½ÇÇè10 - ÁøÆø º¹Á¶È¸·Î

 

I. ÀÌ·Ð

1. ÁøÆøº¯Á¶ ½ÅÈ£ÀÇ º¹Á¶ (Demodulation of AM Signals)

      : AM ½ÅÈ£

     : modulation index

 

Demodulation

±×¸²: ÁøÆøº¯Á¶ ½ÅÈ£ÀÇ º¹Á¶ [From blog.oureducation.in]

 

 

Waveform and spectrum of signals in DSB-WC method: (a) message signal, (b) modulated signal, and (c) demodulated signal.

±×¸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

http://www.evalidate.in/lab2/images/DSB_SCD/DSBD_I1.jpg

±×¸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