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FibreIRS DTT Processor of Global Invacom

•excellentdevicetofilteroutanyunwantedsignals•verysimpledevicesettings•increasesC/Nparametersattheoutput•usefulforbothcoaxialcablesystemsandforthenewfibreopticsystems

TEST REPORT Fibre Optic System for DTT

06-07-08/2012

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A Set of Brick Wall Filters and Signal Amplifiers

TEST REPORT Fibre Optic System for DTT

FibreIRS DTT ProcessorDelivery perfectly clean DTT signals for any

distribution system

GlobalInvacom is a leading company in introducing fiber optics to satellite tv recep-tion and TV distribution net-works. Now they introduced another very useful piece of distribution system that can be very beneficial not only for fiber optics based sys-tems but also for classical coaxial cable systems.

GlobalInvacom’s DTT Pro-cessor is a device installed between a terrestrial anten-na and the remaining part of a distribution system. Its most important function is filtering the signal your antenna picks up. Filter-ing means passing through the desired part of the fre-quency spectrum where the signals of interests are transmitted while blocking everything else from reach-ing the output.

Why is this that impor-tant? Thanks to the filtering, the signal that finally comes to the input of your DVB-T or DAB receiver contains much less noise. The probability of picture pixelation, video/audio glitches or complete loss of reception is greatly reduced. Starting with a clean signal is even more important in a distribution system based on fiber optic components. That’s because we need to convert the elec-trical RF signal existing in the initial stages of such system to modulated light. GlobalInvacom’s converter capable of changing electri-

cal currents into light will be covered in our next test re-port. Such converter if fed with very a noisy input sig-nal might have a problem in generating well modulated light. Typically, the rule is: garbage in = garbage out. If the signal quality is low at the input, it will become even worse at the output. Fortunately, filtering can be used to break this rule.

The FibreIRS DTT Pro-cessor of GlobalInvacom accepts signals from two terrestrial antennas: one re-ceiving terrestrial TV signals and the other digital audio (DAB) signals. The output is

one. That’s because DVB-T TV operates in the 470-862 MHz range while DAB in the 217-230 MHz range. So it is possible to combine them in one RF output.

The basic version of the DTT Processor enables you to select up to six different TV channels. You can buy additional plug-in modules and extend its functional-ity to eight DVB-T channels. Each channel is 8 MHz wide in accordance with a typical terrestrial DVB-T-TV chan-nel plan. Consequently, the

DAB band is treated as one 13 MHz wide channel.

We are used nowadays that one needs to connect a notebook PC to configure a professional system unit. It is convenient when the settings we need to do are complex. But in the case of a DTT processor, the settings are quite simple: the num-ber of a channel you want to be passed through and its signal gain. So it is really

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Jacek PawlowskiTELE-satellite

Test CenterPoland

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DATATECHNICAL

Manufacturer Global Invacom Ltd., Great Britain

Web www.gloablinvacom.com

E-mail sales@globalinvacom.com

Phone +44-1621-743440

Fax +44-1621-743676

Model FibreIRS DTT Processor

Function Filtering and amplifying terrestrial signal

DVB-T

Frequency range 470-862 MHz

Number of channels 6 (expandable to 9)

Broadcast standard 8 MHz

Gain 20 dB

Channel flatness < 2.5 dB

Adjacent channel rejection > 45 dB

DAB

Frequency range 217-230 MHz

Insertion loss < 2 dB

DC power

Input voltage 20 V

Current consumption 1 A

Physical

Size 182 x 205 x 122 mm

Weight 3.7 kg

Operating temperature 0 to +50º C

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20 21TELE-satellite International — The World‘s Largest Digital TV Trade Magazine — 06-07-08/2012 — www.TELE-satellite.com www.TELE-satellite.com — 06-07-08/2012 — TELE-satellite International — 全球发行量最大的数字电视杂志

good that GlobalInvacom’s processor does not require you to connect to a PC.

