Transcript No Slide Title

Andrew Wallace MEng (Hons) AMIEE
Regional Sales Specialist
1. An Introduction To Microwave Theory And Components
Electromagnetic Spectrum
10km
100m
1m
100km
1 km
100m
ELF
VLF LF
1cm
10cm
100mm
1mm
100A
1A
1mm
10mm
0.1mm
10A
MF HF VHF UHF SHF EHF
UV
Microwave
3 x 102
3 x 105
3 x 104
3 x 107
3 x 106
3 x 109
3 x 108
Millimeter
3 x 1011
3 x 1010
X-rays
Infrared
3 x 1013
3 x 1012
3 x 1015
3 x 1014
3 x 1017
3 x 1016 3 x 1018
Microwave Systems
Transmission Lines
Coaxial Conductors
Outer Conductor
Half Wavelength
Inner
Conductor
Er
a
Electric Field
b
Magnetic Field
Impedance :
Z = 138 log10 b
Er
a
Stripline Conductors
Dielectric
material
Ground Plane
Metallic ground
strip
Copper / gold
strip
Ground Plane
Microstrip Conductors
Dielectric
material
Copper / gold
strip
Metallic ground
strip
Ground Plane
Ground Plane
Wave Propagation
lg / 2
b
Side View
lg / 2
a
Cross Section
Electric Field
Magnetic Field
Top View
Waveguide Types
Why 50W Connectors
1.4
Attenuation is
lowest at
77W
50W standard
1.2
Normalized
Values 1
0.8
Power handling
capacity peaks
at 30W
0.6
1
20
30
40
50
60
Characteristic Impedance (W)
70
100
Coaxial Connectors
Connector Standards
GPC 14
Type N
BNC/TNC
Precifix AA
14 mm
7 mm
7 mm
7 mm
50:
DC to 8.5 GHz
IEEE 287 &
75:
DC to 2 GHz
IEC 457
50:
DC to 18 GHz
Mil-C-39012 &
75:
DC to 2 GHz
BS 9210
50:
DC to 4 GHz
Mil-C-39012 &
75:
DC to 2 GHz
BS 9210
50:
DC to 18 GHz
IEEE 287 &
IEC 457
GPC 7
7 mm
50:
DC to 18 GHz
IEEE 287 &
IEC 457
SMA
4 mm
50:
DC to 26 GHz
Mil-C-39012 &
BS 9210
GPC 3.5
3.5 mm
50:
DC to 34 GHz
Type K
2.92 mm
50:
DC to 46 GHz
Connector Types
Connector Handling
Terminations
Attenuators
Limiters
Pout
Watt
Pin Watt
Filters
Load
Directional Couplers
Input
A
C
Coupled
Through
B
Directional Couplers
Coaxial Coupler
Waveguide Coupler
Bridges & Autotesters
Balun
Detector
50W
Source
Test Port
Vdetector
= Const
= Const
[ ]
ZX - 50
ZX + 50
G
ZX
Autotester
Diode Detector
DC Block
C1
DC
Voltage
Output
Microwave
Input
50W
C2
R
Power Splitter
Output
50W
Input
50W
Output
Wilkinson & Resistive Power Dividers
Output A
Input
100W
Loss 3dB
Output B
Output A
Input
16.66W
Loss 6dB
Output B
Circulators & Isolators
A
Low loss A to B
B to C
C to A
B
C
High loss A to C
C to B
B to A
PIN Devices
W
P+
I
N+
W = Width Of Layer I
The YIG Oscillator
H DC
DC Magnetic Field
Electromagnet
YIG sphere
R.F. Input
H AC
AC Magnetic Field
R.F. Output
YIG Frequency
Electromagnet
YIG sphere
Active Device
R.F. Output
Fo = g Ho
Travelling Wave Tubes (TWT)
Focusing Magnet
Cathode
Collector
Microwave Signal
]
[
Electron Flow
Focusing Magnet
R.F. O/P
Axial Velocity Of
Microwave Signal
@
Electron
Velocity
Antennas
Antennas
Tea Time
2. Scalar Analysis : An Introduction To Measurements
And Concepts.
2-Port Scalar Analysis
VINC
DUT
VREF
VTRANS
Scalar Measurement Coefficients
What quantities can be measured by a Scalar Network Analyzer?
