RF Interferences Hunting and Over the Air measurements

RF Interferences Hunting and Over the Air measurements

November 2016

José María Pindado BuendíaField Application Engineer

2 Copyright© ANRITSUSlide Title

Agenda

Anritsu I&M Roadshow

• The wireless challenge• Types of Radio Frequency Interference• What is interference and its source, effects and types on …• Some real examples• Spotting and characterization of RFI• What features do you really need in order to hunt RFI• Interference hunting tools• Handheld based emitter location system MA2700A• Automatic broadband Interference Locating system MX28007A• Automatic Spectrum Monitoring and emitter geolocation


The Wireless Challenge• More transmitters

– spectrum is becoming more and more crowded.

• More mobile devices– stationary TRX are no longer the norm.

• New modulation types– analog signals becoming less common

than digital signals.• More complex modulation

– higher order modulation requires a better RF environment.

• Spectrum re-farming– moving services to different frequencies requires

spectrum clearing and involves different propagation and interference types.

• Wireless connectivity– from “nice to have” to “must have.”


Spain– reported interference cases vs serviceInterference problem in todays dense spectrum

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Radiodifusión Móvil Terrestre Móvil Aeronáutico Móvil Marítimo

Fijo Aficionados Radiolocalización Fijo por Satélite

Telefonía Móvil Telefonía fija Otros (GPS, telemando, etc.)


Spain– Reported interferences in mobile systems

Interference problem in todays dense spectrum


Types of Radio Interference


Types of Electromagnetic Interference (EMI)

Electromagnetic Interference (EMI) is caused by un-desiderated radiated electromagnetic fields or conducted voltages and currents. The interference is produced by a source emitter and is detected by a susceptible victim via a coupling path

Conduction - electric currentRadiation - electromagnetic fieldCapacitive Coupling - electric fieldInductive Coupling - magnetic field

Electromagnetic Effects (EME) Electromagnetic Interference (EMI)

Radio Frequency Interference (RFI)Narrowband EmissionsBroadband Emissions

Electromagnetic Compatibility (EMC)Electromagnetic Pulse (EMP)

Definitions


Types of Radio Frequency Interference (RFI)

Radio Frequency Interference (RFI) CharacteristicsNarrowband Emissions

occupies a very small portion of the radio spectrumthe magnitude is usually expressed in terms of volts per meter (V/m)usually continuous sine waves (CW) and may be continuous or intermittent in occurrencecommunication transmitters such as single-channel AM, FM and SSBShort Range Wireless DevicesSpurious emissions, such as harmonic outputs of narrowband communication transmitters, power-line hum, local oscillators, signal generators, test equipment

and many other man made sources are narrowband emissions.

Narrowband emissions



Radio Frequency Interference (RFI) CharacteristicsBroadband Emissions

may spread its energy across tens of megahertz or moremagnitude is usually expressed in terms of volts per meter per MHz (V/m/MHz)signal is composed of narrow pulses having relatively short rise and fall timesthese may be transient, continuous or intermittent in occurrencee.g. unintentional emissions from communication and radar transmitters, electric switch contacts, computers, thermostats, motor speed controls, thyratron circuits, voltage regulators, pulse generators, arc/vapor lamps, and intermittent ground

connections.e.g. may also result from galactic and solar noise, lightning electromagnetic pulses, and by radio frequency pulses associated with electrostatic discharges.

Broadband emissions



The following types of interference are applicable to Radio Frequency (RF) communications equipment

Receiver Co-Channel InterferenceResults: Receiver desensitization, signal masking, distortion

Receiver Adjacent Signal InterferenceResults: Non linear effects in the RF or mixer stages producing receiver desensitization, intermodulation and cross modulation.

Receiver Out of Band InterferenceResults: An undesired response created by the mixing of an undesired signal with the LO. The undesired signals which mix with the LO and are capable of being translated to the IF stages are the spurious response frequencies. These frequencies and their interference power levels are a function of the receiver’s susceptibility to these responses.

Receiver BlockingResults: A strong signal is desensitizing the receive capability

Receiver problems



The following types of interference are applicable to Radio Frequency (RF) communications equipment

Transmitter Fundamental EmissionsNominal bandwidth (3dB) is too large due to exceeded input power (overdrive).

Transmitter Harmonic EmissionsUndesired signal outputs which are harmonically related to the fundamental signal

Transmitter NoiseBroad-band noise that is a result of the thermal noise generated in the driver and final amplifier stages as well as the synthesizer noise from lower level stages.

