2010 ad symposium presentation template › upload › cmc_upload › all › nf... · measures...

Noise Figure

March 30, 2012

Agilent Technologies

1

Why Do We Care About Noise?

Noise causes system impairments

• Degrades quality of service of TV, cell phones

• Limits range of radar systems

• Increases bit-error rate in digital systems

Ways to improve system signal-to-noise ratio (SNR)

• Increase transmit power

• Decrease path loss

• Lower receiver-contributed noise

• Generally easier and less expensive to decrease receiver noise than to increase transmitted power

I

Q

March 30, 2012


2

What’s the Difference Between Noise Figure

and Phase Noise?

Both are figures-of-merit characterizing the amount

of undesired noise from a component or system

Noise figure characterizes additive noise from

amplifiers, mixers, frequency converters, and antennas

Phase noise characterizes noise around an RF carrier signal

• Most often used for oscillators

or signal sources

• Sometimes used

to look at additive

carrier noise as it

passes through

a component

3

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3

Noise Figure Definition

Noise figure is defined in terms of SNR degradation:

F = (So/No)

(Si/Ni) =

(No)

(G x Ni) (noise factor)

NF = 10 x log (F) (noise figure)

DUT

So/No

Si/Ni

Gain

Test system is assumed to be 50 Ω

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4

Effective Noise Temperature

Available noise power of a passive termination = kTB

• k is Boltzmann’s constant (1.38 x 10-23 J/K)

• kTB = -174 dBm in a 1 Hz bandwidth (@ 290o K)

• For a given system bandwidth, noise is related to temperature

Amount of noise produced by a device can be expressed as an equivalent noise temperature (e.g., 15 dB ENR => 8880K)

Noise factor can be expressed as effective input noise temperature

• Not the physical temperature of the input termination

• Theoretical temperature of input termination connected to a noiseless device resulting in the same output noise power

Te = 290 x (F-1)

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5

Noise Figure Measurement Techniques

Y-factor (hot/cold source)

• Used by NFA and spectrum-analyzer-based solutions

• Uses noise source with a specified “excess noise ratio” (ENR)

• Measures noise figure and gain

Cold source (direct noise)

• Used by vector network analyzers (e.g. PNA-X)

• Uses cold (room temperature) termination only plus separate gain measurement

• Allows single connection S-parameters and noise figure (and more)

+28V

Diode off Tcold

Diode on Thot

Noise source

346C 10 MHz – 26.5 GHz

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6

Y-Factor Technique

Thot (on)

Tcold (off)

Pout (hot)= kBGa(Thot + Te)

Pout (cold)= kBGa(Tcold + Te)

Pout (hot)

Pout (cold) Y =

Thot – Y x Tcold

Y – 1 Te =

Noise Receiver

Te

290 Fsys = 1+

Calibration:

Noise Receiver

DUT

FDUT = Fsys – Frcv - 1

Ga DUT

Y-factor yields gain and noise figure

Unknown variables

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7

Graphical Representation of Y-Factor Technique

Noise Power Out

Pout (cold) Pout (hot)

Pin (cold)

Pin (hot)

DUT

Noise added

by amplifier

Pin

Poutamplifier gain

Nois

e P

ow

er

In

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8

Cold Source Technique

Pout= kBGa(Tcold + Te)

Pout

kToBGa

Fsys =

Noise Receiver DUT

Calibration:

Noise Receiver

FDUT = Fsys – Frcv - 1

GDUT

Need to know available gain very accurately

(Ga is function of S11, S22 and Gs)

Unknown variable

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9

Phase Noise

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10

Phase Noise Overview

What is “Phase Noise”?

• A random, side band noise

• Caused by phase fluctuations of an oscillator

t

P(t)

In the time domain, PN shows as jitters

Phase noise P(f)

In freq. domain, PN appears as noise sidebands

Phase noise

f

Carrier

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11

Phase Noise Overview

How to define “Phase Noise”?

3 elements:

- Offset freq. from carrier freq.

- Power spectral density (in 1 Hz

BW)

- Relative to carrier power in dBc

f0 fm (offset freq.)

