FieldFox Handheld Education Series Part 1: Techniques for Precise Interference Measurements in the Field

Transcription

1 FieldFox Handheld Education Series Part 1: Techniques for Precise Interference Measurements in the Field FieldFox Handheld Education Series Interference Testing Cable and Antenna Measurements Calibration and Alignment Time Domain Measurements Precise Power Measurements Tom Hoppin Business Development Engineer

2 Co-sponsored by Testing Radio Interference Using Agilent FieldFox Handheld Analyzers 2

3 Outline Spectrum Assignments Why interference is important Sources of Interference Interference Classifications Analyzer Specifications Antenna Specifications Measurement Modes

4 (MHz) Licensed and Unlicensed Spectrum Licensed : Protected against harmful interference Unlicensed : Expected amount of interference (Part 15 Rules)

5 Intentional, Unintentional, Incidental Radiators Active transmitters Use RF but not for radio transmission Intentional radiators Broadcast radio and television Cellular Satellite Radar Mobile radio WLAN Cordless phones Unintentional radiators Microwave ovens Radio receiver Industrial heaters MRI equipment Do not use RF Incidental radiators Switching power supplies Clock and control signals Ignition motors Fluorescent lighting

6 Median Noise above ktb (db) Ambient Man-Made Radio Noise Antenna connected Input terminated Frequency (Hz)

7 Measurement Configurations N993xA spectrum analyzer N991xA spec/vna combo

8 Interference Classifications In-band interference Co-channel interference Out-of-band interference Adjacent channel interference Uplink interference Downlink interference

9 In-Band and Co-Channel Interference

10 Out-of-Band Interference

11 Adjacent Channel Interference Channel power Adjacent channel power

12 Downlink and Uplink Interference Interference Interference Downlink spectrogram Uplink spectrogram

13 Near-Far Conditions f 1 f 2 Analyzer display Potential overload of analyzer s front-end f 1 f 2 All signals enter analyzer s front-end

14 Techniques to Avoid Analyzer Overload Filter Avoid saturation and overload of the handheld analyzer Connect with bandpass filter to filter out strong signals Do not point the directional antenna towards the transmitter Turn off preamplifier and increase attenuation (if the sensitivity allows)

15 Key Analyzer Specifications Displayed Average Noise Level (DANL) Also, RBW filter Preamplifier Third order intercept Phase noise Spurious Frequency range

16 RBW and Preamplifier Lower RBW improves DANL Preamp ON RBW=1 khz Narrowband signal Preamp OFF RBW=100 Hz Wideband signal RBW=1KHz Preamp ON Reducing RBW: Narrow-band signals (BW < RBW) Wide-band signals (BW > RBW) Same signal level, lower DANL (improve SNR) Lower signal level, lower DANL (same SNR)

17 FieldFox InstAlign Total amplitude accuracy across frequency and temperature Frequency range 100 khz to 18 GHz >18 GHz to 26.5 GHz (23 C ± 5 C) ( 10 to +55 C) ± 0.35 db ± 0.50 db ± 0.50 db ± 0.60 db Auto correction with 30 sec elapsed time Auto correction with 1 o C instrument change Accurate across -10 to +55 o C No warm-up required

18 Antenna Configurations Antenna patterns Antenna connected directly Omnidirectional Antenna cabled to analyzer High gain Omni Horizontal plane Vertical plane High gain Horizontal plane Vertical plane

19 High Gain versus Omnidirectional Antenna Types Yagi Whip

20 Amplitude Correction and Field Strength Field strength units FieldFox Amplitude correction = antenna gain - cable loss Correction factors editor Corrections.csv

21 Clear/Write and Max Hold Display Modes Max hold trace Fixed carrier Frequency hopping carrier

22 Spectrogram Display Mode Amplitude scale Fixed carrier Frequency hopping carrier Time Frequency

23 Zero Span Display Mode Duration of fcenter Trigger Level Time

24 Waterfall Display

25 Combination Analyzer: 10 Instruments in 1 Cable and antenna analyzer 30 khz to 26.5 GHz Independent signal generator 30 khz to 26.5 GHz Full 2-port vector network analyzer with time domain analysis, 30 khz to 26.5 GHz Vector voltmeter, 2-port 30 khz to 26.5 GHz Spectrum analyzer, with fullband tracking generator 5 khz to 26.5 GHz Interference analyzer Power meter 5 khz to 26.5 GHz Built-in GPS receiver Light weight: 6.6 lbs (3.0 kg) Long battery life: 3.5 hrs Bright display: 6.5 inch TFT MIL-PRF F Class 2 MIL-STD-810G, 511.5, Proc 1 Variable DC source and current monitor Frequency counter 25

26 FieldFox Accessories N9311X log periodic directional antenna MHz to 4 GHz MHz to 8 GHz MHz to 18 GHz N9311X-500 whip antenna, 70 to 1000 MHz N9311X-501 omnidirectional antenna, 700 to 2500 MHz N9311X bandpass filter to 850 MHz to 1915 MHz to 915 MHz to 1990 MHz to MHz N9311X phase stable test cable, type N(m) to N(m)

27 Agilent FieldFox Spectrum Analyzer Family 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, 10 to +55 o C Weather resistant, MIL-PRF-28800F Class 2 design 6.6 pounds (3 kg) Built-in GPS 3.5-hour battery life

28 Conclusions Reviewed radio interference classifications and spectrum use Discussed why interference analysis is important Discussed equipment and antenna requirements Reviewed spectrum analyzer settings for high accuracy Reviewed FieldFox display modes for identifying radio interference Introduced FieldFox as a rugged, lightweight field-ready analyzer

29 For More Information Web: Literature: - Techniques for Precise Interference Measurements in the Field, application note, literature number EN - FieldFox Handheld Analyzers, brochure, literature number EN First in a series of monthly application webcasts Sept 26, 2012: Interference Testing Oct 24, 2012: Cable and Antenna Measurements Nov : Calibration and Alignment Jan : Time Domain Measurements Mar : Precise Power Measurements Registration: Thank you for your time Questions?

30 Appendix: Field Strength Calculations 4 S g S power density, P r P r 2 watt/m received power, watts g gain of receiving antenna relative to isotropic wavelength 2 as E the power density, 68.8 Pr g S, in free space is equal to E E incident field strength in V/m

31 Appendix: Field Strength Calculations (continued) The analyzer measures received power, P, in dbm. r Converting P previous equation. r to watts, the field strength, E (V/m), can be calculated using the Convert E (V/m) to db V/m (db relative to1 V) using db V/m 20log 10 (V/m)/10-6