Eder EIRAS
Noise Seminar
Signal Analysis Specialist
Agilent Technologies
Agenda
• Fundamental noise concepts
• What’s Noise Figure
• Noise figure Measurements
• Agilent Noise Figure Solutions – Demos
• What’s Phase Noise
• Phase Noise Measurements
• Agilent Phase Noise Solutions - Demos
Page 2
Agenda
• Fundamental noise concepts
• What’s Noise Figure
• Noise figure Measurements
• Agilent Noise Figure Solutions – Demos
• What’s Phase Noise
• Phase Noise Measurements
• Agilent Phase Noise Solutions - Demos
Page 3
Noise Can Obscure Weak Signals
Amplified
Signal
(with added
noise)
Small
Signal
Real (Imperfect) Amplifier
• Noise is always present in real system components
• The added noise limits the detection of weak signals
• Noise floor is a crucial parameter for receivers
Page 4
Sources of Noise
Receiver
V+
Power Supply Noise
EMI Noise
Device
Noise
LO
Phase Noise
Page 5
Inherent Noise-Producing Phenomena
• Thermal noise (Johnson noise)
• The kinetic energy of electrons and holes due to their finite temperature
Ptherm= kTB (watts)
Where k = Boltzmann’s constant
T = temperature in K
B = system’s noise bandwidth
• Shot noise
• Due to quantized, random nature of current flow
• Uniform frequency spectrum (like thermal noise)
• Flicker noise (1/f or pink noise)
• A low-frequency phenomenon in which noise power has a 1/f spectral
density
Page 6
Noise Power at Standard Noise Temperature
(290K)
Noise
Source
R+jX
RL - j XL
k = 1.38 x 10-23 joule/K
T = Temperature (K)
B = Bandwidth (Hz)
Available noise power = Pav = kTB
At 290K, Pav = 4 x 10 -21 W/Hz = -174 dBm/Hz
(In deep space, kT = -198 dBm/Hz)
Page 7
Agenda
• Fundamental noise concepts
• What’s Noise Figure
• Noise figure Measurements
• Agilent Noise Figure Solutions – Demos
• What’s Phase Noise
• Phase Noise Measurements
• Agilent Phase Noise Solutions - Demos
Page 8
What Is Noise Figure ? (A Practical Example)
Sin / Nin = 40 dB
Sin
Sin
Sout / Nout = 30 dB
Nout
Nin
a) S/N at amplifier input
Nin
B = 25 MHz
Page 9
Nout
Gain = 20 dB
b) S/N at amplifier output
Sin / Nin
Noise figure (NF) =
Sout / Nout
= 40 dB – 30 dB = 10 dB
Definition of Noise Figure by Equation (Friis, 1944)
N
Nin
a
Nout = Na + Nin • Ga
R
s
Noise Figure = NF (dB) = 10 log
Ga
Nin = kT0B , where T0 = 290K
Sin / Nin
= 10 log
Sout / Nout
FdB = Actual output noise(dBm)
– Noise from “perfect” device(dBm).
Page 10
Na + Nin • Ga
Nin • Ga
= 10 log (noise factor)
= 10 log F
What is the noise figure?
Z0 at 290K
30dB gain
10 MHz bandwidth
No = –70dBm
Noise Figure = a) 24dB?
b) 4dB?
c) 25dB?
d) 6dB?
