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James YoungRohde & Schwarz
James YoungRohde & Schwarz
Improving the accuracy ofEMI emissions testing
Q&AQ&A
Who uses what for EMI?Who uses what for EMI?
CISPR, MIL-STD or Automotive?CISPR, MIL-STD or Automotive?
⇒ Spectrum Analyzers (SA)⇒ Spectrum Analyzers (SA)
⇒ Test Receivers (TR)⇒ Test Receivers (TR)
Software or front panel ?Software or front panel ?
Novice, Capable, Fluent or Expert ?Novice, Capable, Fluent or Expert ?
OverviewOverview
EMI Equipment comparisonEMI Equipment comparison
Making accurate measurementsMaking accurate measurements
⇒ RF / IF overload and Preselection⇒ RF / IF overload and Preselection
⇒ EMI Detectors and Filters⇒ EMI Detectors and Filters
⇒ Spectrum Analyzers (SA)⇒ Spectrum Analyzers (SA)
⇒ Test Receivers (TR)⇒ Test Receivers (TR)
⇒ Preamps, where and when⇒ Preamps, where and when
Spectrum Analyzers for EMISpectrum Analyzers for EMI
Spectrum Analyzers for EMISpectrum Analyzers for EMI
SA setup for EMI ExampleSA setup for EMI Example- Set Start freq, stop freq, RBW and detector from standard- Set Start freq, stop freq, RBW and detector from standard- Span of 1G-30MHz = 970 MHz / 1000 = 1 MHz resolution- Span of 1G-30MHz = 970 MHz / 1000 = 1 MHz resolution- x samples in RBW are stored, 500 or 1000 are displayed- x samples in RBW are stored, 500 or 1000 are displayed
- samples within RBW analyzed or weighted by the detector- samples within RBW analyzed or weighted by the detector
- QP “integrates” voltage in RBW, applies CISPR weighting- QP “integrates” voltage in RBW, applies CISPR weighting
-20
0
20
40
60
80
100
120Level [dBµV]
30M 50M 70M 100M 200M 300M 500M 700M 1G
Spectrum Analyzers for EMISpectrum Analyzers for EMI
QuestionQuestion
- What was wrong with the previous setup?- What was wrong with the previous setup?
AnswerAnswer- Frequency and amplitude accuracy depend on many samples falling within each measurement bin (also called display pixel).- Next “bin” will be 1 MHz away (nearly 10 x 120 kHz)!- Frequency resolution much too course for EMI- Solution?
- Frequency and amplitude accuracy depend on many samples falling within each measurement bin (also called display pixel).- Next “bin” will be 1 MHz away (nearly 10 x 120 kHz)!- Frequency resolution much too course for EMI- Solution?
30M 50M 70M 100M 200M 300M 500M 700M 1G
Spectrum Analyzers for EMISpectrum Analyzers for EMI
Example RevisitedExample Revisited
- Span of 970 MHz / 1001 = 1 MHz resolution- Span of 970 MHz / 1001 = 1 MHz resolution
- If using 120 KHz RBW, CISPR recommends 60 KHz “bin” points (17 x finer than 1 MHz)
- If using 120 KHz RBW, CISPR recommends 60 KHz “bin” points (17 x finer than 1 MHz)
- Solution: subrange in the span- Solution: subrange in the span
-20
0
20
40
60
80
100
120Level [dBµV]
30M 50M 70M 100M 200M 300M 500M 700M 1G
Frequency Accuracy of SAFrequency Accuracy of SA
- SA frequency resolution is far too course for EMI without sub-ranging the CISPR span
- SA frequency resolution is far too course for EMI without sub-ranging the CISPR span
- SA frequency accuracy when exploring peaksinfluenced by Span, RBW, VBW, marker accuracy
- SA frequency accuracy when exploring peaksinfluenced by Span, RBW, VBW, marker accuracy
Spectrum Analyzers for EMISpectrum Analyzers for EMI
Amplitude Accuracy of SAAmplitude Accuracy of SA- 6 dB (EMI) filters- QP and AVE detector times are observed- Data correction for system transducers- EUT specific timing issues are considered- Subranges set properly for sample #- RF and IF stages are not overloaded
- 6 dB (EMI) filters- QP and AVE detector times are observed- Data correction for system transducers- EUT specific timing issues are considered- Subranges set properly for sample #- RF and IF stages are not overloaded
