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dbg
¤ dfmg ®ÉÈ dmg ¢£¤ d ¥§¦¡ mg ® ¡:Ê`b ¨-¸#¹,ËÌdmgÍ ¢7£¤ d ¥§¦¡ mg
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d g _kV z n¶MX { _kq^|PV z ]`Ð:X:n e Z
df@g
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_ X³{ z ³ ¦ [^hãÎsYXBhHvWµÆz X wÜsYe XZtX¶Zt7]`eaYy#qta_q^[^e]XX7z q [ts ]`[te ] sÝz[Gz aYaY[^sY__kX[Æ7Me qtX%_@q^Zm]np]X7aYX:qXYY] s [tee,X=
Zmn/XBX:]ZBZma¶sY]a$[t] {sY[ XMe _#au[^ sn
q^X7Yq^X:ZtX7a@[ e [t]_ka h µÆsY]oZ _#V z n¶MXÆå\VuZm[t]`ÓuX:n¶]a[^sYX { _ zz _]`aYy~npX=npV [^]`_#a º
b
:XµÆä@sYV X'e [t|~]_kXa [^sY_pn { _#qÆ_kp[ e ]aY]`auyB[^sYX ¤ ddmmgÆg e ®Éaln/ dm g d¢7m£g ¤ ]dZ[t¥§_ ¦ ¡ m_#g |GÏ e q^X*dfm[^g ¤sYçXæHZ d d[ ¥§g ¦ ]¡ a mg d b g ]`[ts¶[tsYXy#X7aYX:q ekz |G_pnpV ze [t]_ka
]`]`[t[tssYYsYsY]]®®¶»Yè X X _k_kV V z znn/ÓuÓuauaunn[^[ts s e e [Q[Q ddmmg g ®® »G¡ e d aub n¶¨-k¸ ¹ dfËmg df®ÉmgmgÆ e ¡ aud bn/¨é ¸@d¹,mgËÌ® dmgt»Yg3h h
irz X e q z ³ aYX7]`á[tsuX7qQ dmg aY_#qk dfmgÆ _ka@[ e ]auZr[tsYX :e q^qt]X7q h
Figure 1. How the sum of 3 cosine waves makes an AM wave
2
s(t)
Ac*cos(2pi*fc*t)
1/2*(Ac*ka*Am)*cos(2pi*(fc+fm)*t)
1/2*(Ac*ka*Am)*cos(2pi*(fc−fm)*t)
1.5
1
0.5
0
−0.5
−1
−1.5
−2
0
0.2
0.4
0.6
0.8
1
t(msec)
1.2
1.4
1.6
1.8
2
Figure 2. 3−D representation of the AM signal without carrier shift
1
vq(t)
0.5
0
−0.5
−1
2
5
1.5
4
1
3
2
0.5
0
vi(t)
1
0
t(msec)
Figure 3. 3−D representation of the AM signal with pi/2 carrier phase shift
1.8
1.6
1.4
vq(t)
1.2
1
0.8
0.6
0.4
0.2
0
1
5
0.5
4
0
3
2
−0.5
vi(t)
−1
1
0
t(msec)
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X e q^XGX e Zt³[t_ z _[%]aÌð òñ ze aYX h µÆsYX:qtX { _kq^X [^sYX7³ e q^XB_#|G]`[m[^X:n { q^_k|[^sY]Z
Figure 4. Amplitude Modulation with Binary inputs
2
ka=0.5
s(t)
1
0
−1
−2
0
1
2
3
2
t(msec)
4
5
6
7
ka=1.0
s(t)
1
0
−1
−2
0
1
2
3
4
t(msec)
4
5
6
7
ka=2.0
s(t)
2
0
−2
−4
0
1
2
3
t(mesc)
4
5
6
7
UWi _kVYalX=Z\Zm[^]onp]`_#X7aq e |~X:Z^Z e ykXZt]`y#a ez>ËÌdmg ® » ¢7£¤ d ¥ mgr
_ z [ZÆ]´[^s¶[tsYX :e q^qt]X7qÆ e,
X'¢ dmg ® ¼» ¢£¤ d b »#» ¥ mgj
_ z [Z h
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npX'X
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ö X7]a@q [ X:º a@ [ e Î y#X*®|~ _p»YnpuV ¸@zo¹ e [^® ]`_#»YaÕ »k]oZ ó b ¼Y»# »#Zt¸@_G¹ [ts Î e [ ®ÚËb õ »#»® ˶¸#õÔ¹ hÔ í a¶Î y#® X7aY»YX:Õ q ó ek¼Gz e ¤ ZÎ Ztdlmg X ®É]`Óu X:n ¡:hÊ`b ¨-¸#¹ Î ¢7£¤ d ¥§¦ Î mgçÍ ¢£¤ d ¥§¦¡ mg
¾§dfe@¿lg3ÀJh Á§µÆÂ=ÃfsY¿MXÄjvWÅ wZt]yka ekz ]´[^s«ó ¼ lX:q X7a@[|G_pnpV ze [t]_ka _#V z nMXYqtX=ZmX:a@[tX:n e Z
¤ dmg ® ¡ d b ¨é¸ ¹ ËÌdmgmg ¢£¤ d ¥§¦ ¡ mg ® ¼k»ud b ¨ »@¸ ¹ ¢£¤ d ¥ mgmg ¢£¤ d b »k» ¥ mg ® ¼»ld b ¨é»YÕ ó ¼ ¢7£¤ d ¥ mgtg ¢£¤ d b »k» ¥ mg
µÆsYX { _ zz _]`aYyGÓuy#VYq^X'nYX7Y] [Z [tsYX e l_
X'vWwÇZm]yka ekzJh
ê
AM signal with 75 percent modulation
100
80
60
40
s(t)
20
0
−20
−40
−60
−80
−100
0
0.2
0.4
0.6
0.8
1
t(sec)
1.2
1.4
1.6
1.8
2
Zsd d e,[ g3
gjhîX ]`_#a V zXn÷ lX X 7_ke#V zV n¶zoe [^X:q^n~]´[^X%³±Z d Zm[ VYgÆ|~e Z|~[t]sYaYX%y%Zt[^VYsY|àXWM_ _{5 ±X7qr _#nYZtX ]`
auX Xz _# le,X=
