oscillators and mixers -...
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Oscillators and Mixers
1
Oscillators and MixersOsc ato s a d e s
• RF oscillators• Microwave oscillatorsMicrowave oscillators• Oscillator phase noise• Frequency multipliersFrequency multipliers• Mixers
• Important considerations for oscillators:Tuning range (MHz/V)– Tuning range (MHz/V)
– Frequency stability (PPM/oC)– AM and PM noise (dBc/Hz below carrier, offset from carrier)AM and PM noise (dBc/Hz below carrier, offset from carrier)– Harmonics (dBc below carrier)
2
RF OscillatorsOsc ato s
oio
VAV
AVHAVV
frequency particular aat 01
) ( AH
criterionBarkhausencriterionNyquist
io VAH
V
1 output zero-nonbut input zero
3
RF OscillatorsOsc ato s
• General Analysis– Hartley, Colpitts, Clapp, Pierce oscillator circuits
Figure 12-2 (p. 579) General circuit for a transistor oscillator. The transistor may be either a bipolar junction transistor or a field effect transistor. This circuit can be used for common emitter/source, base/gate, or collector/drain configurations by grounding either V V or V respectively Feedback is provided by connecting node V to V
4
configurations by grounding either V2, V1, or V4, respectively. Feedback is provided by connecting node V3 to V4.
RF OscillatorsOsc ato s
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• Oscillators Using a Common Emitter BJT
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RF OscillatorsOsc ato s
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RF OscillatorsOsc ato s
• Oscillators Using a Common Gate FET
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where
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RF OscillatorsOsc ato s
• Practical Considerations Example 12.1 Colpitts Oscillator– Reactance at transistor ports .oscillator Colpitts MHz 50 aDesign
– Temperature– bias and decoupling circuitry ? theis What 100. of awith
H 0.1 . 1200 ,30
min
3
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min R
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RF OscillatorsOsc ato s
• Crystal Oscillator
)(a
1LCs
)(b0
1
CCCCL
p
Figure 12-4 (p. 584) (a) Equivalent circuit of a crystal. (b) Input reactance
)(bFigure 12-5 (p. 585)Pierce crystal oscillator circuit.
0
0
1 CC
CC
s
9
of a crystal resonator. 0C
Microwave Oscillatorsc owave Osc ato s
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and
in
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Microwave Oscillatorsc owave Osc ato s
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Example 12.2 Negative-Resistance Oscillator Design ,4025.1 having oscillatorport -One o
in
impedance. load 50 afor network matchingload aDesign GHz. 6 .500
S l ti
fZ
12344 12344in
jZjZ
SolutionFigure 12-7 (p. 587) Load matching circuit for the one-port oscillator of Example 12.2.
11
12344 jZLp p
Microwave Oscillatorsc owave Osc ato s
• Transistor Oscillators
L
L
RRRR
in
in
used.y typicallis 3 practice,In 0 choose
22
111S
S
L
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TTL
L
SS
SSSS
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in
1111 11
22out
11
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S
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11inin 11 outout ,1 ZZTT
Microwave Oscillatorsc owave Osc ato s
• Example 12.3 Transistor Oscillator DesignnH 5 a with (CG) FET GaAs using GHz 4at oscillatoror transistaDesign
.5473.0 ,5703.0 ,766.2 ,11672.0 :parameters ( 50 toMatching y.instabilit theincrease togate e with thseriesin inductor
o22
o12
o21
o11 SSSSS
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22o
12o
21o
11 SSSSSolution
,331.08 o22
22
1122
SSSCT
665.022
22
2112
SSSRT
352010459.0Select o
jZT
T
Figure 12-9a (p. 589) Circuit design for the transistor oscillator
13
Figure 12 9a (p. 589) Circuit design for the transistor oscillator of Example 12.3. (a) Oscillator circuit.
Microwave Oscillatorsc owave Osc ato s
4.296.31
o
22
211211in
SSSS
T
T
9.128 3
. 9.184or
inin
in
jXjRZ
jZ
L
linelength 0.262 with 903 in
jjL
Figure 12-9b (p. 589)(b) Smith chart for determining T.
14
Microwave Oscillatorsc owave Osc ato s
• Dielectric Resonator Oscillators
Figure 12-10 (p. 590)(a) Geometry of a dielectric resonator coupled to a microstripline; (b) equivalent circuit.
15
Microwave Oscillatorsc owave Osc ato s
Figure 12 11 (p 591)Figure 12-11 (p. 591)(a) Dielectric resonator oscillator using parallel feedback; (b) dielectric resonator oscillator using series feedback.
16
Oscillator Phase NoiseOsc ato ase No se
Figure 12-13 (p. 594)Output spectrum of a typical RF oscillator. Figure 12-18 (p. 598) Illustrating how localOutput spectrum of a typical RF oscillator. Figure 12 18 (p. 598) Illustrating how local
oscillator phase noise can lead to the reception of undesired signals adjacent to the desired signal.
,log10dBmdBdBm
dBc/Hz BISC
fm
L
Figure 12-15 (p. 596) Noise power versus frequency
17
for an amplifier with an applied input signal.
Mixerse s
Figure 12-30 (p. 617)Frequency conversion using a mixer (a) Up-conversion (b) Down-conversion
18
Frequency conversion using a mixer. (a) Up conversion. (b) Down conversion.
Mixerse s
Figure 12-31 (p. 621)(a) Circuit for a single-ended diode mixer. (b) Idealized equivalent circuit.
19
Mixerse s
Figure 12-33 (p. 623)Circuit for a single-ended FET mixer.
Figure 12-32 (p. 622)Variation of FET transconductanceVariation of FET transconductance versus gate-to-source voltage.
Figure 12-34 (p. 623)Equivalent circuit for the FET mixer of Figure 12.33.
20
Mixerse s
Figure 12-35 (p. 625)B l d i i it ( ) U i 90° h b id (b) U i 180° h b id
21
Balanced mixer circuits. (a) Using a 90 hybrid. (b) Using a 180 hybrid.
Mixerse s
22
Mixerse s
Figure 12-37 (p. 628) Circuit for an image reject mixer.
23
Mixerse s
Figure 12-38 (p. 629) Double balanced mixer circuit.
24
Mixerse s
Figure 12-39 (p. 630)A differential FET mixer.
25
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