TRANSCEIVER 400 MHz MTP700 Portable Radio / Detailed Service Manual 4.1 - 7
Frequency Generating Section
The frequency generating section contains the following components (see Figure 4.1-4):
• TCXO Reference Oscillator.
• Main Synthesizer - consists of the WPIC’s PLL and the Main Voltage Controlled
Oscillator (VCO).
• 2nd Local Oscillator (LO) VCO together with the LMX Dual Synthesizer IC.
• Transmit PLL - consists of TX VCO together with ESCORT Synthesizer IC.
Figure 4.1-4 Frequency Generation - Block Diagram
TCXO Reference Oscillator
All frequencies originate from the Reference oscillator - TCXO. This is a digital tempera-
ture compensated crystal oscillator producing an accurate and stable 16.8 MHz reference
frequency. The 16.8 MHz reference frequency is divided in the WPIC and in the Dual
Synthesizer IC to produce required reference frequency for the other synthesizers.
Main Synthesizer
The Main Synthesizer consists of the WPIC internal PLL modules and an external,
discrete Voltage Controlled Oscillator (VCO) . The output provides the LO signal to down-
convert the received RF signal to the first IF of 109.65 MHz. The output is also routed as
the transmit injection frequency for the ESCORT IC.
Reference
Oscillator
-TCXO–
16.8MHz
RF Section
DOIF
FINIFPOS
Divider
300KHz
OSC_IN
Dual Synthesizer (U1501)
SPI-bus
219.3MHz
LPF
OSC
Second LO
LPF
OSC
Main VCO
LOIN
XTALBASE
CPGITR
WPIC
PRSCIN
Buffer
To RX Mixer
489.65 – 539.65MH
TETRA_RX_LO
TETRA_TX_LO
TX_SOURCE
z
To ESCORT
486.88 – 550.94MHz
Main Synthesizer
VCOCT
Buffer
LPF
OSC
TX VCO
ESCORT
(:41/32)
SPI-bus
SPI-bus
FREQA
FREQB
To TX-LO line-up
380 – 430MHz
I/V-
Converter
IUP
IDOWN
TX Synthesizer
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