RF IMPEDANCE TRANSFORMATION By Forest Cummings, W5LQU And Dave Russell, W2DMR (WHAT THE BOOKS NEVER...
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Transcript of RF IMPEDANCE TRANSFORMATION By Forest Cummings, W5LQU And Dave Russell, W2DMR (WHAT THE BOOKS NEVER...
RF IMPEDANCE TRANSFORMATION
By
Forest Cummings, W5LQU
And
Dave Russell, W2DMR
(WHAT THE BOOKS NEVER TELL YOU)
Transforming
50 450
Turns ratio = 1 : 3
Impedance ratio = 1 : 9
Transforming with a transformer
DEFINITION OF Q
Q = Rp/XpQ = Xs/Rs
Xp RpXs
Rs
SERIES = PARALLEL
= Rp(jXp) / (Rp + jXp)
ALGEBRA
Rp/Rs =
|
|
Q2 + 1
Rs + jXs
MATCH 250 TO 50
250
50
Q2 + 1 = 250/50 = 5Q2 = 4Q = 2Xp =250/2=-125
RpXp
-125 Rs
Xs-100
Q = 2Xs =50(2)=-100
50
100
150
200
0
-50
-100
-150
-200
50 100 150 200R ohms
XC ohms
XL ohms
THE R-X PLANE
+j
-j
50
100
150
0
-50
-100
-150
50 100 150 200 250R
XC
XL
50+j50
150-j100
ZA
Z=70.7 A=45 deg Tan A=Q=1
SERIES IMPEDANCE
Z
B
Z=180 B= -33.7 TanB=Q=0.67
50
100
150
0
-50
-100
-150
50 100 150 200 250 300XC
XL
PARALLEL IMPEDANCE
R = 250 ohms
//XL
//XC
R
50
100
200
0
-5050 100 150 200 250 300
RXC
XL
-125
= 250 // -j125 (50-j100)
-100
-150
-200
150
SERIES = PARALLEL250 to 50 Match
SERIES = PARALLEL
THE L NETWORK
50
Rs
Xs-100
250
RpXc
-125
XL = 100 XL = 100
Equivalentseries circuit
L network matching250 ohms to 50 ohms
Note: Series XL NOT equal to shunt Xc
5050
MATCH 10 TO 50
Rs10
Rp50
Xp-25
Q2 + 1 = 50/10 = 5Q2 = 4Q = 2Xs =2(10)= -20
Q = 2Xp =50/2= -25
Xs-20
ANOTHER L NETWORK
Rp50
Xp-25
10Rs
Xc = -20
Equivalent parallelcircuit
L network matching10 ohms to 50 ohms
XL25
XL25
NOTE: Shunt XL NOT equal to series Xc
50
THE Tee NETWORK(TWO L NETWORKS)
Q2Q1
XC2-250
XC1-167
RL100
Rin50
R500
Q22+1=500/100=5Q2 = 2XC2 = 500/2= -250XL2 = 100(2) = 200
XL2 = 200
Q12+1=500/50=10Q1 = 3XC1 = 500/3 = -167XL1 = 50(3) = 150
XL1 = 150
THE Tee NETWORK(CONTINUED)
XC-100
RL100
Rin50
XL1 = 150 XL2 = 200
100w, 316vp, 2A
1500w1224vp, 8A
THE PI NETWORKALSO TWO L NETWORKS
RL50
Q1 Q2Rin2000
Rs13.8
Q1 = 12, Q12+1 = 145Rs = 2000/145 = 13.8XC1 = 2000/12 = -167XL1 = 13.8(12) = 166
XL1 = 166
XC1-167
Q22 + 1 = 50/13.8 = 3.62Q2 = SQR(2.62) = 1.6XL2 = 13.8(1.6) = 22XC2 = 50/1.6 = -31
XL2 = 22
XC2 -31
THE PI NETWORK(CONTINUED)
RL50
Q1 Q2Rin2000 Rs
13.8XC1-167
Q22 + 1 = 3.62Q2 = 1.6
XC2-31
XL = 166 + 22 = 188
Q12+1 = 145Q1 = 12
JUST REMEMBER THIS !
Rp/Rs =
Q2 + 1
SIMPLE ANTENNA COUPLER
50
45 FOOTLONG WIRE
500 pF
10 uH
GROUND
TUNES 40M – 10M