9c v\u00e0o h\u1eb1ng s\u1ed1 \u0111i\u1ec7n m\u00f4i. \u0110\u01a1n v\u1ecb c\u1ee7a tr\u01b0\u1eddng \u0111i\u1ec7n l\u00e0 V\/m. \u0110\u01a1n v\u1ecb c\u1ee7a tr\u01b0\u1eddng t\u1eeb l\u00e0 A\/m. T\u1ef7 l\u1ec7 E\/H l\u00e0 tr\u1edf kh\u00e1ng kh\u00f4ng gian t\u1ef1 do. \u0110\u1ed1i v\u1edbi s\u00f3ng ph\u1eb3ng trong kh\u00f4ng gian t\u1ef1 do, tr\u1edf kh\u00e1ng s\u00f3ng Z\u2080 l\u00e0 h\u1eb1ng s\u1ed1. N\u00f3 kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o kho\u1ea3ng c\u00e1ch ho\u1eb7c ngu\u1ed3n \u0111i\u1ec3m. S\u00f3ng ph\u1eb3ng trong kh\u00f4ng gian t\u1ef1 do truy\u1ec1n n\u0103ng l\u01b0\u1ee3ng v\u1edbi \u0111\u01a1n v\u1ecb watt tr\u00ean m\u00e9t vu\u00f4ng.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1.4 K\u1ebft n\u1ed1i nhi\u1ec5u v\u00e0 m\u00f4 h\u00ecnh th\u00e0nh ph\u1ea7n r\u1eddi r\u1ea1c<\/h3>\n\n\n\n<p>\u0110\u1ed1i v\u1edbi h\u1ea7u h\u1ebft c\u00e1c \u1ee9ng d\u1ee5ng c\u1ee7a ph\u01b0\u01a1ng tr\u00ecnh Maxwell, ch\u00fang ta m\u00f4 h\u00ecnh h\u00f3a s\u1ef1 t\u01b0\u01a1ng t\u00e1c nhi\u1ec5u b\u1eb1ng c\u00e1c th\u00e0nh ph\u1ea7n t\u1eadp trung t\u01b0\u01a1ng \u0111\u01b0\u01a1ng. V\u00ed d\u1ee5: tr\u01b0\u1eddng \u0111i\u1ec7n bi\u1ebfn \u0111\u1ed5i theo th\u1eddi gian gi\u1eefa hai v\u1eadt d\u1eabn gi\u1ed1ng nh\u01b0 m\u1ed9t t\u1ee5 \u0111i\u1ec7n. Tr\u01b0\u1eddng t\u1eeb bi\u1ebfn \u0111\u1ed5i theo th\u1eddi gian gi\u1eefa hai v\u1eadt d\u1eabn \u0111\u00f3 gi\u1ed1ng nh\u01b0 c\u1ea3m \u1ee9ng t\u01b0\u01a1ng h\u1ed7. M\u1ed9t s\u01a1 \u0111\u1ed3 c\u00f3 th\u1ec3 minh h\u1ecda hai \u0111\u01b0\u1eddng d\u1eabn t\u01b0\u01a1ng t\u00e1c nhi\u1ec5u n\u00e0y.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"800\" height=\"533\" src=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Noise-Coupling-Mechanisms.webp\" alt=\"Noise Coupling Mechanisms\" class=\"wp-image-4657\" srcset=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Noise-Coupling-Mechanisms.webp 800w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Noise-Coupling-Mechanisms-300x200.webp 300w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Noise-Coupling-Mechanisms-768x512.webp 768w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Noise-Coupling-Mechanisms-18x12.webp 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><\/figure>\n\n\n\n<p>\u0110\u1ec3 c\u00e1c m\u00f4 h\u00ecnh nhi\u1ec5u n\u00e0y ch\u00ednh x\u00e1c, m\u1ea1ch ph\u1ea3i c\u00f3 k\u00edch th\u01b0\u1edbc nh\u1ecf so v\u1edbi b\u01b0\u1edbc s\u00f3ng t\u00edn hi\u1ec7u. N\u1ebfu \u0111i\u1ec1u \u0111\u00f3 kh\u00f4ng \u0111\u00fang, ch\u00fang ta v\u1eabn c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng m\u00f4 h\u00ecnh th\u00e0nh ph\u1ea7n r\u1eddi r\u1ea1c \u0111\u1ec3 m\u00f4 t\u1ea3 EMC. T\u1ea1i sao? B\u1edfi v\u00ec c\u00e1c ph\u01b0\u01a1ng tr\u00ecnh Maxwell kh\u00f3 \u00e1p d\u1ee5ng trong nhi\u1ec1u tr\u01b0\u1eddng h\u1ee3p th\u1ef1c t\u1ebf do c\u00e1c bi\u00ean ph\u1ee9c t\u1ea1p. N\u1ebfu m\u00f4 h\u00ecnh r\u1eddi r\u1ea1c c\u00f3 v\u1ebb \u0111\u00fang m\u1ed9t c\u00e1ch t\u01b0\u01a1ng \u0111\u1ed1i, n\u00f3 v\u1eabn h\u1eefu \u00edch. H\u1ea7u h\u1ebft c\u00e1c th\u00e0nh ph\u1ea7n r\u1eddi r\u1ea1c th\u01b0\u1eddng ho\u1ea1t \u0111\u1ed9ng \u0111\u00e1ng tin c\u1eady.<\/p>\n\n\n\n<p>M\u00f4 h\u00ecnh s\u1ed1 kh\u00f4ng ph\u1ea3i l\u00fac n\u00e0o c\u0169ng cho th\u1ea5y ti\u1ebfng \u1ed3n ph\u00e1t sinh t\u1eeb c\u00e1c th\u00f4ng s\u1ed1 h\u1ec7 th\u1ed1ng. M\u00f4 h\u00ecnh c\u00f3 th\u1ec3 l\u00e0 c\u00e2u tr\u1ea3 l\u1eddi, nh\u01b0ng c\u00e1c th\u00f4ng s\u1ed1 h\u1ec7 th\u1ed1ng c\u00f3 th\u1ec3 kh\u00f4ng \u0111\u01b0\u1ee3c bi\u1ebft, t\u00ecm th\u1ea5y ho\u1eb7c hi\u1ec3n th\u1ecb. Trong s\u1ed1 c\u00e1c m\u00f4 h\u00ecnh c\u00f3 s\u1eb5n, m\u00f4 h\u00ecnh th\u00e0nh ph\u1ea7n t\u1eadp trung th\u01b0\u1eddng l\u00e0 l\u1ef1a ch\u1ecdn th\u1ef1c t\u1ebf t\u1ed1t nh\u1ea5t.