basics of phase by niose_sherly joy

7/27/2019 Basics of Phase by Niose_Sherly Joy

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National Workshop on Recent Trends in RFNational Workshop on Recent Trends in RF

and Microwave Techniques and Measurementsand Microwave Techniques and Measurements


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A

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Basics of Phase Noise, Implications, Measurement Methods and Reduction Techniques

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C N

F S O

C F S S

I R F S

P N J

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C

Noise can be defined as any unwanted disturbance thatinterferes with the desired signal which can degrade theperformance of the particular system.

The primary characteristic of noise is its randomness and thisis due to the physical mechanism which generate it.

External Noise Sources

Sources are external to the system.

Internal Noise SourcesNoise created with in the system itself.

Three leading types of noises

Thermal Noise Shot Noise

Flicker Noise


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E

Atmospheric Noise ( up to 30MHz)

Caused by lightning discharges and other natural electrical

disturbances , propagated like radio waves.

Extra terrestrial noise (10MHz to 1.5GHz)

Space noise sources are sub divided into two:

Solar Noise

July 13, 2012 6

Sun is a large body at very high temperature (>60000C onsurface), radiates very broad band frequency spectrum.

Cosmic noise

Stars are also at high temperature, also radiate RF noise.

Industrial Noise (1MHz to 600MHz)

Urban and Industrial areas, the intensity of noise made by

human outstrips that created by any other source.


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Time Domain Frequency Domain


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Thermal noise currentobserved when

a) Standard 50resistor is shortcircuited

across a 50 noisefree resistor

c) AC connectedacross a 50 normalresistor

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Thermal noise power in a conductor is proportional to theabsolute temperature and bandwidth of the measuring system.

Pn T x BW = KTB

whereK = Boltzmanns constant(1.38 x 10-23 J/ K)

0

BW(B) = Bandwidth in Hz

At room temperature of 170C (2900K) for 1.0 Hz BW

Pn = -174dBm/Hz

-174dBm is the minimum noise level that is practicallyachievable, for further reduction the temperature is to be

lowered.

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KTBRV

KTBRRPV

R

V

R

V

R

VP

n

nn

n

L

n

4

44

1

4

2

222

===

===

free R and noise source vn .

A

RL

RL R .

T

.

July 13, 2012 12

qu va en rcu o

a resistor as a noisegenerator


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C..

The ways to reduce thermal noise contents are

Reduce the temperature of operation

Reduce the value of resistor

KTBRVn 4=

Thermal noise is only generated by the

real part of any impedance ie resistor.

The imaginary part does not generatenoise.

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Equivalent Circuit ofa resistor as a noise

generator


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Most important source of noise in active devices, particularlynoticeable in semiconductor devices such as tunnel junctions,

schottky barrier diodes and P-N junctions.

Arises from random flow of carriers through a potential barrier.

The current carriers even under dc conditions are not moving

in a continuous flow since the distance they travel issomewhat different for each carrier, because of their randommotion.

Power spectrum is flat with frequency.

The name shot noise is derived from the fact that when drivinga speaker, excessive shot noise sounds like a shower of leadshot falling on a metallic surface.

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C

Shot noise in a diode is

q = charge of an electron(1.6 x 10-19 coulomb)

Idc = diode dc current (amperes)

BW = Band Width of frequencies involved(Hz)

BWIqi dcnoise = 2

Difficult to calculate for complete transistor, depends on thecurrents in the emitter-base and collector-base diodes.

Device manufactures often specify an equivalent noise

resistance

Resistance value that produces the same amount of thenoise as the devices shot noise when applied to the

thermal noise of Vn.

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=1 106

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= 1 109

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C F

There are two classes of frequency variations :

Discrete Signals

Appear as distinct components,

called as spurious signals. Related to knownphenomena in the signalsource such as power line

Random Signals

Appear as random phase fluctuations and calledas phase noise.

The source of random noise in an oscillatorincludes thermal noise, shot noise and flickernoise.

frequency, vibrationfrequencies or mixer products.


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A

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.

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R .

A .

Phasor representation of

additive noise contribution

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AM components FM components


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I

. I

V() = VO (20 )

VO= 0 =

I

.


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I .

R

V( ) =[ VO+()(2 O+( ))

=

(AM )() = P

(P )

VO =

O =

Oscillators operate in saturation, AM noise component is 20dB lower

than the phase noise component , so is neglected.


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S

,

.

D

T

.

F .


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T

CLRW

A

Ref 10 dBm Att 40 dB

1 AP

*RBW 300 Hz

*

*

VBW 3 Hz

SWT 190 s

-30

-20

-10

0

10

1

Marker 1 [T1 ]

-3.75 dBm

1.039989200 GHz

Marker 2 [T1 ]

-70.16 dBm

1.039974200 GHz

Marker 3 [T1 ]

-68.91 dBm

1.040004200 GHz

.

