TRANSCEIVER 800 MHz
MTP700 Portable Radio / Detailed Service Manual
4.2 - 13
Balun
The Balun transforms the single ended input RF signal to a differential double-ended out-
put. It consists of L507, C523, C522 and L508.
The differential signal is routed to the WPIC (World Phone IC) at pins A4 and B4 (PREINI
and PREINIB) via C651 and C652.
WPIC (Receiver Back End Section)
The differential IF signal is amplified and converted down to baseband signal inside the
WPIC (World Phone IC) by the 2nd LO signal. The 2nd LO signal is routed to the WPIC at
pin D1 and divided by two into the quadrature generator block of the WPIC. The base-
band signal from the mixer passes to an amplifier baseband filter array. The amplified and
filtered signal is passed to the WPIC A/D converter. This A/D converter digitises the ana-
log differential signal as I and Q components. The I and Q components appears as serial
data on the WPIC_SRD line whenever the RX_ACQ line is high. The WPIC_SRD data is
clocked into the DSP baseband port using a clock signal (WPIC_TXCLK) from WPIC.
The DSP performs the functions of digital de-modulation. The WPIC is controlled via
SPIA_MOSI, SPIA_CLK and SPIA_CS0_WPIC from RedCap2.
An internal AGC that is controlled by a control unit, establishes an appropriate attenua-
tion for unwanted signals as well as an appropriate gain for wanted signals. The voltage
at external capacitor C612 indicates the AGC attenuation level for the different input sig-
nal levels. The voltage at the capacitor varies from 1.3V to 2V as a function of the power
of the received signal.
Summary of Contents for IMPRES Tetra MTP700
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