Spectrum Analyzers for EMISpectrum Analyzers for EMI
- STEP SIZE between measurement bins- STEP SIZE between measurement bins
- DWELL TIME at each measurement bin- DWELL TIME at each measurement bin
⇒ SA lacks 2 control parameters for EMI⇒ SA lacks 2 control parameters for EMI
ConclusionConclusion
⇒ Sub-ranging and zero span is an attempt to make SA measure like TR
⇒ Sub-ranging and zero span is an attempt to make SA measure like TR
- Lacks dynamic range and overload protection (later slides)- Lacks dynamic range and overload protection (later slides)
Test Receivers for EMITest Receivers for EMI
Test Receivers for EMITest Receivers for EMI
Receivers for EMIReceivers for EMI
- Frequency Span (start / stop)- Frequency Span (start / stop)
- RBW Filter and detector- RBW Filter and detector
- DWELL TIME at each measurement point- DWELL TIME at each measurement point
- TR adjusts sample x and bins depending on span- TR adjusts sample x and bins depending on span
- Span / x = frequency resolution- Span / x = frequency resolution
- FREQUENCY INCRIMENT (step size independent of RBW) - FREQUENCY INCRIMENT (step size independent of RBW)
- x is often 16,000 – 100,000+- x is often 16,000 – 100,000+
Sample Points ExampleSample Points Example
Example: TR (green) vs. SA (blue) sample pointsExample: TR (green) vs. SA (blue) sample points
020406080
100120
30M 50M 70M 100M 200M 300M 500M 700M 1G
0.00
10.00
20.00
30.00
40.00
50.00
57.00Level [dBµV]
79.94M 85M 90M 95M 100M 109.63MFrequency [Hz]
Samples and BinsSamples and Binssamples
Display BIN
detector
peak
QP
Ave
RMS
detector
peak
QP
Ave
RMSDisplay BIN
Integration of samplesPeak Lost
Freq error
QPPeak
• Bin amplitude is detector value, Bin freq is reported in center• SA has 1001 bins, TR accesses 100,000 bins (from memory)
RBW
RBW
Receiver MeasurementsReceiver Measurements
Frequency Range 6-dB Bandwidth Step Size(<1/2 RBW)
# of measBins
150 kHz to 30 MHz 9 kHz 4 kHz 7,463
30 MHz to 1 GHz 120 KHz 50 KHz 19,400
• CISPR 16 recommends Step size ≤ RBW / 2
80M 85M 90M 95M 100M 110M
Frequency [Hz]
VS
Test Receivers for EMITest Receivers for EMI
- Time dependant on detector and EUT, notmeasurement speed of instruments
- Time dependant on detector and EUT, notmeasurement speed of instruments
Time Penalty ?Time Penalty ?
⇒ TR incorporates EMI control parameters⇒ TR incorporates EMI control parameters
ConclusionConclusion
- STEP SIZE between measurement bin- STEP SIZE between measurement bin
- DWELL TIME at each measurement bin- DWELL TIME at each measurement bin
- # of measurement bins as necessary for accuracy- # of measurement bins as necessary for accuracy
Best Instrument for EMI?Best Instrument for EMI?
Pros and Cons of EachPros and Cons of Each
- SA can also be used for RX and TX measurements- SA can also be used for RX and TX measurements
- SA frequency / amplitude accuracy easily skewed by improper settings and interpretation
- SA frequency / amplitude accuracy easily skewed by improper settings and interpretation
- SA is faster for initial preview- SA is faster for initial preview
- SA sub-ranging negates any speed advantage over TR for EMI
- SA sub-ranging negates any speed advantage over TR for EMI
- TR has little use outside EMI, expensive unit for one use
- TR has little use outside EMI, expensive unit for one use
Which one to use?Which one to use?Use SA or TR to develop “hit list”Use SA or TR to develop “hit list”
Use SA or TR for maximizationUse SA or TR for maximization
TR is optimum for final (dwell time, step size and auto attenuator)
TR is optimum for final (dwell time, step size and auto attenuator)
30 MHz 1 GHz
dBµVdBµV
1 PKCLRWR
SGL
RBW 120 kHzMT 1 sPREAMP ONAtt 30 dB AUTO
100 MHz 200 MHz 300 MHz 400 MHz 500 MHz 600 MHz 700 MHz 800 MHz 900 MHz
-20
-10
0
10
20
30