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1.5 \u00dd ngh\u0129a \u0111\u1ed1i v\u1edbi thi\u1ebft k\u1ebf m\u1ea1ch in (PCB)<\/h3>\n\n\n\n<p>T\u1ea1i sao ch\u00fang ta nghi\u00ean c\u1ee9u l\u00fd thuy\u1ebft n\u00e0y? <a href=\"https:\/\/flj-pcb.com\/vi\/pcb-design\/\" data-type=\"page\" data-id=\"3488\">B\u1ed1 tr\u00ed m\u1ea1ch in (PCB)<\/a>C\u00e2u tr\u1ea3 l\u1eddi \u0111\u01a1n gi\u1ea3n: ch\u00fang ta ph\u1ea3i hi\u1ec3u c\u00e1ch tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb \u0111\u01b0\u1ee3c t\u1ea1o ra. Sau \u0111\u00f3, ch\u00fang ta c\u00f3 th\u1ec3 gi\u1ea3m tr\u01b0\u1eddng RF tr\u00ean b\u1ea3ng m\u1ea1ch in (PCB). \u0110i\u1ec1u n\u00e0y c\u00f3 ngh\u0129a l\u00e0 ch\u00fang ta ph\u1ea3i gi\u1ea3m d\u00f2ng \u0111i\u1ec7n RF trong m\u1ea1ch. D\u00f2ng \u0111i\u1ec7n RF li\u00ean quan \u0111\u1ebfn m\u1ea1ng ph\u00e2n ph\u1ed1i t\u00edn hi\u1ec7u, bao g\u1ed3m vi\u1ec7c \u0111i v\u00f2ng v\u00e0 k\u1ebft n\u1ed1i. D\u00f2ng \u0111i\u1ec7n RF cu\u1ed1i c\u00f9ng t\u1ea1o ra c\u00e1c h\u00e0i v\u00e0 n\u1ed9i dung t\u00edn hi\u1ec7u k\u1ef9 thu\u1eadt s\u1ed1 kh\u00e1c. M\u1ea1ng ph\u00e2n ph\u1ed1i t\u00edn hi\u1ec7u ph\u1ea3i nh\u1ecf nh\u1ea5t c\u00f3 th\u1ec3. \u0110i\u1ec1u n\u00e0y gi\u1ea3m di\u1ec7n t\u00edch v\u00f2ng l\u1eb7p d\u00f2ng \u0111i\u1ec7n RF tr\u1edf v\u1ec1. Qu\u00e1 tr\u00ecnh bypass v\u00e0 coupling li\u00ean quan \u0111\u1ebfn d\u00f2ng \u0111i\u1ec7n l\u1edbn v\u00e0 ph\u1ea3i di\u1ec5n ra qua m\u1ea1ng ph\u00e2n ph\u1ed1i ngu\u1ed3n. Theo \u0111\u1ecbnh ngh\u0129a, m\u1ea1ng ph\u00e2n ph\u1ed1i ngu\u1ed3n c\u00f3 di\u1ec7n t\u00edch v\u00f2ng l\u1eb7p d\u00f2ng \u0111i\u1ec7n RF tr\u1edf v\u1ec1 l\u1edbn.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"666\" height=\"500\" src=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Noise-Coupling-Method.webp\" alt=\"Noise Coupling Method\" class=\"wp-image-4658\" srcset=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Noise-Coupling-Method.webp 666w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Noise-Coupling-Method-300x225.webp 300w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Noise-Coupling-Method-16x12.webp 16w\" sizes=\"(max-width: 666px) 100vw, 666px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">2. \u1ee8ng d\u1ee5ng c\u00e1c ph\u01b0\u01a1ng tr\u00ecnh Maxwell<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">2.1 K\u1ebft n\u1ed1i c\u00e1c ph\u01b0\u01a1ng tr\u00ecnh Maxwell v\u1edbi \u0111\u1ecbnh lu\u1eadt Ohm<\/h3>\n\n\n\n<p>Ch\u00fang ta \u0111\u00e3 gi\u1edbi thi\u1ec7u c\u00e1c \u00fd t\u01b0\u1edfng c\u01a1 b\u1ea3n c\u1ee7a Maxwell \u1edf tr\u00ean. Nh\u01b0ng l\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 \u00e1p d\u1ee5ng ki\u1ebfn th\u1ee9c v\u1eadt l\u00fd v\u00e0 gi\u1ea3i t\u00edch n\u00e0y v\u00e0o EMC tr\u00ean m\u1ea1ch in (PCB)? Ch\u00fang ta ph\u1ea3i \u0111\u01a1n gi\u1ea3n h\u00f3a c\u00e1c ph\u01b0\u01a1ng tr\u00ecnh c\u1ee7a Maxwell \u0111\u1ec3 \u00e1p d\u1ee5ng ch\u00fang cho c\u00e1c \u0111\u01b0\u1eddng d\u1eabn tr\u00ean PCB. Ch\u00fang ta c\u00f3 th\u1ec3 li\u00ean k\u1ebft c\u00e1c ph\u01b0\u01a1ng tr\u00ecnh c\u1ee7a Maxwell v\u1edbi \u0111\u1ecbnh lu\u1eadt Ohm.<\/p>\n\n\n\n<p>\u0110\u1ecbnh lu\u1eadt Ohm trong mi\u1ec1n th\u1eddi gian:<\/p>\n\n\n\n<p>V = I \u00d7 R.<\/p>\n\n\n\n<p>\u0110\u1ecbnh lu\u1eadt Ohm trong mi\u1ec1n t\u1ea7n s\u1ed1:<\/p>\n\n\n\n<p>V_rf = I_rf \u00d7 Z.<\/p>\n\n\n\n<p>\u1ede \u0111\u00e2y, V l\u00e0 \u0111i\u1ec7n \u00e1p, I l\u00e0 d\u00f2ng \u0111i\u1ec7n, R l\u00e0 \u0111i\u1ec7n tr\u1edf v\u00e0 Z l\u00e0 tr\u1edf kh\u00e1ng (Z = R + jX). RF l\u00e0 n\u0103ng l\u01b0\u1ee3ng t\u1ea7n s\u1ed1 v\u00f4 tuy\u1ebfn. N\u1ebfu d\u00f2ng \u0111i\u1ec7n RF t\u1ed3n t\u1ea1i trong m\u1ed9t \u0111\u01b0\u1eddng d\u1eabn PCB c\u00f3 tr\u1edf kh\u00e1ng c\u1ed1 \u0111\u1ecbnh, m\u1ed9t \u0111i\u1ec7n \u00e1p RF s\u1ebd \u0111\u01b0\u1ee3c t\u1ea1o ra. \u0110i\u1ec7n \u00e1p RF t\u1ef7 l\u1ec7 thu\u1eadn v\u1edbi d\u00f2ng \u0111i\u1ec7n RF. L\u01b0u \u00fd: Trong m\u00f4 h\u00ecnh s\u00f3ng, R \u0111\u01b0\u1ee3c thay th\u1ebf b\u1eb1ng Z. Z l\u00e0 m\u1ed9t s\u1ed1 ph\u1ee9c. N\u00f3 bao g\u1ed3m \u0111i\u1ec7n tr\u1edf (ph\u1ea7n th\u1ef1c) v\u00e0 \u0111i\u1ec7n dung (ph\u1ea7n \u1ea3o).