Use Manual

DMR repeater 24/01/2011 Versione 1.3
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Pag. 8 / 31
∞ Frequency self-tuning device
∞ Deviation self-calibration device
∞ Analogical and digital demodulation
∞ RF circuits testing
∞ Phase modulator calibration
∞ RF output power control
∞ Low frequency lines management
∞ DMR protocols management
∞ Digital signals processing
∞ Management, conditioning and routing of traffic and remote control signals from and towards
external world
3
3
.
.
3
3
R
R
E
E
C
C
E
E
I
I
V
V
E
E
R
R
Receiver can be supplied as single or double for space diversity reception. Main and diversity channels are
completely independent and coherent (sharing the same local oscillators) and they are designed according to a
triple conversion heterodyne structure, with 45 MHz and 10.7 MHz intermediate frequencies and with
vectorial conversion to base-band.
Channel standard bandwidth is 12.5 KHz, but the receiver is prepared to accept also a settable channel
bandwith of 25 KHz (with double funnel option) for special applications.
Vectorial receiver gives to the DSP input the electromagnetic field vector, as received from antennas, without
performing any demodulation. By this way the DSP can sum with the appropriate phases the received signals
to obtain a “soft diversity” reception. This corresponds to an electronic antennas alignment in order to receive
the maximum available information along the incoming signal direction.
III° LO 10.7MHz II° LO 34.3MHz
I° LO Frx+45MHz (VHF)
I° LO Frx-45MHz (UHF)
Input filter and low
noise amp.
High IP3 MixerXTAL filter
45MHz
XTAL filter
10.7MHz
Micro-
controller
IF system
A further input (TX Test input), common for both receivers (main and diversity) is available, for the receiver
self-test and for modulator calibration. Through a DSP command, the receiver can switch its input onto test
signal generated inside transmission synthesizer module. That signal, amplitude calibrated by Factory, is
modulated at receiving frequency and received by DSP. A fundamental test loop is close by this way.