n~X=Z ³G[^sYX ekX ls _ _#X7ZtqQ]`aunYXQX
X e,z
_#X lX=ekn qtek_@Ztq^Z_#[tZ^sYZ XeGZ e z _ |Ge Xnz _ _ { e n b=ôhT @³ X
¤ dmg ® ¼» ¢£¤ d b »k» ¥ mg½¨ b df ó Õî¼ ¢£¤ d b » ¥ mg½¨ ó Õî¼ ¢£¤ dfø#Ö ¥ mgtg
]a X[^sYXl_ X7q 5 nYX
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ù ® á
_G[tsuXl_ X7qnpX
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dê g
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XP]`[ts|G]aY]|PVY|
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eZtsYal_n±| sYe_ï ¯]`|BVuVYZt| ]aYy±
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e Z]a XQ[tsYXZtä@V e qtX e,
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¼
t[ susY]Z%X:qtÊ »ZtX~_ zÈ Vpß [^]`®g_# a Ztáß ä@{ _#V q%È e qtnpX X® d [ [ e g »/] ®Bz Z{ bG_k_#q ac¸sYsu] z _X~ÚZt»ä@[tV_e eau:qtn ekX d [V g z®e ® [t»±X±»u{ È _# q e au® n Ê ß ß gè ©h÷ß ßí a ghP{ _#_k q |~¸]`Y[tscVYÚ[t[t]aYsY»Ìy«X~d sYÈ zX X z ee ZmauX~_ n {Wq^X dò{¼kX7g q [^r_X X [^e sYZ^_#XZmV Vuez |Gn«YXGMq^X7X7[^Yals q^npe X:][ ïZtX7{ _#a@_ q[{
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X e Z á
dý g
¤ dfmg ® Ëdfmg ¤ õ È dmg ® ËÌdmg ¤ çæHd ¥ ¸ ¦¡ mg§¨ È Ëdfmg
ß
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dó g
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X%Z sYX7|~X%]oZWyk]
X7a]a
"!
#$! "!
&%$')(+*,'(
.-
m(t)
Soutput(t)
-fc
+fc
square(t)
Figure 5. The diagram illustrating how to
make AM waves with square wave as the carrier
UWi _kVYalX=Z\Zm[^]onp]`_#X7aq e ê aPvWw}Zm³pZm[tX:|]`[ts
e q^] e z X :e q^qt]X7q e |~ z ]´[^VunpX eY ZmV s'[ts e [¤ dmg ® ¡ d È ¨B¸ ¹ ËÌdmgtg ¢£¤ d ¥§¦ ¡ mg©e aun
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ddf=g3g3h h È~ÈG® ®Ú»ub Õ ¼Be aue n aun ¸@¹ ¸@¹ ®®Ú b
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0/
/
1
32
2
ý
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]`d [^n Z g3he lÑ Zm_#_ q z Vp7[^e X ZmX
,ekd zn Vug3X _#s a e zZƳ/M[\X7rX:_Ba¶[tq^_#X:aYnYX:V Z X= n/_kV y#z qtnX e l[ X%z ³ nYhH]Zm [t_~]aY ykXVu] Zt_ksYV X:n¶z n¶MsYX X :e e q Vu[tZtsYXq^[tX7sYXX :X e ekq^qt]X7[tq_#aYs X:e Z ZÆh MX7X:aâZmVYuYqtX=ZtZtX:n h
Figure 6: AM signals with variable carrier amplitudes and their FFTs
s(t)
2
50
0
10
20
30
t(msec)
s(t)
5
50
1000
2000
3000
frequency(Hz)
4000
5000
a=1,ka=2
50
0
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20
30
t(msec)
40
50
0
0
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3000
frequency(Hz)
60
a=0.5,ka=1
4000
5000
a=0.5,ka=1
40
20
0
10
20
30
t(msec)
1
40
50
0
0
1000
2000
3000
frequency(Hz)
60
a=0,ka=1
4000
5000
a=0,ka=1
40
0
−1
0
100
0
−2
0
150
a=1,ka=2
2
s(t)
40
0
−5
a=1,ka=1
100
0
−2
s(t)
150
a=1,ka=1
20
0
10
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30
t(msec)
40
50
0
0
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3000
frequency(Hz)
4000
5000
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ó
8
9;:= <
97: <
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d b »@g
9
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