<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2.2 C\u00f4ng th\u1ee9c tr\u1edf kh\u00e1ng cho d\u00e2y d\u1eabn\/\u0111\u01b0\u1eddng d\u1eabn tr\u00ean b\u1ea3ng m\u1ea1ch in (PCB)<\/h3>\n\n\n\n<p>C\u00f3 nhi\u1ec1u c\u00e1ch \u0111\u1ec3 bi\u1ec3u di\u1ec5n tr\u1edf kh\u00e1ng, t\u00f9y thu\u1ed9c v\u00e0o vi\u1ec7c ch\u00fang ta xem x\u00e9t tr\u1edf kh\u00e1ng s\u00f3ng ph\u1eb3ng hay tr\u1edf kh\u00e1ng m\u1ea1ch. \u0110\u1ed1i v\u1edbi d\u00e2y d\u1eabn ho\u1eb7c \u0111\u01b0\u1eddng d\u1eabn tr\u00ean b\u1ea3ng m\u1ea1ch in (PCB), ch\u00fang ta s\u1eed d\u1ee5ng:<\/p>\n\n\n\n<p>T\u1ea7n s\u1ed1 g\u00f3c:<\/p>\n\n\n\n<p>\u03c9 = 2\u03c0f.<\/p>\n\n\n\n<p>\u0110i\u1ec7n c\u1ea3m c\u1ea3m \u1ee9ng:<\/p>\n\n\n\n<p>X_L = 2\u03c0fL.<\/p>\n\n\n\n<p>\u0110i\u1ec7n dung ph\u1ea3n kh\u00e1ng:<\/p>\n\n\n\n<p>X_C = 1 \/ (2\u03c0fC).<\/p>\n\n\n\n<p>\u0110i\u1ec7n tr\u1edf:<\/p>\n\n\n\n<p>Z = R + jX_L + 1\/(jX_C) = R + j\u03c9L + 1\/(j\u03c9C).<\/p>\n\n\n\n<p>Khi m\u1ed9t linh ki\u1ec7n c\u00f3 \u0111i\u1ec7n tr\u1edf v\u00e0 \u0111i\u1ec7n c\u1ea3m \u0111\u00e3 bi\u1ebft, v\u00ed d\u1ee5 nh\u01b0 m\u1ed9t h\u1ea1t ferit tr\u00ean d\u00e2y d\u1eabn, m\u1ed9t \u0111i\u1ec7n tr\u1edf, m\u1ed9t t\u1ee5 \u0111i\u1ec7n ho\u1eb7c c\u00e1c thi\u1ebft b\u1ecb c\u00f3 c\u00e1c th\u00e0nh ph\u1ea7n ph\u1ee5, ch\u00fang ta ph\u1ea3i xem x\u00e9t r\u1eb1ng tr\u1edf kh\u00e1ng thay \u0111\u1ed5i theo t\u1ea7n s\u1ed1.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2.3 C\u01a1 ch\u1ebf l\u1ef1a ch\u1ecdn \u0111\u01b0\u1eddng d\u1eabn hi\u1ec7n t\u1ea1i<\/h3>\n\n\n\n<p>Tr\u00ean m\u1ed9t t\u1ea7n s\u1ed1 nh\u1ea5t \u0111\u1ecbnh (kHz), \u0111i\u1ec7n kh\u00e1ng th\u01b0\u1eddng l\u1edbn h\u01a1n \u0111i\u1ec7n tr\u1edf (R). Tuy nhi\u00ean, \u0111i\u1ec1u n\u00e0y kh\u00f4ng ph\u1ea3i l\u00fac n\u00e0o c\u0169ng \u0111\u00fang. D\u00f2ng \u0111i\u1ec7n lu\u00f4n ch\u1ecdn \u0111\u01b0\u1eddng d\u1eabn c\u00f3 \u0111i\u1ec7n tr\u1edf nh\u1ecf nh\u1ea5t. D\u01b0\u1edbi m\u1ed9t t\u1ea7n s\u1ed1 nh\u1ea5t \u0111\u1ecbnh (kHz), \u0111i\u1ec7n tr\u1edf c\u00f3 th\u1ec3 l\u00e0 \u0111\u01b0\u1eddng d\u1eabn nh\u1ecf nh\u1ea5t. Tr\u00ean m\u1ed9t t\u1ea7n s\u1ed1 nh\u1ea5t \u0111\u1ecbnh (kHz), \u0111i\u1ec7n kh\u00e1ng c\u00f3 th\u1ec3 chi\u1ebfm \u01b0u th\u1ebf. Nhi\u1ec1u m\u1ea1ch \u0111i\u1ec7n ho\u1ea1t \u0111\u1ed9ng \u1edf t\u1ea7n s\u1ed1 cao h\u01a1n kHz, do \u0111\u00f3, quan ni\u1ec7m \u0111\u01a1n gi\u1ea3n \u201cd\u00f2ng \u0111i\u1ec7n ch\u1ecdn \u0111\u01b0\u1eddng d\u1eabn c\u00f3 \u0111i\u1ec7n tr\u1edf nh\u1ecf nh\u1ea5t\u201d kh\u00f4ng c\u00f2n gi\u1ea3i th\u00edch \u0111\u1ea7y \u0111\u1ee7 c\u00e1ch d\u00f2ng \u0111i\u1ec7n l\u01b0u th\u00f4ng tr\u00ean \u0111\u01b0\u1eddng truy\u1ec1n.<\/p>\n\n\n\n<p>\u0110\u1ed1i v\u1edbi c\u00e1c d\u00e2y d\u1eabn mang d\u00f2ng \u0111i\u1ec7n c\u00f3 t\u1ea7n s\u1ed1 tr\u00ean 10 kHz, d\u00f2ng \u0111i\u1ec7n s\u1ebd ch\u1ecdn \u0111\u01b0\u1eddng d\u1eabn c\u00f3 tr\u1edf kh\u00e1ng nh\u1ecf nh\u1ea5t. N\u1ebfu tr\u1edf kh\u00e1ng t\u1ea3i \u0111\u01b0\u1ee3c k\u1ebft n\u1ed1i v\u1edbi d\u00e2y, c\u00e1p ho\u1eb7c \u0111\u01b0\u1eddng d\u1eabn v\u00e0 l\u1edbn h\u01a1n \u0111i\u1ec7n dung song song tr\u00ean \u0111\u01b0\u1eddng truy\u1ec1n, th\u00ec c\u1ea3m \u1ee9ng s\u1ebd chi\u1ebfm \u01b0u th\u1ebf. N\u1ebfu t\u1ea5t c\u1ea3 c\u00e1c d\u00e2y k\u1ebft n\u1ed1i c\u00f3 ti\u1ebft di\u1ec7n t\u01b0\u01a1ng t\u1ef1, \u0111\u01b0\u1eddng d\u1eabn c\u00f3 di\u1ec7n t\u00edch v\u00f2ng l\u1eb7p nh\u1ecf nh\u1ea5t s\u1ebd c\u00f3 c\u1ea3m \u1ee9ng nh\u1ecf nh\u1ea5t. Di\u1ec7n t\u00edch v\u00f2ng l\u1eb7p c\u00e0ng nh\u1ecf, c\u1ea3m \u1ee9ng c\u00e0ng nh\u1ecf. V\u00ec v\u1eady, d\u00f2ng \u0111i\u1ec7n s\u1ebd ch\u1ea3y theo h\u01b0\u1edbng \u0111\u00f3.