40
50
60
10 20 30 40 50 60 70 80 90
FREQUENCY 931.9200000 MHz
LEVEL QPK dBµV
10 20 30 40 50 60 70 80 90
FREQUENCY 931.9200000 MHz
LEVEL QPK dBµV
10 20 30 40 50 60 70 80 90
FREQUENCY 931.9200000 MHz
LEVEL QPK dBµV
FCC15RB
Date: 8.SEP.2003 14:13:12
Making accurate measurementsMaking accurate measurements
Overload protectionOverload protection
Detectors for EMIDetectors for EMI
PreampsPreamps
RBW Filters for EMIRBW Filters for EMI
Accurate MeasurementAccurate Measurement
Accuracy killersAccuracy killers
160 dB = 10e8 or 8 orders of magnitude160 dB = 10e8 or 8 orders of magnitude
EMC engineers don’t know what signalsthey are looking for initially
EMC engineers don’t know what signalsthey are looking for initially
Dynamic range of SA / TR is ~160 dBDynamic range of SA / TR is ~160 dB
- Overloads (RF and IF)- Incorrect detector settings- Preamplifiers improperly used- Improper RBWs
- Overloads (RF and IF)- Incorrect detector settings- Preamplifiers improperly used- Improper RBWs
RF OverdriveRF Overdrive
RF: Watch for harmonics of large signalsRF: Watch for harmonics of large signals
- Use attenuator to set mixer input level- Use attenuator to set mixer input level
Mixer Level
RF Attenuation sets mixer input level
Ref Level
Max Input LevelIn
put
1st
mix
er
RF Overload Example RF Overload Example
Example: amplified signal at 500 MHzExample: amplified signal at 500 MHz
Ref 0 dBm 496 MHz
A
496 MHz
1 SA
496 MHz
AVG
496 MHzRBW 3 MHz
496 MHz VBW 10 MHz 496 MHzSWT 10 ms
496 MHzAtt 10 dB
496 MHz*
496 MHz 496 MHz 496 MHz 496 MHz 496 MHz 496 MHz 496 MHz 496 MHz 496 MHz 496 MHz
Center 1 GHz
496 MHz
Span 2 GHz
496 MHz
200 MHz/
496 MHz
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
496 MHz1
Marker 1 [T1 ] 3.03 dBm 496.000000000 MHz
2
Marker 2 [T1 ] -48.80 dBm 996.000000000 MHz
3
Marker 3 [T1 ] -48.60 dBm 1.500000000 GHz
MARKER 1
496 MHz
Date: 23.JUN.2004 20:33:37
IF OverdriveIF Overdrive
IF: Watch for overload flagsIF: Watch for overload flags
- Set IF gain using “ref Level”- Set IF gain using “ref Level”
Mixer Level
Ref Level sets IF Gain
Ref LevelIn
put
1st
mix
er
IF G
ain
- Use Ref Level to set IF Gain- Use Ref Level to set IF Gain
IF Overload ExampleIF Overload Example
Example: +6 dBm PulseExample: +6 dBm Pulse
1 AP
10 dB
CLRWR
10 dB
A
10 dB 10 dB 10 dB 10 dB 10 dB 10 dB 10 dB 10 dB 10 dB 10 dBRBW 3 MHz
10 dB VBW 10 MHz 10 dB
SWT 5 ms
10 dB
Ref 0 dBm
10 dB
Center 502.0534106 MHz
10 dB
Span 990.2160153 MHz
10 dB
99.02160153 MHz/
10 dB
Att 10 dB
10 dB*
10 dB
OVLD
10 dB
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10 dB
1
Marker 1 [T1 ] 6.13 dBm
502.053410569 MHz
RF ATTENUATION
10 dB
Date: 23.JUN.2004 20:55:20
Preselection FilteringPreselection Filtering
Preselector is a “tracking” RF filterPreselector is a “tracking” RF filter
Cure: preselect filtering of signals before RF or IFCure: preselect filtering of signals before RF or IF
- SA may not warn of RF or IF overdrive- SA may not warn of RF or IF overdrive
- IF overload won’t show on display - IF overload won’t show on display
- ALL RF power (noise & signals) go into mixer- ALL RF power (noise & signals) go into mixer
- high amplitude signals outside displayed span caninfluence amplitude and may be aliased
- high amplitude signals outside displayed span caninfluence amplitude and may be aliased
- Signals outside display ruin amplitude reading- Signals outside display ruin amplitude reading
Preselection SimplePreselection Simple
V(f)
f
B1
V(f)
B 2
Mixer stagePre-selection
Overdrive and PreselectionOverdrive and Preselection
Example: +10 dBm signal at 500 MHz causing overdriveExample: +10 dBm signal at 500 MHz causing overdrive
CLRWR
1.000272533 GHz
A
1.000272533 GHzRef 0 dBm 1.000272533 GHz
*
1.000272533 GHz
1 PK
1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHzAtt 20 dB
