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Presentation on theme: "www.agilent.com/find/backtobasics Back to Basics - 2008 Power Measurement Basics."— Presentation transcript:

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2 Back to Basics Power Measurement Basics

3 asics Objectives On completion of this module, you will be able to understand: the importance of power measurements Three basic types of power measurements Power meter/sensor measurement method Two most prevalent sensor technologies Advanced measurements used for the latest RF & microwave applications Calculate power measurement uncertainty Outline Agilent’s broad range of power measurement solutions

4 Power Measurement Basics asics Agenda Importance of Power Measurements Average, Peak and Pulse Power Power Meter & Sensor Measurement Method Sensor Technologies Agilent Power Measurement Solutions Time-Gated Power Measurements Advanced Power Measurements Measurement Uncertainty, Standards and Traceability Agilent Power Sensor Selection Guides (Appendix)

5 Power Measurement Basics asics Signal Power Levels are Critical Too low: Too high:...Or even worse! Signal buried in noise Nonlinear distortion...

6 Power Measurement Basics asics DC V Inc V Ref Z O Z S R L V R L Z S I Why Not Measure Voltage? R L Z S V – + ± I Low Frequency P = IV = V 2 /R High Frequency I and V vary with position Power is constant Amplitu de t P I V DC component of power AC component of power

7 Power Measurement Basics asics Importance of Power Measurements Average, Peak and Pulse Power Power Meter & Sensor Measurement Method Sensor Technologies Agilent Power Measurement Solutions Time-Gated Power Measurements Advanced Power Measurements Measurement Uncertainty, Standards and Traceability Agilent Power Sensor Selection Guides (Appendix) Agenda

8 Power Measurement Basics asics Basic power unit is the watt (W) 1 W = 1 A x 1 V Units and Definitions Power = energy transferred per unit time A logarithmic (decibel) scale is often used to compare two power levels Relative power in decibels (dB): Absolute power is expressed by assigning a reference level to P ref in dBm:

9 Power Measurement Basics asics t Average over many modulation cycles AM Pulsed Average over many pulse repetitions Average Power

10 Power Measurement Basics asics Pulse Power Power Time A(pulse width) Duty Cycle = ABAB (pulse repetition interval) B Pulse Power = Average Power/Duty Cycle Rectangular pulse Constant duty cycle Pulse power

11 Power Measurement Basics asics Maximum power in the envelope of a signal Peak Envelope Power For pulses that are not rectangular

12 Power Measurement Basics asics Average Power Pulse Power Peak Envelope Power Summary: Types of Power Measurement Pulse power Average power EPM power meter EPM-P or P-Series Average power

13 Power Measurement Basics asics Agenda Importance of Power Measurements Average, Peak and Pulse Power Power Meter & Sensor Measurement Method Sensor Technologies Agilent Power Measurement Solutions Time-Gated Power Measurements Advanced Power Measurements Measurement Uncertainty, Standards and Traceability Agilent Power Sensor Selection Guides (Appendix)

14 Power Measurement Basics asics Instruments That Measure RF & Microwave Power Spectrum Analyzer Network Analyzer Power Meter and Sensor Vector Signal Analyzer ± 0. 0X dB ± 0. X dB or greater Traceability Frequency selective Broadband

15 Power Measurement Basics asics The Power Meter and Sensor Method DC or low-frequency equivalent RF power Power Sensor Power Meter Display (dBm or W) Thermistor Thermocouple Diode Detector

16 Power Measurement Basics asics Agenda Importance of Power Measurements Average, Peak and Pulse Power Power Meter & Sensor Measurement Method Sensor Technologies Agilent Power Measurement Solutions Time-Gated Power Measurements Advanced Power Measurements Measurement Uncertainty, Standards and Traceability Agilent Power Sensor Selection Guides (Appendix)

