I/Q Analyzer-Magnitude: The display here captures the entire signal in the time domain over a bandwidth of almost 27 MHz, making precise triggering easier.

I/Q Analyzer-HiRes Spectrogram: The gapless displayshows the PLC signal with a bandwidth of 21.33 MHz over9.375 ms with a time resolution of 2.4 µs.

I/Q Analyzer-HiRes Zoom: This uncompressed displaycan be scrolled over the entire range of measurementvalues.

Description:Initially, the service was limited to the short wave frequency band. The excludedfrequency blocks protected wireless services in the corresponding bands. The frequency range has since expanded well into the VHF range and also makes use of intelligent frequency management.

The analysis uses I/Q mode, which acquires and saves 250,000I/Q pairs as a block. This allows gapless display of time versusfrequency. Within this block, a POI (probability of intercept) of100 % is offered, which can indicate results down into the nanosecond range depending on the settings.

1 TETRA – Terrestrial Trunked Radio

Description:The base station transmits a training sequence every 14.167 ms, which is visiblein time domain.

3

I/Q Analyzer-HiRes Spectrogram: Downlink – Extraneous signals are easily traced because they differ in frequency, bandwidth, and burst duration.

Time Domain (Scope): A different view shows onechannel only. It reveals the GSM time slots (577 µs) and even different modulation schemes (GMSK forGSM, 8-PSK for EDGE).

Description:GSM stations are subject to the same standards worldwide. A frame is 4.615 mslong and has 8 timeslots with a burst length of 577 µs. The frequency spacing is200 kHz. Since a GSM signal is broader than this, adjacent channels are not usedat the same location/base station.

High field strengths are present at a GSM base station. IDA worksin environments of up to 100 V/m. A 20 dB attenuator is recom-mended for above 10 V/m. Gapless monitoring for up to 24 h is possible with Time Domain (Scope). Apply the IDA I/Q Analyzerin order to even indicate BCCH signaling!

6

UMTS – Universal Mobile Telecommunications System (3G)

Spectrogram: Shows both UMTS up- and downlink.

In-band interference can often be made easier to see by carefulalignment of the antenna or by shielding the payload signal(e.g. behind a building or vehicle).

9

ATC – Air Traffic Control2

PMR – Public Mobile Radio (with interference)

Spectrum: Display shows a modulated and an unmodulated signal as well as a small carrier of unknown origin.

I/Q Analyzer-Persistence: Display shows a transmission at446.04375 MHz with neighboring transmissions (blue cloud)that may interfere with adjacent channels.

I/Q Analyzer-HiRes Spectrogram Zoom: The imageshows more details of the transient response and howadjacent channels are affected by this.

Description:The example shows images of a case of interference caused by the transient response of a device.

If the spectrum does not give any answers, other displays suchas "Time Domain Scope" or "I/Q Analyzer" may help to trackdown the cause.

4

LTE – Long Term Evolution (4G)

Description:LTE uses widely differing frequencies and various procedures.

In-band interference can often be made easier to see by carefulalignment of the antenna or by shielding the payload signal(e.g. behind a building or vehicle).

7

Bluetooth

Spectrum: Bluetooth Inquiry Mode – The device is searching for other devices. This uses every second frequency and leaves a gap around 2.42 GHz.

I/Q Analyzer-Persistence: Persistence shows a 7.8 mssection of 25 MHz.

I/Q Analyzer-HiRes Spectrogram: The display showsthe typical pattern for Inquiry Mode.

Description:Bluetooth uses the frequency range between 2.402 and 2.480 MHz in the ISMband, in which 79 channels are defined. Frequency hopping principle repeats thechannel sequence only after one day! The Burst length is 625 µs. Based on packetsize, frequency is swapped after 3.125 ms maximum.

Interference on Bluetooth is usually rare because of thechanging frequency, short range, and error correction.

10

Pager

I/Q Analyzer-HiRes Spectrogram Zoom: The modulation becomes “transparent”. Transmitteroverlaps would be visible, even with small time offsetson the same frequency.

Description: The service is FSK modulated (frequency shift keying), based on thePOCSAG protocol. It switches every 28 seconds between three RF channels and canalso be blanked. In the example, up to three stations at different distances are usingeach frequency in turn. The high frequency resolution shows that time overlaps (confusion areas) should not be suspected, as these would otherwise be easily seen.

Use a wide span to get an initial overview and then reduce it for more exact analysis.Use HiRes Spectrogram (optimized time and frequency resolutionat once) in order to indicate FSK modulation scheme.

5

Spectrum: Since the stations only transmit for 90 µsevery 10 ms, detection using Spectrum is unlikely. The Night view mode shown here reduces eye strain.

I/Q Analyzer-Persistence: The display shows the expectedDECT bursts (blue cloud). The yellow colored intermodulationproducts come from neighboring GSM downlinks.