1.000272533 GHz*
1.000272533 GHz
141.6135906 MHz/
1.000272533 GHz
Start 400 MHz
1.000272533 GHz
Stop 1.816135906 GHz
1.000272533 GHzRBW 3 MHz
1.000272533 GHz VBW 10 MHz 1.000272533 GHzSWT 10 ms
1.000272533 GHz
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
1.000272533 GHz
1
Marker 1 [T1 ] -43.41 dBm 1.000272533 GHz
2
Marker 2 [T1 ] -54.36 dBm 1.501204189 GHz
MARKER 1
1.000272533 GHz
Date: 8.SEP.2003 13:03:46
Overdrive and PreselectionOverdrive and Preselection
Example2: Moving overload off screen won’t clear overloadExample2: Moving overload off screen won’t clear overload
CLRWR
600 MHz
A
600 MHzRef 0 dBm 600 MHz
*
600 MHz
1 PK
600 MHz 600 MHz 600 MHz 600 MHz 600 MHz 600 MHz 600 MHz 600 MHz 600 MHz 600 MHzAtt 20 dB
600 MHz*
600 MHz
121.6135906 MHz/
600 MHz
Start 600 MHz
600 MHz
Stop 1.816135906 GHz
600 MHzRBW 3 MHz
600 MHz VBW 10 MHz 600 MHzSWT 10 ms
600 MHz
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
600 MHz
1
Marker 1 [T1 ] -43.41 dBm 1.000272533 GHz
2
Marker 2 [T1 ] -54.58 dBm 1.501204189 GHz
START FREQUENCY
600 MHz
Date: 8.SEP.2003 13:04:13
Overdrive and PreselectionOverdrive and Preselection
Example3: Activating Preselector clears overload by filtering the fundamentalExample3: Activating Preselector clears overload by filtering the fundamental
CLRWR
1.000272533 GHz
A
1.000272533 GHzRef 0 dBm 1.000272533 GHz
*
1.000272533 GHz
1 PK
1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHz 1.000272533 GHzAtt 20 dB
1.000272533 GHz*
1.000272533 GHz
141.6135906 MHz/
1.000272533 GHz
Start 400 MHz
1.000272533 GHz
Stop 1.816135906 GHz
1.000272533 GHzRBW 3 MHz
1.000272533 GHz VBW 10 MHz 1.000272533 GHzSWT 10 ms
1.000272533 GHz
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
1.000272533 GHz
1
Marker 1 [T1 ] -43.41 dBm 1.000272533 GHz
2
Marker 2 [T1 ] -54.36 dBm 1.501204189 GHz
MARKER 1
1.000272533 GHz
Date: 8.SEP.2003 13:03:46
CLRWR
600 MHz
A
600 MHzRef 0 dBm 600 MHz
*
600 MHz
1 PK
600 MHz 600 MHz 600 MHz 600 MHz 600 MHz 600 MHz 600 MHz 600 MHz 600 MHz 600 MHzAtt 20 dB
600 MHz*
600 MHz
121.6135906 MHz/
600 MHz
Start 600 MHz
600 MHz
Stop 1.816135906 GHz
600 MHzRBW 3 MHz
600 MHz VBW 10 MHz 600 MHzSWT 10 ms
600 MHz
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
600 MHz
1
Marker 1 [T1 ] -43.41 dBm 1.000272533 GHz
2
Marker 2 [T1 ] -54.58 dBm 1.501204189 GHz
START FREQUENCY
600 MHz
Date: 8.SEP.2003 13:04:13
CLRWR
A
Ref 0 dBm
*1 PK
Att 20 dB*
121.6135906 MHz/Start 600 MHz Stop 1.816135906 GHz
RBW 3 MHzVBW 10 MHzSWT 10 ms
PS
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
1
Marker 1 [T1 ] -62.14 dBm 1.000272533 GHz
2
Marker 2 [T1 ] -63.57 dBm 1.501204189 GHz
Date: 8.SEP.2003 13:04:47
PRF, Dwell time and DetectorsPRF, Dwell time and Detectors
EUT / Detector dwell time requirementsEUT / Detector dwell time requirements
- Must capture “worst case” emissions of EUT- Must capture “worst case” emissions of EUT
- Cycle time, modulation, and pulse repetition frequency may require extended dwell in each subrange (QP,AVE, RMS)
- Cycle time, modulation, and pulse repetition frequency may require extended dwell in each subrange (QP,AVE, RMS)
- Test Receivers include this parameter-Since tuning each bin, can dwell as long as necessary
- Spectrum Analyzers have a workaround-Zero Span is a way to trick SA into dwelling at tuned bin-Must do calculation since overall sweep time is controlled-Dwell time = sweep time / measurement bins
- Test Receivers include this parameter-Since tuning each bin, can dwell as long as necessary
- Spectrum Analyzers have a workaround-Zero Span is a way to trick SA into dwelling at tuned bin-Must do calculation since overall sweep time is controlled-Dwell time = sweep time / measurement bins
Detector SettingsDetector Settings
Quasipeak ???? Quasipeak ????