Transmitter IntermodulationThese are the undesired signals that result from the local mixing of a transmitter’s output emission with that of another transmitter. The mixing usually occurs in the non-linear circuits of a transmitter whose antenna receives a high level of RF from another transmitter antenna in close proximity. The mixing products are radiated by the transmitter’s antenna as possible co-channel or adjacent signal interference signals.

Transmitter problems



A harmonic is a signal or wave whose frequency is an integer multiple of the frequency of some reference signal or wave

In an ideal system, the fast Fourier transform (FFT) of a sinusoid would result in a single peak at a specific frequency.

In real-world systems, non-linearity and noise result in imperfections. When a signal of a particular frequency f1 passes through a nonlinear system, the output of the system consists of f1 and its harmonics.

Harmonics



Intermodulation results from two or more signals appearing in a nonlinear circuit.

Sum and difference frequencies are created from the mixing of fundamentals and harmonics.

Because intermodulation involves the mixing of multiple signals, it will only occur when all component signals are present (W-CDMA!).

Intermodulation



The junction between two pieces of metal can create a rectifier (diode), especially when corrosion is present.

This effect can generate spurious signals that are then radiated by metallic elements in the joint.

Aged or wrong made cables, connectors and distribution units are usually involved in this kind of broadband intermodulation

Rusty towers and guy can also be seen as a radiating source, because they have long metal elements, and are close to powerful transmitters.

Utility poles/wires, metal fences, and gutters are also prime suspects.

Passive Intermodulation

Copyright© ANRITSU15Slide Title

What is interference and its source, effect and types on …



on GSM serviceIM2 interference due to BCCH mixing

What are Interference and its source, effect and types …

on UMTS serviceIM3 and IM4 interference

On DVB-Tdue to LTE 800 blocking TV RX

LTE 800 on CATV networksLTE ingress into cable systems may create digital video pixilationCable system egress into the wireless spectrum may effect data transfer speed from mobile phones

LTE 800 on PMSE networks


What do we observe in real world?


Real world interference

Cellular repeaters or bidirectional amplifiers (BDAs) can be used to extend cellular coverage in buildings or in fringe areas.

May also be installed on boats.

The main interference issues are the retransmission of unwanted signals at the input of the BDA as well as malfunctioning BDAs (Noise!).

Difficult to troubleshoot but a very common source of interference in the cellular bands.

Repeaters / BDAs



Unmodulated sources are devices which unintentionally generate RF signals.

Common sources are electric motors, faulty transformers, vehicle ignition systems, electrical fences, fluorescent lighting, etc.

Easy to recognize, often shows up as jumps in the noise floor or a wide, random spectral pattern.

RFI from unmodulated sources



Deliberate interference may be narrowband (e.g. talking on a public safety frequency) or broad-band (jamming).

Pirate or unlicensed (“free-band”) operations can also cause issues to licensed users.

Sources may be mobile, possibly to avoid detection / radiolocation.

Although most businesses and individuals are very cooperative in resolving interference, deliberate interferers will usually deny or conceal their activities.

Deliberate Interference



Jammers are typically easy to identify and locate

strong, broad, always-on signal.

Tend to increase the noise floor even outside of their nominal operating range

Interference from Radio Jammers


Some real examples I


PIM & interferences LNB Sat

Interferences – real examples


Unlocked LO & switched noise

Interferencias – ejemplos reales


Spotting and characterization of RFI


Receive filterfor out of band signal

suppression

Spotting and characterization of Interference

• Check for interference at receiver– At the tower for Cellular or complaint area for Two Way or in

the complaint area for Broadcast

– Allow the RX pre-filter to eliminate the strong side emissions

– Measure noise floor from a receive antenna• Same receive pattern as the radio

– Get a visual ID on the interfering signal• Characterize signal so you will know it later

Important – Use Bandpass Filters



• Look on the Receive frequencies– Signals passed by the radio’s receive

filter (pre-selector) affect the receiver’s front end causing:

• A reduction in sensitivity

• Apparent lower C/I

– It’s called Receiver De-Sensitization• Or Blocking if severe

– Interfering signals do not need to be on your receive channel!

• They only need to make it through the Rx filter

Interferer WantedChannel

Interference – just make it through the RX filter



• Know your bands– Which signals belong to you?– Which signals do not belong to you?

– How does a modulation scheme look like? Not only the own ones.

• Study national frequency plan of Spectrum Regulation Authority in order find potential original assigned band for the signal in question

You should know “your spectrum”



• Develop libraries of common signals

– For your

• Area and• Frequency Bands • Cellular shapes (GSM,

UMTS, LTE)• Broadcast shapes (DVB-x)• PMR shapes (TETRA,

NXDN, DMR)• Analog shapes (NBFM)

– Work with a• Spectrum analyzer and/or • Channel Scanner

– Know what’s not right!