O . E:

W VCXO .

Center 1.0399892 GHz Span 100 kHz10 kHz/

-90

-80

-70

-60

-50

-40

23

Date: 1.JAN.2000 02:54:22


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J

, B/H

1 H

Two ways of describing effectively the same parameter, choicedepends upon the application.

phase noise -10MHz TCXO

Offset SSB Phase

Noise

Phase

Noise

10Hz -90dBc/Hz

100Hz -120dBc/Hz .

,

. T

.T D M (TDM)

.

(typ.)at

10MHz

1kHz -135dBc/Hz10kHz -150dBc/Hz

100kHz -155dBc/Hz

Specification

Integrated Phase Jitter

RMS

(12kHz to 20MHz) typ.

1ps


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J J

J

N RMS ( )

RF .

o It is possible to quote phase jitter in two formats.

J


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U

.

I RMS,

.


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.

July 13, 2012 32Basics of Phase Noise, Implications, Measurement Methods and Reduction Techniques

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A

Absolute Phase Noise

T

.

A

Specified on sources or complete

system

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U

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C

Residual (Additive/Two port ) Phase noise

N , .

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() .

T

.

E: N , , .


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C

Two-port Vs Absolute Phase Noise

T

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A

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S , S N R (SNR) .

P :

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E ()

T 1 2

. T LO

M

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1LO

2 LO

LO .


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LO

.

P L

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F

:

D R S

D C S

A M C S


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C LO

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B C

[ ]t)(tf2]sinV

e(t)[1V)V(t 0

0

0 ++=

dt

(t)d

2

1(t))A(t 0

+=

D D ,

.

D A, .

D .S

.

July 13, 2012 45

)f(V 0S )(S)(S)(S)(S

2A fffff =

Basics of Phase Noise, Implications, Measurement Methods and Reduction TechniquesVSSC/ISRO


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D C

There are a number of ways to specify phase noise:

o Single Sideband Phase Noise (t) (dBC/Hz)

o Spectral Density of Frequency Fluctuations Sf(f) ( Hz2/Hz)

o pec ra ens y o ase uc ua ons

(Radians2/Hz)

o Two Point Allan Variance y()

o Incidental Frequency Modulation f(Hz)

o Incidental Phase modulation (Radians)


( ) ( / )


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() (BC/H)

E

1 H .

PowerSignalTotalBandSideHz1SingleaindensityPowerL(f) =

Simple and most commonmethod.

Directly measured in

spectrum analyzer.

The unit of dBc/Hz refer to

dB below the carrier

measured in a 1Hz

bandwidth.


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D F F () H2/H

One sided spectral distribution of the frequency

fluctuations per Hz bandwidth.

Sf(f) = (f rms)2 /BWfrms = RMS value of a peak frequency modulation

BW = Bandwidth of frms measurement

This is the power spectral density of the frequency

discriminators output.

It is directly measured by connecting an audio spectrum

analyzer to the output of a frequency discriminator whoseinput is the oscillator under measured.


D () 2/H


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D () 2/H

It is often referred to as the spectral density and describes

the energy distribution as a continuous function, expressed

in units of energy per Hz bandwidth

S(f) = (2rms )/BW

2rms= RMS value of peak phase modulation

= an w use o measure rms

This is the power spectral density of the phase

demodulators output.

It is directly measured by connecting an audio spectrumanalyzer to the output of a phase demodulator whose input

is the oscillator under measured.



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A () Also known as short term stability, a time domain

measure of oscillator instability.

Directly measured using a frequency counter torepetitively measure the oscillator frequency over a time

period (gate time).

The Allan variance is the expected value of the RMSchange in frequency with each sample normalized by the

oscillator frequency.

Allan Variance for 10MHz OCXOseconds stability

0.01 1x10-10

0.1 5x10 -11

1.0 1x10-11



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I F H

Always specified with a lower and upper frequency limit.

Often used to specify overall oscillator instability, generally inFM receivers where the video pass band is the frequency limit.

Calculated by taking the square root of the spectral density ofthe frequency fluctuations integrated from a lower frequency

.

Directly measured by passing the output of a frequencydiscriminator whose input is the oscillator under test, through aband pass filter and determining the RMS frequency variation.

=b

a

f

f

ff dffS )(


I


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I

This is a measure of the total RMS phase instability over aband of offset frequencies.

Preferred for phase modulated signals, since it provides a

better measure of overall oscillator instability.

Calculated by taking the square root of the spectral density ofthe hase fluctuations inte rated from lower fre uenc limit toan upper frequency limit.

Directly measured by passing the output of a phasediscriminator whose input is the oscillator under test, through aband pass filter and determining the RMS phase variation.

