ÇÍ£¬ÎÈƵÐÔÄܼ«ºÃ¡£
(4) ÓÉÓÚ¾§ÕñµÄQÖµºÍÌØÐÔ×迹?¶¼ºÜ¸ß£¬ËùÒÔ¾§ÕñµÄгÕñµç×èÒ²ºÜ¸ß£¬Ò»°ã¿É´ï1010?ÒÔÉÏ¡£ÕâÑù¼´Ê¹Íâµç·½ÓÈëϵÊýºÜС£¬´ËгÕñµç×èµÈЧµ½¾§Ìå¹ÜÊä³ö¶ËµÄ×迹 ÈԺܴó£¬Ê¹¾§Ìå¹ÜµÄµçѹÔöÒæÄÜÂú×ãÕñ·ùÆðÕñÌõ¼þµÄÒªÇó¡£
2. ÃÜÀÕ(Miller)Õñµ´µç·
ÓÒͼÊdz¡Ð§Ó¦¹ÜÃÜÀÕÕñµ´µç·¡£Ê¯Ó¢¾§Ìå×÷Ϊµç¸ÐVDD Ôª¼þÁ¬½ÓÔÚÕ¤¼«ºÍÔ´¼«Ö®¼ä¡£LC²¢Áª»Ø·ÔÚÕñµ´ÆµÂÊ
61~122?H 300p µãµÈЧΪµç¸Ð£¬×÷ΪÁíÒ»µç¸ÐÔª¼þÁ¬½ÓÔÚ©¼«ºÍÔ´¼«Ö®
¼ä£¬¼«¼äµçÈÝCgd×÷Ϊ¹¹³Éµç¸ÐÈýµãʽµç·ÖеĵçÈÝÔª
Cgd ¼þ¡£ÓÉÓÚCgdÓÖ³ÆΪÃÜÀÕµçÈÝ£¬¹Ê´Ëµç·ÓÐÃÜÀÕÕñµ´µç·֮³Æ¡£
1MHz 10M? ÃÜÀÕÕñµ´µç·ͨ³£²»²ÉÓþ§Ìå¹Ü£¬ÔÒòÊÇÕýÏòÆ«ÖÃ
2.2k 0.02? ʱ¾§Ìå¹Ü·¢Éä½áµç×è̫С£¬ËäÈ»¾§ÕñÓë·¢Éä½áµÄñîºÏºÜÈõ£¬µ«Ò²»áÔÚÒ»¶¨³Ì¶ÈÉϽµµÍ»Ø·µÄ±ê×¼ÐÔºÍƵÂʵÄÎÈ
¶¨ÐÔ£¬ËùÒÔ²ÉÓÃÊäÈë×迹¸ßµÄ³¡Ð§Ó¦¹Ü¡£ ÃÜÀÕÕñµ´µç·
3. ·ºÒô¾§ÌåÕñµ´µç·
²¢ÁªÐÍ·ºÒô¾§ÌåÕñµ´µç·£¬¼ÙÉè·ºÒô¾§ÕñΪÎå´Î·ºÒô£¬±ê³ÆƵÂÊΪ5MHz£¬»ùƵΪ1MHz£¬ÔòLC1»Ø·±ØÐëµ÷гÔÚÈý´ÎºÍÎå´Î·ºÒôƵÂÊÖ®¼ä¡£
ÔÚ5MHzƵÂÊÉÏ£¬LC1»Ø·³ÊÈÝÐÔ£¬Õñµ´µç·Âú×ã×é³É·¨Ôò£¬¶ø¶ÔÓÚ»ùƵºÍÈý´Î·ºÒôƵÂÊÀ´Ëµ£¬LC1»Ø·³Ê¸ÐÐÔ£¬µç·²»·ûºÏ×é³É·¨Ôò£¬²»ÄÜÆðÕñ¡£¶øÔÚÆߴμ°ÆäÒÔÉÏ·ºÒôƵÂÊ£¬LC1»Ø·Ëä³ÊÏÖÈÝÐÔ£¬µ«µÈЧÈÝ¿¹¼õС£¬´Ó¶øʹµç·µÄµçѹ·Å´ó±¶Êý¼õС£¬»·Â·ÔöÒæСÓÚ1£¬²»Âú×ãÕñ·ùÆðÕñÌõ¼þ¡£LC1»Ø·µÄµç¿¹ÌØÐÔÈç(b)ͼËùʾ¡£
X
C1 L 4 5 6 7 0 1 2 3 f(MHz)
C3 C2
(a) ²¢ÁªÐÍ·ºÒô¾§ÌåÕñµ´µç· (b) LC1»Ø·µÄµç¿¹ÌØÐÔ
4.´®ÁªÐ;§ÌåÕñµ´Æ÷
´®ÁªÐ;§ÌåÕñµ´Æ÷Êǽ«Ê¯Ó¢¾§ÕñÓÃÓÚÕý·´À¡Ö§Â·ÖУ¬ÀûÓÃÆä´®ÁªÐ³ÕñʱµÈЧΪ¶Ì·Ԫ¼þ£¬µç··´À¡×÷ÓÃ×îÇ¿£¬Âú×ãÕñ·ùÆðÕñÌõ¼þ£¬Ê¹Õñµ´Æ÷ÔÚ¾§Õñ´®ÁªÐ³ÕñƵÂÊfqÉÏÆðÕñ¡£ VCC R? 680 C3 R b1 C1 20k Cp 3.8?F L C? 300p