17 Power Measurement Basics asics Thermistors One of the earliest types of power sensors Have been replaced in most applications by thermocouples and diode detectors Still used for power transfer standards in metrology applications Thermistor mount Thermistor : Semiconductor that changes resistance due to change in temperature

18 Power Measurement Basics asics C c Thermocouples A junction of two dissimilar metals generates a voltage related to temperature Junction temperature is directly related to RF power RF Power C b RF Input Hot Junction Hot Cold Cold Junction To DC Voltmeter Thin-Film Thermocouples

19 Power Measurement Basics asics Diode Detectors C b R matching V o + - R s V s Depend on the rectifying characteristics of non-linear microwave detection curve 50 dB

20 Power Measurement Basics asics Power Sensor Technologies Comparison 848xA/B/H thermocouple sensor 848xD, E441x, E9300, E9320, N1920 diode sensor 478A/8478B thermistor sensor (30dB) (50dB) (up to 90dB)

21 Power Measurement Basics asics Power Sensor Chopper Diode Detector Power Meter Synchronous Detector LPFADCRanging BPF Squarewave Generator µProcessor AC 220 Hz DC RF DAC AUTOZERO Power Sensor and Meter Signal Path

22 Power Measurement Basics asics Wide Dynamic Range CW Power Sensors – 70 to + 20 dBm = 90 dB Dynamic Range Calibration Data Contain Input power level vs freq vs temperature

23 Power Measurement Basics asics Agenda Importance of Power Measurements Average, Peak and Pulse Power Power Meter & Sensor Measurement Method Sensor Technologies Agilent Power Measurement Solutions Time-Gated Power Measurements Advanced Power Measurements Measurement Uncertainty, Standards and Traceability Agilent Power Sensor Selection Guides (Appendix)

24 Power Measurement Basics asics Agilent Power Meters Product Portfolio Power Meters (11 models) P-Series (2 models) 30MHz Video Bandwidth N1911A (US$7,501) N1912A (US$10,547) EPM-P Series (2 models) 5MHz Video Bandwidth E4416A (US$4,523) E4417A (US$7,111) EPM Series (2 models) Broadband, for all signal types E4418B (US$3,550) E4419B (US$6,092) 432A P-Series LXI (1 model) 30MHz Video Bandwidth N8262A (US$11,784) Broadband, for all signal types U2000 Series (4 models) U2000A ($3,087) U2001A ($2,371) U2002A ($3, 807) U2004A ($2,675) Peak & Average Power MetersAverage Power Meters Performance / Price

25 Power Measurement Basics asics CCDF statistical analysis Pulse parameters analysis Max/Min Limit Test Data logging for 7 Days N1911/12A P- Series N8262A LXI power meter N1918A-100 Power Analysis Software U2000 USB power sensor Compatible with Power Analysis Manager Software N1918A-100 Multichannel measurements display

26 Power Measurement Basics asics U2000 Series USB Power Sensors Display Power Measurement on a PC or other Agilent instruments Work with laptop Work with N9340A HHSA

27 Power Measurement Basics asics Instrument Compatibility with USB Sensor N9020A MXA Vector Signal Analyzer N5242A PNA-X Vector Network Analyzer N9340 Hand Held Spectrum Analyzer E506x & E507X ENA Vector Network Analyzer E836xB PNA Vector Network Analyzer N5182A MXG Vector Signal Generator Now! Soon!!

28 Power Measurement Basics asics U2000 USB Sensor Target Applications Key Advantages Lower cost solution with equivalent bench power meter performance Simplified your measurement setup with USB plug & play Optimize you test rack space by going powermeter-less Ideal for manufacturing testsIdeal for long distance antenna test  Key Advantages  Simplified setup  Hassle-free calibration – internal zeroing  Long distance measurements with USB-to-LAN hub Design for field applications  Key Advantages  Light weight and small size, plug and play. Easy to carry for field applications Design for satellite receiver tests  Support long distance, multi-channel operations E5813A Multi-list view & channel mathematics

