FieldFox Handheld Education Series Part 5: Techniques for Precise Power Measurements in the Field FieldFox Handheld Education Series • Interference Testing • Cable and Antenna Measurements • Calibration and Alignment • Time Domain Measurements • Precise Power Measurements • Precise Data Correlation www.agilent.com/find/FieldFoxWebcasts Tom Hoppin Business Development Engineer Co-sponsored by © 2012 Agilent Technologies March 27, 2013 Techniques for Precise Power Measurements in the Field Outline • Power Fundamentals • Types of Power Sensors and Receivers • Average Power Measurements • Pulsed and Peak Power Measurements • Measurement Accuracy • Other Types of Power Measurements • Conclusions Importance of Power Measurements • Critical to system performance at every level • Measurements required at • Prototyping • Manufacturing • Installation • Maintenance • Troubleshooting • Measurements must be • Accurate • Repeatable • Traceable Power Definitions • Power = energy transferred per unit of time • Units in Watts (W) 1 W = 1 Volt x 1 Ampere • Measured using Power Sensor or Tuned Receiver • Relative Power in decibels (dB) = 10 log (P2/P1) • Absolute Power in decibels (dBm) = 10 log (P/1mW) • Average and Peak Measurements Available Field Measurements of RF Power Meter Laptop with Software USB Cable Sensor (up to 4) Spectrum Analyzer USB Sensor (up to 20) Spectrum Analyzer USB Cable RF Jumper Cable USB Sensor (No sensor required) Power Sensors And Signal Processing Simplified Block Diagram Input Sensor Element Amp Filter ADC 50MHz Reference MPU Display (dBm or W) Power Meter USB Power Sensor Sensor Types 50MHz Reference • Thermal Based • Diode Based Thermal-Based Sensors • True power in signal • Average power only Thermistor Thermocouple • Temperature = Resistance • Used in bridge circuit • Metrology and transfer standards • Temperature = Voltage • More rugged than thermistor • Less sensitive to ambient temp. • Low RF Sensitivity (-20dBm) • Sensitive to ambient temp. • Slow measurement speed • Medium RF Sensitivity (-35dBm) • Indirectly calibrated using 50MHz Meter-based USB Meter-based Diode-Based Sensors Square-law Linear Vout (log) Sensor Front-End Diode Pin Vout 50 ohm C Pin -70dBm • Rectified and filtered • Average power • Peak power (square-law region) • High sensitivity (-70dBm) • Wide dynamic range (90dB) • Calibration data (power, frequency, temp.) is stored • Indirectly calibrated using 50MHz reference • 30-minute warm-up -20dBm +20dBm 90dB Meter-based USB Tuned Receiver Power Measurements Simplified Block Diagram Digital Domain Mixer Amp Input ~ Local Oscillator ADC Calibration Reference Filter Log Amp Resolution or Channel • Downconverted, filtered and detected • High Sensitivity (-137/-153 dBm) • Wide Dynamic Range (>105 dB) • No warm-up, InstAlign (FieldFox) • Rugged • Average power only • Lower accuracy than power sensor Filter Video Display Measuring CW Signals 1 6 GHz, -20 dBm Spectrum Analyzer Display U2000A Marker 2 N9938A FieldFox 1 Power Sensor Compensate #2 for the RF cable loss 2 Tuned Receiver (CPM)* *Channel Power Meter (CPM) Option Internal Attenuator 10 dB Cable Offset 0.6 dB. Span (Channel Width) Measuring Multi-tone Signals 1 Power Sensor Spectrum Analyzer Display 2 Channel Power* Signal BW *Span = 3MHz 2 Select only one tone Ideally, 5 tones with each tone at -27dBm results in a total average power = -20 dBm *Span = 200kHz Modulated Signals 1 Power Sensor Spectrum Analyzer Display 2 Channel Power* Signal BW Digital Mod, 5Msps, 32QAM, Root Nyquist 0.5 Definitions of Pulsed Waveform Parameters Power Peak Width Pulse Repetition Interval (PRI) Average time Width Duty Factor (DF) = PRI Peak Power = Average DF Pulsed Modulated Waveforms Spectrum Analyzer Display 1 Power Sensor 2 Channel Power* Width = 20msec PRI = 100msec DF = 20% Average = -27 dBm Peak (calculated) = -20 dBm Detection and Filtering in Peak Power Measurements Simplified Block Diagram of Diode Sensor Input Amp Diode Detector Filter Video Filter ADC MPU High Sample Rate Two layer detection • Wideband diode detection at RF • ADC sampling of the video Wideband Filtering • Video BW > Signal BW Display (dBm or W) Measurements using a Peak Power Sensor N934x HSA Spectrum Analyzer Display Peak power sensor Peak power meter or HSA 30MHz VBW for 13 nsec rise/fall time Measure peak power, average power, peak-average, width, PRI, DF, rise time, fall time 1us pulse with 10 us PRI at 40 GHz Spectrum Analyzer in Zero Span Mode Spectrum Analyzer Display • Markers measure peak power, width and PRI • Limited to narrow BW signals Spectrum Analyzer Display (Zero