• Insertion Loss/Gain
• Return Loss, VSWR (Reflection Coefficient)
• Relationship between reflection expressions
t = magnitude of transmission coefficient
r = magnitude of reflection coefficient
VSWR =
(Biggest = 1 , Smallest = 0)
1+r
1-r
Return Loss = -20 log10(r) dB
r=|G|
t=|T|
Return Loss - Some Typical Values
Return loss
VSWR
Short / Open circuit
0dB
±1
Matched load
Theory
Practice
dB
40dB
1
1.02
0
0.01
Matched antenna (Broadband)
14 - 26dB
1.1 - 1.5
0.05 - 0.2
Typical component
14dB
1.5
0.2
Adapter (Co-ax)
>26dB
<1.1
<0.05
Waveguide / Co-ax transition
14 - 26dB
1.1 - 1.5
0.05 - 0.2
Waveguide flange
26 - 34dB
1.04 - 1.1
0.02 - 0.05
Scalar Analyzer Block Diagram
Display
Detector
DUT
Source
Ramp
Generator
Frequency Response
Basic System - Single Detector
Simple Return Loss Measurement
DUT
RF OUT
Coupled
port
Detector
Return Loss and Insertion Loss
Basic system - Autotester and Detector
Sources Of Error
A
B C
C
B
RF
Test Points
Wanted
Reflected
Signal
Wanted
Reference
Signal
Source
Match
A
Adapter
DUT
Load Match
Adapter
Directivity
Test Port
Match
Wanted
Transmitted
Signal
Transmission Errors - Frequency Response
DUT
Detector
Frequency
Response
Frequency Response
Of Cables
Transmission Errors - Source & Load Match
Calibration
Detector
lo
DUT
rs
r1
r2
rd
Transmission Uncertainty (worst case) u = (rs * rd) + (rs * r1 * lo ) + (rd * r2 * lo) + (rs * r1 * r2 * rd * lo)
or in dB = 20 log10 (1 + u)
Reflection Errors - Frequency Response
Autotester
Autotester test
port frequency
response
Reflection Errors - Directivity & Source Match
Where:
rs
D
ra
DUT
ra
rm
rs
D
= Actual Reflection Coefficient
= Measured Reflection Coefficient
= Test Port Match
= Directivity
ra = rm + [D+ rs ra2]
Use Of Adapters
Waveguide Return Loss - single coupler
Single coupler solution
Waveguide Return loss - dual coupler
Dual couplers measure incident and reflected power
Antenna Return Loss
PX
PX
Interference
PX
PINC
PREF
AC Detection
PX
P
PX
REF
Interference
P RF
ON
PX
P RF
OFF
P
REF
P
= P
REF
+P
X
= PX
X
INC
P RF
ON
- P RF
= P REF
OFF
= P REF
+P
X
-P
X
Frequency and Time Domain
Frequency Domain Measure: Power
Spectrum
Insertion loss
Return loss
Group delay
Defines if the system is working
Time Domain
Identifies the position of the fault
Installation and Maintenance
Loose Connection
Damaged Cable
Installation and Maintenance
Control Room
Fault
Waveguides
Transmitter
/receiver
Real Pulse TDR
Sampling
Oscilloscope
Step-function
Generator
DUT
Sampling
Gate
STDR Using a Scalar Analyzer
Scalar Analyzer
Vo
2
Detector
Vo exp (j2pbL)
4
Fault at distance L
reflection coefficient G
Vo
Swept
Frequency
Source
Divider
LOAD
L
Frequency Domain To Time Domain Conversion
F(f) is the complex reflection coefficient
in the frequency domain
0
Frequency
F(t)
-dB
F(t) is the reflection coefficient in the
time domain for an impulse excitation
1
f(t)
0
Time
Advantages of Synthetic TDR
Higher RESOLUTION
Capable of eliminating effects of DISPERSION
Excitation BANDWIDTH known exactly
Full oscillator OUTPUT POWER for all spectral
components
Free choice of start and stop frequencies for
BANDPASS measurements
Fault Location Range
Range (ns) =
Number of Frequency Points
4 x Bandwidth
If the bandwidth is in units of GHz then the range is
in nanoseconds.