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2.4 \u1ea2nh h\u01b0\u1edfng c\u1ee7a \u0111i\u1ec7n c\u1ea3m nh\u1ecf \u0111\u1ebfn n\u0103ng l\u01b0\u1ee3ng RF<\/h3>\n\n\n\n<p>M\u1ed7i \u0111\u01b0\u1eddng d\u1eabn c\u00f3 tr\u1edf kh\u00e1ng h\u1eefu h\u1ea1n. Tr\u1edf kh\u00e1ng c\u1ea3m \u1ee9ng c\u1ee7a \u0111\u01b0\u1eddng d\u1eabn l\u00e0 l\u00fd do duy nh\u1ea5t khi\u1ebfn n\u0103ng l\u01b0\u1ee3ng RF c\u00f3 th\u1ec3 t\u1ed3n t\u1ea1i tr\u00ean b\u1ea3ng m\u1ea1ch in (PCB). C\u00e1c d\u00e2y n\u1ed1i d\u00e0i gi\u1eefa chip silicon v\u00e0 pad g\u1eafn c\u0169ng c\u00f3 th\u1ec3 g\u00e2y ra n\u0103ng l\u01b0\u1ee3ng RF. Vi\u1ec7c b\u1ed1 tr\u00ed \u0111\u01b0\u1eddng d\u1eabn tr\u00ean b\u1ea3ng m\u1ea1ch c\u00f3 th\u1ec3 t\u1ea1o ra tr\u1edf kh\u00e1ng cao, \u0111\u1eb7c bi\u1ec7t khi c\u00e1c \u0111\u01b0\u1eddng d\u1eabn d\u00e0i. M\u1ed9t \u0111\u01b0\u1eddng d\u1eabn d\u00e0i c\u00f3 ngh\u0129a l\u00e0 chi\u1ec1u d\u00e0i kh\u1ee9 h\u1ed3i c\u1ee7a n\u00f3 c\u0169ng d\u00e0i. \u0110i\u1ec1u n\u00e0y g\u00e2y ra \u0111\u1ed9 tr\u1ec5 th\u1eddi gian trong \u0111\u01b0\u1eddng d\u1eabn. M\u1ed9t t\u00edn hi\u1ec7u c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c ph\u00e1t ra tr\u01b0\u1edbc khi t\u00edn hi\u1ec7u tr\u01b0\u1edbc \u0111\u00f3 quay tr\u1edf l\u1ea1i. Trong mi\u1ec1n t\u1ea7n s\u1ed1, m\u1ed9t \u0111\u01b0\u1eddng d\u1eabn \u0111\u01b0\u1ee3c coi l\u00e0 \u201cd\u00e0i\u201d khi t\u1ed5ng chi\u1ec1u d\u00e0i c\u1ee7a n\u00f3 l\u1edbn h\u01a1n kho\u1ea3ng \u03bb\/10 \u1edf t\u1ea7n s\u1ed1 hi\u1ec7n di\u1ec7n trong \u0111\u01b0\u1eddng d\u1eabn.<\/p>\n\n\n\n<p>T\u00f3m l\u1ea1i: \u0110i\u1ec7n \u00e1p RF qua m\u1ed9t tr\u1edf kh\u00e1ng t\u1ea1o ra d\u00f2ng \u0111i\u1ec7n RF. D\u00f2ng \u0111i\u1ec7n RF n\u00e0y c\u00f3 th\u1ec3 ph\u00e1t x\u1ea1 n\u0103ng l\u01b0\u1ee3ng v\u00e0o kh\u00f4ng gian t\u1ef1 do v\u00e0 vi ph\u1ea1m gi\u1edbi h\u1ea1n EMC. C\u00e1c v\u00ed d\u1ee5 n\u00e0y li\u00ean k\u1ebft c\u00e1c ph\u01b0\u01a1ng tr\u00ecnh Maxwell v\u1edbi vi\u1ec7c b\u1ed1 tr\u00ed m\u1ea1ch in (PCB) th\u00f4ng qua c\u00e1c ph\u00e9p t\u00ednh \u0111\u01a1n gi\u1ea3n.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2.5 Quy t\u1eafc tay ph\u1ea3i \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh h\u01b0\u1edbng d\u00f2ng t\u1eeb<\/h3>\n\n\n\n<p>Maxwell cho bi\u1ebft, d\u00f2ng \u0111i\u1ec7n \u0111\u01b0\u1ee3c t\u1ea1o ra khi c\u00f3 s\u1ef1 di chuy\u1ec3n c\u1ee7a \u0111i\u1ec7n t\u00edch tr\u00ean m\u1ed9t \u0111\u01b0\u1eddng d\u1eabn. D\u00f2ng \u0111i\u1ec7n t\u1ea1o ra m\u1ed9t tr\u01b0\u1eddng t\u1eeb. C\u00e1c \u0111\u01b0\u1eddng s\u1ee9c t\u1eeb theo d\u1ecdc theo \u0111\u01b0\u1eddng d\u1eabn. S\u1eed d\u1ee5ng quy t\u1eafc tay ph\u1ea3i \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh h\u01b0\u1edbng c\u1ee7a d\u00f2ng s\u1ee9c t\u1eeb. H\u01b0\u1edbng ng\u00f3n c\u00e1i theo h\u01b0\u1edbng c\u1ee7a d\u00f2ng \u0111i\u1ec7n. C\u00e1c ng\u00f3n tay cu\u1ed9n l\u1ea1i s\u1ebd ch\u1ec9 ra h\u01b0\u1edbng c\u1ee7a tr\u01b0\u1eddng t\u1eeb xung quanh \u0111\u01b0\u1eddng d\u1eabn. M\u1ed9t tr\u01b0\u1eddng t\u1eeb bi\u1ebfn \u0111\u1ed5i theo th\u1eddi gian s\u1ebd t\u1ea1o ra m\u1ed9t tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb vu\u00f4ng g\u00f3c. Ph\u00f3ng x\u1ea1 t\u1ea7n s\u1ed1 v\u00f4 tuy\u1ebfn (RF) l\u00e0 s\u1ef1 k\u1ebft h\u1ee3p c\u1ee7a tr\u01b0\u1eddng t\u1eeb v\u00e0 tr\u01b0\u1eddng \u0111i\u1ec7n. C\u00e1c tr\u01b0\u1eddng n\u00e0y c\u00f3 th\u1ec3 tho\u00e1t ra kh\u1ecfi b\u1ea3ng m\u1ea1ch in (PCB) th\u00f4ng qua ph\u00f3ng x\u1ea1 ho\u1eb7c d\u1eabn truy\u1ec1n d\u1ecdc theo c\u00e1c d\u00e2y c\u00e1p k\u1ebft n\u1ed1i.<\/p>\n\n\n\n<p>L\u01b0u \u00fd r\u1eb1ng tr\u01b0\u1eddng t\u1eeb ch\u1ea1y quanh m\u1ed9t \u0111\u01b0\u1eddng bi\u00ean v\u00f2ng k\u00edn. Tr\u00ean b\u1ea3ng m\u1ea1ch in (PCB), ngu\u1ed3n t\u1ea1o ra d\u00f2ng \u0111i\u1ec7n RF t\u1eeb ngu\u1ed3n \u0111\u1ebfn t\u1ea3i qua m\u1ed9t \u0111\u01b0\u1eddng d\u1eabn. D\u00f2ng \u0111i\u1ec7n RF ph\u1ea3i quay tr\u1edf l\u1ea1i ngu\u1ed3n (theo \u0111\u1ecbnh lu\u1eadt Amp\u00e8re). \u0110i\u1ec1u n\u00e0y t\u1ea1o th\u00e0nh m\u1ed9t v\u00f2ng l\u1eb7p d\u00f2ng \u0111i\u1ec7n RF. V\u00f2ng l\u1eb7p n\u00e0y kh\u00f4ng nh\u1ea5t thi\u1ebft ph\u1ea3i l\u00e0 h\u00ecnh tr\u00f2n, nh\u01b0ng th\u01b0\u1eddng c\u00f3 d\u1ea1ng xo\u1eafn \u1ed1c. V\u00ec \u0111\u01b0\u1eddng d\u1eabn quay tr\u1edf l\u1ea1i t\u1ea1o th\u00e0nh m\u1ed9t v\u00f2ng k\u00edn, n\u00f3 t\u1ea1o ra m\u1ed9t tr\u01b0\u1eddng t\u1eeb. Tr\u01b0\u1eddng