Signal Libraries

Frequency (MHz)-4 -3 -2 -1 0 1 2 3 4

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Frequency (MHz)-4 -3 -2 -1 0 1 2 3 4

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Frequency (MHz)-2 -1 0 1 2

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Frequency (MHz)-8 -6 -4 -2 0 2 4 6 8

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Frequency (MHz)-20 -15 -10 -5 0 5 10 15 20

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TD-SCDMA W-CDMA

WLAN 11gFrequency (MHz)

-8 -6 -4 -2 0 2 4 6 8-120

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Mob WiMax


What features do you really need?Characterizing Interference with spectral

analysis


Characterizing Interference with spectral analysis

• Signal parameters– Center Frequency– Occupied Bandwidth– Channel Power– Transmission shape / envelope– Time based characteristics

• Pulse Duration (PD)• Pulse Repetition Frequency (PRF)

– Location based parameters• Time• GPS location

– Weather conditions– Propagation environment

• Rural• Suburban• Urban

Documentation of all measurable signal parameters

Signals may be linked to other signalsLook for a trace that turns on and offLook for carriers that turn on and off when your interference turns on and off



• The most fundamental display in interference hunting is a spectral display (amplitude vs. frequency).

• A max hold function is also important in detecting short duration signals or looking for an elevated noise floor.

Spectral Display – Amplitude versus frequency


Characterizing Interference with spectral analysisSeveral traces operating in different trace modes

A max. of 3 traces can have completely different setups

NormalMax-Hold

E.g. for short transmissions

Min-HoldE.g. for remaining signal

Dual trace spectrum helps see what’s happeningTrace features

Trace HoldRecall Trace



• To look for intermittent signals near or on a legitimate signal

– Auto-Mask allows “save on event” waveform capture

– Auto Mask can save traces when the mask is violated

• Allows for quick analysis of data captured over several hours or days

– Upper and lower mask created automatically

• Can be round or square• User sets number of points

– Look for unusual events within the Rx channel or band

Auto mask feature



• Bursty Signals– Many digital signals are bursty

• On 50% of the time, or less• Wi-Fi• LTE Uplink• WCMDA Uplink• CDMA Uplink• Bluetooth• Industrial automation

– Use “Burst Detect” to view these signals reliably

• Trace mode that detects pulses over 200 micro seconds reliably

• Makes direction finding much, much, faster

Burst Detect for bursty Signals



• A Spectrogram shows frequency, time, and level information and is extremely useful in analyzing signals.

• GPS referenced spectrogram• Record Spectrogram

Spectrogram Analysis

Up to 15600 traces, over 3 daysZero Span operation possible



• Use the spectrogram to look for signals that change its keying over time

• Signals may occur at specific times of the day, or days of the week– Gas stations sending the day’s

receipts in by satellite– A car with a jammer on its

weekday commute– Teachers that want to stop

cheating during tests– Meeting leaders who don’t want

interruptions– High average BTS power at the

rush hour when loaded to capacity

– When a RF Lab is testing new circuits




• Use the spectrogram to look for signals that change frequency and amplitude over time

– e.g. due to temperature– e.g. due to changing reflections

• People• Cars • Etc.

– Displayed signal is unstable in frequency

• From a cell phone booster with insufficient input to output isolation

• Common consumer grade equipment issue




• Demodulate the signal in order to prove the signal type

– For cellular signals• Find Cell ID• Find network owner by

Base Station Colour Code– Prove if it’s GSM, UMTS, LTE

• By modulation scheme analysis

– Find Owner and Cell ID in case of PMR signals

– IQ Capturing• Record signal for post analysis• Files are MATLAB compatible• Replay captured signal using

e.g. MS2830A

Signal analysis, demodulation and decoding



• Audio demodulation means listening to the signal

• Audio demodulation allows– AM / FM / PM demodulation

(NBFM, WBFM, SSB, etc.)• Measure audio parameters

– Modulation Rate, RMS, Pk-Pk/2, SINAD, THD, and Distortion/Total

– Audio Spectrum– Audio Waveform

• Station ID / call signs• Language and content• Even digital signals can sometimes be

identified using audio demodulation

Audio Analysis


Interference Hunting Tools



• Spectrum and Signal Analyzer– Spectrum Analyzer Key Capabilities

• Fast Sweep

• Burst Sweep Mode

• Wide RBW range

• High Dynamic Range

– Signal Strength Tools– EMF Tools– Channel Power / Occ. BW measurements– Trace Types

• Max-Hold

• Normal

• Min-Hold

– Averaging• Trace Averaging

• Video Bandwidth Filter

Spectrum Master MS2720T family



• Frequency– 9 kHz - 9 GHz– 9 kHz - 13 GHz– 9 kHz - 20 GHz– 9 kHz - 32 GHz– 9 kHz - 43 GHz

• RBW– 1 Hz - 10 MHz

• Average display noise level– -164 dBm/Hz (typ.) (1 GHz, preamp ON)

• TOI– +20 dBm (typ.)

