On site RF troubleshooting for installation and maintenance

Transcription

1 On site RF troubleshooting for installation and maintenance Measure of interferers, high power for microwave links or low power for Base Stations uplink Troubleshooting of cables, or waveguides, and antennas by ROS measurements, DTF measurements, cable loss measurements 1 S

2 Techniques to Troubleshoot Interference in the Field 2

3 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 3

4 Measurement Configurations N993xA spectrum analyzer N991xA spec/vna combo 4

5 Interference Classifications In-band interference Co-channel interference Out-of-band interference Adjacent channel interference Uplink interference Downlink interference 5

6 In-Band and Co-Channel Interference 6

7 Out-of-Band Interference

8 Adjacent Channel Interference Channel power Adjacent channel power 8

9 Downlink and Uplink Interference Interference Interference Downlink spectrogram Uplink spectrogram 9

10 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 10

11 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) 11

12 Key Analyzer Specifications Displayed Average Noise Level (DANL) Also, RBW filter Preamplifier Third order intercept Phase noise Spurious Frequency range 12

13 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) 13

14 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

15 Amplitude Correction and Field Strength Field strength units FieldFox Amplitude correction = antenna gain - cable loss Correction factors editor Corrections.csv 15

16 Clear/Write and Max Hold Display Modes Max hold trace Fixed carrier Frequency hopping carrier 16

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

18 Waterfall Display 18

19 Why is Cable and Antenna Testing Important? Verify transmission performance Measure installed antenna performance and isolation Determine the location of damaged components Types of Cable Damage Failed seal at a cable splice (liquid ingress) Failed solder joint at connector interface Cut, crushed and/or weather-induced cracks Minimum bend radius exceeded Images courtesy of John Arthur, Wireless EDGE

20 Cable Loss Measurement Techniques Traditional 2-Port Loss Measurement Novel 1-Port Loss Measurement Open or Short Power Sensor-Based Loss Measurement USB Cable Power Sensor

21 Cable Loss Measurement Examples 2-Port and 1-Port Cable Loss Open or Short

22 What is a Distance-to-Fault (DTF) Measurement? Measurement technique to determine the location of problems along a cable or transmission line Damaged Cable Input Pulse Reflected Pulse Transmitted Pulse DTF (meters) = VF = v c cable = 1 ε r time round trip 2 ( 1) [ v ] cable = time c = speed of light εr = relative round trip 2 dielectric constant of c ε r material

23 DTF Measurement Velocity Factor (VF) (M2) (M3) End of Cable FieldFox Cable Adapter Cable 50-ohm 4m 9.8m Load (M2) (M3)

24 DTF Multiple Reflections Open 50-ohm (M4) (M5) Multiple reflections may create additional responses past the cable end Swap the load from Open to 50-ohm, observe changes in response FieldFox Adapter Open / 50-ohm (M4) (M5)

25 Entering Cable Parameters Manual Entry Select/Create Cable File RG8U Cable Specs FieldFox DTF Cable Spec Menu

26 Application Example: Estimating Velocity Factor FieldFox VF =? Open

27 Calibrating for 1-Port Measurements CalReady (built-in) QuickCal Open Load* Mechanical Open Short Load Adapter Calibration Plane Adapter Calibration Plane Calibration Plane Jumper Cable Jumper Cable Factory Calibrated * Load Optional Requires Mechanical Cal Kit

28 Calibrating for 2-Port Measurements CalReady (built-in) QuickCal Open Load* Open Load* Thru 1 2 Calibration Plane Adapter Calibration Plane Jumper Cable Factory Calibrated * Load Optional Mechanical cal requires O, S, L during step 1

29 FieldFox Guided Calibration Cal Wizard FieldFox recommends calibration type Simple setup process Cal Wizard for step-by-step connections

30 Waveguide Measurements with Field Fox Coax jumper cable Calibration Plane Waveguide Waveguide to Coax Adaptor DUT Measure Length with CAT DTF or NA Time Domain VF = function of frequency Length Calibration Plane Port Extension available with NA Select [Media] = Waveguide 30

31 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 31

32 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) 32

33 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

34 Thank you for your time Questions?