1 Hz BW

SSB

P0

dBc/Hz @ offset freq. fm


Overview of PN Measurement Methods

Basic concepts for PN measurement

• A pure sine wave: V(t)=V0sin 2f0t

• Contaminated with noises (A(t): AM noise; (t): M noise)

V(t) = V0 [1+A(t)]sin[2(f0t+(t))]

1) Direct Spectrum Analysis 2) Demodulate + Baseband Analysis

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13

Direct Spectrum Measurement Method

• Easy to configure and use

• Quick phase noise check

• Log pot

• Spot frequency (PN change vs. time)

• rms PN, rms Jitter, residual FM

• X-Series phase noise application automates

the PN measurements

• Limited by SA internal PN floor

• Caution: Direct Spectrum method requires

AM << PM

DUT

Phase noise result in Log Plot

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Why is phase noise important for radar app?

Vehicle-mounted radar

• Highest performance radar transceiver

designs demand the best phase noise to

find moving targets, fast or slow

Better PN lower skirt

Better chance to find Doppler

reflection signals

V target Faster Slower

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15

Frequency

Power

Frequency

Power

OFDM sub-

carriers

Local oscillator

with phase noise

Phase noise

Frequency

Power

Down-converted

OFDM sub-carriers

with LO phase noise

added

Why is phase noise important for comms

app?

• Better PN of the LO improves sub-channel resolution

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16

Power Measurements

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17

Power Suite Measurements

[Meas] Standard spectrum analyzer measurements menu

NEW!

Segnali digitali come processi statistici

Media tradizionale Power Average

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19

Misura della potenza di canale

• Molti analizzatori di spettro moderni consentono il calcolo

della potenza in un intervallo di frequenza (channel power)

• La misura e’ eseguita applicando la seguente formula:

Pch: Potenza di canale

Bs: Banda di calcolo

Bn: ENBW della RBW

applicata

N : numero di punti di misura

pi: potenza misurata nel punto

di misura i-esimo

La formula e’ espressa in termini lineari

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20

Channel Power

Integrates the power across the RF

channel

Emulates a power meter

No bandpass filter required when in a

multicarrier environment

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21

Occupied Bandwidth

Measures the occupied bandwidth of

a digital carrier

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22

Adjacent Channel Power (ACP) Measures leakage into adjacent channels

Distortion (TOI or SHD)

Phase Noise

Filter effectiveness

[Meas], {ACP}

Use Noise Corrections

[Meas Setup], {More 1 of 3}, {More 2 of 3}, {Noise Corrections On}

Use Noise Floor Extension

[Mode Setup], {Noise Reduction}. {NFE On}

See demo PXA ACP measurement.doc

Play PXA Power Suite-1-acp.wmv

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23

CCDF

Complementary Cumulative Distribution Function

Instantaneous Envelope Power

Compared to Gaussian noise

Peak to average ratio

Modulation Filtering dependent

Modulation format dependent

Data format dependent

Symbol sequence dependent

Helps designers specify components

From spectrum analyzer display

Meas hard key

CCDF soft key

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24

Burst Power

Transmit power delivered to the antenna at the base transceiver station

Time gated or time slot dependent power measurement

Basic pulse parameters

Distortion Testing

Second order distortion

Uses one base tone

Measures at twice the base tone frequency

Third order distortion

Uses two base tones

Third order distortion measurement

Harmonic distortion

Uses one base tone

Measures distortion at integer multiples of the base tone

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26

Third Order Distortion

Uses two base tones at upper and lower locations (omega 1 and omega 2)

Measures intermodulation distortion at

the upper location (2 x omega 2 – omega 1)

and the lower location (2 x omega 1 – omega 2)

Third order distortion moves at three times the movement of the base tones level

TOI calculation

The intercept point is where the level of the distortion equals the level of the base tones

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28

TOI measurement Use Auto Tune to obtain the first measurement

Use measure setup to optimize the measurement for speed or accuracy

TOI measurement

Zero span

Play PXA Power Suite-3-toi.wmv

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30

Harmonics - Harmonic distortion measurement

Auto Sense fundamental and setup the measurement

Zero span sweep at the harmonic frequencies saves time

Harmonics measurement optimization

Measure setup

Res BW

Dwell Time

Average

Harmonics

Range Table

Set Harmonic 1

Auto fill

Res BW

Dwell Time

Noise Floor Extension

Play PXA Power Suite-2-harmonics.wmv

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32

Scalar Measurements

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33

Why Source Control?

DUT

Controlled

Source

Receiver/

Controller

Signal analyzer (SA) alone SA + controlled source

stimulus

response

DUT

Transmitter Receiver

• Perform transmitter tests

• Characterize unknown signals

Carrier power

Power v. frequency

Sidebands

Harmonics

Phase noise

Spurs

Modulations

…

• Perform stimulus-response tests

• Characterize unknown DUT

behavior w/ known signals

Filter test (bandwidth, pass-band

flatness…)

Amp. test (Gain compression, harmonics..)