Convert to distance by multiplying by 3 x 108 x Vr
Fault Location Resolution
Maximum available resolution is given by:
Resolution =
1.21
Bandwidth
This is the time difference between two
discontinuities which are just separable
Resolution is NOT point spacing.
Fault Location In Coax
Fault Location In Waveguides
Detector
3-Resistor
Power
Divider
Coax to
Waveguide
Adapter
Waveguide
Calibration
Load
Dispersion
In dispersive transmission lines wavelength
is not inversely proportional to frequency. Thus the
period of the observed ripples will vary
Frequency
Fourier Transform
Time
This leads to impulse spreading
Non-Linear Sweep
Coax Line ‘Single Fault’
Linear Sweep
0
Frequency
Waveguide ‘Single Fault’
Non-Linear Sweep
0
Frequency
Lunch
3. Spectrum Analysis : An Introduction To Measurements
And Concepts.
Signal Analysis
Amplitude
Frequency
Time
Amplitude
Amplitude
Time
Domain
Oscilloscope
Time
Frequency domain
Spectrum Analyzer
Frequency
Oscilloscope Display
E max
E min
Time
1/ Fm
Amplitude
% modulation
=
E max - E min
E max + E min
x100
Spectrum Analyzer Display
Carrier
Upper
sideband
Lower
sideband
Modulation
frequency = Fm
Carrier
frequency = F c
Fc- F m
Fc
Fc+ F m
Spectrum Analyzer Block Diagram
Detector
Log
Amp
Mixer
Input
Attenuator
Voltage
controlled
oscillator
IF
Amplifier
IF
Filters
Video
Filters
Ramp
generator
Display
Microwave Spectrum Analyzer
Harmonic Mixer and Tracking Preselector
RF
Input
IF
output
YIG
filter
X1
X2
X3
Local
oscillator
X4
Preselected
Fundamental
2nd Harmonic
3rd Harmonic
Microwave Spectrum Analyzer
‘Harmonic’
Mode
Input
'Fundamental'
Mode
To 479.3
MHz IF
4.5 - 9.2 GHz
4.5 GHz
4.96 GHz
4.48 GHz
Harmonic Distortion
Amplitude
Fc
2Fc
3Fc
Frequency
A practical example illustrates the method:
Harmonic Number Carrier
Voltage Ratio
2
-30dB
1/32
3
-38dB
1/79
4
-45dB
1/178
= 100
1 / (32)2 + 1 / (79) 2 + 1 / (178) 2
Total harmonic distortion
= 3.42%
Spurious Signals
Amplitude
Non harmonically
related spurious
Fc
2Fc
3Fc
Frequency
Amplitude Modulation
Carrier
Determined by
modulation depth
Upper
sideband
Lower
sideband
Modulation
Carrier
frequency = Fm
Frequency=Fc
% modulation =
sideband amp
x100
2x carrier amp
(on linear scale)
F-F
C
m
Fc
F +F
C
m
AM Spectrum With Modulation Distortion
Distortion
components
Fc -2Fm
Fc-F
m
Fc
F c+Fm
Fc +2Fm
Receiver Mode
%
AM DEMODULATION
25
20
15
10
5
0
5
10
15
20
25
Ref 2.010914MHz
Zero span Res bw 30kHz
200us /div
Modulation Asymmetry
Amplitude
difference
Mixed AM and FM causes asymmetrical sidebands
Frequency Modulation Spectrum Analyzer Display
Modulation frequency =
frequency of sideband spacing
Modulation Index =
Frequency deviation
Modulation frequency
Fc
FM-Bessel Zero
Carrier Null
Fc
FM Demodulation
FM
1.0kHz mod.freq..
3kHz deviation
1kHz /div
Ref 150.000000MHz
FM demod Res bw 10kHz
500 ms/div
Intermodulation Measurement
Signal
Generator
F1
Device
under
test
Signal
Generator
F2
Spectrum Analyzer
Signal Combiner
2 Tone Intermodulation Analysis
F1
2F 1 - F 2
3F1- 2F2
F2
2F 2- F
1
3F2- 2F
1
Effect Of Input Level On Signal To Noise
20
30
Signal-tonoise
ratio (dB)
40
10kHz
Bandwidth
50
60
70
1 kHz
Bandwidth
80
90
100
110
-90
-70
-50
-30
Input mixer level (dBm)
-10
0
Effect of Input Level On Distortion
20
3rd order
Intermodulation
products
30
40
Distortion
free
dynamic
range
(dB)
50
60
2nd harmonic
70
80
90
100
110
-90
-70
-50
-30
-10
Input mixer level (dBm)
0
10
30
Optimum Dynamic Range
20
10kHz
Bandwidth
30
3rd order
intermod.