29 Power Measurement Basics asics Agilent Power Sensor Families 8480 Series Power Sensors Average power measurements using diode and thermocouple technology E-Series Power Sensors E441XA Wide Dynamic Range CW Sensor E9300 Wide Dynamic Range Average Power Sensor E9320 Peak and Average Sensor (<5MHz) P-Series Power Sensors Peak & Average power measurements of wide bandwidth modulated signal using diode technology

30 Power Measurement Basics asics Average/CW Power Sensors POWER FREQUENCY 848X B-Series 0 to +44 dBm 848X H-Series -10 to +35 dBm 848X A-Series -30 to + 20 dBm 848X D-Series -70 to -20 dBm 8481B 8482B 8481H 8482H 8487A Q8486A W8486A R8486A 8485A 8481A 8482A 8483A 8487D Q8486D R8486D 8485D 8481D 100 kHz 10 MHz 50 MHz 2 GHz 4.2 GHz 18 GHz 26.5 GHz 33 GHz 40 GHz 50 GHz 75 GHz 110 GHz OPT 33 V V V8486A 9 kHz 6 GHz E9304A E9301A E9300A OPT -H to +20 dBm E441X Series -60 to +20 dBm E930X Series E9301H E9300H -50 to +30 dBm E930X A/H-Series E9301B E9300B -30 to +44 dBm E930X B-Series OPT 33 E4413A E4412A 848X Average Diode Sensor 848X Average Thermocouple Sensor E441X 1-Path Diode CW-only Sensor E930X 2-Path Diode True-Average sensor OPT –H24 E9300A OPT –H25 OPT -H19 E9304A Compatible with EPM, EPM-P and P-series power meters

31 Power Measurement Basics asics E9323A (5MHz BW) E9322A (1.5MHz BW) Peak & Average/CW & Wideband Power Sensors POWER FREQUENCY -35 to + 20 dBm 100 kHz 10 MHz 50 MHz 2 GHz 4.2 GHz 18 GHz 26.5 GHz 33 GHz 40 GHz 50 GHz 75 GHz 110 GHz V V 9 kHz 6 GHz -65 to +20 dBm -60 to +20 dBm N192X Peak, Average, rise time, fall time, pulse width sensor E932X Peak and Average/CW sensor N1922A (30MHz BW) N1921A (30MHz BW) E9327A (5MHz BW) E9326A (1.5MHz BW) E9325A (300kHz BW) E9321A (300kHz BW) N192X A-Series E932X A-Series Compatible with P- series Compatible with EPM-P & P-Series

32 Power Measurement Basics asics P-Series Power Sensors Internal Zero and Cal Internal zero and calibration within the N1921A/22A sensors N1921/22A Wideband Power Sensor Block Diagram RF Input To wideband amplifier and 100 MHz Sampler Voltage Reference From CAL DAC Zero and Cal Path Switching Diode Detectors  Minimizing set up and calibration time  Eliminates multiple connections with external calibration source  Reduce measurement uncertainties

33 Power Measurement Basics asics 80 dB dynamic range with any signal type Low-Power Path High-Power Path RF Input E9300 Average Power Sensor Technology Two-path design Diode stack/attenuator/diode stack topology Automatic path switching (– 60 to –10 dBm) (–10 to +20 dBm)

34 Power Measurement Basics asics Sensor Diode Bulkhead RF IN 50 ohms Load Filter * (300 kHz, 1.5 MHz, 5 MHz lowpass) Chopper CW Differential Amp Switched Gain Preamp GAIN SELECT SERIAL BUS Av. PATH ISOLATE Normal (Peak) Path Variable Gain Differential DC Coupled Amplifier * (300 kHz, 1.5 MHz, 5 MHz) PEAK AUTO-ZERO Thermistor Bias I 2 C Buffer Gain / Mode Control Sensor ID E 2 PROM Thermistor -t° 3 dB 50-ohm load Average-Only Path * Bandwidth is sensor dependent E9320: Two Sensors in One Package