• 20 MHz demodulation bandwidth• IF output at 140 MHz with 30 MHz bandwidth• Burst Detect capability (captures 200 μs bursts the first time, every time)

Spectrum Master MS2720T family

Various demodulation capabilities



• Frequency– 9 kHz - 3 GHz– 9 kHz - 4 GHz– 9 kHz - 6 GHz

• RBW– 100 Hz - 3 MHz– 1 Hz - 3 MHz

• Average display noise level– -162 dBm/Hz (typ.) (1 GHz,

preamp ON)

• TOI– +25 dBm (typ.)

• 20 MHz demodulation bandwidth

Spectrum Master MS27xxE family

Various demodulation capabilities



• Multipurpose instrument– Cable- and Antenna Analyzer– Spectrum Analyzer– Signal Analyzer– Signal Generator– Coverage & Interference Mapping– Interference Analyzer

• Frequency– 500 kHz - 1,6 GHz– 500 kHz - 6 GHz

• RBW– 10 Hz - 3 MHz

• Average display noise level– -162 dBm/Hz (typ.) (1 GHz, preamp

ON)• TOI

– +25 dBm (typ.)• 10 MHz demodulation bandwidth

LMR Master S412E

Various demodulation capabilities• NBFM• NXDN,• DMR,• ITC-R PTC,• TETRA• LTE 10 MHz• WiMAX


Handheld based emitter location

MA2700A


MA2700A

MA2700A for manual sniffing andtaking bearings for locating purposes

Built-in electronic compassBuilt-in GPS receiverBuilt-in preamplifierTrigger for saving vectors

Easy no-tool attachment of antennasErgonomic design

Instrument in front of the hipsAntenna operation by one hand

Light weight Several available antennas

Handheld Emitter Location


Available LF / VHF Antennas

Handheld Emitter Location

Directional LF Antennas2000-1777-R 9 kHz to 20 MHz2000-1778-R 20 MHz to 200 MHz2000-1779-R 200 Mz to 500 MHz

Port Extender for MA2700A2000-1798-R DC to 6 GHz


MA2700A Handheld emitter localizationAvailable UHF / Mw Antennas


MA2700A Handheld emitter localizationAvailable Antennas

Directional Antenna for MA2700AFrequency: 698 MHz to 2500 MHz N(f)Gain: 2 - 10 dBi typ.Order number 2000-1715-R

BPF for MA2700A2000-1739-R 880 MHz - 915 MHz,2000-1740-R 1710 MHz - 1785 MHz2000-1741-R 1920 MHz - 1980 MHz2000-1742-R 832 MHz - 862 MHz2000-1743-R 2500 MHz - 2570 MHz2000-1799-R 2305 MHz - 2320 MHz2000-1734-R 699 MHz - 715 MHz2000-1735-R 776 MHz - 788 MHz 2000-1736-R 815 MHz - 850 MHz2000-1737-R 1711 MHz - 1756 MHz2000-1738-R 1850 MHz - 1910 MHz


MS2700A – typical results

MA2700A Handheld emitter localization


Automatic broadband Interference Locating

systemMX28007A


Automatic broadband direction finding systemMX28007A – a typical interference scenario

Complains about broadband interferenceLocation unknown, seems to come everywhere


Automatic broadband direction finding systemMX28007A

Mobile Direction Finding 9 kHz - 43 GHzMobile system to find interference sources using Windows based tablet/laptopMX28007A Mobile Interference Hunter™Roof-top-mounted directional antenna arrayMS2720T Spectrum Master with Interference Mapping

Automatically “Locate while drive”Take large number of measurements and calculate signal location using mathematical algorithms

Finds all Types of InterferenceBursty signals with Burst Detect™Narrowband InterferenceModulated Signals


Automatic broadband direction finding systemMX28007A

Single or multiple emitter detection modes

make it easy to use for any type of emitter detection application e.g. multiple emitter mode is ideal for locating multiple cable TV interferersMultiple TRX operating the same RF

A spectrum clearing mode using channel power measurements that map signals above a certain power thresholdCompatible to any kind of Spectrum Master, LMR Master, VNA Master, Site Master, BTS Master


