4.1 - 16
MTP700 Portable Radio / Detailed Service Manual
TRANSCEIVER 400 MHz
Frequency Generating Section, Detailed Circuit Description
See Figure 4.1-8
This section describes the circuits that generate all the required frequencies for the
required transmitter and receiver functions. These circuits are described as follows:
•
TCXO REF. Oscillator.
•
Main VCO and Main Synthesizer.
•
Second LO VCO and Dual Synthesizer RF section.
•
Transmit PLL - TX VCO with the ESCORT Synthesizer IC.
Figure 4.1-8 Frequency Generation Section - Block Diagram
TCXO Reference Oscillator
The TCXO oscillator Y1301 is the reference frequency source for all the radio
synthesizers. The output of the oscillator is a 16.8 MHz stable temperature-compensated
reference clock. This oscillator’s centre frequency is adjustable by means of a PWM DAC
(256 steps) to warp the radio frequency in order to lock to the base station. This 16.8 MHz
signal from pin 3 of the TCXO is routed into the following devices:
1. To WPIC’s K6 XTALBASE pin via C1301. The signal is divided by 4 to produce the 4.2
MHz reference signal, which is used for the Main Synthesizer PLL.
2.
To LMX Dual Synthesizer’s OSCIN pin via C1505. The signal is divided to produce the
300 kHz reference signal for the second LO PLL.
The reference signal is also routed from WPIC’s pin F10 (16.8_MHz_CLK) to GCAP3
(and subsequently to RedCap2) to clock the digital circuits.
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
Содержание IMPRES Tetra MTP700
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