t\u1eeb t\u1ea1o ra m\u1ed9t tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb ph\u00e1t x\u1ea1. Trong v\u00f9ng g\u1ea7n, c\u00e1c th\u00e0nh ph\u1ea7n t\u1eeb c\u00f3 th\u1ec3 chi\u1ebfm \u01b0u th\u1ebf. Nh\u01b0ng trong v\u00f9ng xa, t\u1ef7 l\u1ec7 E\/H (\u0111i\u1ec7n tr\u1edf s\u00f3ng) kho\u1ea3ng 120\u03c0 \u03a9, ho\u1eb7c 377 \u03a9. Gi\u00e1 tr\u1ecb n\u00e0y kh\u00f4ng ph\u1ee5 thu\u1ed9c v\u00e0o ngu\u1ed3n. V\u00ec v\u1eady, trong v\u00f9ng xa, c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng \u0103ng-ten v\u00f2ng v\u00e0 b\u1ed9 thu nh\u1ea1y \u0111\u1ec3 \u0111o th\u00e0nh ph\u1ea7n t\u1eeb. D\u00f2ng \u0111i\u1ec7n nh\u1eadn \u0111\u01b0\u1ee3c l\u00e0 E\/(120\u03c0) trong A\/m n\u1ebfu E l\u00e0 V\/m. B\u1ea1n c\u0169ng c\u00f3 th\u1ec3 \u0111o ph\u1ea7n \u0111i\u1ec7n t\u1eeb b\u1eb1ng c\u00e1c c\u00f4ng c\u1ee5 ph\u00f9 h\u1ee3p trong v\u00f9ng g\u1ea7n.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"449\" src=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Right-Hand-Rule.webp\" alt=\"Right-Hand Rule\" class=\"wp-image-4661\" srcset=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Right-Hand-Rule.webp 800w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Right-Hand-Rule-300x168.webp 300w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Right-Hand-Rule-768x431.webp 768w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Right-Hand-Rule-18x10.webp 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">2.6 T\u1ea7m quan tr\u1ecdng c\u1ee7a m\u1ea1ch k\u00edn<\/h3>\n\n\n\n<p>M\u1ed9t c\u00e1ch nh\u00ecn \u0111\u01a1n gi\u1ea3n kh\u00e1c v\u1ec1 RF tr\u00ean PCB \u0111\u01b0\u1ee3c th\u1ec3 hi\u1ec7n qua c\u00e1c m\u1ea1ch \u0111i\u1ec7n \u0111i\u1ec3n h\u00ecnh trong c\u00e1c h\u00ecnh v\u1ebd. S\u1eed d\u1ee5ng ph\u00e2n t\u00edch mi\u1ec1n th\u1eddi gian v\u00e0 mi\u1ec1n t\u1ea7n s\u1ed1. \u0110\u1ecbnh lu\u1eadt Kirchhoff v\u00e0 Ampere cho r\u1eb1ng m\u1ed9t m\u1ea1ch \u0111i\u1ec7n ph\u1ea3i c\u00f3 m\u1ed9t v\u00f2ng l\u1eb7p \u0111\u00f3ng \u0111\u1ec3 ho\u1ea1t \u0111\u1ed9ng. \u0110\u1ecbnh lu\u1eadt \u0111i\u1ec7n \u00e1p c\u1ee7a Kirchhoff cho r\u1eb1ng t\u1ed5ng \u0111i\u1ec7n \u00e1p quanh b\u1ea5t k\u1ef3 v\u00f2ng l\u1eb7p \u0111\u00f3ng n\u00e0o l\u00e0 b\u1eb1ng kh\u00f4ng. \u0110\u1ecbnh lu\u1eadt Ampere cho r\u1eb1ng d\u00f2ng \u0111i\u1ec7n t\u1ea1o ra c\u1ea3m \u1ee9ng t\u1eeb t\u1ea1i m\u1ed9t \u0111i\u1ec3m, d\u1ef1a tr\u00ean d\u00f2ng \u0111i\u1ec7n v\u00e0 h\u00ecnh h\u1ecdc.<\/p>\n\n\n\n<p>N\u1ebfu kh\u00f4ng c\u00f3 m\u1ea1ch k\u00edn, t\u00edn hi\u1ec7u kh\u00f4ng th\u1ec3 truy\u1ec1n t\u1eeb ngu\u1ed3n \u0111\u1ebfn t\u1ea3i tr\u00ean \u0111\u01b0\u1eddng truy\u1ec1n. Khi c\u00f4ng t\u1eafc \u0111\u00f3ng, m\u1ea1ch \u0111\u01b0\u1ee3c h\u00ecnh th\u00e0nh v\u00e0 d\u00f2ng \u0111i\u1ec7n xoay chi\u1ec1u (AC) ho\u1eb7c m\u1ed9t chi\u1ec1u (DC) ch\u1ea3y qua. Trong mi\u1ec1n t\u1ea7n s\u1ed1, d\u00f2ng \u0111i\u1ec7n n\u00e0y l\u00e0 n\u0103ng l\u01b0\u1ee3ng t\u1ea7n s\u1ed1 cao (RF). Kh\u00f4ng c\u00f3 lo\u1ea1i d\u00f2ng \u0111i\u1ec7n ri\u00eang bi\u1ec7t trong mi\u1ec1n th\u1eddi gian ho\u1eb7c mi\u1ec1n t\u1ea7n s\u1ed1. Ch\u1ec9 c\u00f3 m\u1ed9t d\u00f2ng \u0111i\u1ec7n t\u1ed3n t\u1ea1i v\u00e0 ch\u00fang ta c\u00f3 th\u1ec3 quan s\u00e1t n\u00f3 trong c\u1ea3 hai mi\u1ec1n. \u0110\u01b0\u1eddng d\u1eabn tr\u1edf l\u1ea1i RF ph\u1ea3i t\u1ed3n t\u1ea1i t\u1eeb t\u1ea3i \u0111\u1ebfn ngu\u1ed3n, n\u1ebfu kh\u00f4ng m\u1ea1ch kh\u00f4ng th\u1ec3 ho\u1ea1t \u0111\u1ed9ng. Do \u0111\u00f3, c\u1ea5u tr\u00fac PCB ph\u1ea3i tu\u00e2n th\u1ee7 c\u00e1c \u0111\u1ecbnh lu\u1eadt Maxwell, Kirchhoff v\u00e0 Ampere.<\/p>\n\n\n\n<p>T\u1ea5t c\u1ea3 c\u00e1c \u0111\u1ecbnh lu\u1eadt n\u00e0y \u0111\u1ec1u kh\u1eb3ng \u0111\u1ecbnh: \u0111\u1ec3 m\u1ea1ch \u0111i\u1ec7n ho\u1ea1t \u0111\u1ed9ng nh\u01b0 mong \u0111\u1ee3i, ph\u1ea3i c\u00f3 m\u1ed9t m\u1ea1ng l\u01b0\u1edbi v\u00f2ng k\u00edn. M\u1ed9t s\u01a1 \u0111\u1ed3 s\u1ebd minh h\u1ecda m\u1ed9t m\u1ea1ch \u0111i\u1ec7n \u0111i\u1ec3n h\u00ecnh nh\u01b0 v\u1eady. Khi d\u00f2ng \u0111i\u1ec7n \u0111i t\u1eeb ngu\u1ed3n \u0111\u1ebfn t\u1ea3i, \u0111\u01b0\u1eddng d\u1eabn d\u00f2ng \u0111i\u1ec7n tr\u1edf v\u1ec1 ph\u1ea3i t\u1ed3n t\u1ea1i. \u0110\u00f3 ch\u00ednh l\u00e0 \u0111\u1ecbnh lu\u1eadt Kirchhoff v\u00e0 Amp\u00e8re.