Download No Slide Title

Time
Voltage
Voltage
Sources Generate Sine Waves
Oscilloscope
Frequency
Spectrum Analyzer
This is the ideal output: most specs deal with deviations from the
ideal and adding modulation to a sine wave
3-6 GHz
Source Basics
Millimeter
Microwave
RF
20-50 GHz
300 GHz
Copyright
2000
Types of Sources

CW
– generates

a single frequency, fixed sine wave
Swept
– sweeps
over a range of frequencies
– may be phase continuous

Signal Generator
– adds
modulation
– produces “real world” signal
Source Basics
Copyright
2000
CW Source Specifications
...Frequency



Range: Range of frequencies covered by the source
Resolution: Smallest frequency increment.
Accuracy: How accurately can the source frequency be
set.
EXAMPLE
Accuracy =
Voltage
Uncertainty
t aging
=
t cal =
CW frequency = 1 GHz
aging rate = 0.152 ppm/year
time since last calibrated = 1 year
_
=
 Accuracy +
Frequency
Source Basics
f CW =
+_ f CW * t aging * t cal
152
Hz
Copyright
2000
CW Source Specifications
...Amplitude





Range (-136dBm to +13dBm)
Accuracy (+/- 0.5dB)
Resolution (0.02dB)
Switching Speed (25ms)
Reverse Power Protection
Source protected from accidental transmission from
DUT
What ismax
P
Voltage
DUT
out?
How
accurate is
this number?
min
What is P
Frequency
Source Basics
Copyright
2000
out?
CW Source Specifications
...Spectral Purity



Phase Noise
Residual FM
Spurious
Residual FM is the
integrated phase noise
over 300 Hz - 3 kHz BW
CW output
phase
noise
non-harmonic spur
~65dBc
harmonic spur
~30dBc
sub-harmonics
0.5 f0
2 f0
Source Basics
f0
Copyright
2000
CW Source Specifications
... Spectral Purity: Phase Noise
CW output
measured as dBc/Hz
frequency
TRACE A:
Ch1 PM PSD
A Marker
10 000 Hz
75 dBc/Hz
LogMag
5 dBc/div
-105 dBc/Hz
-125 dBc/Hz
Source Basics
1k
10k
100k
Copyright
2000
RF CW Block Diagram
Synthesizer Section
Frac-N
Output Section
Output
Attenuator
ALC
Modulator
Phase
Detector
VCO
divide
by X
Reference
Oscillator
Reference Section
Source Basics
ALC
Driver
ALC Detector
ALC = automatic level control
Copyright
2000
RF CW Block Diagram
Reference Section
to synthesizer section
divide
by X
Phase
Detector
Optional External
Reference Input
Source Basics
Reference Oscillator (TCXO or OCXO)
Aging Rate
TCXO
+/- 2ppm/year
OCXO
+/- 0.1 ppm /year
Temp.
+/- 1ppm
+/- 0.01 ppm
Line Voltage
+/- 0.5ppm
+/- 0.001 ppm
Copyright
2000
RF CW Block Diagram
Synthesizer Section
...produces accurate, clean signals
N = 93.1
Front
panel
control
Frac-N
5MHz
to output section
Phase
Detector
X
VCO
2
multiplier
931 MHz
5MHz
from reference section
Source Basics
465.5 MHz
Copyright
2000
RF CW Block Diagram
Synthesizer Section
PLL / Fractional - N
...suppresses phase noise
phase noise of source
reference
oscillator
phase
detector
noise
20logN
VCO noise
Source Basics
phase-locked-loop (PLL)
bandwidth selected for
optimum noise performance
broadband
noise floor
frequency
Copyright
2000
RF CW Block Diagram
Output Section

