½ÇÇè10 - ÁøÆø º¹Á¶È¸·Î
I. ÀÌ·Ð
1. ÁøÆøº¯Á¶ ½ÅÈ£ÀÇ º¹Á¶
(Demodulation of AM Signals)
: AM ½ÅÈ£
:
modulation index
±×¸²: ÁøÆøº¯Á¶ ½ÅÈ£ÀÇ º¹Á¶ [From blog.oureducation.in]
±×¸²: AM ½ÅÈ£ º¹Á¶ ÁÖÆļö ¿µ¿ª¿¡¼ÀÇ °íÂû [From N. M. Ngo]
2. AM ½ÅÈ£ º¹Á¶È¸·ÎÀÇ Á¾·ù
¤· ´ÙÀÌ¿Àµå °ËÆıâ(detector)
-
Series-diode detector
-
Shunt-diode detector
±×¸²: ´ÙÀÌ¿Àµå °ËÆÄȸ·Î. ÁÂ: Á÷·Ä ´ÙÀÌ¿Àµå Çü, ¿ì: º´·Ä ´ÙÀÌ¿Àµå Çü
¤· Produc detector
- ±¹ºÎ¹ßÁø±â(LO; local oscillator)´Â º¹Á¶ÇÏ·Á´Â ½ÅÈ£ÀÇ carrier ½ÅÈ£¿Í ºñµ¿±â
±×¸²: DSB-SC ½ÅÈ£ÀÇ product detector °³³ä
¤· Synchrous detector [From www.electronics-notes.com]
- Product dectector¿Í À¯»çÇÑ °³³ä. LO ½ÅÈ£°¡ º¹Á¶ÇÏ·Á´Â AM ½ÅÈ£ÀÇ carrier ½ÅÈ£¿Í µ¿±â
- °¡Àå ¿ì¼öÇÑ Æ¯¼º Á¦°ø
3. ´ÙÀÌ¿Àµå Æ÷¶ô¼± °ËÆıâ
¤· ´ÙÀÌ¿Àµå Æ÷¶ô¼± °ËÆıâ(envelope detector) ȸ·Î
¤· AM ½ÅÈ£
- Àü´Ü¿¡¼ÀÇ Ãâ·ÂÀúÇ×(Rs)¿Í ½ÅÈ£¼¼±â ¹üÀ§ ÇÊ¿ä
¤· Á¤·ù±â(Rectifier)
- ´ÙÀÌ¿Àµå D1ÀÌ ºñ¼±Çü ¼ÒÀÚÀ̹ǷΠº¹Á¶½Ã ½ÅÈ£ ¿Ö°î ¹ß»ý
- Threshold°¡ ³·Àº Schottky diode »ç¿ë
- ´ÙÀÌ¿ÀµåÀÇ ¼ø¹æÇâ RF ÀúÇ× Rf°¡ R1º¸´Ù ÈξÀ À۾ƾßÁö AM °ËÆıâÀÇ È¿À²ÀÌ ³ô´Ù.
¤· Æ÷¶ô¼± °ËÆıâ (Envelope detector)
- ij¸®¾î ½ÅÈ£ (ÁÖÆļö fc)´Â Â÷´ÜÇÏ°í º¯Á¶½ÅÈ£ (ÃÖ´ë ÁÖÆļö fm,max)´Â Åë°úÇÏ´Â LPF
- Æ÷¶ô¼± °ËÆıâÀÇ ½ÃÁ¤¼ö
³Ê¹« Ŭ °æ¿ì º¯Á¶ ÁøÆøÀÇ º¯È¸¦ µû¶ó°¡Áö ¸øÇÔ.
³Ê¹« ÀÛÀ» °æ¿ì º¹Á¶µÈ ½ÅÈ£¿¡ ¸®ÇÃÀÌ ¸¹ÀÌ ¹ß»ýÇÏ°í Ãâ·ÂÀÌ °¨¼Ò.
¹Ý¼ÛÆÄ Áֱ⺸´Ù ÈξÀ ±æ¾î¾ß ÇÏ¸ç ½ÅÈ£ÀÇ ÁÖ±â(ÃÖ´ë ÁÖÆļö ¼ººÐÀÇ Á¤ÇöÆÄ ÁÖ±â)º¸´Ù ÈξÀ ÀÛ¾Æ¾ß ÇÔ.
- ´ÙÀ½ ´Ü°èÀÇ ÀԷ°ú ÀÓÇÇ´ø½º°¡ Á¤Çյǵµ·Ï ÀûÀýÇÑ °ª »ç¿ë
- ´ÙÀ½ Á¶°ÇÀ» ¸¸Á·Çϵµ·Ï ¼³°è
: C1 ÃæÀü ½ÃÁ¤¼ö
: C1 ¹æÀü ½ÃÁ¤¼ö
¶Ç´Â
fc : ij¸®¾î ÁÖÆļö
fm : º¯Á¶½ÅÈ£ ÁÖÆļö
m : º¯Á¶Áö¼ö(modulation index)
¤· Carrier Remnant Suppressor
- Æ÷¶ô¼± °ËÆı⸦ Åë°úÇÑ ½ÅÈ£¿¡ carrier ½ÅÈ£¼ººÐÀÌ µé¾î ÀÖÀ½.
- ij¸®¾î ½ÅÈ£ (ÁÖÆļö fc)´Â Â÷´ÜÇÏ°í º¯Á¶½ÅÈ£ (ÃÖ´ë ÁÖÆļö fm,max)´Â Åë°úÇÏ´Â LPF
- Rl-C1
ÇÊÅÍ¿Í R2-C2 ÇÊÅÍ´Â 2´Ü LPF¸¦ ±¸¼ºÇÑ´Ù.