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"449\" src=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Closed-Loop-Circuit.webp\" alt=\"Closed-Loop Circuit\" class=\"wp-image-4655\" srcset=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Closed-Loop-Circuit.webp 800w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Closed-Loop-Circuit-300x168.webp 300w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Closed-Loop-Circuit-768x431.webp 768w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Closed-Loop-Circuit-18x10.webp 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><\/figure>\n\n\n\n<p>H\u00ecnh v\u1ebd th\u1ee9 hai s\u1ebd th\u1ec3 hi\u1ec7n m\u1ed9t c\u00f4ng t\u1eafc v\u00e0 m\u1ed9t b\u1ed9 \u0111i\u1ec1u khi\u1ec3n E n\u1ed1i ti\u1ebfp. Khi c\u00f4ng t\u1eafc \u0111\u00f3ng, m\u1ea1ch ho\u1ea1t \u0111\u1ed9ng. N\u1ebfu c\u00f4ng t\u1eafc m\u1edf, m\u1ea1ch kh\u00f4ng ho\u1ea1t \u0111\u1ed9ng. Trong mi\u1ec1n th\u1eddi gian, t\u00edn hi\u1ec7u mong mu\u1ed1n truy\u1ec1n t\u1eeb ngu\u1ed3n \u0111\u1ebfn t\u1ea3i. T\u00edn hi\u1ec7u ph\u1ea3i c\u00f3 \u0111\u01b0\u1eddng d\u1eabn tr\u1edf l\u1ea1i, th\u01b0\u1eddng qua m\u1ed9t tham chi\u1ebfu \u0111\u1ea5t 0V. D\u00f2ng \u0111i\u1ec7n RF ch\u1ea3y t\u1eeb ngu\u1ed3n \u0111\u1ebfn t\u1ea3i v\u00e0 tr\u1edf l\u1ea1i qua \u0111\u01b0\u1eddng d\u1eabn c\u00f3 tr\u1edf kh\u00e1ng th\u1ea5p nh\u1ea5t. Th\u01b0\u1eddng \u0111\u01b0\u1eddng d\u1eabn n\u00e0y l\u00e0 qua m\u1ed9t \u0111\u01b0\u1eddng d\u1eabn \u0111\u1ea5t ho\u1eb7c m\u1eb7t ph\u1eb3ng, m\u1ed9t m\u1eb7t ph\u1eb3ng g\u01b0\u01a1ng. S\u1eed d\u1ee5ng \u0111\u1ecbnh lu\u1eadt Amp\u00e8re \u0111\u1ec3 gi\u1ea3i th\u00edch d\u00f2ng \u0111i\u1ec7n RF.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"533\" src=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Description-of-a-Closed-Loop-Circuit.webp\" alt=\"Description of a Closed-Loop Circuit\" class=\"wp-image-4656\" srcset=\"https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Description-of-a-Closed-Loop-Circuit.webp 800w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Description-of-a-Closed-Loop-Circuit-300x200.webp 300w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Description-of-a-Closed-Loop-Circuit-768x512.webp 768w, https:\/\/flj-pcb.com\/wp-content\/uploads\/2026\/01\/Description-of-a-Closed-Loop-Circuit-18x12.webp 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">3. T\u1ed1i thi\u1ec3u h\u00f3a d\u00f2ng t\u1eeb (T\u1ed1i thi\u1ec3u h\u00f3a d\u00f2ng t\u1eeb t\u1eeb t\u00ednh)<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">3.1 C\u01a1 ch\u1ebf t\u1ea1o ra d\u00f2ng t\u1eeb<\/h3>\n\n\n\n<p>Tr\u01b0\u1edbc khi t\u00ecm hi\u1ec3u \u201cc\u00e1ch EMI xu\u1ea5t hi\u1ec7n tr\u00ean PCB\u201d, ch\u00fang ta c\u1ea7n n\u1eafm r\u00f5 c\u00e1ch c\u00e1c \u0111\u01b0\u1eddng t\u1eeb tr\u01b0\u1eddng h\u00ecnh th\u00e0nh tr\u00ean c\u00e1c \u0111\u01b0\u1eddng truy\u1ec1n. D\u00f2ng t\u1eeb l\u00e0 kh\u00e1i ni\u1ec7m c\u1ed1t l\u00f5i. D\u00f2ng t\u1eeb h\u00ecnh th\u00e0nh khi d\u00f2ng \u0111i\u1ec7n ch\u1ea1y qua m\u1ed9t tr\u1edf kh\u00e1ng c\u1ed1 \u0111\u1ecbnh ho\u1eb7c bi\u1ebfn \u0111\u1ed5i. Tr\u1edf kh\u00e1ng t\u1ed3n t\u1ea1i trong c\u00e1c \u0111\u01b0\u1eddng d\u1eabn, ch\u00e2n linh ki\u1ec7n, l\u1ed7 vias, v.v. N\u1ebfu d\u00f2ng t\u1eeb t\u1ed3n t\u1ea1i tr\u00ean PCB, Maxwell cho r\u1eb1ng c\u00e1c \u0111\u01b0\u1eddng d\u1eabn n\u0103ng l\u01b0\u1ee3ng RF c\u0169ng t\u1ed3n t\u1ea1i. Nh\u1eefng \u0111\u01b0\u1eddng d\u1eabn n\u00e0y c\u00f3 th\u1ec3 ph\u00e1t x\u1ea1 v\u00e0o kh\u00f4ng gian t\u1ef1 do ho\u1eb7c truy\u1ec1n \u0111i qua c\u00e1c d\u00e2y c\u00e1p.