8

WLAN – Wireless Local Area Network

Spectrum: Display shows active channel in Max tracewith typical dips.

Time Domain (Scope): Time Domain shows the time behavior. This is a valuable aid to correctly establishing the trigger level.

Description: At 2.4 GHz among other frequencies. Time and frequency multiplexingcan barely be assessed using spectrum analysis only.

11

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Spectrum: Spectrum of an individual station showing the typical hump right of center.

Time Domain (Scope): Signal course reveals typicalTETRA single timeslot (14,167 ms) and double timeslot.

Spectrum: Simultaneous display of a 20 MHz span that is refreshed every 39 ms ensures correct classification of interference.

Spectrogram: A time resolution of 500 ms was selected in order to show wireless traffic and interference carriers over a long period.

I/Q Analyzer-Persistence: Display of probability densityfunction unveils even shortest signals. It offers 100%P.O.I. (probability of intercept) down to Nano secondpulses.

The IDA is optimized to deal with these problems thanks to the 50 dB range attenuator switchable in 1 dB steps and the preamplifier with its high inter-modulation immunity. IDA can handle field strengths of up to 100 V/m and in most cases can measure a radar signal as well as reliably detect the minimalinterference carriers on the security frequency without an external attenuator.

PLC – Power Line Communications

Spectrum: The Max Hold trace shows all three hopping frequencies of a pager.

Spectrogram: The display summarizes 500 ms in oneline of the spectrogram (time resolution). By that it is possible to recognize the switching interval of 28 s between three frequencies.

GSM – Global System for Mobile Communications (2G)

Time Domain (Scope): The display shows the accumulatedsignal course of 25 channels simultaneously by applying aCBW of 5 MHz around the center frequency of 955 MHz.

I/Q Analyzer-HiRes Spectrogram: In-band interference is more easily seen in this view, depending on the occupation density.

I/Q Analyzer-HiRes Spectrogram Zoom: Regular structures can still be seen even in densely occupiedareas with the zoomed view.

DECT – Digital Enhanced Cordless Telecommunications

Description: Operates in Germany between 1.88 and 1.9 GHz with a CBW of 1.728 MHz.The transmission is broader than the spacing. Each frame lasts 10 ms and has 24 timeslots(12 each for uplink and downlink). Fixed parts idle mode shows a 90 µs burst every 10 ms(except EcoDECT). The burst length rises to 370 µs spaced precisely every 5 ms, but not necessarily on the same frequencies for a voice link between the fixed part and portable part.

The question whether an IM3 product is “home made” can be answeredeasily using the 5 dB keys. True IM3 does not alter with attenuation. The origin of IM3 can only be determined with difficulty in the field. The modulation locations (gutters, rusty bolts, own radio receiver) are inaccessible.

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Analyzing short therm signals such as WLAN is easier when applying Max trace in spectrum. In some cases Act trace can be useful, too, in order to indicate modulation schemes.

I/Q Analyzer-HiRes Spectrogram: The gapless spectrogram delivers the evidence for GSM intermodulation. The 550 µs burst can be seen at some points.

Description:In Germany UMTS uplink lies between 1.920 MHz and 1.980 MHz whereas UMTSdownlink lies between 2.110 MHz and 2.170 MHz. The bandwidth of one UMTS channel is 5 MHz. Based on WCDMA access UMTS applies PSK or QAM modulation.

I/Q Analyzer-HiRes Spectrogram Zoom: Shows the area of importance (trigger point) in a gapless spectrogram.

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Description:Two opposing requirements apply to air fields. Radar may be present at a field-strength much higher than 140 dBµV/m whereas an interference carrier withinthe air traffic control band can be well below 0 dBµV/m.

Spectrum: The spectrum shows even distribution due to the dense occupancy of the message space. This canchange in case of multipath propagation.

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I/Q Analyzer-Persistence: The overview in I/Q Modeshows the continuous carrier of the fixed stations.

In contrast to most other digital transmission methods, a TETRA signal is based on a single I/Q modulated carrier (typically �/4-DQPSK).

HiRes Spectrogram: No further signal information even when applying a time resolution of just 4.8 µs!

Spectrum: In band interference is hardly visible within the spectrum because the data space is fully utilized. Single-FFT windows are offered with up to 20 MHz spans ensuring uninterrupted capture of whole signal (even with interferers) without need of ‘stitching’ mode.

http://signals.narda-sts.com www.narda-ida.com

Light, portable signal analyzer for detecting, analyzingand localizing RF signals and interference in the frequencyrange from 9 kHz to 6 GHz. IDA 2 combines a frequencyscanner / receiver, transmitter detector, spectrum analyzer,signal analyzer and triangulation software in a single mobile device. The sets also include precision directional antennas withbuilt in switchable preamplifier and electronic compass.

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