L
C1 Re C2 C3 Cb Rb2 2.2k Re C2 1600p ´®ÁªÐ;§ÌåÕñµ´µç·
ÕâÖÖÕñµ´Æ÷ÓëÈýµãʽÕñµ´Æ÷»ù±¾ÀàËÆ£¬Ö»²»¹ýÔÚÕý·´À¡Ö§Â·ÉÏÔö¼ÓÁËÒ»¸ö¾§Õñ¡£
Àý6-3 ͼ(a)ÊÇÒ»¸öÊý×ÖƵÂʼƾ§Õñµç·£¬ÊÔ·ÖÎöÆ乤×÷Çé¿ö¡£
½â ÏÈ»³öV1¹Ü¸ßƵ½»Á÷µÈЧµç·£¬Èçͼ (b)Ëùʾ£¬0.01?FµçÈݽϴó£¬×÷Ϊ¸ßƵÅÔ·µç·£¬V2¹ÜÊÇÉäËæÆ÷¡£
ÓɸßƵ½»Á÷µÈЧµç·¿ÉÒÔ¿´µ½£¬V1¹ÜµÄc¡¢e¼«Ö®¼äÓÐÒ»¸öLC»Ø·£¬ÆäгÕñƵÂÊΪf0?12?4.7?10?330?10?6?12?4.0MHz
ËùÒÔÔÚ¾§Õñ¹¤×÷ƵÂÊ5MHz´¦£¬´ËLC»Ø·µÈЧΪһ¸öµçÈÝ¡£¿É¼û£¬ÕâÊÇÒ»¸öƤ¶û˹Õñµ´µç·£¬¾§ÕñµÈЧΪµç¸Ð£¬ÈÝÁ¿Îª3-10pFµÄ¿É±äµçÈÝÆð΢µ÷×÷Óã¬Ê¹Õñµ´Æ÷¹¤×÷ÔÚ¾§ÕñµÄ±ê³ÆƵÂÊ5MHzÉÏ¡£
£«VCC C? c 20k b v 20p 10/3p e 200p c 5MHz b v 330p v 14.7?H 330p 4.7?? 5.6k e 200p 10/3p 1.5k 20p 0.01? 2.7k (b)
(a) Àý6-4 ÒÑ֪ʯӢ¾§ÌåÕñµ´µç·ÈçͼËùʾ£¬ÊÔÇó£º
1) »³öÕñµ´Æ÷µÄ¸ßƵµÈЧµç·£¬²¢Ö¸³öµç·µÄÕñµ´ÐÎʽ£» 2) Èô°Ñ¾§Ì廻Ϊ1MHz£¬¸Ãµç·ÄÜ·ñÆðÕñ£¬ÎªÊ²Ã´£¿ 3) ÇóÕñµ´Æ÷µÄÕñµ´ÆµÂÊ£»
4) Ö¸³ö¸Ãµç·²ÉÓõÄÎÈƵ´ëÊ©¡£
330?F 10k £«VCC 10pF ÎÈѹ 10?F 0.01?F b 20-5pF 4.7? 6.8pF 200pF 330pF 7MHz 100pF 2k4.2?? 330pF 7MHz 1k 200pF 20-5pF10pF 0.01?? 2.7k ½â£º (2) ÒªÏëµç·ÆðÕñ£¬ce¼ä±ØÐë³ÊÏÖÈÝÐÔ£¬4.7?HºÍ330pF²¢Áª»Ø·µÄгÕñƵÂÊΪ£¬
f0?12?LC20pF ?12?4.7?10?6?330?10?12?1?109?4.04?106?4MHz6.28?39.4 4MHz=f0>1MHz£¬»Ø·¶ÔÓÚ1MHz³ÊÏÖ¸ÐÐÔ£¬²»Âú×ãÈýµã·¨Ôò£¬ËùÒ԰Ѿ§Ì廻Ϊ1MHz£¬¸Ãµç·²»ÄÜÆðÕñ¡£
