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Weight in package ............................................................................................. 0.5 kg
2.5
Design and operation overview
2.5.1 Principle of operation
The IT-14 Analyzer is a receiver of DVB-T signals with demodulation of the traffic stream to MPEG-2.
The input tuner is a super heterodyne receiver with triple frequency conversion (auto or manual frequency
tuning). Modulation error ratio MER and constellation diagram are measured in the process of DVB-T signal
demodulation based on vector analysis. Bit error ratio BER in digital stream is determined by means of
analysis of Viterbi and Reed-Solomon decoders operation. Channel power is measured by means of analog-
to-digital converter after signal detection at output of logarithmic detector of the amplifier of the third IF. Level
of analog channels is detected with peak detector. Power of digital channels and noise level are detected
with average detector. The principle of spectrum analyzer is based on sequential analysis method with
spectrum indication on the LCD display.
The view displayed on the screen in the MER/BER mode DVB-T signals reception quality parameters
measurement is the numeric values of the measured digital parameters (MER, bit error ratio BER before and
after Viterbi decoder and erroneous packets counter after Reed-Solomon decoder). The constellation
diagram mode shows the vector structure of the quadrature components of the demodulated digital signal on
the phase plane. The signal level measurement mode in a frequency point displays for the analog signals:
the numeric value of the signal level, V/A and C/N ratios, for digital signals: the value of the actual channel
power.
2.5.2 Block diagram
The block diagram of IT-14 is shown in Figure 2.5.1.
Low-pass filter
(LPF)
Band-pass filter
IF2 36,125 MHz
(BPF1)
Band-pass filter
IF2 39 MHz
(BPF2)
Local oscillator
28,3 MHz
(LO)
Power unit
(PU)
After the low-pass filter (LPF), the input signal if necessary is strengthened by the wide-band amplifier
(Amp) or reduced by the attenuator (A). Then the signal is converted into the second IF 39 MHz in level
Amplifier
0/11dB (Amp)
DVB-T
demodulator
(Dm)
Mixer
(M)
Signal detector
(SD)
Keyboard
(K)
Figure 2.5.1
7
Attenuator
0/20/40dB (A)
Band-pass filter
IF3 10,7 MHz
(BPF3)
Analog-to-digital
converter (ADC)
Nonvolatile
memory
(NVRAM)
Tuner
45-900 MHz
(T)
Logarithmic gain
amplifier limiter
(LGAL)
Control unit
(CU)
Liquid-crystal
display
(LCD)
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