2. Source Basics Copyright
2000
Sources Generate Sine Waves
Voltage
Time
Voltage
Frequency
This is the ideal output: most specs deal with deviations from the
ideal and adding modulation to a sine wave
RF Microwave Millimeter
20-50 GHz 300 GHz
3-6 GHz
Spectrum Analyzer
Oscilloscope
3. Source Basics 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
5. Source Basics Copyright
2000
CW Source Specifications
...Frequency
Voltage
Frequency
Uncertainty
Range: Range of frequencies covered by the source
Resolution: Smallest frequency increment.
Accuracy: How accurately can the source frequency be
set.
EXAMPLE
Accuracy =
= CW frequency = 1 GHz
= aging rate = 0.152 ppm/year
= time since last calibrated = 1 year
+
_ fCW
taging cal
t
* *
fCW
taging
cal
t
Accuracy = 152
Hz
+
_
6. Source Basics Copyright
2000
CW Source Specifications
...Amplitude
DUT
Source protected from accidental transmission from
DUT
Voltage
Frequency
How
accurate is
this number?
What is P out?
What is P out?
max
min
Range (-136dBm to +13dBm)
Accuracy (+/- 0.5dB)
Resolution (0.02dB)
Switching Speed (25ms)
Reverse Power Protection
7. Source Basics Copyright
2000
Phase Noise
Residual FM
Spurious
CW Source Specifications
...Spectral Purity
non-harmonic spur
~65dBc
harmonic spur
~30dBc
CW output
Residual FM is the
integrated phase noise
over 300 Hz - 3 kHz BW phase
noise
0.5 f0 f0
2f0
sub-harmonics
16. Source Basics Copyright
2000
Applications & Critical Specifications
As a Local Oscillator
IF signal transmitter output
poor phase noise spreads
energy into adjacent
channels
poor frequency accuracy
will cause transmitter to
be at the wrong
frequency
DUT
17. Source Basics Copyright
2000
Applications & Critical Specifications
Amplifier Testing
f2
f1
fU = 2f2 - f1
fL = 2f1 - f2
spurious signals from
source can corrupt
measurement
frequency
test system third order
products will also fall here
output RF
isolator
f1
f2
DUT
Intermodulation
Distortion
18. Source Basics Copyright
2000
Applications & Critical Specifications
Receiver Testing
IF Rejection Curve
Frequency
Level
(dBm)
spur from source and/or high levels
of phase noise can cause a good
receiver to fail
source output
IF
signal
in-channel signal
(modulated signal)
out-of-channel signal
(CW or modulated signal)
DUT
Receiver Selectivity
19. Source Basics Copyright
2000
Agilent Families of CW Generators
RF
Microwave
Agilent 8664/65 family
100 MHz - 6 GHz
Low out channel noise
AM/FM/Pulse.
Agilent 8662/63 family
100 KHz - 2.5 GHz
Low in channel noise
AM/FM/Phase/Pulse
Agilent 83711/12B
family
10 MHz - 20 GHz
CW only
21. Source Basics Copyright
2000
Sweeper Specifications
...Frequency
ramp sweep
– accuracy
– sweep time
– resolution
step sweep
– accuracy
– number of points
– switching time
time
f2
t2
t1
f1
t4
t3
t1 t2
f4
f3
f1
f2
22. Source Basics Copyright
2000
Sweeper Specifications
...Amplitude
Frequency Sweep
Level Accuracy
Flatness
Source Match (SWR)
Power Sweep
Power Sweep Range
Power Slope Range
Source Match (SWR)
flatness spec
level accuracy
spec
f1 f2
frequency
power
power
}
P2
P1
power sweep
range
t1 t2
23. Source Basics Copyright
2000
Applications & Critical Specifications
Frequency Response
– Frequency Accuracy
– Output Power (Level) Accuracy
– Flatness
– Speed
– residual FM
Amplifier Compression
– Power Range
24. Source Basics Copyright
2000
Applications & Critical Specifications
Frequency Response Testing
LO
Sweeper Input
Frequency Accuracy
Output Power (Level) Accuracy
Flatness
Speed
residual FM
25. Source Basics Copyright
2000
Applications & Critical Specifications
Frequency Response Testing
Center 2 450.212 MHz Span 1 099.577 MHz
1
1
3
5 6
BW: 429.600 MHz
CF: 2405.782 MHz
Q: 5.60
Loss: -0.84 dB
1:Transmission Log Mag 5.0 dB/ Ref -15.00 dB
-35
-30
-25
-20
-10
-5
0
5
Abs
dB
Ch1
Who Cares About Accuracy?
26. Source Basics Copyright
2000
Applications & Critical Specifications
Amplifier Compression
Power In
1 dB compression
point
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.
