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Designing a System
• Key considerations are the amplifier and antenna
combination
• Determining what Power Amplifier to select depends on
– The test level required by the standard
– The type of modulation required
– The antenna efficiency (Gain)
– The test environment
– Cable and other component losses
2
Usable Amplifier Power • Saturated Power (Psat) Vs Linear Power (P1dB)
• Definitions
– Psat – Highest power that the amplifier can generate
– P1dB – Highest power where Pin Vs Pout curve is considered to
be straight
3
Effect of Saturation on Modulation
CW Input
Level
required for
10V/m
Modulation
CW Input
Level
required for
10V/m
Modulation
O/P Modulation
Matches the Input
O/P Modulation
does not Match
the Input
Requirement of IEC 61000-4-6
CW Input
Level
required for
10Vemf
5.1dB Increase
3.1 to 7.1dB
Increase
Potential Change to IEC 61000-4-3
CW Input
Level
required for
10Vemf
5.1dB Increase
3.1 to 7.1dB
Increase
CW Input
Level
required
for 18V/m
5.1dB Reduction
>3.1dB
Reduction
Effect of Saturation on Modulation
CW Input
Level
required for
200V/m
Modulation
O/P Modulation
Matches the Input
Pulse
Harmonics
Unwanted signals produced at multiples of the required fundamental frequency
Broadband, power and field measuring devices cannot distinguish between the
fundamental and harmonics
Under testing possible
False failures can be caused
It may appear that an DUT has a problem at a frequency but it could be that
the problem is at the harmonic frequency
User may waste time and money on an incorrect fix
Most antenna have better gain at higher frequencies
This can magnify the level of the harmonic compared to the fundamental
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1 2 3 4 5 6 7 8 9 10 11 12 13
Rela
tiv
e L
ev
el
Harmonic Number
Harmonics of a Square Wave
Harmonic Distortion
f1 3 x f1
Antenna Gain
Frequency
IEC 61000-4-3 requires that the level of the harmonics measured at
the uniform plane is at least 6dB less than the fundamental signal
Coupling devices
20
CDN M CDN A CDN S CDN T
Current injection probe
EM clamp Attenuation clamp
(decoupling only)
Calibration adapters
Coupling Devices
• CDN
– Good Decoupling performance
• Majority of the injected signal goes towards the DUT
• Very little signal goes back to the mains or AE
– Most efficient Device
• Least power required from the amplifier
– Needs to be inserted in the cable
• May not always be convenient
• Can affect normal operation of the DUT
Testing with Coupling Devices other than a CDN
• EM Clamp
– Like a CDN have good Decoupling performance
• Majority of the injected signal goes towards the DUT
• Very little signal goes back to the mains or AE
– Not as efficient as a CDN
• Requires more power from the amplifier
– Physically larger than a CDN
• May not always be convenient
– Clamp on device
• Does not require cable under test to be broken
22
Testing with Coupling Devices other than a CDN
• BCI Clamp
– No Decoupling performance
• Injected signal goes in both directions
• Same signal goes to the mains or AE
– Not as efficient as a CDN or EM Clamp
• Requires more power from the amplifier
– Clamp on device
• Does not require cable under test to be broken
23
Bulk Current Injection (BCI)
Power required depends on the test level and the selected BCI Probe
Power = I2 * 50 plus the Insertion loss of the probe
Testing with Coupling Devices other than a CDN
• Both devices have a low source impedance
• Not 150 Ω
• Although the calibration procedure is the same
• Attempt to achieve target level at output of the calibration jig
• When connected to a DUT with low common mode impedance much higher currents
can be induced compared to a CDN
• User is required to monitor the RF current on the cable under test and limit it to the
maximum level possible from a CDN
• Imax = U0/150
27
150 Ω
Vemf
I = Vemf /150