40
50
60
2nd harmonic
70
1kHz
Bandwidth
80
90
100
110
-90
-70
-50
-30
-10
0 10
Input mixer level (dBm)
30
Nomograph To Determine IM Products
+25
+30
+20
+20
0
0
+15
+10
5
10
+10
0
10
20
+5
-10
15
30
0
-20
20
40
-5
-30
25
50
-10
-40
30
60
-20
-50
35
70
-30
-60
40
80
-40
Intercept
point (dBm)
-70
Signal
level (dBm)
2nd Order
3rd Order
45
90
Intermodulation
products dB down
Intermodulation Intercept Point
+30
Intercept point
+20
Output
level
(dBm)
+10
0
Fundamental
-10
-20
-30
-40
3rd order
products
-50
-60
-70
-60
-50
-40
-30
Input level (dBm)
-20
-10
0
Square Wave
Spectrum Analyzer
1/t
F
F = Pulse repetition frequency (PRF)=1/T
t = Pulse width
Oscilloscope
T=1/F
t
Pulsed RF
Spectrum Analyzer
P.R.F
f=1/t
1/T
Oscilloscope
T
t
Pulsed RF
1
Wider pulse than 1 Narrower lobes
PRF and Line density same
High PRF - Low line density
3
PRF lower than 1 Higher line density
Pulse width and lobes same
2
4
PRF and line density same as 3
Wider pulse-Narrow lobes
Pulse Modulation
B.W.<0.3xP.R.F.
1. Line spacing constant
in frequency
2. Displayed amplitude
independent of
resolution bandwidth
3. Line spacing independent
of sweep time
Envelope display, or
pulse mode
B.W.>1.7xP.R.F
1. Pulse spacing independent
of frequency span
2. Displayed amplitude
changes with resolution
bandwidth
3. Pulse spacing changes
with sweep time
Zero Span
Amplitude
Time
Frequency = Reference Frequency
Bandwidth = Resolution Bandwidth
Displays change in amplitude with time
1. Amplitude demodulation
2. RF rise and fall times
3. Pulse ringing, overshoot and droop
Understanding Spectrum Analyzer Controls
Detector
Log
Amp
Mixer
Input
Attenuator
IF
Amplifier
IF
Filters
Video
Filters
Voltage
controlled
oscillator
Ramp
generator
Display
Resolution Bandwidth
Wide
resolution
bandwidth
Narrow bandwidth reveals fine details
Narrow
Narrow
resolution
bandwidth
Resolution Bandwidth
Wide Filter
Narrow Filter
100Hz Span
Noise Floor
Resolution
bandwidth
100kHz
10kHz
Noise
floor
-90 dBm
-100 dBm
1kHz
100Hz
-120dBm
110dBm
10Hz
-130dBm
Noise floor drops as the resolution bandwidth is reduced
Sweep Speed
Correct Sweep Speed
Sweep speed too fast
Video Bandwidth
Input
Output
RF
Input
To display
Resolution
filters
Local
oscillator
Need slower sweep to achieve
noise smoothing
Detector
Video
bandwidth
Sideband Noise
A narrow resolution filter is not enough A low noise local oscillator is also essential
Local oscillator noise
sidebands can obscure
low level signals
close to the carrier
Typical Sideband Noise
-30
10Hz
100Hz
1kHz
10kHz
100kHz
1MHz
-40
3Hz
Resolution
bandwidths
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
Noise
dBc/1Hz
10Hz
100Hz
1kHz
10kHz
Frequency offset from carrier
100kHz
1MHz
10MHz
Residual FM
Poor quality
High quality
RF Attenuator
Input
Input
Attenuator
Resolution
filters
IF Amplifier
Local oscillator
To increase sensitivity
Increase IF amplifier gain - But noise will increase
Reduce input Attenuator - But may introduce Intermodulation
Residual Responses
Amplitude
Frequency
Andrew Wallace MEng (Hons) AMIEE
Regional Sales Specialist
Tea Time