ALC
–maintains
output
power by
adding/subtracting
power as needed

from
synthesizer
section
ALC
Modulator
Output
Attenuator
source output
Output Attenuator
–mechanical
or
electronic
–provides attentuation
to achieve wide output
range (e.g. -136dBm to
+13dBm)
ALC
Driver
ALC Detector
ALC = automatic level control
Source Basics
Copyright
2000
mWave CW Block Diagram
Reference Section
Frac
N
ALC
Modulator
Phase
Det
Output
Attenuator
VCO
Sampler
by X
Ref Osc
YIG
Oscillator
Phase
Detector
Tuning
Coils
ALC
Driver
Frac-N
Synthesizer
Section
Phase
Detector
VCO
Source Basics
ALC Detector
Output Section
Copyright
2000
Applications & Critical Specifications

Local Oscillator
– phase
noise
– frequency accuracy

Amplifier Distortion
– spurious
– TOI

(for system)
Receiver Testing
– Spurious
spurious
 level accuracy

Source Basics
Copyright
2000
Applications & Critical Specifications
As a Local Oscillator
DUT
IF signal
poor frequency accuracy
will cause transmitter to
be at the wrong
frequency
Source Basics
transmitter output
poor phase noise spreads
energy into adjacent
channels
Copyright
2000
Applications & Critical Specifications
Amplifier Testing
f1
DUT
Intermodulation
Distortion
output RF
f2
isolator
f1
fL = 2f1 - f2
f2
test system third order
products will also fall here
spurious signals from
source can corrupt
measurement
fU = 2f2 - f1
frequency
Source Basics
Copyright
2000
Applications & Critical Specifications
Receiver Testing
Receiver Selectivity
in-channel signal
(modulated signal)
IF
signal
out-of-channel signal
(CW or modulated signal)
DUT
source output
IF Rejection Curve
Level (dBm)
spur from source and/or high levels
of phase noise can cause a good
receiver to fail
Frequency
Source Basics
Copyright
2000
Applications & Critical Specifications

Frequency Response
–
–
–
–
–

Amplifier Compression
–
Source Basics
Frequency Accuracy
Output Power (Level) Accuracy
Flatness
Speed
residual FM
Power Range
Copyright
2000
Applications & Critical Specifications
Amplifier Compression
Power Range

1 dB compression
point
Power In
The 1 dB compression point is a common amplifier specification used to
identify the linear operating range of an amplifier. Power sweep is available
on some Agilent sources.
Source Basics
Copyright
2000
Signal Generators

Calibrated modulation
– Analog (AM, FM, PM, Pulse)
– Digital (I-Q)
– Format Specific(TDMA,CDMA, etc.)
Source Basics
Copyright
2000
Modulation
...Where the information resides
p f(t)f+ (t)]
V= A(t) sin[2
AM, Pulse
FM
PM
V= A(t) sin[
q (t)]
Source Basics
Copyright
2000
Modulation: Analog
Amplitude Modulation
Voltage
Carrier
Time
Important Signal Generator Specs
for Amplitude Modulation

Modulation



Source Basics
Modulation frequency
Linear AM
Log AM
Depth of modulation (Mod
Index)
Copyright
2000
Modulation: Analog
Frequency Modulation
p cf b
A sin[2
t + m(t)]
V=
b=D F
dev
/F
Important Signal Generator Specs
for Frequency Modulation
mod
Voltage



Time


Source Basics
Frequency Deviation
Modulation Frequency
dcFM
Accuracy
Resolution
Copyright
2000
Modulation: Analog
Phase Modulation
V=
Voltage
b = Df
A sin[2 p
t + m(t)]
c f b
peak
Important Signal Generator Specs
for Phase Modulation
Time




Source Basics
Phase deviation
Rates
Accuracy
Resolution
Copyright
2000
Modulation: Analog
Pulse Modulation
T
Rate=1/T
Important Signal Generator Specs
for Pulse Modulation
Power
Rise
time
Pulse
On/Off ratio

t

Time

Width

1/T
Pulse width
Pulse period
On/Off ratio
Rise time
Power
1/t
Source Basics
Copyright
2000
Digital Modulation
...signal characteristics to modify
Amplitude
Frequency
Phase
Both Amplitude
and Phase
Source Basics
Copyright
2000
Digital Modulation
Polar Display: Magnitude & Phase Represented Together
Phase
0 deg