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3.2 Nguy\u00ean l\u00fd h\u1ee7y d\u00f2ng t\u1eeb<\/h3>\n\n\n\n<p>\u0110\u1ec3 lo\u1ea1i b\u1ecf d\u00f2ng \u0111i\u1ec7n RF tr\u00ean b\u1ea3ng m\u1ea1ch in (PCB), ch\u00fang ta s\u1eed d\u1ee5ng ph\u01b0\u01a1ng ph\u00e1p \u201ch\u1ee7y t\u1eeb th\u00f4ng\u201d ho\u1eb7c \u201cgi\u1ea3m thi\u1ec3u t\u1eeb th\u00f4ng\u201d. C\u00e1c \u0111\u01b0\u1eddng t\u1eeb tr\u01b0\u1eddng ch\u1ea1y theo m\u1ed9t h\u01b0\u1edbng xung quanh \u0111\u01b0\u1eddng d\u1eabn. N\u1ebfu ch\u00fang ta l\u00e0m cho \u0111\u01b0\u1eddng d\u1eabn tr\u1edf v\u1ec1 RF song song v\u00e0 g\u1ea7n v\u1edbi \u0111\u01b0\u1eddng d\u1eabn ngu\u1ed3n, th\u00ec t\u1eeb tr\u01b0\u1eddng c\u1ee7a \u0111\u01b0\u1eddng d\u1eabn tr\u1edf v\u1ec1 s\u1ebd ch\u1ea1y ng\u01b0\u1ee3c v\u1edbi t\u1eeb tr\u01b0\u1eddng c\u1ee7a \u0111\u01b0\u1eddng d\u1eabn ngu\u1ed3n. Khi c\u00e1c tr\u01b0\u1eddng t\u1eeb ch\u1ea1y theo h\u01b0\u1edbng ng\u01b0\u1ee3c nhau, ch\u00fang s\u1ebd tri\u1ec7t ti\u00eau l\u1eabn nhau. N\u1ebfu t\u1eeb th\u00f4ng kh\u00f4ng mong mu\u1ed1n gi\u1eefa ngu\u1ed3n v\u00e0 \u0111\u01b0\u1eddng d\u1eabn tr\u1edf v\u1ec1 b\u1ecb tri\u1ec7t ti\u00eau ho\u1eb7c gi\u1eef \u1edf m\u1ee9c nh\u1ecf, d\u00f2ng \u0111i\u1ec7n RF b\u1ee9c x\u1ea1 ho\u1eb7c d\u1eabn truy\u1ec1n s\u1ebd kh\u00f4ng t\u1ed3n t\u1ea1i, tr\u1eeb khi \u1edf c\u00e1c c\u1ea1nh nh\u1ecf c\u1ee7a \u0111\u01b0\u1eddng d\u1eabn. Kh\u00e1i ni\u1ec7m tri\u1ec7t ti\u00eau t\u1eeb th\u00f4ng r\u1ea5t \u0111\u01a1n gi\u1ea3n. Tuy nhi\u00ean, trong thi\u1ebft k\u1ebf, c\u1ea7n l\u01b0u \u00fd c\u00e1c b\u1eaby v\u00e0 sai s\u00f3t nh\u1ecf. M\u1ed9t sai s\u00f3t nh\u1ecf c\u00f3 th\u1ec3 g\u00e2y ra nhi\u1ec1u v\u1ea5n \u0111\u1ec1 ph\u1ee9c t\u1ea1p, khi\u1ebfn vi\u1ec7c g\u1ee1 l\u1ed7i tr\u1edf n\u00ean kh\u00f3 kh\u0103n.<\/p>\n\n\n\n<p>Ph\u01b0\u01a1ng ph\u00e1p h\u1ee7y t\u1eeb tr\u01b0\u1eddng \u0111\u01a1n gi\u1ea3n nh\u1ea5t l\u00e0 s\u1eed d\u1ee5ng m\u1eb7t ph\u1eb3ng h\u00ecnh \u1ea3nh (m\u1eb7t ph\u1eb3ng g\u01b0\u01a1ng). D\u00f9 b\u1ea1n b\u1ed1 tr\u00ed m\u1ea1ch \u0111i\u1ec7n t\u1ed1t \u0111\u1ebfn \u0111\u00e2u, tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb v\u00e0 t\u1eeb tr\u01b0\u1eddng v\u1eabn lu\u00f4n t\u1ed3n t\u1ea1i. Nh\u01b0ng n\u1ebfu b\u1ea1n h\u1ee7y c\u00e1c \u0111\u01b0\u1eddng t\u1eeb tr\u01b0\u1eddng, nhi\u1ec5u \u0111i\u1ec7n t\u1eeb (EMI) s\u1ebd bi\u1ebfn m\u1ea5t. \u0110\u01a1n gi\u1ea3n nh\u01b0 v\u1eady.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3.3 M\u1eb9o t\u1ed1i \u01b0u h\u00f3a d\u00f2ng \u0111i\u1ec7n trong thi\u1ebft k\u1ebf m\u1ea1ch in (PCB)<\/h3>\n\n\n\n<p>L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 lo\u1ea1i b\u1ecf flux trong thi\u1ebft k\u1ebf m\u1ea1ch in (PCB)? C\u00f3 nhi\u1ec1u m\u1eb9o kh\u00e1c nhau. Kh\u00f4ng ph\u1ea3i t\u1ea5t c\u1ea3 \u0111\u1ec1u tr\u1ef1c ti\u1ebfp lo\u1ea1i b\u1ecf flux. M\u1ed9t s\u1ed1 m\u1eb9o ph\u1ed5 bi\u1ebfn:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>S\u1eed d\u1ee5ng b\u1ea3ng m\u1ea1ch \u0111a l\u1edbp v\u1edbi vi\u1ec7c ph\u00e2n b\u1ed5 l\u1edbp ch\u1ed3ng \u0111\u00fang c\u00e1ch v\u00e0 ki\u1ec3m so\u00e1t tr\u1edf kh\u00e1ng.<\/li>\n\n\n\n<li>\u0110\u01b0\u1eddng d\u1eabn t\u00edn hi\u1ec7u \u0111\u1ed3ng h\u1ed3 g\u1ea7n m\u1eb7t \u0111\u1ea5t tr\u1edf l\u1ea1i (trong m\u1ea1ch in nhi\u1ec1u l\u1edbp). \u0110\u1ed1i v\u1edbi m\u1ea1ch in m\u1ed9t m\u1eb7t ho\u1eb7c hai m\u1eb7t, s\u1eed d\u1ee5ng \u0111\u01b0\u1eddng d\u1eabn m\u1eb7t \u0111\u1ea5t ho\u1eb7c \u0111\u01b0\u1eddng d\u1eabn b\u1ea3o v\u1ec7 g\u1ea7n \u0111\u01b0\u1eddng d\u1eabn t\u00edn hi\u1ec7u \u0111\u1ed3ng h\u1ed3.<\/li>\n\n\n\n<li>H\u01b0\u1edbng d\u00f2ng t\u1eeb tr\u01b0\u1eddng t\u1eeb b\u00ean trong c\u00e1c g\u00f3i nh\u1ef1a v\u00e0o \u0111i\u1ec3m tham chi\u1ebfu 0V \u0111\u1ec3 gi\u1ea3m b\u1ee9c x\u1ea1 c\u1ee7a linh ki\u1ec7n.<\/li>\n\n\n\n<li>Ch\u1ecdn c\u00e1c linh ki\u1ec7n logic m\u1ed9t c\u00e1ch c\u1ea9n th\u1eadn \u0111\u1ec3 gi\u1ea3m thi\u1ec3u ph\u1ed5 t\u1ea7n s\u1ed1 v\u00f4 tuy\u1ebfn (RF) m\u00e0 c\u00e1c linh ki\u1ec7n ph\u00e1t ra. S\u1eed d\u1ee5ng c\u00e1c thi\u1ebft b\u1ecb c\u00f3 t\u1ed1c \u0111\u1ed9 bi\u00ean ch\u1eadm h\u01a1n khi c\u00f3 th\u1ec3.