35 Power Measurement Basics asics Agenda Importance of Power Measurements Average, Peak and Pulse Power Power Meter & Sensor Measurement Method Sensor Technologies Agilent Power Measurement Solutions Time-Gated Power Measurements Advanced Power Measurements Measurement Uncertainty, Standards and Traceability Agilent Power Sensor Selection Guides (Appendix)

36 Power Measurement Basics asics Time-Gated Power Measurements EDGE signal (GSM) Peak, average and peak-to-average ratio of a single burst Optimize for ‘burst’ type of signals such as EDGE, WiMAX, WLAN

37 Power Measurement Basics asics Sensors for Time-Gated Measurements Sensor rise/fall time requirements For characterizing overshoot: < 1/8 signal rise time For average power: same as signal rise time E9320 peak/average sensors 200 ns rise time (typical), up to 5MHz VBW TDMA, CDMA and W-CDMA wireless formats P-Series wideband power sensors < 13 ns rise time and fall time, 30MHz VBW Radar and pulsed component test, WiMAX, WLAN wireless formats

38 Power Measurement Basics asics Length 1 Length 4 Length 3 Length 2 Start 1 Start 2 Start 3 Ext Trigger Start 4 Delay Triggering and Measurement Capabilities EPM-P and P-Series Power Meters Triggers Average Peak Level = Internal External GPIB

39 Power Measurement Basics asics Agenda Importance of Power Measurements Average, Peak and Pulse Power Power Meter & Sensor Measurement Method Sensor Technologies Agilent Power Measurement Solutions Time-Gated Power Measurements Advanced Power Measurements Measurement Uncertainty, Standards and Traceability Agilent Power Sensor Selection Guides (Appendix)

40 Power Measurement Basics asics GSM (0.3 GMSK) cdma2000 Digital Wireless Communications Technology Drivers Aerospace and Defence (Radar) TDMA system Time-gated average power Fast measurements 3G technology Peak-to-average ratio CCDF WiMAX Broadband communications Burst power measurements CCDF

41 Power Measurement Basics asics Video BW High-speed sampling measurement path (EPM-P/E9320) Detected envelope power Sufficient video (modulation) bandwidth High-frequency modulated signal power Power Sensor Peak Power Measurement System Key system characteristics: RF IN Wide dynamic range High-speed, continuous sampling

42 Power Measurement Basics asics P-Series Power Meters and Sensors Key Measurements Peak, average, peak-to-average ratio rise time, fall time, pulse width, pulse period, duty cycle; time-gated and free-run measurements CCDF statistical analysis

43 Power Measurement Basics asics P-Series Measurement Display Graphical trace setup Marker measurements and analysis MKR 1 MKR 2

44 Power Measurement Basics asics Statistical Analysis  Allows 4 trace – Ch 1, Ch 2, Gaussian, Reference  2 Markers reading, delta reading  User settable input Tabular form Graphical form CCDF curve shows how many % of time the signal power is at or above a given power level. Sample cdmaOne signal

45 Power Measurement Basics asics Agenda Importance of Power Measurements Average, Peak and Pulse Power Power Meter & Sensor Measurement Method Sensor Technologies Agilent Power Measurement Solutions Time-Gated Power Measurements Advanced Power Measurements Measurement Uncertainty, Standards and Traceability Agilent Power Sensor Selection Guides (Appendix)

46 Power Measurement Basics asics Sources of Power Measurement Uncertainty Sensor and Source Mismatch Errors Power Sensor Errors Power Meter Errors Mismatch Sensor Meter

47 Power Measurement Basics asics Sensor and Source Mismatch Signal Source Power Sensor Power Meter Ideal impedance = Z 0 Impedance  Z 0 VSWR

