2. 大綱
• 雙埠網路的功率-增益關係式
• 電晶體放大器穩定性
• 提高穩定性的方法
• 功率轉換增益與雙埠同時共軛匹配的困難
• 單向功率轉換增益
• 雙埠同時共軛匹配與最大功率轉換增益
Department of Electronic Engineering, NTUT2/38
3. 功率-增益關係式
2 2
2
212 2
22
1 1
1 1
s LL
T
AVS in s L
P
G S
P S
− Γ − Γ
= =
− Γ Γ − Γ
2 2
2
212 2
11
1 1
1 1
s LL
T
AVS s out L
P
G S
P S
− Γ − Γ
= =
− Γ − Γ Γ
2
2
212 2
22
11
1 1
LL
p
in in L
P
G S
P S
− Γ
= =
− Γ − Γ
2
2
212 2
11
1 1
1 1
sAVN
A
AVS s out
P
G S
P S
− Γ
= =
− Γ − Γ
• 功率轉換增益GT (Transducer Power Gain)
• 操作功率增益Gp (Operating Power Gain)
• 可資用功率增益GA (Available Power Gain)
Transistor
[S]
+
−
sE
sZ
LZ
PAVNPAVS PLPin
Ms
interface interface
ML
輸入總是匹配,考慮不同輸出匹配
輸出總是匹配,考慮不同輸入匹配
同時考慮不同輸入、輸出匹配
Department of Electronic Engineering, NTUT3/38
4. 範例
• 計算下圖電路之PAVS, Pin, PAVN, 與 PL
1 50Z = Ω
Input
Matching
Network
Output
Matching
Network+
−1 10 0E = ∠
2 50Z = Ω
0.5 120sΓ = ∠ inΓ
outΓ 0.4 90LΓ = ∠
sZ inZ outZ LZ
[ ]S
[ ] 11 12
21 22
0.6 160 0.045 16
2.5 30 0.5 90
S S
S
S S
∠ − ∠
= =
∠ ∠ −
Transistor S parameters:
12 21
11
22
0.627 164.6
1
L
in
L
S S
S
S
Γ
Γ = + = ∠ −
− Γ
12 21
22
11
0.471 97.63
1
s
out
s
S S
S
S
Γ
Γ = + = ∠ −
− Γ
2 2
2
212 2
22
1 1
9.43
1 1
s LL
T
AVS in s L
P
G S
P S
− Γ − Γ
= = =
− Γ Γ − Γ
( )or 9.75 dB
見投影片第四章 slide 17 見投影片第四章 slide 18
Department of Electronic Engineering, NTUT4/38
5. 範例
2
2
212 2
22
11
13.51
1 1
LL
p
in in L
P
G S
P S
− Γ
= = =
− Γ − Γ
( )or 11.31 dB
2
2
212 2
11
1 1
9.55
1 1
sAVN
A
AVS s out
P
G S
P S
− Γ
= = =
− Γ − Γ
( )or 9.8 dB
in AVS sP P M= T p sG G M=and ( )
9.43
0.698 1.56 dB
13.51
T
s
p
G
M
G
= = = = −
( )( ) ( )
2 2
2
1 1
0.6983 1.56 dB
1
s in
s
s in
M
− Γ − Γ
= = = −
−Γ Γ
L AVN LP P M= T A LG G M=and ( )
9.43
0.9874 0.055 dB
9.55
T
L
A
G
M
G
= = = = −
( )( ) ( )
2 2
2
1 1
0.9874 0.055 dB
1
L out
L
out L
M
− Γ − Γ
= = = −
− Γ Γ
2 2
1
1
10
0.25 W
8 8 50
AVS
E
P
R
= = =
⋅
( )0.25 W 0.1745 Win sP M= ⋅ =
( )0.25 W 2.358 WL TP G= ⋅ =
2.358 WL AVN LP P M= = ⋅ 2.39 WAVNP =
由投影片第四章 slide 19:
由投影片第四章 slide 20:
真正進電晶體的功率
訊號源的可資用功率
Department of Electronic Engineering, NTUT5/38
6. 穩定性
12 21
11
221
L
in
L
S S
S
S
Γ
Γ = +
− Γ
12 21
22
111
s
out
s
S S
S
S
Γ
Γ = +
− Γ
• 放大器的穩定性是設計的第一步,使用散射參數的觀念可以很容易
評估放大器是否穩定。
• 當輸入埠或輸出埠展現出負電阻性質時,放大器不穩定而可能發生
振盪,即 或 ( or for a unilateral device)。1inΓ > 1outΓ > 22 1S >11 1S >
Transistor
[S]+
−
sE
sZ
outΓ
LZ
inΓ
sΓ LΓ
• 一個雙埠網路接上任意的source與load之後,在某個操作頻率下若為
