Guardian G25AMK005, Техническое руководство

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3-4 G U A R D I A N V H F 1 1 0 W M O B I L E
Mode Description
TX/RX (SR bit 7) Set in active transmit mode, front end TX/RX control
STD/SIDE (SR bit 8) Set to use radio antenna, reset to use accessory connector RF port
CTX (FPGA output) Set in active transmit mode to enable the RF power amplifier
3.2.3.2 Frequency Control
The frequency of operation in both transmit and receive is controlled by the H8 setting in the synthesizer through the
serial bus. To set the desired frequency, the appropriate TX or RX synthesizer enable S-R bit must be set, the serial
data loaded into the synthesizer chip, and the DAC2 output A synthesizer coarse tune set to the appropriate value for
the frequency according to the EEPROM calibration table. Synthesizer lock is monitored by the out-of-lock (OOL)
input. Once the synthesizer lock is achieved, the transmitter or receiver is enabled with the appropriate control bits
3.3VRX enable, CTX, and TX/RX. Economizing the synthesizer function is implemented by controlling the
3.3VTXS/RXS bits and by controlling the EM main divider enable bit in the synthesizer control word. If the
frequency is unchanged, the synthesizer serial data need not be reloaded when coming out of economize
.
3.2.3.3 12-Bit DAC
DACLDA, DACADCCLK, and DACDOUT control the 12-bit DAC for IFAGC, TXVCOMOD, REFOSCMOD,
and VATT.
3.2.3.4 Reference Oscillator Temperature Compensation
The H8 software constantly monitors the reference oscillator crystal temperature using the XTALMON line. The
temperature data is used to lookup the compensation factor in the transceiver’s EEPROM calibration table. This
compensation factor is written into the DSP, added as a dc offset reference oscillator modulation signal, and used as
a dc offset in receive mode.
3.2.3.5 Receiver Control
Setting 3.3VRXE enables the linear receiver chain. The DSP implements software AGC system to control the gain
of the linear receiver chain. The H8 controller monitors the actual received signal level by reading RSSI. At all
times during receive the RXVTF DAC2 output C must be set to the value in the EEPROM calibration table
corresponding to the receive frequency used. This makes the receiver’s front-end tunable filter centered on the
desired frequency. At all times in receive modes the second LO DAC2 line output B must be controlled using data
from the EEPROM calibration table and indexed with oscillator temperature data XTALMON. The temperature
compensates the second LO in the receiver chain.
3.2.3.6 Transmitter Control
The radio uses a complex H8 software-based algorithm to dynamically control the transmit power of the radio. The
inputs to the power control algorithm are: requested power level (0.1W, 0.5W, 1W, 2W, or 5W), PA calibration
data in the EEPROM, supply voltage BATMON (used for monitoring), transmit frequency, PA current, (used for
monitoring), and PA temperature (used for monitoring).
The power control algorithm takes these inputs and uses them to control the following outputs to provide a steady
RF power output with a clean rise and fall at switch on/off.
Output Description
PWRSET (DAC1 output A) Sets the power level in the power amplifier ALC loop
PABIAS1 (DAC1 output B) Adjusts the bias in the final driver stage
PABIAS2 (DAC1 output C) Adjusts the bias in the final driver stage
3.2.3.7 TX/RX Switching
The procedure needed to quickly switch the transceiver from receive to transmit and back again is to shut down the
current mode, lock the synthesizer in the new mode on the new frequency, and enable the transmitter or receiver, as
required.