Effective Input Noise Temperature (Te)
Output Noise Power
N
Nin
R
s
Na
-Te
Page 12
0
Te
Source Temperature (K)
a
Ga
Nout
Noise Temperature
an alternative to Noise Figure
ideal network
kToB
Σ
kTeB
To;Z0
Te
Z0
No = kT0BG + kTeBG
= k(T0 + Te)BG
Cascade Formula
G1
G2
F1
F2
NF of a two-stage system =
F12 = F1 +
F2-1
G1
Fn+1 - 1
NF of an n-stage system = Σ Fn+1 = Σ Fn +
Σ Gn
Where Σ Fn is the cumulative NF up to the nth stage,
and Σ Fn+1 is the cumulative NF up to the (n+1)th stage
Page 14
Importance of Knowing NF: Satellite Example
Transmitter:
ERP
Path Losses
Rx Antenna Gain
Power to Rx
Power to antenna: +40 dBm
Frequency: 12 GHz
Antenna gain: +15 dB
+55 dBm
-200 dB
+60 dB
-85 dBm
ERP =
+55 dBm
Receiver:
S/N = 4 dB
Noise @ 290K
Noise in 100 MHz BW
Receiver NF
Rx Sensitivity
-174 dBm/Hz
+80 dB
+5 dB
-89 dBm
• Choices to increase margin by 3 dB:
1. Double transmitter power
2. Increase gain of antennas by 3 dB
3. Lower the receiver NF by 3 dB
Page 15
Receiver NF: 5 dB
Bandwidth: 100 MHz
Antenna Gain: +60 dB
Agenda
• Fundamental noise concepts
• What’s Noise Figure
• Noise figure Measurements
• Agilent Noise Figure Solutions – Demos
• What’s Phase Noise
• Phase Noise Measurements
• Agilent Phase Noise Solutions - Demos
Page 16
Y-Factor (Hot/Cold) Method
Output Power
Nin= kB (Th or Tc)
Ga
Nh
Slope = kBGa
Nout= Nh or Nc
Na
R
s
Nc
Y = Nh / Nc
Na
-Te
Tc
Source Temp (K)
Th
• Hot and cold noise sources are applied separately to the DUT and the
output power is measured
• The avalanche diode is a popular hot/cold noise source
Page 17
Agilent Noise Sources
Matching Pad
Noise
Output
Bias
Input
Excess Noise Ratio = ENR (dB) = 10 log
Th - Tc
T0
(T0 = 290K)
• A calibration report (ENR versus frequency) is provided with each source
• Broadband and capable of electronic switching between Tc and Th
• The diode is designed for stability over time
• Source match is improved with a built-in matching pad
Page 18
Calibrating Out NF of Measurement System
Noise
Source
Variable
Attenuator
DUT
F1 , G1
F2
F12
By cascade equation:
F1 = F12 -
• F12 (F of system) is measured with DUT connected
• F2 is measured by connecting source directly to analyzer
F2 - 1
, then uncertainty increases
• If F12 ≅
G1
Page 19
F2 - 1
G1
Y- Factor Method
NOISE
DUT
SOURCE
PRECISION IF
ATTENUATOR
  Th

 Tc

Y
−
1
−
−
1


  290 
290



F = 10 log  
Y −1




F = ENR − 10 log(Y − 1)
if TC = 290 K
Where Y = Change in IF attenuator to maintain reading on
detector as source switched ON and OFF
Beware High DUT NF!
Y =
Nh
=
Nc
Na + kThBG
Na + kTcBG
If F is large, Na >> kTBG and Y ≅ 1
Therefore:
The Y-factor method is not suitable for
very high noise figures (≥ 30 dB)
Page 21
The NFA Also Measures DUT Gain
Slope = kBG1G2
Nh_mea
s
Slope = kBG2
Nh_cal
Nc_meas
G1 =
Nc_cal
Nh_meas – Nc_meas
Nh_cal – Nc_cal
G1(dB) = 10 log G1
Tc
Page 22
Source Temp (K)
Th
Devices That Can Be Tested with Agilent NFAs and
SA-Based Solutions
• Passive two-port devices
Receiver
IF
• Active two-port devices
• Mixers and receivers
LO
Mixer
Passive
2-Port
FET,
Transistor
Page 23
Amplifier
LO
Agenda
• Fundamental noise concepts
• What’s Noise Figure
• Noise figure Measurements
• Agilent Noise Figure Solutions – Demos
• What’s Phase Noise