GlobalInvacom’s FibreIRS DTT Processor not only passes through the desired TV channels and blocks the rest of the spectrum but also amplifies their signal. The unit is enclosed in a metal case designed to be mounted on a wall on two screws. It has an external AC/DC plug type adapter. After unscrewing two screws and removing the cover, you get access to the interior of the processor. Every mod-ule has an eight position DIP switch you use to set the de-sired channel number (from 21 through 69) and to turn a module on or off. A piece of foiled paper is attached to the internal surface of the cover. It’s a short list of op-erating instructions, as how to turn the module on/off and how to set the channel number. A few clicks with a small screwdriver is enough to do all that setting. A green LEDs mounted on the top of each module signals which one is turned on.

Except for that, every unit has its own red knob for ad-justing channel gain. The nominal adjustment range is 30 dB. There is also one slide switch enabling you to additionally boost the out-put by about 20 dB (18 dB in the specs). It adds this extra gain to all passed through channels. It may be very useful when you deal with very extended or complex cable networks in which you expect significant attenua-tion.

For best performance, the input signal should be above

60 dBµV for DVB-T and not more than 65 dBµV for DAB. The output of every channel should be adjusted optimal-ly to 70 dBµV if you connect the GlobalInvacom ODU32 RF-to-light converter to the processor. If your antenna has a built in amplifier – no problem. The DTT Processor generates 12 V to power the amplifier.

We started our test with a real world signal. In our test location in Western Poland, two DVB-T multiplexes are available. They are trans-mitted on channels E41 and E45. The signal level was slightly above 66 dBµV – ex-actly as needed. As you can see on the attached screen shots, the input signal con-tained some undesired sig-nals too. These were some analog TV channels which are still transmitted as well as some spurious signals produced mainly in the an-tenna amplifier. But the output of the DTT Proces-sor was completely free of them. Only the two digital channels were left. We ad-justed the output of every channel to 70 dbµV without any problem.

But that’s not all. The car-rier-to-noise (C/N) param-eter measured at the output was better than that at the input by 12 dB! For example for E45 channel, it rose from 31.1 dB to 43.7 dB. We were really astonished because we had not expected such significant improvement in signal quality.

We checked the gain ad-justment range for every channel. We got 26 dB ad-justment range for E41 and 24.5 dB for E45. A little

Very good adjacent channel separationFlat pass bandWide range of signal gain adjustmentVery easy setup requiring no PC but just a screwdriver

none

Expert Opinion

less than specified (30 dB) but still quite a lot. The ad-ditional output boost that could be turned on with a switch was 18.4 dB and 17.2 dB respectively. Almost ex-actly in line with the speci-fication (20 dB). Of course, we had absolutely perfect video when we connected a DTT receiver to the proces-sor output.

Finally, we fed the pro-cessor with a white noise generator signal to exam-ine the frequency response. As our screen shots clearly show, the performance of the filters was awesome. We sometimes use the term “brick wall’ for a filter with extremely steep roll-offs. That’s the term you can certainly use for GlobalIn-vacom’s FibreIRS DTT Pro-cessor. Its SAW filters do a very good job. You can see it in the other screen shots shown in this report. Also

the passband is very flat – another desired feature of a good filter.

We did not have an op-portunity to check the DAB band but after such impres-sive results with TV chan-nels, we have no doubt that also this band is processed equally well. For DAB, Glo-balInvacom uses a Low Pass Filter.

To sum it up – the proces-sor delivers what its specifi-cation promises. The output signal is exceptionally clean and its C/N improves more than anybody could expect. We can heartily recommend using GlobalInvacom Fi-breIRS DTT Processor not only for any fiber optic sys-tem but also for the usual coax cable distribution net-works. We are sure that the end users will be completely satisfied with the quality of terrestrial signals delivered to their outlets.

1. The original input signal picked up by a terrestrial antenna. There are 2 DVB-T signals at 634 and 666 MHz (channel 41 and 45) and a lot of unwanted noise.2. After passing FibreIRS DTT Processor, only the desired DVB-T signals remain.3. A test with a white noise generator proves excellent adjacent channels rejection.4.Sharp roll-off and flat pass band - splendid frequency characteri-stics of one of the FibreIRS DTT Processor channel filters.

TELE-satellite Test Editor Jacek Pawlowski at work. The FibreIRS DTT Processor is connected to a professional signal anaylzer. the analyzer‘s video output is fed into the laptop to generate the screenshots for this report.