oscillators and mixers -...

Oscillators and Mixers

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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


• 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

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configurations by grounding either V2, V1, or V4, respectively. Feedback is provided by connecting node V3 to V4.


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0 0

0

3

2

1

3223

020211

3131

VVV

YYYYGYgGGYYgGY

YGYGYY

mimi

ii

• Oscillators Using a Common Emitter BJT

0 4

3

00

3223

VGgGg mm

0 1

323

331

VV

YYYgYGYY

m

i0

:1 ,1 ,1

321

332211

XXXBXBXBX

0

where

331

43

jBBBjGVVV

i signsamethe:

21

XX

XGgX

i

m

0111

0323 BBjjBgm

capacitors:oscillatorcomponent. typeopposite :sign same the: ,

21

3

21

XXColpittsX

XX

0111

0321

BGg

B

BBB

minductors , :oscillator

inductor capacitors , :oscillator

21

3

21

XXHartley

XXXColpitts

5

23 BGB icapacitor 3

21

Xy


Colpitts :oscillator H tl ill t

L

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LL

CXLXLXHartley

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011 , ,

:oscillator

CC

LCC

21

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1

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C

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210

1

0

mgC

CCL

2

21

21

30

m

Gg

LL

LLC

1

2130

6

iGC1 iGL2


• Oscillators Using a Common Gate FET

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where

0

43

322

VVVVGYYYgG omo

21

3

i dcapacitors , :oscillator

component. typeopposite :

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X

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oom

oom

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inductor

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022130

itinductors , :oscillator

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0

3

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capacitor

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LLC

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m

mgXXXX

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321 0 01213 GLLLC

7

oGX1


• 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

S l tiQQ

LRGg iim

– Inductor loss

333 1 :impedanceInductor LjRYZ pF 200pF 1001

213

2021

21

CCLCC

CCSolution

21312130

333

111111

p

CCLCRG

CCL

j

i

pF 2001 31.0 11

30

3021

RGCCQLR i

11 1 RG

CCi

11

73523721

1

3

2120

L

CL

CCGR

i

1

3

2120

1LL

CCGg

GR im

i

15

13.611

30

1

3

2120

max

LQ

CL

CCRR

i

8

1.5max

min R

Q


• 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

,,

and

in

LT sZsIZsIZjssI

,,,

0000

Is

TTT s

sZsIZsIZ

0

0

, 00

Is

T

IZ

II

Z

ininin

0,,,

IZZjIjXjIRjIZ

0, 00

T

T

IsZIZjs

sIZ

in

in

00

0

XXRR

IZZ

L

L

2

, 00

TT

IsT

IZ

ZIZj

sZ

in0in

0in

0in

0in

0

0

in

10

ZZZZ

ZZZZ

ZZZZ

XX

L

LL

L

0Im

TT

T

ZI

Z

Z

10

in0in0in0L I


0l diF

0

RIXIR

RI

XXI

R TTTT

0

0 load, passive aFor

ininin

in RI

XXXI

RRIXIR

L

LLL

stability oscillatormax in result -high

00

inin

QXXIR

IIL

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


• Transistor Oscillators

L

L

RRRR

in

in

used.y typicallis 3 practice,In 0 choose

22

111S

S

L

LT

TTL

L

SS

SSSS

XX

11211211inin

in

1111 11

22out

11

ZZS

S

L

L

12

TTLL SS 2222

11inin 11 outout ,1 ZZTT


• 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

.15552.0 ,1826.1 ,9675.2 ,3518.2 o

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

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Figure 12 9a (p. 589) Circuit design for the transistor oscillator of Example 12.3. (a) Oscillator circuit.


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.

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• Dielectric Resonator Oscillators

Figure 12-10 (p. 590)(a) Geometry of a dielectric resonator coupled to a microstripline; (b) equivalent circuit.

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Figure 12 11 (p 591)Figure 12-11 (p. 591)(a) Dielectric resonator oscillator using parallel feedback; (b) dielectric resonator oscillator using series feedback.

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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

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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

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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.

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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.

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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

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Balanced mixer circuits. (a) Using a 90 hybrid. (b) Using a 180 hybrid.

Mixerse s

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Mixerse s

Figure 12-37 (p. 628) Circuit for an image reject mixer.

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Mixerse s

Figure 12-38 (p. 629) Double balanced mixer circuit.

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Mixerse s

Figure 12-39 (p. 630)A differential FET mixer.

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