- ´ÙÀ½ Á¶°ÇÀ» ¸¸Á·Çϵµ·Ï ¼³°è
¤· DC Monitor
- ¹Ý¼ÛÆÄÀÇ ÁøÆøÀ» ÃøÁ¤ÇÏ¿© °ËÆıâ Àü´Ü°è ÁõÆø±âÀÇ AGC ½ÅÈ£·Î »ç¿ëÇϱâ À§ÇØ R3¿Í C3 ¸¦ »ç¿ëÇÏ¿© °ËÆÄµÈ DC ½ÅÈ£ ÃøÁ¤
- R3, C3´Â C2¿¡ °É¸®´Â DC Àü¾Ð (ij¸®¾î ÁøÆøÀÇ Á¦°ö¿¡ ºñ·Ê) ÃøÁ¤
- R1C1
ÇÊÅÍÀÇ µ¿ÀÛ¿¡ ¿µÇâÀ» ÁÖÁö ¾Ê±â À§ÇØ ´ÙÀ½ Á¶°ÇÀ» ¸¸Á·Çϵµ·Ï ¼³°è
- DC ¼ººÐ¸¸ ³²µµ·Ï Â÷´Ü ÁÖÆļö°¡ ´ÙÀ½°ú °°µµ·Ï ¼³°è
¤· DC Offset Remover
- ¹Ý¼ÛÆÄ ÁøÆøÀÇ Á¦°ö¿¡ ºñ·ÊÇÏ´Â DC ½ÅÈ£´Â C4¿Í RL·Î ±¸¼ºµÈ HPF¿¡ ÀÇÇØ Á¦°ÅµÊ.
- R1C1
ÇÊÅÍÀÇ µ¿ÀÛ¿¡ ¿µÇâÀ» ÁÖÁö ¾Ê±â À§ÇØ ÀÓÇÇ´ø½º°¡ Ä¿¾ß ÇÔ.
- °ËÆÄµÈ ½ÅÈ£¸¦ Åë°ú½ÃÅ°±â À§ÇØ Â÷´Ü ÁÖÆļö°¡ ´ÙÀ½À» ¸¸Á·Çϵµ·Ï ¼³°è
: HPF cutoff
4. AM º¹Á¶±â ±Ô°Ý
¤· Discrete-components circuit
- ¼±Çü¼º(linearity): vm vs vout curve
- Frequency response flatness
- Dynamic range: max (vm) / min
(vm)
- Distortion: total harmonic
distortion
¤· Envelope detector IC: ADL5511
- Input signal frequency range: DC
- 6 GHz
- Input signal power range: -29
dBm to 17 dBm per 50 ¥Ø, 46 dB dynamic range
- Conversion gain: 1.42 V/Vrms
- Intercept: -5 mV
- Envelope bandwidth: 130 MHz
- Envelope delay (latench): 2 ns
- Power supply: 4.75 - 5.25 V,
21.5 mA (normal); power-down mode 0.13 mW
- Separate true RMS output
5. ¼³°è ¿¹Á¦
¤· ´ÙÀ½ ±Ô°ÝÀÇ AM º¹Á¶±â ¼³°è
vs : fc = 130
kHz (carrier frequency)
Ps : -30 dBm to 20 dBm (Vpeak^2/(2*50) = Ps), 10 mV
- 3.16 V
Rf = 10 ¥Ø
(diode RF resistance) (for theoretical calculation)
fm = 100
Hz - 15 kHz (modulation signal frequency)
Rs = 50 ¥Ø
D1 = 1N914, 1N3604, BA281 (Si), 1N60P, 1N34A, AA143,
AA118 (Ge), MBD501, BAT85S ISS86 (Schottky)
C1 = 1 nF,
R1 = 10 k¥Ø
R2 = 100 k¥Ø, C2 = 56 pF
R3 = 330 k¥Ø, C3 = 470 ¥ìF
RL = 330 k¥Ø, C4 = 47 ¥ìF
1) C1 °áÁ¤
2) R1 °áÁ¤
3) R2, C2 °áÁ¤
: R1C1 ÇÊÅÍÀÇ µ¿ÀÛ¿¡ ¿µÇâÀ» ÁÖÁö ¾Ê±â À§ÇØ
4) R3, C3 °áÁ¤
R3, C3´Â C2¿¡ °É¸®´Â DC Àü¾Ð (ij¸®¾î ÁøÆø¿¡ ºñ·Ê) ÃøÁ¤
: R1C1 ÇÊÅÍÀÇ µ¿ÀÛ¿¡ ¿µÇâÀ» ÁÖÁö ¾Ê±â À§ÇØ
5) RL, C4 °áÁ¤
: R1C1 ÇÊÅÍÀÇ µ¿ÀÛ¿¡ ¿µÇâÀ» ÁÖÁö ¾Ê±â À§ÇØ
: HPF cutoff
¤· ¼³°èÇÑ AM º¹Á¶±â Çؼ®
1) Àü´ÞÇÔ¼ö(transfer function) °è»ê
m = 0.25, 0.5, 0.75ÀÇ ¼¼ °¡Áö °æ¿ì
2) µ¿Àû¿µ¿ª(dynamic range) °è»ê
vm: m = 0.25, 1 kHz
vs = 0.01 V to 10 V
Plot vo vs vs
Plot vdc vs vs
3) Input spectrum and output spectrum
vm: m = 0.25, 1 kHz
vs = 2 V