3£©ÒòΪʯӢ¾§ÌåµÄ±ê³ÆƵÂÊΪ7MHzËùÒÔ¸ÃÕñµ´Æ÷µÄ¹¤×÷ƵÂʼ´Îª7MHz¡£ 4£©¸Ãµç·²ÉÓõÄÎÈƵ´ëÊ©ÓУº (a) ²ÉÓþ§ÌåÕñµ´µÄ¿ËÀ²¨µç·£» (b) Õñµ´ÓëÉ伶¸úËæÆ÷ÊÇËÉñîºÏ£» (c) ÓÃÉ伶¸úËæÆ÷½øÐиôÀ룻
(d) µçÔ´½øÐÐÎÈѹ£¬ÒÔ±£¾§Ìå¹Ü²ÎÊýµÄÎȶ¨ÐÔ
6.6 ÆäËüÐÎʽµÄÕñµ´Æ÷
6.6.1 ѹ¿ØÕñµ´Æ÷(VCO)
ѹ¿ØÕñµ´Æ÷ÊÇÒÔijһµçѹÀ´¿ØÖÆÕñµ´ÆµÂÊ»òÏàλ´óСµÄÒ»ÖÖÕñµ´Æ÷£¬³£ÒÔ·ûºÅVCO(Voltage Controlled Oscillator)´úÖ®¡£
ÔÚµç×ÓÉ豸ÖУ¬Ñ¹¿ØÕñµ´Æ÷µÄÓ¦Óü«Îª¹ã·º£¬Èç²ÊÉ«µçÊÓ½ÓÊÕ»ú¸ßƵͷÖеı¾»úÕñµ´µç·¡¢¸÷ÖÖ×Ô¶¯ÆµÂÊ¿ØÖÆ(AFC)ϵͳÖеÄÕñµ´µç·¡¢ËøÏ໷·(PLL)ÖÐËùÓõÄÕñµ´µç·µÈ¾ùΪѹ¿ØÕñµ´Æ÷¡£Õñµ´Æ÷Êä³öµÄ²¨ÐÎÓÐÕýÏÒÐ͵ģ¬Ò²Óз½²¨Ð͵ġ£
1. ±äÈݶþ¼«¹Üѹ¿ØÕñµ´Æ÷µÄ»ù±¾¹¤×÷ÔÀí
ÔÚÕñµ´Æ÷µÄÕñµ´»Ø·Éϲ¢½Ó»ò´®½ÓijһÊܵçѹ¿ØÖƵĵ翹Ԫ¼þºó£¬¼´¿É¶ÔÕñµ´ÆµÂÊʵÐпØÖÆ¡£Êܿص翹Ԫ¼þ³£ÓñäÈݶþ¼«¹ÜÈ¡´ú¡£ C4 C4 (¸ôÖ±) C C 11 L L Cj Cj C2 C3 C2 C3 ±äÈݶþ¼«¹ÜµÄµçÈÝÁ¿CjÈ¡¾öÓÚÍâ¼Ó¿ØÖƵçѹµÄ´óС£¬¿ØÖƵçѹµÄ±ä»¯»áʹ±äÈݹܵÄCj±ä»¯£¬CjµÄ±ä»¯»áµ¼ÖÂÕñµ´ÆµÂʵĸı䡣
¶ÔÓÚͼÖУ¬ÈôC1¡¢C2Öµ½Ï´ó£¬C4ÓÖÊǸôÖ±µçÈÝ£¬ÈÝÁ¿ºÜ´ó£¬ÔòÕñµ´»Ø·ÖÐÓëLÏಢÁªµÄ×ܵçÈÝΪ
C?Cj??C3´®C2´®C1??Cj?C1C2C3?Cj?C?
C1C2?C2C3?C1C4±äÈݹÜÊÇÀûÓð뵼ÌåPN½áµÄ½áµçÈÝÊÜ¿ØÓÚÍâ¼Ó·´ÏòµçѹµÄÌØÐÔ¶øÖƳɵÄÒ»ÖÖ¾§Ìå¶þ¼«¹Ü£¬ËüÊôÓÚµçѹ¿ØÖƵĿɱäµç¿¹Æ÷¼þ£¬Æäѹ¿ØÌØÐԵĵäÐÍÇúÏßÈçͼËùʾ¡£Í¼ÖУ¬·´Ïòƫѹ´Ó3VÔö´óµ½30Vʱ£¬½áµçÈÝCj´Ó18pF¼õСµ½3pF£¬µçÈݱ仯±ÈԼΪ6±¶¡£
¶ÔÓÚ²»Í¬µÄCj£¬Ëù¶ÔÓ¦µÄÕñµ´ÆµÂÊΪ
fmin?12?Cjmax?C?)(VRΪ×îС)
fmax?1(VRΪ×î´ó)
2?L(Cjmin?C?) Cj(pF) 20 18 15 10 5 3 ¨CVR(V) 30 20 10 3 0 ͨ³£½«fmaxºÍfminµÄ±ÈÖµ³ÆΪƵÂʸ²¸ÇϵÊý£¬ÒÔ·ûºÅKf±íʾ£¬ÉÏÊöÕñµ´»Ø·µÄƵÂʸ²¸ÇϵÊýΪ
Cjmax?C?fmaxKf??