48 Power Measurement Basics asics Calculation of Mismatch Uncertainty Signal Source (1 GHz, 0 dBm) Power Meter N1921A = ± 2 x x x 100% = ± 2.09% Mismatch Uncertainty = ± 2 x  x  x 100% SOURCE SENSOR VSWR = 1.26 VSWR = 1.2 SENSO R  =  = SOURCE VSWR  1 VSWR  1 =  Power Sensor

49 Power Measurement Basics asics Power Sensor Cal Factor Uncertainties Various sensor losses - heat DC Power Sensor Power Meter P r Sensing Element P i P gl Cal Factor :  e P K b = gl P i  e = Effective Efficiency) Printed on sensor label (8480 series) Stored in EEPROM (E-series and P-series) Calibration factor, Kb, takes into account the imperfect efficiency of the sensor and the mismatch loss

50 Power Measurement Basics asics Power Meter Instrumentation Uncertainties Zero Set Noise Drift Power Reference Uncertainty  0.4 % (25  10degC) Instrumentation Uncertainty  0.8 %

51 Power Measurement Basics asics Calculating Power Measurement Uncertainty Mismatch uncertainty:± 2.09% Power linearity:± 2.0% 1 Cal factor uncertainty:± 1.8% 1 Power reference uncertainty:± 0.4% 1 Instrumentation uncertainty:± 0.8% 1 Specifications apply for an E9301A sensor and Agilent power meter over a temperature range of 25 ±10 degrees C. 1. Identify significant uncertainties 2. Combine uncertainties Worst-case or Root Sum of the Squares (RSS) method

52 Power Measurement Basics asics Worst-Case Uncertainty All sources of error at their extreme values Errors add constructively Worst-case situation is assumed In our example measurement: 2.09% + 2.0% + 1.8% + 0.4% + 0.8% = ± 7.09% Or, in log terms: % = 10 log ( ) = dB – 7.09% = 10 log ( ) = – 0.32 dB Extremely conservative

53 Power Measurement Basics asics RSS (Root Sum of the Squares) Uncertainty* Power Reference Uncertainty 0.4 Normal Instrumentation Uncertainty 0.8 Normal Combined Standard Uncertainty = u c = RSS of u i * In accordance to guidelines published in the ISO Guide to the Expression of Uncertainty in Measurement and ANSI/NCSL Z , US Guide to the Expression of Uncertainty in Measurement.

54 Power Measurement Basics asics Combined Standard Uncertainty (u c ) In our example: = (1.48) + (1.0) + (0.9) + (0.2) + (0.4) ucuc Expanded uncertainty (k = 2) =  1.99% = k x u c =  3.98% = 10 log ( ) = dB 10 log (1  ) = – 0.18 dB Worst-case dB – 0.18 dB Agilent AN covers uncertainty calculations  Confidence level of 95.45%

55 Power Measurement Basics asics National Standards and Traceability NIST (USA), NPL (UK) Commercial Standards Laboratory Manufacturing Facility Use r Rising Costs, Better Accuracy National Reference Standard (Microcalorimeter) Working Standards Measurement Reference Standard Transfer Standard General Test Equipment Thermistors are used for metrology applications

56 Power Measurement Basics asics Summary Accurate power measurements (made with a power meter/sensor combination) are crucial in RF and microwave applications. The three fundamental power measurements are average, peak and pulse. Modern wireless and radar technologies require time-gated and advanced measurements. Measurement uncertainty is often calculated using the RSS method. The accuracy of Agilent power sensors is traceable to national standards. Agilent provides solutions for basic and advanced measurements.

57 Power Measurement Basics asics For More Information Agilent Website URL: Agilent Literature Application Note AN 1449–1, 2, 3 and 4, Fundamentals of RF and Microwave Power Measurements (Parts 1, 2, 3 and 4). Product Note, Choosing the Right Power Meter and Sensor (Lit. No E). Application Note AN 64-4D, 4 steps for making better power measurements (Lit. No E)

58 Power Measurement Basics asics Questions and Answers


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