=b

a

f

f

dffS )(



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There are three fundamental ways to measure these

perturbations of the signal

Direct Spectrum Measurement

Spectrum Analyzer Method

Heterodyne Frequency Measurement

Measurement with frequency discriminator Measurement with phase detector

Phase Detector Method

Phase Detector Method with PLL Controlled Reference

PLL Method with Cross Correlation

Delay Line Method


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A

D S A .

M ,

. M C L LT. M LPN

.

P BW BIF 1H BW.


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C

LPN= LPN () 10 BNIF

LPN, B NIF , 1 W 1H

L PN, RMS

B NIF, 1 W

B NIF


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C

D ,

3B .

LPN()= LPN () 10

CLRWR

A

Ref 10 dBm Att 40 dB

1 AP

*RBW 300 Hz

*

*

VBW 3 Hz

SWT 190 s

PRN

-70

-60

-50

-40

-30

-20

-10

0

10

1

Marker 1 [T1 ]

-3.75 dBm

1.039989200 GHz

2

Marker 2 [T1 ]

-70.16 dBm

1.039974200 GHz

3

Marker 3 [T1 ]

-68.91 dBm

1.040004200 GHz

RBW+ .

L( ) = LPN () LT M

BW .


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Center 1.0399892 GHz Span 100 kHz10 kHz/

-90

-80

Date: 1.JAN.2000 02:54:22

LT = 3.75B

LPN () = 70.16B

BRBW = 300HL () = 70.16 10300 (3.75)

=91.2B91.2B

C B


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C B

C RBW

.

I RBW , IF .

D U T (DUT) S A.

S A

.


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,

A


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A


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H F

Time domain method.

Down converts the signal under test to an intermediate

frequency.

High resolution frequency counter repeatedly counts the

,

measurement held constant. This allows several calculations of the fractional

frequency,, over the time period used.

Allan Variance

y () computed from which is the timedomain correspondence to (f) in the frequency domain.


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Feeds the signal under test into a frequency discriminator

and monitors the output on a low frequency spectrum

analyzer.

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FM

DiscriminatorBaseband

Analyzer

ow ass

FilterOUT


D


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July 13, 2012 62Basics of Phase Noise, Implications, Measurement Methods and Reduction TechniquesVSSC/ISRO

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D


D C


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D C

To maintain quadrature, PLL technique is used to correct

the reference source.


C C


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D


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A FM

RF . O

.


Comparison of Phase Noise Measurement Methods


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Phase Noisemeasurement

Method

Advantage Disadvantage

Direct measurement

with spectrumanalyser

Easy setup/easy operation No calibration necessary

AM noise and phase noise cannot be

separated.

No carrier suppression: Restricted dynamic range

Overlap of RBW filter shape at low offset

Measurement accuracy limited by LO

Phase Detector

Method

+

PLL controlled

reference

AM noise and phase noiseseparated

Carrier suppression

- high dynamic range

- small offsets

Noise of LO of SA of minor

importance Measurement of two

identical oscillators possible

(3dB correction)

Complicated setup

Calibration required

Very complicated calibration in between

PLL bandwidth


Cont


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Phase Noise

measurement

Method

Advantage Disadvantage

Cross correlation

method

Improvement of phase

noise of test system /

reference oscillator (up to

Longer measurement time for

extremely low phase noise

Very complex setup

Delay line method

Suitable for high drifting

oscillators

No reference oscillator

necessary

AM suppression

Complicated setup

Complicated calibration

Restricted measurement range



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N

.

F

U

F FM/ M

C

S

D .



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A

.

B ,

.

I

(10 MH) P L L (PLL).


Cont..


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C : H .

U N B S.

C .

G C A C:

S

R .

F , , D .

G B GPS

.


Signal Sources


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Quartz crystal based oscillator

O

.

W

Q, ,

.

Phase Locked Oscillator

I , L O T

P L L (PLL).

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Crystal oscillators produce asmall fraction of undesirableenergy (phase noise).

The response usually comprisesof three distinct slopescorresponding to three primary

the oscillator.

July 13, 2012 74

Region A: It is flicker FM noise , magnitude is determined by

the quality of crystal.

Region B: It is the 1/F noise and is by the semiconductor

activity.

Region C: It is the white noise or broadband noise.


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30 . C (C)

0.25 DC .

C C (C)

, 0.1.

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C C (C) D C C (DC)

O , .

S 1 1010 DC .

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Type of Oscillator SSB phase noise

Standard crystal Oscillator 130B/H 1 KH

TCXO -140dBc/Hz at 1 KHz offset

OCXO -150dBc/Hz at 1KHz offset

Comparison of phase noise


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C MH GH .

P ( N2 ) 20 N B.