無條件穩定無條件穩定無條件穩定無條件穩定(unconditionally stable),表示在該頻率下Zin與Zout的實部
都是大於0的(正電阻性)。若該網路為有條件穩定有條件穩定有條件穩定有條件穩定(potentially unstable),
表示它接上某些source與load的阻抗時,將在該操作頻率下使Zin與Zout
的實部小於0(負電阻性)。
Department of Electronic Engineering, NTUT6/38
7. 穩定性考量
1sΓ <
12 21
22
11
1
1
s
out
s
S S
S
S
Γ
Γ = + <
− Γ
1LΓ <
12 21
11
22
1
1
L
in
L
S S
S
S
Γ
Γ = + <
− Γ
( )22 11 12 21
2 2 2 2
22 22
L
S S S S
S S
∗∗
− ∆
Γ − =
− ∆ − ∆
( )11 22 12 21
2 2 2 2
11 11
s
S S S S
S S
∗∗
− ∆
Γ − =
− ∆ − ∆
11 22 12 21S S S S∆ = −
• 某個操作頻率下,要達到穩定的
反射係數條件:
• 能讓 的 值 (臨界),於Smith Chart上為一圓形軌跡。LΓ1inΓ =
• 穩定圓:
and Transistor
[S]+
−
sE
sZ
outΓ
LZ
inΓ
sΓ LΓ
• 能讓 的 值 (臨界),於Smith Chart上為一圓形軌跡。sΓ1outΓ =
and
where
任何被動元件的
反射係數皆小於1
Department of Electronic Engineering, NTUT7/38
8. 輸出與輸入穩定圓
12 21
2 2
22
L
S S
r
S
=
− ∆
( )22 11
2 2
22
L
S S
C
S
∗∗
− ∆
=
− ∆
12 21
2 2
11
s
S S
r
S
=
− ∆
( )11 22
2 2
11
s
S S
C
S
∗∗
− ∆
=
− ∆
• 輸出穩定圓 (Output Stability Circle values for )LΓ 1inΓ =
圓心
半徑
• 輸入穩定圓( Input Stability Circle values for )
圓心
半徑
sΓ 1outΓ =
1inΓ =
1outΓ =
LC
Lr
LC
sC
sr
sC
-planeLΓ
-planesΓ
12 21
11
22
1
1
L
in
L
S S
S
S
Γ
Γ = + =
− Γ
12 21
22
11
1
1
s
out
s
S S
S
S
Γ
Γ = + =
− Γ
Department of Electronic Engineering, NTUT8/38
9. 判斷穩定區
LC
LC
Lr 1inΓ =
sr
sC
sC
1outΓ =
• 穩定圓的軌跡是一個圓形,代表反射係數將高於1的臨界線。
• 問題:穩定圓內或圓外才是穩定? 可使用 與 來幫助判斷。11S
-planeLΓ -planesΓ
Output Stability Circle Input Stability Circle
22S
?
?
?
?
Department of Electronic Engineering, NTUT9/38
10. 判斷 平面的穩定區域
LC
LC
Lr
1inΓ =
11 1S <
12 21
11
221
L
in
L
S S
S
S
Γ
Γ = +
− Γ
0LΓ =
LC
LC
0LΓ =
Lr
1inΓ =
• 方法: 若故意令 ,可知 ,此時 。0LΓ = 11in SΓ =0LZ Z=
-planeLΓ -planeLΓ
LΓ
Case (1): 11 1S >Case (2):
stable region stable region
11 1in SΓ = < 11 1in SΓ = >
圓外穩定 圓內穩定
Department of Electronic Engineering, NTUT10/38
11. 判斷 平面的穩定區域
12 21
22
111
s
out
s
S S
S
S
Γ
Γ = +
− Γ
22 1S < 22 1S >
sΓ
Case (1): Case (2):
stable region stable region
-planesΓ -planesΓ
0sΓ =0sΓ =
sC sC
sC
srsr
sC
1outΓ = 1outΓ =
• 方法: 若故意令 ,可知 ,此時 。0sΓ = 22out SΓ =0sZ Z=
圓外穩定 圓內穩定
22 1out SΓ = < 22 1out SΓ = >
Department of Electronic Engineering, NTUT11/38
14. 穩定測試(使用數學式/數值判斷法)
2 2 2
11 22
12 21
1
1
2
S S
K
S S
− − + ∆
= >
• Rollet’s Condition (K-∆ test):
無條件穩定無條件穩定無條件穩定無條件穩定之數學條件
11 22 12 21 1S S S S∆ = − <且
K-∆測試使用兩個數學因素,能表明電路是否「穩定」,但無法用來比較不同
電路、不同偏壓下的相對穩定性,即不能表明「有多穩定」。
