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Idiomas disponibles
Idiomas disponibles
1.4 Multipath channel simulation. Echoes generator.
The channel simulator implemented in the MO-170 allows the user to simulate
both dynamic and static multipath scenarios. Up to 6 echoes (including the main path)
of variable amplitude, delay, phase and Doppler frequency can be selected.
The time-varying complex-baseband channel is simulated in the digital domain
according to the following equation:
τ
=
ρ
h
t
e
; (
)
1
Echoes 2 to 6 have amplitude ρ
. Echo number 1 has amplitude ρ
frequency f
D,n
frequency f
. Its delay is assumed 0 and therefore it is taken as the time base
D,1
reference for all the other echoes.
When f
= 0 for all n, the channel does not vary in time and h(t;τ) = h(τ). This is
D,n
the channel used to characterise fixed or roof-top reception. It's usually nonetheless
useful to add some Doppler (1 or 2 Hz) to a static channel in order to slowly stir its
phase.
For echo number n, n = 1...6, its amplitude ρ
formula:
where A
is the amplitude of echo number n referred to the echo of maximum
n
amplitude of the channel and expressed in dBc (valid range is 0 dBc down to —40 dBc
in 0.1 dB steps). Note that the echo of maximum amplitude is not necessarily the first
echo as happens, for instance, when pre-echoes are present in the channel. The
above formula normalises the channel so that the total power of the DVB-T signal
(sum of echoes) remains equal to the nominal DVB-T signal power when no echoes
are present.
The range of echo delays goes from 0 to 447.9 µs, 511.9 µs and 597.2 µs for 8, 7,
and 6 MHz channels, respectively. In all cases, the delay for each of the six echoes
can be incremented in steps of 0.1 µs.
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6
∑
π
+
φ
π
+
ρ
j
f
t
j
f
2 (
)
2 (
e
D
1 ,
1
D
,
n
n
=
n
2
, constant phase φ
n
, constant phase φ
1
is computed using the following
n
A
n
20
10
ρ
=
n
A
6
n
∑
10
10
=
n
1
OP-170-E USER'S MANUAL
+
φ
δ
−
τ
t
)
t
n
(
)
n
, delay τ
, and pure Doppler
n
n
, and Doppler
1
06/2006
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