(No.RA075<Rev.001>)1-21
2.4.5 PLL Frequency Synthesizer
2.4.5.1
TCXO (X700)
TCXO (X700) generates a reference frequency of 19.2MHz for the PLL frequency synthesizer. This reference signal is buffered by
Q700 and IC703. And it is distributed to PLL (IC100), IF IC (IC600), and MPU/DSP (IC706).
The frequency adjustment is achieved by adjusting a D/A converter (IC715) output in the voltage of the control terminal of TCXO. The
resolution of adjusting frequency is approximately 8Hz.
2.4.5.2
VCO
There are VCO-A and VCO-B, which generate 8 times the transmit frequency and first local frequency. The VCO output is divided by
8 with a prescaler.
The VCO-B (Q107) generates part of the first local signal for the receiver and the carrier for the transmitter. The VCO oscillation
frequency range is 312 to 401.6MHz. The transmit frequency range is 39 to 50MHz. The 1st local signal frequency range is 49.7 to
50.195MHz.
The VCO-A (Q105) generates the 1st local signal for the receiver.
VCO oscillation frequency range is 230.4 to 314.4MHz. The 1st local signal frequency range is 28.8 to 39.3MHz.
The VCO oscillation frequency is determined by voltage control terminals "CV" and "ASSIST".
The voltage control terminal "CV" is controlled by PLL IC (IC100). The voltage control terminal "ASSIST" is controlled by the control
voltage from D/A converter (IC715).
For the modulation input terminal, "VCO_MOD" of VCO-B, the output frequency changes according to the applied voltage. This is used
to modulate the VCO output.
2.4.5.3
PLL IC
PLL IC (IC100) compares a difference in phases of the VCO oscillation signal and the TCXO reference frequency. And it returns the
difference voltage to the VCO CV terminal and realizes the "Phase Locked Loop". This allows the VCO oscillation frequency to
accurately match (lock) the desired frequency.
When the frequency is controlled by the PLL IC (IC100), the frequency convergence time increases as the frequency difference
increases when the set frequency is changed. To supplement this, the MPU/DSP (IC706) is used before control by the PLL IC to bring
the VCO oscillation frequency close to the desired frequency. As a result, the VCO CV voltage does not change and is always stable
at approximately 2.5V.
The modulation input terminal, "PLL_MOD" of the PLL IC (IC100), is used to modulate the VCO output. The modulation data is
generated by the IC706.
The desired frequency is set for the PLL IC by the MPU/DSP (IC706) through the 3-line "SDO1", "P_SCK1", "/PCS_RF" serial bus for
PLL. MPU/DSP (IC706) monitors through the "PLD", whether the PLL IC (IC100) is locked or not. If the VCO does not lock to desired
frequency (unlock), the "PLD" logic is low.
2.4.6 Control Circuit
The control circuit consists of MPU/DSP (IC706) and its peripheral circuits. MPU/DSP (IC706) mainly performs the following;
(1) Switching between transmission and reception by PTT signal input.
(2) Reading system, zone, frequency, and program data from the memory circuit.
(3) Sending frequency program data to the PLL.
(4) Controlling the audio mute circuit by decode data input.
2.4.6.1
MPU/DSP
The MPU/DSP (IC706) is 32bit RISC processor and fixed floating-Point VLIW DSP Fixed/Floating-Point VLIW DSP, equipped with
peripheral function.
This MPU/DSP operates at 288MHz (MAX) clock and 3.3V/1.8V/1.2V DC. Controls the flash memory, Mobile DDR, the receive circuit,
the transmitter circuit, the control circuit, and the display circuit and transfers data to or from an external device.
2.4.6.2
Memory Circuit
Memory circuit consists of the MPU/DSP, the Mobile DDR (IC702), and the flash memory (IC701). The flash memory has capacity of
512Mbit that contains the transceiver control program for the MPU/DSP (IC706) and stores the data. It also stores the data for
transceiver channels and operating parameter that are written by the FPU. This program can be easily written from external devices.
The Mobile DDR has capacity of 512Mbit. The MPU/DSP copies the program to the Mobile DDR from Flash memory.
Flash memory
Note:
The flash memory stores the data that is written by the FPU (KPG-D1/D1N), tuning data (Deviation, Squelch, etc.), and firmware
program (User mode, Test mode, Tuning mode, etc.).
Mobile DDR
Note:
Mobile DDR is used as a work area of the MPU/DSP (IC706).