Source Basics
Magnitude is an absolute value
Phase is relative to a reference signal
Copyright
2000
Digital Modulation
Signal Changes or Modifications
Phase
0 deg
Magnitude Change
Phase
0 deg
Phase Change
0 deg
0 deg
Both Change
Frequency Change
Source Basics
Copyright
2000
Digital Modulation
...Binary Phase Shift Keying (BPSK)
V= A sin[2
p ft f+ (t)]
f (t) =
f1
f2
Source Basics
Copyright
2000
Digital Modulation
BPSK IQ Diagram
Q
1
0
I
One Bit Per Symbol
Symbol Rate = Bit Rate
Source Basics
Copyright
2000
Digital Modulation
...Quadrature Phase Shift Keying (QPSK)
p ftf+ (t)]
V= A sin[2
f (t) =
Source Basics
f1 = 3p /4
f2 = p /4
f3 = - p /4
f4 = - 3p
/4
Copyright
2000
Digital Modulation
QPSK IQ Diagram
01
Q
00
I
11
Source Basics
10
Copyright
2000
Digital Modulation
p/4 DQPSK IQ Diagram Q
I
Source Basics
Copyright
2000
Digital Modulation
Modulation Accuracy
Q
Magnitude Error (IQ error mag)
Error Vector
Test
Signal
f
Ideal (Reference) Signal
Phase Error (IQ error phase)
I
Source Basics
Copyright
2000
Applications and Critical Specifications
Analog and Digital

Receiver Sensitivity
–
–
–

Receiver Selectivity
–
–
–

phase noise
spurious
spectral accuracy
Spectral Regrowth
–
Source Basics
frequency accuracy
level accuracy
error vector magnitude
ACP performance
Copyright
2000
Applications and Critical Specifications
Receiver Sensitivity

Frequency Accuracy
frequency inaccuracy
amplitude inaccuracy
Want to measure
sensitivity in a channel
Measurement impaired by
frequency inaccuracy
input for signal
generator
DUT
Source Basics
Copyright
2000
Applications and Critical Specifications
Receiver Sensitivity

Level Accuracy
Customer is testing a -110 dB sensitivity pager:
X= Failed unit
O=Passed unit
-110 dB specification
X
X
X X X
O
Actual output power= -114 dBm
Set source to -115 dBm
Frequency
Case 1: Source has +/-5 dB of
output power accuracy at
-100 to -120 dBm output power.
Source Basics
-110 dB specification
X
X
Set source to -111 dBm
O O O
Actual output power= -112 dBm
O
Frequency
Case 2: Source has +/-1 dB of
output power accuracy at
-100 to -120 dBm output power.
Copyright
2000
Applications and Critical Specifications
Receiver Sensitivity

Error Vector Magnitude (EVM)
e.g. TETRA Signal
p /4 DQPSK
EVM < 1.0%
Source Basics
Error
Vector
Copyright
2000
Applications and Critical Specifications
Receiver Selectivity


Phase Noise
Spurious
in-channel signal
(modulated signal)
IF
signal
out-of-channel signal
(CW or modulated signal)
DUT
IF Rejection Curve
Level (dBm)
spur from source and/or high
levels of phase noise can cause a
good receiver to fail
Frequency
Source Basics
Copyright
2000
Applications and Critical Specifications
Receiver Selectivity
Spectral Accuracy:
 EVM
 ACP
Source Basics
GSM Signal
0.3GMSK
Copyright
2000
Applications and Critical Specifications
Spectral Regrowth

ACP Performance
DUT
Output from amplifier
Input from signal generator
Source Basics
Copyright
2000