⇒ QP is an attempt to quantify a signalsImpact on a radio receiver (annoyance)⇒ QP is an attempt to quantify a signalsImpact on a radio receiver (annoyance)
Quasipeak restrictions Quasipeak restrictions
- Dwell time (per step or subrange) at least 1 second- Dwell time (per step or subrange) at least 1 second
- PRF issues increase dwell time requirements- PRF issues increase dwell time requirements
- Factors: amplitude, frequency, pulse repetition frequency- Factors: amplitude, frequency, pulse repetition frequency
Detector SettingsDetector Settings
Peak Detector Peak Detector
Average or RMS DetectorAverage or RMS Detector
- Peak gives “worst case”- Peak gives “worst case”
- Safest detector: Often fast enough to see most signals even if instrument settings are not “optimum”
- Safest detector: Often fast enough to see most signals even if instrument settings are not “optimum”
- Average detector used above 1 GHz for FCC and CE tests- Average detector used above 1 GHz for FCC and CE tests
- Watch RBW (1MHz or 120 KHz above 1GHz?)- Watch RBW (1MHz or 120 KHz above 1GHz?)
- dwell for at least 100 mS at each bin for proper integration- dwell for at least 100 mS at each bin for proper integration
- RMS for ultra wide band, dwell time critical for integration- RMS for ultra wide band, dwell time critical for integration
Detector Settings ExampleDetector Settings Example
Example: -40 dBm signal at 280 MHz measures with RMSExample: -40 dBm signal at 280 MHz measures with RMS
Ref -20 dBm Att 10 dB
CLRWR
A
50 MHz/Start 0 Hz Stop 500 MHz
RBW 120 kHz
SWT 175 ms
*1 RM
VBW 1 MHz
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
1
Marker 1 [T1 ]
-49.64 dBm 280.000000000 MHz
Date: 23.JUN.2004 21:44:15
Detector Settings ExampleDetector Settings Example
Example2: Same -40 dBm but with Ave and same settingsExample2: Same -40 dBm but with Ave and same settings
Ref -20 dBm Att 10 dB
CLRWR
A
50 MHz/Start 0 Hz Stop 500 MHz
RBW 120 kHz
SWT 175 ms
*1 RM
VBW 1 MHz
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
1
Marker 1 [T1 ]
-49.64 dBm 280.000000000 MHz
Date: 23.JUN.2004 21:44:15
Ref -20 dBm Att 10 dB
CLRWR
A
50 MHz/Start 0 Hz Stop 500 MHz
RBW 120 kHz
SWT 175 msVBW 1 MHz
*1 AV
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
1
Marker 1 [T1 ] -56.89 dBm 280.000000000 MHz
Date: 23.JUN.2004 21:44:41
Detector Settings ExampleDetector Settings ExampleRef -20 dBm Att 10 dB
CLRWR
A
50 MHz/Start 0 Hz Stop 500 MHz
RBW 120 kHz
SWT 175 ms
*1 RM
VBW 1 MHz
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
1
Marker 1 [T1 ]
-49.64 dBm 280.000000000 MHz
Date: 23.JUN.2004 21:44:15
Ref -20 dBm Att 10 dB
CLRWR
A
50 MHz/Start 0 Hz Stop 500 MHz
RBW 120 kHz
SWT 175 msVBW 1 MHz
*1 AV
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
1
Marker 1 [T1 ] -56.89 dBm 280.000000000 MHz
Date: 23.JUN.2004 21:44:41
Ref -20 dBm Att 10 dB
CLRWR
A
50 MHz/Start 0 Hz Stop 500 MHz
*1 QP
RBW 120 kHzVBW 1 MHzSWT 175 ms
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
1
Marker 1 [T1 ] -76.57 dBm 280.000000000 MHz
Date: 23.JUN.2004 21:45:04
Example3: Same -40 dBm but with QP and same settingsExample3: Same -40 dBm but with QP and same settings
Transducer correctionTransducer correction
- CISPR needed a way to eliminate effects of variability inchambers, antennas and cable losses
- CISPR needed a way to eliminate effects of variability inchambers, antennas and cable losses
- Standards require normalization of these effects to compare results to limit line