<\/li>\n\n\n\n<li>Gi\u1ea3m \u0111i\u1ec7n \u00e1p \u0111i\u1ec1u khi\u1ec3n RF t\u1eeb c\u00e1c b\u1ed9 \u0111i\u1ec1u khi\u1ec3n \u0111\u1ed3ng h\u1ed3 (TTL\/CMOS) \u0111\u1ec3 gi\u1ea3m d\u00f2ng \u0111i\u1ec7n RF tr\u00ean c\u00e1c \u0111\u01b0\u1eddng d\u1eabn.<\/li>\n\n\n\n<li>Gi\u1ea3m \u0111i\u1ec7n \u00e1p nhi\u1ec5u gi\u1eefa c\u00e1c l\u1edbp ngu\u1ed3n v\u00e0 l\u1edbp \u0111\u1ea5t.<\/li>\n\n\n\n<li>Khi nhi\u1ec1u ch\u00e2n thi\u1ebft b\u1ecb chuy\u1ec3n \u0111\u1ed5i c\u00f9ng l\u00fac \u0111\u1ec3 \u0111i\u1ec1u khi\u1ec3n m\u1ed9t t\u1ea3i \u0111i\u1ec7n dung l\u1edbn, h\u00e3y \u0111\u1ea3m b\u1ea3o cung c\u1ea5p \u0111\u1ee7 t\u1ee5 \u0111i\u1ec7n c\u00e1ch ly cho linh ki\u1ec7n.<\/li>\n\n\n\n<li>K\u1ebft th\u00fac \u0111\u00fang c\u00e1ch c\u00e1c \u0111\u01b0\u1eddng d\u1eabn t\u00edn hi\u1ec7u \u0111\u1ed3ng h\u1ed3 v\u00e0 t\u00edn hi\u1ec7u \u0111\u1ec3 tr\u00e1nh hi\u1ec7n t\u01b0\u1ee3ng dao \u0111\u1ed9ng, v\u01b0\u1ee3t qu\u00e1 v\u00e0 thi\u1ebfu h\u1ee5t.<\/li>\n\n\n\n<li>S\u1eed d\u1ee5ng b\u1ed9 l\u1ecdc \u0111\u01b0\u1eddng truy\u1ec1n d\u1eef li\u1ec7u v\u00e0 b\u1ed9 ch\u1eb7n ch\u1ebf \u0111\u1ed9 chung tr\u00ean c\u00e1c m\u1ea1ng c\u1ea7n thi\u1ebft.<\/li>\n\n\n\n<li>\u0110\u1ed1i v\u1edbi c\u00e1c c\u00e1p I\/O ngo\u1ea1i vi, h\u00e3y s\u1eed d\u1ee5ng t\u1ee5 \u0111i\u1ec7n bypass \u0111\u00fang c\u00e1ch (kh\u00f4ng d\u00f9ng l\u00e0m t\u1ee5 c\u00e1ch ly).<\/li>\n\n\n\n<li>\u0110\u1ed1i v\u1edbi c\u00e1c linh ki\u1ec7n ph\u00e1t ra nhi\u1ec1u n\u0103ng l\u01b0\u1ee3ng RF ch\u1ebf \u0111\u1ed9 chung, h\u00e3y trang b\u1ecb cho ch\u00fang m\u1ed9t b\u1ed9 t\u1ea3n nhi\u1ec7t c\u00f3 ti\u1ebfp \u0111\u1ea5t.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">3.4 C\u00e1c nguy\u00ean nh\u00e2n kh\u00e1c g\u00e2y ra nhi\u1ec5u \u0111i\u1ec7n t\u1eeb (EMI) tr\u00ean b\u1ea3ng m\u1ea1ch in (PCB)<\/h3>\n\n\n\n<p>Xem danh s\u00e1ch cho th\u1ea5y d\u00f2ng t\u1eeb ch\u1ec9 l\u00e0 m\u1ed9t ph\u1ea7n c\u1ee7a nhi\u1ec5u \u0111i\u1ec7n t\u1eeb (EMI) tr\u00ean b\u1ea3ng m\u1ea1ch in (PCB). C\u00e1c nguy\u00ean nh\u00e2n kh\u00e1c bao g\u1ed3m:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>D\u00f2ng \u0111i\u1ec7n ch\u1ebf \u0111\u1ed9 chung v\u00e0 d\u00f2ng \u0111i\u1ec7n ch\u1ebf \u0111\u1ed9 vi sai gi\u1eefa m\u1ea1ch v\u00e0 c\u00e1p I\/O.<\/li>\n\n\n\n<li>C\u00e1c v\u00f2ng l\u1eb7p \u0111\u1ea5t t\u1ea1o ra c\u1ea5u tr\u00fac tr\u01b0\u1eddng t\u1eeb.<\/li>\n\n\n\n<li>C\u00e1c th\u00e0nh ph\u1ea7n ph\u00e1t x\u1ea1.<\/li>\n\n\n\n<li>S\u1ef1 kh\u00f4ng t\u01b0\u01a1ng th\u00edch tr\u1edf kh\u00e1ng.<\/li>\n<\/ul>\n\n\n\n<p>L\u01b0u \u00fd: H\u1ea7u h\u1ebft b\u1ee9c x\u1ea1 EMI xu\u1ea5t ph\u00e1t t\u1eeb \u0111i\u1ec7n \u00e1p ch\u1ebf \u0111\u1ed9 chung. Tr\u00ean m\u1ea1ch in ho\u1eb7c m\u1ea1ch \u0111i\u1ec7n, c\u00e1c m\u1ee9c \u0111i\u1ec7n \u00e1p ch\u1ebf \u0111\u1ed9 chung n\u00e0y c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c chuy\u1ec3n \u0111\u1ed5i th\u00e0nh c\u00e1c tr\u01b0\u1eddng \u0111i\u1ec7n t\u1eeb nh\u1ecf.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">K\u1ebft lu\u1eadn<\/h2>\n\n\n\n<p>\u0110\u1ec3 lo\u1ea1i b\u1ecf nhi\u1ec5u \u0111i\u1ec7n t\u1eeb (EMI) tr\u00ean b\u1ea3ng m\u1ea1ch in (PCB), h\u00e3y b\u1eaft \u0111\u1ea7u b\u1eb1ng c\u00e1ch gi\u1ea3m d\u00f2ng t\u1eeb. N\u00f3i th\u00ec d\u1ec5, nh\u01b0ng l\u00e0m th\u00ec kh\u00f3. N\u0103ng l\u01b0\u1ee3ng t\u1ea7n s\u1ed1 v\u00f4 tuy\u1ebfn (RF) l\u00e0 v\u00f4 h\u00ecnh v\u00e0 kh\u00f3 ph\u00e1t hi\u1ec7n. B\u1eb1ng c\u00e1ch x\u00e1c \u0111\u1ecbnh v\u1ecb tr\u00ed d\u00f2ng \u0111i\u1ec7n RF ch\u1ea3y v\u00e0 h\u01b0\u1edbng ch\u1ea3y c\u1ee7a n\u00f3, k\u1ebft h\u1ee3p v\u1edbi c\u00e1c m\u1eb9o tr\u00ean v\u00e0 c\u00e1c \u0111\u1ecbnh lu\u1eadt c\u1ee7a Maxwell, Kirchhoff v\u00e0 Ampere, b\u1ea1n c\u00f3 th\u1ec3 thu h\u1eb9p khu v\u1ef1c nghi ng\u1edd. Sau \u0111\u00f3, x\u00e1c \u0111\u1ecbnh ngu\u1ed3n nhi\u1ec5u EMI th\u1ef1c s\u1ef1 v\u00e0 lo\u1ea1i b\u1ecf n\u00f3.<\/p>","protected":false},"excerpt":{"rendered":"<p>In PCBs, many things can cause EMI. For example: radio frequency currents, common-mode voltages, ground loops, impedance mismatch, and magnetic 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