fminCjmin?C?2. VCOµÄʵ¼Êµç·
ij²ÊÉ«µçÊÓ½ÓÊÕ»úVHFµ÷гÆ÷ÖеÚ6-12Ƶ¶ÎµÄ±¾Õñµç·ÈçͼËùʾµç·ÖУ¬¿ØÖƵçѹVCΪ0.5-30V£¬¸Ä±äÕâ¸öµçѹ£¬¾Íʹ±äÈݹܵĽáµçÈÝ·¢Éú±ä»¯£¬´Ó¶ø»ñµÃƵÂʵı仯¡£ÓÉͼ(b)¿É¼û£¬ÕâÊÇÒ»µäÐ͵ÄÎ÷ÀÕÕñµ´µç·£¬Õñµ´¹Ü³Ê¹²¼¯µç¼«×é̬£¬Õñµ´ÆµÂÊԼΪ170-220MHz £¬ÕâÖÖͨ¹ý¸Ä±äÖ±Á÷µçѹÀ´ÊµÏÖƵÂʵ÷½ÚµÄ·½·¨£¬Í¨³£³ÆΪµçµ÷г£¬Óë»ú
еµ÷гÏà±ÈËüÓкܴóµÄÓÅÔ½ÐÔ¡£
+VCC L? 1000pF 5.6k? 47pF L 1.5pF 6pF 15pF Cj 15pF 47pF 18pF 18pF 6pF L 15k? 47k? D 1.2k? Vc 0.5~30V
(a) µçÊÓ½ÓÊÕ»úVHF±¾Õñµç· (b)
6.6.2 ¼¯³Éµç·Õñµ´Æ÷
1. ²î·Ö¶Ô¹ÜÕñµ´µç·
ÔÚ¼¯³Éµç·Õñµ´Æ÷À¹ã·º²ÉÓÃÈçͼ (a)ËùʾµÄ²î·Ö¶Ô¹ÜÕñµ´µç·£¬ÆäÖÐV2¹Ü¼¯µç¼«Íâ½ÓµÄLC»Ø·µ÷гÔÚÕñµ´ÆµÂÊÉÏ¡£(b)ͼΪÆä½»Á÷µÈЧµç·¡£(b)ͼÖÐRceΪºãÁ÷Ô´I0µÄ½»Á÷µÈЧµç×è¡£
ÕâÊǹ²¼¯¨C¹²»ù·´À¡µç·¡£ÓÉÓÚ¹²¼¯µç·Óë¹²»ùµç·¾ùΪͬÏà·Å´óµç·£¬ÇÒµçѹÔöÒæ¿Éµ÷ÖÁ´óÓÚ1£¬¸ù¾Ý˲ʱ¼«·¨Åжϣ¬ÔÚV1¹Ü»ù¼«¶Ï¿ª£¬ÓÐvb1?? vbe(ve2)??vc2??vb1?£¬ËùÒÔÊÇÕý·´À¡¡£ÔÚÕñµ´ÆµÂʵ㣬²¢ÁªLC»Ø·×迹×î´ó£¬Õý·´À¡µçѹvf(vo)×îÇ¿£¬ÇÒÂú×ãÏàλÎȶ¨Ìõ¼þ¡£
VCC
V2 + C1 L V1 Rce L C RL vo + +
vi ¨C V2 V1 ¨C RL vo VBB
¨C Io £¨a£© £¨b£©
2. ÔË·ÅÕñµ´Æ÷
ÆäÕñµ´ÆµÂÊΪf0?1
2?(L1?L2?2M)C Cb ¨C ¨C vo vo
+ + C1 C3 L2
C M C2 L1
(a)µç¸ÐÈýµãʽÔË·ÅÕñµ´Æ÷ (b) ÔË·ÅƤ¶û˹µç·
ÔË·ÅÈýµãʽµç·µÄ×é³ÉÔÔòÓ뾧Ìå¹ÜÈý¶Ëʽµç·µÄ×é³ÉÔÔòÏàËÆ£¬¼´Í¬ÏàÊäÈë¶ËÓë