• 西元1992年,Edwards推導出一個新的穩定性參數,稱為µ因子。
若µ > 1,該電路為無條件穩定;並且,電路的電路的電路的電路的µ值越大值越大值越大值越大,,,,表示電路越表示電路越表示電路越表示電路越
穩定穩定穩定穩定。。。。因此, µ因子可以表明不同電路、不同偏壓下的穩定性。
2
11
22 11 12 21
1
1
S
S S S S
µ ∗
−
= >
− ∆ +
K > 1 與 |∆| < 1 必須同時滿足
Department of Electronic Engineering, NTUT14/38
15. 範例
判斷這個電晶體在這些頻率下的穩定性。
2 2 2
11 22
12 21
1
1
2
S S
K
S S
− − + ∆
= >
11 22 12 21 1S S S S∆ = − <
• 一顆偏壓在VCE = 15 V、IC = 15 mA的BJT,在頻率 f = 500 MHz,
1 GHz, 2 GHz, 以及4 GHz時的散射參數如下所列:
2
11
22 11 12 21
1
1
S
S S S S
µ ∗
−
= >
− ∆ +
( )22 11
2 2
22
L
S S
C
S
∗∗
− ∆
=
− ∆
12 21
2 2
22
L
S S
r
S
=
− ∆
( )11 22
2 2
11
s
S S
C
S
∗∗
− ∆
=
− ∆
12 21
2 2
11
s
S S
r
S
=
− ∆K ∆
0.482 0.221 123∠ −
0.857 0.173 162.9∠ −
(GHz)f
0.5
1
µ
0.49
−
sC sr
1.36 157.6∠ 0.558 2.8 57.86∠ 2.18
1.28 169∠ 0.315 2.62 51.3∠
(GHz)f
0.5
1
LC Lr
1.71
Department of Electronic Engineering, NTUT15/38
16. 範例
( )22 11
2 2
22
L
S S
C
S
∗∗
− ∆
=
− ∆
12 21
2 2
22
L
S S
r
S
=
− ∆
( )11 22
2 2
11
s
S S
C
S
∗∗
− ∆
=
− ∆
12 21
2 2
11
s
S S
r
S
=
− ∆
sC sr
1.36 157.6∠ 0.558 2.8 57.86∠ 2.18
1.28 169∠ 0.315 2.62 51.3∠
(GHz)f
0.5
1
LC Lr
1.71
Department of Electronic Engineering, NTUT16/38
31. 輸出並聯電阻的穩定原理 (II)
Department of Electronic Engineering, NTUT
Term
Term2
Z=50 Ohm
Num=2
R
R1
R=500 Ohm
S2P
SNP1
File="MyTransistor.s2p"
21
Ref
Term
Term1
Z=50 Ohm
Num=1
indep(S_StabCircle1) (0.000 to 51.000)
S_StabCircle1
indep(L_StabCircle1) (0.000 to 51.000)
L_StabCircle1
500 Ω
輸出穩定圓
合在一起看,重新畫穩定圓
31/38
32. 功率轉換增益GT (Transducer Power Gain)
• 雙埠同時共軛匹配:最大轉換增益匹配
2 2 2 2
2 2
21 212 2 2 2
22 11
1 1 1 1
1 1 1 1
s L s L
T
s in L s out L
G S S
S S
− Γ − Γ − Γ − Γ
= =
− Γ Γ − Γ − Γ − Γ Γ
Transistor
[S]+
−
sE
sZ
LZ
見第三章投影片slide 23
Department of Electronic Engineering, NTUT
inΓ
1E
oZ
oZ
Transistor
oG
Output
matching
LG
Input
matching
sG
s in
∗
Γ = Γ L out
∗
Γ = ΓoutΓ
• 功率轉換增益 GT
inΓsΓ LΓoutΓ
輸出端的匹配目標輸入端的匹配目標
32/38
33. 欲達到雙埠同時共軛匹配的困難之處
Department of Electronic Engineering, NTUT
• 雙埠同時共軛匹配:最大轉換增益匹配
12 21
11
221
L
in
L
S S
S
S
Γ
Γ = +
− Γ
見第三章投影片slide 17,18
12 21
22
111
s
out
s
S S
S
S
Γ
Γ = +
− Γ
inΓ
1E
sZ
LZ
Transistor
oG
Output
matching
LG
Input
matching
sG
sΓ LΓoutΓ
• 困難之處困難之處困難之處困難之處:左右交相賊
LΓ inΓ
s in
∗
Γ = Γ
outΓ
L out
∗
Γ = Γ
sΓ L
′Γ
匹配目標 匹配目標
意思是說,當輸入匹配好了,輸出匹配卻跑掉了;然後
你再配好輸出之後,換輸入又跑掉了。接著再配輸入,
輸出又跑掉,一直輪迴。此現象肇因於左式的何項此現象肇因於左式的何項此現象肇因於左式的何項此現象肇因於左式的何項????