Span) Frequency Marker Zero Span Requires: RBW > Signal BW VBW > Signal BW Time Adjacent Channel Power Main Adjacent ACP = unwanted energy in nearby channels Power Sensor Accuracy Thermocouple Error (dB) CW Only Sensor High DR Diode With Dual Path (including attenuator Requires increased meter averaging at low power levels Input Power (dBm) Pulse width 50=usec, PRI=1ms, averaging=64 FieldFox Channel Power Meter (CPM) Accuracy Error (dB) CPM with InstAlign +/- 0.35 dB typ. At low power levels, the FieldFox greatly reduces overall measurement time Input Power (dBm) Pulse width 50=usec, PRI=1ms, averaging=64 FieldFox InstAlign Total amplitude accuracy across frequency and temperature Frequency Range Spec (23 +/- 5°C) Spec (-10 to +55°C) Typical (23 +/- 5°C) Typical (-10 to +55°C) 100 kHz to 18 GHz +/- 0.8 dB +/- 1.0 dB +/- 0.35 dB +/- 0.50 dB >18 GHz to 26.5 GHz +/- 1.0 dB +/- 1.2 dB +/- 0.50 dB +/- 0.60 dB • No warm-up required • Accurate across -10 to +55oC • Auto amplitude correction with 2oC change Measurement Comparison Over Frequency Average Power Measurement, CW Signal E4413A FieldFox N1914A Freq (GHz) Sensor (dBm) CPM (dBm) 0.1 -0.07 -0.10 18 -2.90 -2.84 26.5 -3.75 -3.71 FieldFox InstAlign provides automatic internal alignment FieldFox Rugged to MIL-PRF-28800F Class 2 MIL-spec durability Meets MIL-PRF-28800F Class 2 requirements Type tested and meets MIL-STD-810G, Method 511.5 Procedure I requirements for operation in explosive environments Field-proof Completely sealed instrument enclosure provides measurement stability in harsh environments 3-year warranty ensures field confidence (standard on all FieldFox analyzers) Low Emissions, meets CISPR Pub 11, class B Water-resistant chassis, keypad, and case withstand wide temperature ranges, and salty, humid environments • Case withstands shock and vibrations • Wide operating temperature -10 to +55 °C (14 to 131 °F) • Wide storage temperature -51 to +71 °C (-60 to 160 °F) Agilent FieldFox Spectrum Analyzer Family N9912A option 230/231 4/6GHz N9935A 9 GHz N9936A 14 GHz N9937A 18 GHz N9938A 26.5 GHz N9913/4/5/6/7/8A w/option 231 Spectrum and VNA Combination Analyzers Also available with options for Cable and Antenna Testing (CAT) • Carry precision with you - Agilent-quality measurements • Full amplitude accuracy of ±0.6 dB at turn-on, -10oC to +55oC • Weather resistant, MIL-PRF-28800F Class 2 design • 6.6 pounds (3 kg) • Built-in GPS • Four hour battery life Conclusions • Discussed average and peak power measurements • Reviewed the various types of power sensors • Compared measurements using power sensors and FieldFox CPM • Discussed the accuracies of power measurements • FieldFox built-in channel power measurement is a great choice for accurate, repeatable and traceable power measurements in the field For More Information Web: www.agilent.com/find/FieldFox Email: [email protected] Literature: - Techniques for Precise Interference Measurements in the Field, application note, literature number 5991-0418EN - Techniques for Precise Cable and Antenna Measurements in the Field, application note, literature number 5991-0419EN - FieldFox Handheld Analyzers, brochure, literature number 5990-9779EN 5th in a series of application webcasts • Sept 26, 2012: Interference Testing • Oct 24, 2012: Cable and Antenna Measurements • Nov 28 2012: Calibration and Alignment • Jan 23 2013: Time Domain Measurements • Mar 27 2013: Precise Power Measurements • Precise Data Correlation Registration: www.agilent.com/find/FieldFoxWebcasts Co-sponsored by Thank you for your time Questions? © 2012 Agilent Technologies References • Agilent Application Note 1449-1, Fundamentals of RF and Microwave Power Measurements (Part 1), Introduction to Power, History, Definitions, International Standards & Traceability, Literature Number 5988-9213EN, April 2003 • Agilent Application Note 1449-2, Fundamentals of RF and Microwave Power Measurements (Part 2), Power Sensors and Instrumentation, Literature Number 59889214EN, July 2006 • Agilent Application Note, Fundamentals of RF and Microwave Power Measurements (Part 4), An Overview of Agilent Instrumentation for RF/Microwave Power Measurements Power Sensors and Instrumentation, Literature Number 5988-9216EN, September 2008 • Agilent Application Note, “Solutions for Minimizing Measurement Uncertainty and Quick and Easy Estimation of Uncertainty Due to Mismatch,“ Literature Number 5991-0673EN, June 2012 • Agilent Power Sensor Uncertainty Spreadsheet, found at http://www.home.agilent.com/agilent/redirector.jspx?action=ref&cname=AGILENT_EDITORI AL&ckey=1511287&lc=eng&cc=US&nfr=-11143.0.00