=(N)

Degradation20 B

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2 6

3 9

4 12

5 14

10 20

20 26

100 40


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W,() =

, B/H

() = , B/H

1 AP

CLRWR

A

Att 40 dB *Ref 1.8 dBm

*

*

RBW 1 kHz

VBW 10 Hz

SWT 50 s

*

-20

-10

0

1

Marker 1 [T1 ]

1.71 dBm

18.817600000 MHz

Delta 1 [T1 ]

-77.38 dB

25.000000000 kHz

Fundamental oscillator


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Center 18.8176 MHz Span 500 kHz50 kHz/

-90

-80

-70

-60

-50

-40

-30

20

1

A

Ref 15 dBm Att 50 dB *

*

*

RBW 1 kHz

VBW 10 Hz

SWT 50 s*

10

1Marker 1 [T1 ]

11.39 dB

376.500000000 MHz

Delta 1 [T1 ]

-57.81 dB

25.000000000 kHz

Date: 10.JUL.2012 07:36:05

CLRWR

Center 376.501 MHz Span 500 kHz50 kHz/

1 AP

-80

-70

-60

-50

-40

-30

-20

-10

0

1

Date: 10.JUL.2012 11:47:05

20 times multiplied output

C A


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Parameter Quartz Oscillators Atomic Oscillators

TCXO MCXO OCXO Rubidium Cesium

Accuracy

(per year)

2 x 10-6 5x 10-8 1 x 10-8 5 x 10-10 2 x 10-11

Aging/Year 5x 10-7 2x 10-8 5x 10-9 2 x 10-10 0

Temp.Stab. 5 x 10-7

-

3 x 10-8

-

1 x 10-9

-

3 x 10-10

-

2 x 10-11

-,

Stability,() (=1) 1 x 10-9

3 x 10-10

1 x 10-12

3 x 10-12

5 x 10-11

Size(cm3) 10 30 20-800 200-800 6,000

Warm up

Time (min)

0.03(to 1x10-6)

0.03(to 2x10-8)

4

(to 1x10-8)

3(to 5x10-10)

20(to 2x10-11)

Power(W)(at lowest temp.)

0.04 0.04 0.6 20 30

Price($) 10-100


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There are a number of sources that sum up to form the PLLnoise profile

VCO

PLL Dividers Reference Source

The hase noise characteristic will also be influenced b thePLL bandwidth of the frequency locking circuitry.

Within the PLL bandwidth, the phase noise corresponds to theadditive noise of several PLL components such as divider,phase detector and of the multiplied reference signal.

Due to the multiplying effect in the PLL, phase noise is higherthan that of the reference oscillator.

July 13, 2012 81


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B


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C ( 1H)

P .

D ,

.

W PLL BW, PLL ,

.

B

P VCO .


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C B


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B .

B

L PLL .

, .

B

L .

T PLL .

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B

C ,

PLL .

P .

M B .

M BW

. T BW

PLL.

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C F B


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VCO 10KH = 111BC/H (S VCO) P PLL

= + 20 N + 10

= 210 + 20 260 + 10 4106

= 210 + 48.3 + 66

= 95.6B/H

C 1040MH

R

16MH

P

LBW

= 140B + 20 260

= 91.7B/H

S .


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N 260R 4

P

S

210B/H

(

)

P

140B/H

(

)


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O :P N

F (1/ )

F C

P N

.

C

C


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C , .

L 1/

(1) (2) ().

I Q, ,

.

D L Q 6B.

D B

.

F 0/(2QL) , .


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A

,

1/ ,

= 0 X=0

"" ( = 0 B/).

= 1 " 1/"

( = 20 B/).

T

= 2, 3, 4,

.

. 9B/O , . BJT FET.

S

T(T 2).A

10 I.


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Leeson equation provides how circuit noise and circuit

elements factor into the phase noise measurement.


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T PLL

.

T F : I PLL/F PLLVCO

R SM

P S

L CV


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C

G VCO


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T .

T .

T .

.

I ,

. M 20N

N .


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C . I ,

DC .

I DC DC ( L D O )

.

S ( L ESR) .

D .

RF F .

O F C

.


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After putting LDO

July 13, 2012 94

U RF


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U RF

.

P S (V) (V)

PCB . VCO PCB

VCO

.

July 13, 2012 95


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V

I =20 ((

)/(2 ))

L

F

C

F L V (13.5, 20H 2 KH).

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: ,

, C

C H: 5 3 .

: C MIL

) .

F ,

.

W , TCXO OCXO

.


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During vibrationBefore vibration


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July 13, 2012 99

Oscillator card packed in Silicon Vibration IsolatorOscillator card packed with foam packing


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During vibrationBefore vibration


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F

. I PLL ,

..

W

.

T

.


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O

,

.

,

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F S A , C R


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F S A , C R

L N E S D , C.D. M,

J.A.C

P N S S (T A) ,W.P.R

E C S , K & D

M M S: P AT S M T I


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basics of phase by niose_sherly joy

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