Testing Radio Interference Gustaaf Sutorius Application Engineer © 2012 Agilent Technologies Agenda Fieldfox Workshop 10.30 – 11.00: Vector Network Analyzer Fundamentals 11.00 – 12.30: Making precise RF&uWave measurements in the field 12.30 – 13.30: Lunch 13.30 – 14.30: Making precise cable and antenna measurements 14.30 – 14.45: break 14.45 – 15.45: Techniques to troubleshoot interference in the field 15.45: Drinks © 2012 Agilent Technologies Agilent Spectrum Analyzer Portfolio for Interference Test © 2012 Agilent Technologies Other tools for interference… N6841A RF Sensor GPS antenna GPS Power Data RF Inputs RF Sensor Key Benefits: • • • • N6841A 20 MHz - 6 GHz, 20 MHz info BW Sealed/ Weatherproof: IP 67! Synchronization < 20 nS! Proven Reliability © 2012 Agilent Technologies Testing Radio Interference Using Agilent FieldFox Handheld Analyzers 5 © 2012 Agilent Technologies Testing Radio Interference Agenda: 1. What is Radio Interference 2. Spectrum Assignments 3. Sources of Interference 4. Interference Classifications 5. Analyzer Specifications 6. Antenna Specifications 7. Measurement Modes 6 © 2012 Agilent Technologies What is Radio interference •IEEE Interference event definition: Interference Event = a Quantified threshold of Interference has been exceeded • Dynamic Spectrum Access: White Space/Cognitive radio/Digital Dividend • ISM band (ISM = Industrial, Scientific, Medical) “Listen before talk” in WLAN 802.11 • Example: London Olympic games 2012 Olympics report.pdf page 25 and 31 © 2012 Agilent Technologies Testing Radio Interference Agenda: 1. What is Radio Interference 2. Spectrum Assignments 3. Sources of Interference 4. Interference Classifications 5. Analyzer Specifications 6. Antenna Specifications 7. Measurement Modes 8 © 2012 Agilent Technologies Spectrum Assignments: USA example © 2012 Agilent Technologies Licensed and Unlicensed Spectrum (MHz) Licensed : Protected against harmful interference Unlicensed : Expected amount of interference (Part 15 Rules) © 2012 Agilent Technologies Testing Radio Interference Agenda: 1. What is Radio Interference 2. Spectrum Assignments 3. Sources of Interference 4. Interference Classifications 5. Analyzer Specifications 6. Antenna Specifications 7. Measurement Modes 11 © 2012 Agilent Technologies Intentional, Unintentional, Incidental Radiators Intentional radiators Active transmitters • Broadcast radio and television • Cellular • Satellite • Radar • Mobile radio • WLAN • Cordless phones Unintentional radiators Use RF but not for radio transmission • Microwave ovens • Radio receiver • Industrial heaters • MRI equipment Incidental radiators Do not use RF • Switching power supplies • Clock and control signals • Ignition motors • Fluorescent lighting © 2012 Agilent Technologies Ambient Man-Made Radio Noise Median Noise above kTB (dB) Antenna connected Input terminated Frequency (Hz) © 2012 Agilent Technologies Testing Radio Interference Agenda: 1. What is Radio Interference 2. Spectrum Assignments 3. Sources of Interference 4. Interference Classifications 5. Analyzer Specifications 6. Antenna Specifications 7. Measurement Modes 14 © 2012 Agilent Technologies Interference Classifications • In-band interference • Co-channel interference • Out-of-band interference • Adjacent channel interference • Uplink interference • Downlink interference © 2012 Agilent Technologies In-Band and Co-Channel Interference © 2012 Agilent Technologies Out-of-Band Interference © 2012 Agilent Technologies Adjacent Channel Interference Channel power Adjacent channel power © 2012 Agilent Technologies Downlink and Uplink Interference Interference Interference Downlink spectrogram Uplink spectrogram © 2012 Agilent Technologies Near-Far Conditions f1 f2 Analyzer display Potential overload of analyzer’s front-end f1 f2 All signals enter analyzer’s front-end © 2012 Agilent Technologies Techniques to Avoid Analyzer Overload Avoid saturation and overload of the handheld analyzer Filter – 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) © 2012 Agilent Technologies Testing Radio Interference Agenda: 1. What is Radio Interference 2. Spectrum Assignments 3. Sources of Interference 4. Interference Classifications 5. Analyzer Specifications 6. Antenna Specifications 7. Measurement Modes 22 © 2012 Agilent Technologies Key Analyzer Specifications Displayed Average Noise Level (DANL) Also, • RBW filter • Preamplifier • Third order intercept • Phase noise • Spurious Frequency range © 2012 Agilent Technologies RBW and Preamplifier Preamp ON Lower RBW improves DANL RBW=1 kHz Narrowband signal Preamp OFF RBW=1KHz RBW=100 Hz Wideband signal Preamp ON Reducing RBW: Narrow-band