Power Range
27. Source Basics Copyright
2000
Synthesized Sweep Generators
Agilent 83750 Series
Step/Analog sweep
AM/FM/Phase modulation
10MHz to 20GHz
up to 110GHz with 83550 series
modules and amplifier
Agilent 8360L Series
Step/Analog sweep
8510/8757 Compatibility
10MHz to 50GHz
up to 110GHz with 83550 series
modules
31. Source Basics Copyright
2000
Modulation: Analog
Amplitude Modulation
Important Signal Generator Specs
for Amplitude Modulation
Voltage
Time
Carrier
Modulation
Modulation frequency
Linear AM
Log AM
Depth of modulation (Mod
Index)
32. Source Basics Copyright
2000
Modulation: Analog
Frequency Modulation
Voltage
Time
Important Signal Generator Specs
for Frequency Modulation
V= A sin[2 f t + m(t)]
p c b
F /F
dev mod
b = D
Frequency Deviation
Modulation Frequency
dcFM
Accuracy
Resolution
33. Source Basics Copyright
2000
Modulation: Analog
Phase Modulation
b = Df peak
V= A sin[2 p f t + m(t)]
Important Signal Generator Specs
for Phase Modulation
Phase deviation
Rates
Accuracy
Resolution
Voltage
Time
c b
34. Source Basics Copyright
2000
Modulation: Analog
Pulse Modulation
Time
Pulse
On/Off ratio
Rise
time
Rate=1/T T
Width
Power
t
1/t
1/T
Power
Important Signal Generator Specs
for Pulse Modulation
Pulse width
Pulse period
On/Off ratio
Rise time
36. Source Basics Copyright
2000
Digital Modulation
Polar Display: Magnitude & Phase Represented Together
Magnitude is an absolute value
Phase is relative to a reference signal
Phase
0 deg
37. Source Basics Copyright
2000
Digital Modulation
Signal Changes or Modifications
Phase
0 deg
Magnitude Change
Phase
0 deg
Phase Change
Frequency Change
Both Change
0 deg
0 deg
40. Source Basics Copyright
2000
Digital Modulation
...Quadrature Phase Shift Keying (QPSK)
V= A sin[2 ft + (t)]
f(t) =
f1 = 3 /4
p
f2 = /4
p
f3 = - /4
p
f4 = - 3
/4
p
p f
43. Source Basics Copyright
2000
Digital Modulation
Modulation Accuracy
I
Q Magnitude Error (IQ error mag)
Error Vector
Ideal (Reference) Signal
Phase Error (IQ error phase)
Test
Signal
f
44. Source Basics Copyright
2000
Digital Signal Generator Block Diagram
IQ Modulator
– modulation
quality
Baseband Generator
– modulation quality
– adjacent channel
performance
– supported modulation
formats
reference section
(supplies timing)
to output section
45. Source Basics Copyright
2000
Digital Modulation
PSK Implementation: IQ Method
p/2
Carrier
Good Interface with Digital Signals and
Circuits
Can be Implemented with Simple Circuits
Can be Modified for Bandwidth Efficiency
I:
Q:
46. Source Basics Copyright
2000
Digital Signal Generator Block Diagram
IQ Modulator
p/2
DAC
DAC
Ext I
Ext Q
from synthesizer
section
to output section
Q from Baseband Generator
I from Baseband Generator
47. Source Basics Copyright
2000
Digital Signal Generator Block Diagram
Baseband Generator
DAC
DAC
Pattern RAM Constellation
Map and
Baseband Filters
Timing
Data
Data Clock
Symbol
Clock
From CPU
I
Q
Analog
Reconstruction
Filters
48. Source Basics Copyright
2000
Digital Signal Generator
Format Specific Digital Signals
NADC (TDMA IS-54)
Parameter Specification
Access Method TDMA/FDD
Modulation p/4 DQPSK
Channel Bandwidth 30 kHz
Reverse Channel
Frequency Band
824 - 849 MHz
Forward Channel
Frequency Band
869 - 894 MHz
Filtering 0.35 RRC
49. Source Basics Copyright
2000
Digital Signal Generator
Access and Framing
one frame = 1944 bits (972 symbols) = 40ms; 25frames/sec
slot 1 slot 2 slot 3 slot 4 slot
5 slot 6
324 bit (162 symbols) = 6.667ms
G R Data Sync Data SACCH
CDVCC Data
6 6 16 28 122 12 12
122 Mobile to Base Station
50. Source Basics Copyright
2000
Applications and Critical Specifications
Analog and Digital
Receiver Sensitivity
– frequency accuracy
– level accuracy
– error vector magnitude
Receiver Selectivity
– phase noise
– spurious
– spectral accuracy
Spectral Regrowth
– ACP performance
51. Source Basics Copyright
2000
Applications and Critical Specifications
Receiver Sensitivity
Want to measure
sensitivity in a channel
Measurement impaired by
frequency inaccuracy
frequency inaccuracy
amplitude inaccuracy
input for signal
generator
DUT
Frequency Accuracy
52. Source Basics Copyright
2000
Applications and Critical Specifications
Receiver Sensitivity
Customer is testing a -110 dB sensitivity pager:
-110 dB specification
Case 1: Source has +/-5 dB of
output power accuracy at
-100 to -120 dBm output power.
Set source to -115 dBm
Actual output power= -114 dBm
X
X
X X
X
O
Case 2: Source has +/-1 dB of
output power accuracy at
-100 to -120 dBm output power.
-110 dB specification
Set source to -111 dBm
Actual output power= -112 dBm
X
X
O O
O
O
X= Failed unit
O=Passed unit
Frequency Frequency
Level Accuracy
53. Source Basics Copyright
2000
Applications and Critical Specifications
Receiver Sensitivity
Error Vector Magnitude (EVM)
Error
Vector
p
e.g. TETRA Signal
/4 DQPSK
EVM < 1.0%
54. Source Basics Copyright
2000
Applications and Critical Specifications
Receiver Selectivity
IF Rejection Curve
Frequency
Level
(dBm)
spur from source and/or high
levels of phase noise can cause a
good receiver to fail
IF
signal
in-channel signal
(modulated signal)
out-of-channel signal
(CW or modulated signal) DUT
Phase Noise
Spurious