Freq-translating device (FTD) test (Freq

responses, conversion loss, harmonics…)

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34

http://www.camelspit.org/images/x10rf/x10_remote_final.jpg

Connecting the signal source w/ X-Series analyzer

X-Series Source

Trigger in

Trigger out

Trigger out

Trigger in

10 MHz out Ref in

VISA Interface

(GPIB/USB/LAN) (GPIB/USB/LAN)

VISA interface type

USB

GPIB

LAN

A pair of BNC cables for HW triggering*

Feq. Ref. lock-in** *: Can be eliminated if using “SW triggering”

**: Not required, but may improve the accuracy

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35

Frequency sweep, standard

Defaulted sweep mode

Best for filter tests

Frequency responses

BW and shape factor

Pass-band flatness

Filter

fSS= fSA

Opt ESC

Source

X-Series

Sweep: f1 f2

Sweep: f1 f2

Take advantages of powerful X-Series

mark functions for filter characterization

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36

Harmonic sweep

SS/SA Freq sweep ratio:

: Multiplier = (Num./Den.)

Useful for Amp/Mixer/Filter test Harmonic responses (0 < < 1)

Sub-harmonic behavior (> 1)

Amp

fSS= fSA

Opt ESC

Source

X-Series

Sweep: f1 f2

Sweep: f1 f2

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37

Offset sweep

fSS= fSA + foffset/SS • SS/SA sweep from different starts

• Best for mixer tests

Conversion loss

Conversion frequency accuracy

Source

Opt ESC

X-Series

Sweep: f1 f2

Sweep: (f1 - fLO f2 - fLO)

RF

LO

IF

(700 to 800 MHz)

(200 to 300 MHz)

(500 MHz)

For: fLO < fRF

March 30, 2012


38

http://www.spectrummicrowave.com/mixers.asp

Reverse sweep

fSS= - fSA + foffset/SS • SS freq. sweeps: high low /SA always: low

high

• Best for mixer tests

Lower side-band characterization

Swept LO test

Source

Opt ESC

X-Series

Sweep: f1 f2

Sweep: (fRF – f1 fRF – f2)

RF

LO

IF

(800 to 700 MHz)

(200 to 300 MHz)

(1,000 MHz)

P

f LO

(fixed)

RF

(SS)

IF

(SA)

Reverse

sweep

Forward

sweep

For: fLO > fRF

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39

http://www.spectrummicrowave.com/mixers.asp

Power sweep

Amp Opt ESC

Source

X-Series

Power Sweep:

P1 P2

• SS RF output power sweeps

• Fixed or swept frequency

• Useful for Amp test Gain compression

Cut-off power level

Gain

Cut-off level

1-dB gain

compression

Initial power level

Power sweep range & On/Off

Count for system loss/gain

Set power resolution

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40

Normalization, Open/Short cal

Normalization

– To remove systemic errors

– Under “Trace” menu

Open/Short cal

– For 1-port return-loss meas.

– Graphic guide

– Under “Trace” menu

Reference line w/ a “thru” connection for measuring

system response w/o DUT

March 30, 2012


41

dB

No reflection

(ZL = Zo)

r

RL

VSWR

0 1

Full reflection

(ZL = open, short)

0 dB

1

= Z L - Z O

Z L + O Z

Reflection

Coefficient =

V reflected

V incident

= r F G

= r G Return loss = -20 log(r),

Voltage Standing Wave Ratio

VSWR = Emax

Emin =

1 + r

1 - r

Emax

Emin

1. Reflection Parameters

March 30, 2012


42

E4440AU-015 Accessory Kit

Item Description Specifications Qty 1 RF Bridge 300 kHz o 6 GHz, Type

N, 50

1

2 Power Divider DC to 18 GHz, Type N, 50

1

3 Coaxial

Terminator

DC to 18 GHz, Type N, 50

1

4 Coaxial Short DC to 18 GHz, Type N

(m), 50

1

5 Coaxial Cable 2 ft, Type N-N, 50 2

6 6 dB Coaxial

Attenuator

DC to 18 GHz, Type N

(m), 50

1

• Provides the accessories you will need for Open/Short Cal

and Return Loss measurements up to 6 GHz

March 30, 2012 Agilent Technologies

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