Mobile Interference Hunting System

Vehicle Position

Position Estimate



Vehicle Position

Position Estimate


Automatic Spectrum Monitoring and emitter geolocation


Spectrum Today – Crowded and Expensive

• Cellular network operators have invested billions of dollars purchasing rights to use frequency spectrum

• Carriers and other spectrum users need to protect their investments and quality of service

• Interference mitigation is a top priority for optimizing network performance and maximizing revenue

• Exploding demand for more bandwidth is driving the need to identify and repurpose under-utilized spectrum

* NTIA - United States Frequency Allocations, 300 MHz to 3 GHz


Automatic Spectrum Monitoring

• The overall of spectrum monitoring activities is to support the proper functioning of the general process of spectrum management. Central objectives for spectrum managers include the following– Spectrum efficiency in determining planned and

actual frequency usage and occupancy, assessing availability of spectrum for future uses;

– Compliance with national spectrum management regulations to shape and sustain radio environments and user behavior, maximizing the benefit of the spectrum resource to society;

– Resolution of interference problems for existing and potential users.

Goal of Spectrum Monitoring



• Discover and facilitate removal of interference sources– Interference may be intermittent, periodic, and frequency-agile– Need the ability to examine logged data

• Frequency and bandwidth• Date and time of first and last intercept• Patterns of unwanted signal activity• Occupancy report

(usage number vs frequency)• Characterize unwanted signal behavior• Locate the interference source

Why 24/7 Spectrum Monitoring Is Needed



Teleport & Cellular

Broadcast

Maritime

Oil and Gas

DAS Systems

GovernamentMilitary

VSAT Terminals & Hubs

Spot Beam Sig. Analysis

MilSatCom

PPDR

Short & LongTerm EMF

Key Applications



Desired characteristic for a Remote Spectrum Probe

Broad frequency rangeFast survey or scan ratesHigh sensitivity, inc. PreAmp and narrow RBW settingsApplicable in high signal environments (high IP3)Local or remote computer controlAdd. Application specific software packages

Performance – Insight – Reliability - Scalability


MS27101AHalf Rack x 1USingle Input

MS27102AIP67 Outdoor Rated1 or 2 Input Ports

MS27103AFull Rack x 2U12 or 24 Input Ports


OEMPCB Only

MS2710xA Remote Spectrum Monitors



• 9 kHz to 6 GHz frequency coverage– Spectrogram operation mode

• Fast sweep speed– Up to 24 GHz/sec

• High dynamic range– > 106 dB dynamic range– –165 dBm/Hz DANL with preamplifier on– +10 dBm Third Order Intercept (TOI)– Spectrum Trace with up to 4000 points

• Excellent spectral purity– < -70 dBc input-related spurious– -88 dBm residual spurious– -100 dBc/Hz phase noise @ 10 kHz

20 MHz instantaneous FFT bandwidthIQ capture in block and streaming modeIntegrated preamplifierIntegrated GPS receiver Gigabit Ethernet for high speed communications4 GB internal memory available for storing filesSignal ID software (*)AM/FM/SSB Demodulation (*)(*)

Under development

MS2710xA Performance Highlights



• Two-way communication with remote probes provided by Gbit Ethernet– Documented SCPI commands available for users to write their

own scripts and applications…develop custom programs• Enabling security agencies and contractors to create proprietary

secure applications– Standard user interface using built in web server allows

multi-user view and operation• Full control of instrument configuration• View trace data and spectral traces parallel on PC, Tablet or

Smartphone

MS2710xA Performance – Operation modes



– Anritsu ‘Vision’ PC software tools

• VISION Acquirepoll probes for spectrum information, database creation andadministration

• VISION Monitor automatically capture spectrum data, set thresholds and generate alarms, keep spectrum history and provide reports on network health

• VISION Locate use three or more probes to geo-locate location of signals and inteferers.

• SpectraVisionautomatically capture and demodullate spectrum data, set thresholdsand generate alarms, keep spectrum history and and provide reporting.

MS2710xA Performance – Operation modes



Edit probe information and

scan settings

Edit limit lines and apply retroactively to historical trace data

View synchronized historical or live data from numerous probes

Generate pass/fail reports

VISION Monitor Functions



• Launched via Vision Monitor

• At least three probes must be able to “see” the target signal

• Emitter geolocation– PDOA or– TDOA

VISION Locate



• Parallel control ofseveral spectrumprobes

• Fully automated scan and demodulation capabilities

• Record and replay• Automated

alarming• Channel Scanner

SpectraVision – Signal Analysis for LMR, DVB-S and Cellular Standards

RF Interferences Hunting and Over the Air measurements

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Transcript of RF Interferences Hunting and Over the Air measurements