signals (BW < RBW) Same signal level, lower DANL (improve SNR) Wide-band signals (BW > RBW) Lower signal level, lower DANL (same SNR) © 2012 Agilent Technologies FieldFox InstAlign Total amplitude accuracy across frequency and temperature • • • • Frequency range (23 °C ± 5 °C) (–10 to +55 °C) 100 kHz to 18 GHz ± 0.35 dB ± 0.50 dB >18 GHz to 26.5 GHz ± 0.50 dB ± 0.60 dB Auto correction with 30 sec elapsed time Auto correction with 1 oC instrument change Accurate across -10 to +55 oC No warm-up required © 2012 Agilent Technologies Testing Radio Interference Agenda: 1. What is Radio Interference 2. Spectrum Assignments 3. Sources of Interference 4. Interference Classifications 5. Analyzer Specifications 6. Antenna Specifications 7. Measurement Modes 26 © 2012 Agilent Technologies Antenna Configurations Antenna connected directly Antenna patterns Antenna cabled to analyzer Horizontal plane Omni Omnidirectional High gain Vertical plane Horizontal plane High gain Vertical plane © 2012 Agilent Technologies High Gain versus Omnidirectional Antenna Types Yagi Whip © 2012 Agilent Technologies Amplitude Correction and Field Strength Field strength units FieldFox Amplitude correction = antenna gain - cable loss Correction factors editor Corrections .csv © 2012 Agilent Technologies Testing Radio Interference Agenda: 1. What is Radio Interference 2. Spectrum Assignments 3. Sources of Interference 4. Interference Classifications 5. Analyzer Specifications 6. Antenna Specifications 7. Measurement Modes 30 © 2012 Agilent Technologies Clear/Write and Max Hold Display Modes Max hold trace Fixed carrier Frequency hopping carrier © 2012 Agilent Technologies Amplitude scale Spectrogram Display Mode Fixed carrier Frequency hopping carrier Time Frequency © 2012 Agilent Technologies Waterfall Display © 2012 Agilent Technologies Lab TIME © 2012 Agilent Technologies Zero Span Display Mode Duration of Signal @ fcenter Trigger Level Time © 2012 Agilent Technologies Measurement Configurations N993xA spectrum analyzer N991xA spec/VNA combo © 2012 Agilent Technologies Other Agilent Handheld Spectrum Analyzers N9344C SA 1 MHz to 20 GHz N9340B/42C SA 100 KHz to 3/7 GHz N9343C SA 1 MHz to 13.6 GHz © 2012 Agilent Technologies Channel Scanner Top/Bottom horizontal listing to sort on frequency, power, or Carrier ID. Ideal for coverage test, band clearance, and spectrum monitoring. Time Chart Top /Bottom list >20 channels 20 channels fast sweep time Time Chart monitors signals in time (burst signal analysis) for power variations © 2012 Agilent Technologies Data Mapping with Google Earth & MapInfo Collect data and log it with the GPS Option and Channel Scanner & Marker logging feature. Generates data files to use with Google Earth & MapInfo © 2012 Agilent Technologies Accessories N9311X log periodic directional antenna -504 700 MHz to 4 GHz -508 680 MHz to 8 GHz -518 680 MHz to 18 GHz N9311X-500 whip antenna, 70 to 1000 MHz N9311X-501 omnidirectional antenna, 700 to 2500 MHz N9311X bandpass filter -550 814 to 850 MHz -553 1845 to 1915 MHz -551 880 to 915 MHz -554 1910 to 1990 MHz -552 1707.5 to 1787.5 MHz N9311X phase stable test cable, type N(m) to N(m) © 2012 Agilent Technologies Summary • 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 Handheld Spectrum Analyzer series for Drive tests – coverage mapping © 2012 Agilent Technologies For More Information Web: www.agilent.com/find/FieldFox Literature: - Techniques for Precise Interference Measurements in the Field, application note, literature number 5991-0418EN - FieldFox Handheld Analyzers, brochure, literature number 5990-9779EN Thank you for your time Questions? © 2012 Agilent Technologies Agenda Fieldfox Workshop 10.30 – 11.00: Vector Network Analyzer Fundamentals 11.00 – 12.30: Making precise RF&uWave measurements in the field 12.30 – 13.30: Lunch 13.30 – 14.30: Making precise cable and antenna measurements 14.30 – 14.45: break 14.45 – 15.45: Techniques to troubleshoot interference in the field 15.45: Drinks © 2012 Agilent Technologies Appendix: Field Strength Calculations S= 4π Pr gλ2 S = power density, watt/m 2 Pr = received power, watts g = gain of receiving antenna relative to isotropic λ = wavelength 2 E as the power density, S , in free space is equal to E= 120π 68.8 Pr λ g E = incident field strength in V/m © 2012 Agilent Technologies Appendix: Field Strength Calculations (continued) The analyzer measures received power, Pr , in dBm. Converting Pr to watts, the field strength, E (V/m), can be calculated using the previous equation. Convert E (V/m) to dBµV/m (dB relative to 1µV) using [ dBµV/m = 20log10 (V/m)/10 -6 ] © 2012 Agilent Technologies