Radiated Immunity Power required depends on the test level and the selected antenna
Trade of between efficiency and size
Larger antenna are more efficient, if they will fit in the chamber
Basic Radiated Field/Power Calculation
Power required to generate a field of E V/m
at a distance d metres from the antenna
Power (watts) = (E2 * d2) /( 30 * g)
g = 10 (G/10) {g = ratio gain, G = gain (dBi) }
Additional Factors to be included
Chamber variation
No chamber is perfectly uniform
The ‘so called’ uniform area can have variation up to 6dB
Potentially you could require 6dB more power = 4 times more
Additional Factors to be included
Modulation
80% Sinusoidal Amplitude Modulation (AM)
Requires 1.82 (= 3.24) times the power or +5.1dB
Pulse Modulation (Pulse) and Frequency Modulation (FM)
Requires no additional power
0
5
10
15
20
25
30
0 1000 2000 3000 4000 5000 6000T
est F
ield
V/m
Frequency MHz
Radiated System (80MHz to 6GHz)
Chamber1
C
1
2
3
4
Switch1
-
ITS6006
Coupler1
Coupler2
Coupler3
C
1
2
Switch2
-
ITS6006 or External Switch
SigGen1
(none) -
ITS6006
Amp1
(none) -
80RF1000-500 or -10000
Amp2
(none) -
AS 0825-300 or -500
Amp3
(none) -
AS1860-50
Antenna1
STLP 9128E
Antenna2
STLP 9149
PowerMeter1
(none) -
PM6006
PowerMeter2
(none) -
PM6006
PowerMeter3
(none) -
PM6006
StressSensor1
0
5
10
15
20
25
30
0 1000 2000 3000 4000 5000 6000
Test
Fie
ld V
/m
Frequency MHz
Radiated System (80MHz to 6GHz)
Chamber1
C
1
2
3
4
Switch1
-
ITS6006
Coupler1
Coupler2
Coupler3
C
1
2
Switch2
-
ITS6006 or External Switch
C
1
2
3
Switch3
SigGen1
(none) -
ITS6006
Amp1
(none) -
80RF1000-500 or -10000
Amp2
(none) -
AS 0825-300 or -500
Amp3
(none) -
AS1860-50
Antenna1
STLP 9128E
Antenna2
3161-1
PowerMeter1
(none) -
PM6006
PowerMeter2
(none) -
PM6006
PowerMeter3
(none) -
PM6006
StressSensor1
Antenna3
3161-2
Antenna4
3161-3
Loss in Cables and components
Test Rack to Antenna
1.5m rack to penetration (Loss 0.25 dB @ 1GHz)
5m penetration to floor panel (underfloor cable) (Loss 0.8 dB @ 1GHz)
3m floor panel to antenna (Loss 0.5 dB @ 1GHz)
Internal to rack
0.4m RF switch output – rack bulkhead (Loss 0.1 dB @ 1GHz)
0.4m Directional Coupler output – RF switch input (Loss 0.1 dB @ 1GHz)
Werlatone C5982 Directional Coupler (Loss 0.1 dB @1GHz)
RF Switch – 2 Way N type (Loss 0.1 dB @ 1 GHz)
TOTAL LOSS 1.95 dB @ 1 GHz
Would be lower at 80MHz but much higher at 3GHz
Typical example
37
Frequency Loss Chamber AM Power
MHz dB dB Watts
80 2 3 494.5
85 2 3 492.2
90 2 3 489.9
95 2 3 482.2
100 2 3 468.9
110 2 3 430.6
120 2 3 368.1
130 2 3 422.9
140 2 3 391.1
150 2 3 333.4
160 2 3 298.8
170 2 3 313.4
180 2 3 310.4
190 2 3 303.6
200 2 3 310.4
220 2 3 309.1
240 2 3 344.5
260 2 3 374.3
280 2 3 340.6
300 2 3 336
350 2 3 320.2
400 2 3 348.3
500 2 3 307.2
600 2 3 339
700 2 3 335.1
800 2 3 316.3
900 2 3 350.9
1000 2 3 339
5dB
Frequency Loss Chamber AM Power
MHz dB dB Watts
80 2 4 622.5
85 2 4 619.5
90 2 4 616.6
95 2 4 606.9
100 2 4 590.4
110 2 4 542.1
120 2 4 463.7
130 2 4 532.1
140 2 4 492.2
150 2 4 420
160 2 4 375.9
170 2 4 394.7
180 2 4 391.1
190 2 4 382
200 2 4 391.1
220 2 4 389.2
240 2 4 433.6
260 2 4 471.1
280 2 4 428.7
300 2 4 422.9
350 2 4 402.8
400 2 4 438.7
500 2 4 386.6
600 2 4 426.8
700 2 4 421.9
800 2 4 398.2
900 2 4 441.7
1000 2 4 426.8
Frequency Loss Chamber AM Power
MHz dB dB Watts
80 2 5 783.5
85 2 5 779.9
90 2 5 776.4
95 2 5 764
100 2 5 743
110 2 5 682.4
120 2 5 583.6
130 2 5 670.1
140 2 5 619.5
150 2 5 528.5
160 2 5 473.4
170 2 5 496.7
180 2 5 492.2
190 2 5 480.9
200 2 5 492.2
220 2 5 489.9
240 2 5 546
260 2 5 593
280 2 5 539.5
300 2 5 532.1
350 2 5 507.1
400 2 5 552.1
500 2 5 486.4
600 2 5 537.2
700 2 5 531.1
800 2 5 501.3
900 2 5 556
1000 2 5 537.2
7dB 6dB
Summary
• In order to accurately design a system the following
information is required:
– Required Frequency range and Field level
– Modulation type
– Chamber dimensions
– Chamber performance
– Cable routing, lengths
38