Aeroflex 2050T SERIES Especificaciones descargar pdf (Pagina 13)

For the very latest specifications visit www.aeroflex.com

After you have set the 2968 correctly for the required uplink

scrambling, it may be necessary to re-start the BER measurement

on the base station so that it can re-synchronise its BER meas-

urement to the correct PRBS.

Note that the 2968 manual test screen display of the MCC/MNC/

BCC parameters always shows the values indicated by the base

station synchronisation burst, whether or not it is auto updating to

these values.

QQ33..1188::

Can the 2968 signal generator compensate for cable

loss, attenuators, splitters etc.?

AA33..1188::

Yes. The compensation applies to all 2968 RF generator

signals, not just TETRA, hence it is set up under the main instru-

ment set-up menus rather than the TETRA system specific menus.

Press the HELP / SET-UP hardkey then the softkeys SET-UP, TEST

OPTIONS, rf port setup, then set the "RF Gen level offset" for the

required compensation. Negative values compensate for an

external loss, positive values compensate for an external gain.

QQ33..1199::

Why does the signal generator level setting show a

reverse video asterisk next to it?

AA33..1199::

This is a warning that the 2968 has been set to compen-

sate for an external gain or loss (see A3.18 above). If the com-

pensation is no longer required, reset the RF Gen level offset to 0

dB.

QQ33..2200::

Can I use the 2968 to test receiver selectivity?

AA33..2200::

The 2968 can provide the T1 wanted signal used for per-

forming tests of adjacent channel rejection, co channel rejection,

spurious response rejection and blocking rejection, as defined in

the TETRA radio conformance test specification ETSI EN 300

394-1. You will need additional equipment to generate the T2

interfering TETRA signal (e.g. IFR 2050T) and the T3 interfering

CW signal (e.g. IFR 2040 series) and to combine the signals.

QQ33..2211::

Can the IFR 2968 be used for dynamic (fading) sensitivi-

ty tests?

AA33..2211::

The IFR 2968 can be used in conjunction with an exter-

nal fading simulator to produce the signals for dynamic sensitivity

tests. IFR does not supply fading simulators, and we are not in a

position to evaluate or recommend third party fading simulators.

However, the following companies are known to produce fading

simulators:

Elektrobit (www.elektrobit.com)

Sofimation (www.sofimation.com)

The above is not necessarily a complete list

Normally you will need to cycle the IFR 2968 [RF SELECT] hardkey

until you have selected 2-port operation, with the signal genera-

tor output on the TNC port, and the mobile or base station trans-

mitter connected to the N-type port. If the mobile or base station

has a single antenna connection for Rx and Tx, you will need a

combiner between the fading simulator output and the antenna

connection (and possibly an attenuator to protect the fading sim-

ulator output). Fading simulators typically require a fairly high RF

input level, hence the use of the 2968 TNC port which can gen-

erate a TETRA signal at a maximum level of -20 dBm. Normally the

level of the faded signal is controlled by the fading simulator, not

by the 2968 RF GEN LEVEL which remains at the level required

by the fading simulator input. Note that dynamic sensitivity tests

require a much greater number of samples for statistical validity

than do static sensitivity tests, which means that they are normal-

ly only performed for R&D or conformance testing purposes.

Section 4 Q&A: Testing the audio performance of

TETRA mobiles

QQ44..11::

Can I perform audio testing whilst the IFR 2968 is in TETRA

mode?

AA44..11::

Yes. Press the [AF TEST] hardkey and you have access to

the 2968's audio generators and audio analysis facilities, includ-

ing an audio frequency spectrum analyser. Refer to the 2968

TETRA supplement issue 10, chapter 4, pages 34 and 35 for

details. Refer to the main 2965A/2966A/2967/2968 Operating

Manual for details of AF TEST mode. The 2968 continues to gen-

erate a TETRA signal, thus maintaining the mobile in conversation,

whilst in AF TEST mode.

QQ44..22::

Can I use an external audio source to modulate the 2968

TETRA signal for testing the mobile's audio circuitry and earpiece

/ loudspeaker?

AA44..22::

Not directly. Audio signals carried on a TETRA RF signal

have to be digitised and encoded with a TETRA codec. The IFR

2968 does not incorporate a TETRA codec, and the cost of licens-

ing the TETRA codec precludes IFR from offering this as an option

for the IFR 2968. However, testing with external audio sources is

possible, see A4.3 below.

QQ44..33::

How can I test the mobile's audio circuitry with the 2968?

AA44..33::

The 2968 provides a "TALKBACK" function, i.e. it stores the

digitised and encoded speech transmitted by the mobile and

replays it to the mobile's receiver 2 seconds later. In a duplex call,

this is a continuous process. In a simplex call, the last 2 seconds

of speech is stored and played back repeatedly. This avoids the

need for the 2968 to include a TETRA codec, since the speech is

stored and re-transmitted in its already encoded form.

The Talkback facility can be used for testing with external audio

sources by setting up a duplex call and testing transmit and

receive audio functions together. Connect the required external

audio source to the mobile's audio input, e.g. an accessory

remote microphone input, and set the 2968 to talk-back mode.

The audio input to the mobile should be heard or received at the

mobile audio output after a 2s delay, subject to any degradations

introduced in the mobile's audio input / output circuitry and

TETRA codec.

With the mobile set up in a duplex call in talk-back, you can also

select [AF TEST] mode and make use of the 2968 audio genera-

tion and audio analysis facilities for performing a complete end-

to-end test of the mobile's audio transmit and audio receive per-

formance.

Alternatively, you can use the 2968's TETRA encoded 1 kHz test

tone for testing the mobile's audio receive performance in isola-

tion, which can be useful in determining the source of a problem

(receive or transmit) if the combined audio transmit / receive per-

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 23 24

Comentarios a estos manuales

Sin comentarios

Aeroflex 2050T SERIES Especificaciones Pagina 13

Comentarios a estos manuales