Measuring DVB-T Signals - Digital Video and Audio Broadcasting Technology - page 385

21 Measuring DVBT Signals

The DVB-T standard and its complicated COFDM modulation method
have now been discussed thoroughly. The present chapter deals with
methods for testing DVB-T signals in accordance with the DVB Meas-
urement Guidelines ETR 290 and also beyond these. The requirement for
measurements is much greater in DVB-T than in the other two transmis-
sion path systems DVB-C and DVB-S due to the highly complex terrestrial
transmission path, the much more complicated DVB-T modulator and the
analog IQ modulator used there in most cases. DVB-T measuring tech-
niques must cover the following interference effects:

• Noise (AWGN)

• Phase jitter

• Interferers

•

Multipath reception

• Doppler effect

• Effects in the single-frequency network

• Interference with the adjacent channels (shoulder attenuation)

• I/Q errors of the modulator:

-

I/Q amplitude imbalance

- I/Q phase errors

- lack of carrier suppression

The test instruments used in DVB-T measuring techniques are essen-
tially comparable to those used in broadband cable measuring techniques.
The following are required for measuring DVB-T signals:

• A modern spectrum analyzer

• a DVB-T test receiver with constellation analyzer

• a DVB-T test transmitter for measurements on DVB-T receivers

The DVB-T test receiver is by far the most important measuring means
in DVB-T. Due to the pilot signals integrated in DVB-T, it allows the most
extensive analyses to be performed on the signal without using other aids,