33/38
34. 單向轉換增益 GTU
11in SΓ =
1E
oZ
oZ
Transistor
oG
Output
matching
LG
Input
matching
sG
sΓ LΓ22out SΓ =
2 2
2
212 2
11 22
1 1
1 1
s L
TU s o L
s L
G S G G G
S S
− Γ − Γ
= =
− Γ − Γ
sG oG LG
(dB) (dB) (dB) (dB)TU s o LG G G G= + +
• 單向轉換增益GTU (Unilateral Transducer Power Gain)
• Gs與GL表示輸入/輸出電路的匹配增益(或損耗)。
12 0S =
見本章slide 3
Unilateral (S12=0): 表示port 2的入射不會穿過
電晶體而對port 1造成影響,而可得Γin=S11。
2 2
2
212 2
22
1 1
1 1
s LL
T
AVS in s L
P
G S
P S
− Γ − Γ
= =
− Γ Γ − Γ
12 21
11
221
L
in
L
S S
S
S
Γ
Γ = +
− Γ
12 21
22
111
s
out
s
S S
S
S
Γ
Γ = +
− Γ
輸入與輸出
各自獨立了
Department of Electronic Engineering, NTUT34/38
35. 最大單向轉換增益
11S
1E
oZ
oZ
Transistor
oG
Output
matching
,maxLG
Input
matching
,maxsG
11s S∗
Γ = 22L S∗
Γ =22S
11s S∗
Γ = 22L S∗
Γ =
,max 2
11
1
1
sG
S
=
−
,max 2
22
1
1
LG
S
=
−
2
,max ,max ,max 212 2
11 22
1 1
1 1
TU s o LG G G G S
S S
= =
− −
• 最大單向轉換增益GTU,max (Maximum Unilateral Transducer Power Gain)
Optimize and to provide maximum gain in Gs and GL.sΓ LΓ
and
2
2
11
1
1
s
s
s
G
S
− Γ
=
− Γ
2
2
22
1
1
L
L
L
G
S
− Γ
=
− Γ
and
and
12 0S =
輸入與輸出端可以各自獨立設計共軛匹配電路,不會互相影響。
知電晶體在某偏壓下的S參數,
可約略看出其特性。如何看如何看如何看如何看????
Department of Electronic Engineering, NTUT35/38
36. 雙向情況(Bilateral Case):雙埠同時共軛匹配
inΓ
1E
oZ
oZ
Transistor
oG
Output
matching
LG
Input
matching
sG
sΓ LΓoutΓ
s in
∗
Γ = Γ L out
∗
Γ = Γ
• 雙埠同時共軛匹配條件下的最大功率轉換增益GT,max
and
22
1 1 1
1
4
2
Ms
B B C
C
± −
Γ = and
12 21
11
221
L
in s
L
S S
S
S
∗ Γ
Γ = Γ = +
− Γ
12 21
22
111
s
out L
s
S S
S
S
∗ Γ
Γ = Γ = +
− Γ
and
22
2 2 2
2
4
2
ML
B B C
C
± −
Γ =
2 2 2
1 11 221B S S= + − − ∆
2 2 2
2 22 111B S S= + − − ∆
1 11 22C S S∗
= − ∆ 2 22 11C S S∗
= − ∆
where
12 0S ≠
Bilateral: 表示port 2的入射會穿過電晶體而對
port 1造成影響,即ΓL的變化將使Γin跟著變化。
11s S∗
Γ = 22L S∗
Γ =與注意:不再是unilateral下的
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37. 最大穩定增益(MSG)與可資用增益(MAG)
2 2
2
212 2
22
1 1
1 1
s L
T
in s L
G S
S
− Γ − Γ
=
− Γ Γ − Γ
inΓ
1E
oZ
oZ
Transistor
oG
Output
matching
LG
Input
matching
sG
sΓ LΓoutΓ
s in Ms
∗
Γ = Γ = Γ L out ML
∗
Γ = Γ = Γ
( )
2
2 21 2
,max 212 2
1222
11
1
1 1
ML
T
Ms ML
S
G S K K
SS
− Γ
= = − −
− Γ − Γ
• 雙埠同時共軛匹配條件下的最大功率轉換增益GT,max
and
• 最大穩定增益(Maximum Stable Gain, MSG)定義在
穩定因子K =1 (穩定臨界)時:
21
12
MSG
S
G
S
=
(potentially unstable)
(unconditionally stable)
單顆電晶體在穩定條件下,
匹配後的理論增益極限。
Department of Electronic Engineering, NTUT37/38