• Phase Noise Measurements
• Agilent Phase Noise Solutions - Demos
Page 24
Agilent Noise Figure Solutions Portfolio
PNA-X
PSA Series
Highest Performance
Spectrum Analyzers
NFA Series
Highest Performance
Network Analyzer
Only Dedicated Noise
Figure Analyzers
MXA
Price
Super Mid-range
Signal Analyzer
EXA
Economy-Class
Signal Analyzer
ESA Series
Economy Portable
Spectrum Analyzers
Performance
Page 25
346A
ENR ≅ 6 dB
Na
Tc
Th
Source Temperature (K)
Output Power (W)
Output Power (W)
Agilent 346 Series Noise Sources
346B/C
ENR ≅ 15 dB
Na
Tc
Th
Source Temperature (K)
• 346A: 10 MHz to 18 GHz, nominal ENR of 6 dB
• 346B: 10 MHz to 18 GHz, nominal ENR of 15 dB
• 346C: 10 MHz to 26.5 GHz, nominal ENR of 15 dB
• 346C K01: 1 GHz to 50 GHz, nominal ENR of 20 dB
• Can be used with NFA Series, PSA, ESA-E with noise figure option, and
MXA/EXA with N9069A noise figure application
Page 26
Agilent SNS Series Noise Sources
• N4000A: 10 MHz to 18 GHz, nominal ENR of 6 dB
• N4001A: 10 MHz to 18 GHz, nominal ENR of 15 dB
• N4002A: 10 MHz to 26.5 GHz, nominal ENR of 15 dB
• Can be used with NFA Series noise figure analyzers, ESA-E with noise
figure option, and MXA/EXA with N9069A noise figure application
• ENR data is stored in EPROM and automatically downloaded to analyzer
• Source temperature is monitored by a built-in thermistor for compensation
NF_102 Noise Figure Basics
Page 27
January 2008
Demo
Solution used for the demo: MXA N9020A + Noise Figure application
www.agilent.com/find/MXA
MXG Additive AWGN Impairments
Agenda
• Fundamental noise concepts
• What’s Noise Figure
• Noise figure Measurements
• Agilent Noise Figure Solutions – Demos
• What’s Phase Noise
• Phase Noise Measurements
• Agilent Phase Noise Solutions - Demos
Page 30
Phase Noise
Phase Noise
Practical sinusoids are never perfect!
t
v(t) = (V0 + ε(t)).cos(ωt + φ(t))
ε(t) = instantaneous amplitude fluctuations
φ(t) = instantaneous phase fluctuations
LONG-TERM FREQUENCY STABILITY
f
time
(days, months, years)
Slow change in average or
nominal frequency
SHORT-TERM FREQUENCY STABILITY
f
fo
time (seconds)
Instantaneous frequency variations
around the nominal frequency
Concept of Phase Noise
f0
Ideal Signal
f0
Real Life Signal
TYPES OF SHORT TERM NOISE
MKR 9.999 999 581 8 GHz
REF
8.3 dBm
ATTEN 28 dB
8.28 dBm
RES BW
10 Hz
CENTER 9.999 999 482 GHz
RES BW 18 Hz
VIEW 1 Hz
SPAN 500 Hz
SWP 150 sec
Deterministic (Discrete) - "Spurious"
Continuous (Random) - "Phase Noise"
UNIT OF MEASURE
L(f)
Usually phase noise is quantified as
L(f) - defined as single sideband power due to phase fluctuations referenced to the
carrier frequency power:
In a 1 Hz bandwidth at a frequency f Hz from the carrier
Divided by the signal's total power
L(f) has units of dBc/Hz
L
(f) =
LOG A
L (f)
AMPLITUDE
Area 1 Hz bandwidth
LOG f
Total area under the curve
1 Hz
f 0
Page 36
f 0 + fm
FREQUENCY
Typical Phase Noise Plot
8640B
8684B
EXTCARRIER
FM
OFF,= + 7.70DE
4 AVERAGES
FREQ
+ X7 REF,
09Hz
320 KHZ PK
[hp]
APR 4
DEV FM
13:40 / 14:02
50
40
30
20
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
-150
10
1
Hz
100
1K
L
10K
100K
(f) [dBc/Hz] vs f [Hz]
1M
10M
40MHz
Carrier phase noise in a Doppler
Radar
clutter
f
Reflected signal from building
at f Hz.