- Standards require normalization of these effects to compare results to limit line
Transducers and PRFTransducers and PRF
- Chamber ruled by Normalized Site Attenuation (NSA)- Chamber ruled by Normalized Site Attenuation (NSA)
- Transducers and connections used correction factors derivedfrom actual calibrations
- Transducers and connections used correction factors derivedfrom actual calibrations
Resolution Bandwidth FiltersResolution Bandwidth Filters
Unit dB V
A
SWT 5 ms
Ref Lvl
97 dB V
Ref Lvl
97 dB V
RF Att 20 dB
Center 100 MHz Span 1 MHz100 kHz/
2MA
RBW 100 kHz
VBW 10 MHz
IN11MA1MAX
2VIEW2VIEW 2MA1MA
0
10
20
30
40
50
60
70
80
90
-3
97
6dB RBW
3dB RBW
PreampsPreamps
Preamps: When are they needed? Preamps: When are they needed?
- Generally needed above 7 GHz- Generally needed above 7 GHz
- Below 7 GHz ONLY if stringent limit line or long cables- Below 7 GHz ONLY if stringent limit line or long cables
Preamps: Where to put them?Preamps: Where to put them?
- Preamps amplify signal and noise- Preamps amplify signal and noise
- Real goal of preamp is PRESERVE signalto noise ratio (best at the antenna)
- Real goal of preamp is PRESERVE signalto noise ratio (best at the antenna)
- Low level signals require amplification at antenna, before signal is subjected to path loss of cables
- Low level signals require amplification at antenna, before signal is subjected to path loss of cables
PreampsPreamps
Preamp S/N Ratio examplePreamp S/N Ratio example
S N
S N S N
S N
S N S N
Preamp near EMI receiver
Preamp at antenna
Common Cables loss
½ dB per meter at 1GHz
3 dB per meter at 40 GHz
PreampsPreamps
Preamps Preamps
- Must have high gain & low noise figure (amp contributed noise)- 1-18 GHz gain around 30 dB with NF of 3.2 dB or less- 18-26 GHz gain around 35 dB with NF of 3.0 dB or less- 26-40 GHz gain around 50 dB with NF of 2.8 dB or less
- Must have high gain & low noise figure (amp contributed noise)- 1-18 GHz gain around 30 dB with NF of 3.2 dB or less- 18-26 GHz gain around 35 dB with NF of 3.0 dB or less- 26-40 GHz gain around 50 dB with NF of 2.8 dB or less
- Noise Figure equation states the 1st gain/loss encountered has the most impact on s/n ratio
- Noise Figure equation states the 1st gain/loss encountered has the most impact on s/n ratio
S NRF Thermal Noise (N0)
Noise contributed by preamp (NF)
PreampsPreamps
Know your Preamp overload range and behaviorKnow your Preamp overload range and behavior
- Know the preamp range (what is the max signal input without compression or damage)
- Know the preamp range (what is the max signal input without compression or damage)
- Must keep preamp in linear region- Must keep preamp in linear region
- Watch RF input levels to 1st mixer system check if unsure (variable attenuator)- Watch RF input levels to 1st mixer system check if unsure (variable attenuator)
- Non-wave guide antennas have a direct connection to the FET, watch static discharge
- Non-wave guide antennas have a direct connection to the FET, watch static discharge
PreampsPreamps
ConclusionConclusion
RF & IF OverloadsRF -> Harmonics IF -> If overload flag
Attenuator Ref Level
RF & IF OverloadsRF -> Harmonics IF -> If overload flag
Attenuator Ref Level
Preampsamplify at antenna know linear region below 1gz
system check (attenuator) static
Preampsamplify at antenna know linear region below 1gz
system check (attenuator) static
TR vs. SASpan Subranges step size resolution
dwell time overloading preselection
TR vs. SASpan Subranges step size resolution
dwell time overloading preselection