Tx
Rx
Reflected signal from car
at f+ ∆f Hz.
How local oscillator phase noise
can obscure the returned Doppler
signal from the moving object.
LO phase noise improvement
Doppler signal
unresolved
Doppler signal
resolved
Noise in Digital Radio
Amplitude Noise
Phase Noise
Page 40
Agenda
• Fundamental noise concepts
• What’s Noise Figure
• Noise figure Measurements
• Agilent Noise Figure Solutions – Demos
• What’s Phase Noise
• Phase Noise Measurements
• Agilent Phase Noise Solutions - Demos
Page 41
Phase Detector Technique
Low Freq. Spectrum
Analyzer displays
Sφ(fm)
Phase Detector
Unit Under Test
Reference
(same freq. as
UUT)
Spectral
density
of
phase
Sφ(fm) =
fluctuations
Reference Source/PLL
Measurement Technique
MICROWAVE
DOWNCONVERTER
BASEBAND TEST SET
∆Vrms(f)
OSCILLATOR
UNDER-TEST
= Kφ ∆φ rms(f) [V]
PHASE
DETECTOR
BASEBAND
ANALYSIS
HARDWARE
SIGNAL CONDITIONING
BASEBAND OUTPUT
SIGNAL
REFERENCE
SOURCE
RF OUT
TUNING
VOLTAGE
PHASE-LOCK
LOOP
The Spectrum Analyzer Method
RF Spectrum Analyzer
Unit Under Test
Measure C/N at the required
frequency offset.
The Spectrum Analyzer Method
The Spectrum Analyzer Method
• How to define Phase
Noise on a spectrum
analyzer?
P0
4 elements:
dBc/Hz
1) Carrier frequency
2) Offset freq. from carrier freq.
1 Hz BW
3) Power spectral density (in 1 Hz
BW)
4) Relative to carrier power in dBc
dBc/Hz @ offset freq. fm
Assuming AM noise << PN
f0
fm (offset freq.)
The Spectrum Analyzer Method
8563A SPECTRUM ANALYZER
9
kHz - 26.5 GHz
Oscillator
Under-Test
- Easy to configure/use
–
Measures total noise (phase noise + AM noise)
–
Device drift limits close-to-carrier capability
–
SA internal LO limits overall sensitivity
Agenda
• Fundamental noise concepts
• What’s Noise Figure
• Noise figure Measurements
• Agilent Noise Figure Solutions – Demos
• What’s Phase Noise
• Phase Noise Measurements
• Agilent Phase Noise Solutions - Demos
Page 48
Overview of Agilent PN Measurements
solutions
• Direct Spectrum Analysis
PSA/Opt. 226
• Carrier removal+ BB Analysis
E5052B
Signal Source Analyzer
ESA/Opt. 226
856X/85671A
MXA/EXA with
N9068A
• PN measurements made easy by a
general-purpose SA w/ PN
personality
E5505A
PN Measurement Solution
• More focused measurements
• Dedicated to component tests
Phase Noise: Measurements on X series
•
Log Plot; one button measurement to
measure the phase noise in the desired
frequency range..
•
Spot Frequency; one button measurement to
measure the phase noise at certain offset in
the time domain faster.
•
Monitor Spectrum; allows to watch the signal
spectrum without exit from the Phase Noise
mode. Subset of General Purpose SpecAna
•
IQ Waveform; general purpose IQ waveform
measurement without exit from the Phase
Noise mode.
Log Plot Measurement: Using Markers
Up to 12 markers can be used in
addition to the Decade Table.
Integrated Phase Noise
measurements like RMS Noise (in
Degree, Radian, Jitter) plus Residual
FM can be measured using up to 12
Band Power markers
Log Plot: DANL Display and Cancellation
Use DANL display to determine
whether the measured phase noise is
from the DUT, or is due to the
instrument DANL
Improve measurement accuracy by
using PN cancellation feature
Demo
Solution used for the demo: MXA N9020A + Phase Noise application
MXG vector signal generator
www.agilent.com/find/MXA
www.agilent.com/find/MXG
MXG Additive Phase Noise
Impairments