Technical Manual

Controller Board
Appendix A - 700/800 MHz Circuit Descriptions
A-13
ATLAS 4500 Multimode Station Technical Manual July 2021
A.4.2.2 Exciter Interface
The Exciter interface has 30 pins. The Exciter interface provides ~13.8 V at ~0.6 A.
The interface includes:
• Synth – 4 x Lines are provided for 4 VCO controls, 3 x synth frequency setting
lines, lock alarm.
• I2C bus for exciter serial flash and FPGA ARM communication from the
Controller
• TXVCO volts monitor line. Exciter PTT line from the Controller,
• The main data stream using 3 x I2S data communication lines from DSP, 2 Serial
data lines from the Controller board for diagnostic use.
• 1 pps line to FPGA for similcast.
• FPGA PTT, FPGA TP G line, FPGA TP H line (initially used).
• The Controller can sense the presence of external 10 MHz reference (>~0 dBm
0.5 Vpp) using Ex ref line. The Controller can select External reference using
Ext osc sw line. This is done by software control to allow correct handover.
A.4.2.3 RX Interface
There are RX interfaces for 2 receivers. This allows a second diversity RX option.
The RX connector is a 30-pin connector. Most lines are common for both. This
includes 12-V and 3.3-V supplies, I2C bus for the serial flash used for synthesizer
band selection and PLL gain.
The Controller sets the channel frequency through the common PLLDAT and
PLLCLK and RX1 EN and RX2 EN lines. Each of the 2 VCO bands is selected by
means of 2 VCO band lines. Each RX VCO control voltage can be monitored on
each RX1VCO and RX2VCO line.
A.4.2.4 DSP Interface
The DSP overall controls the base station.
The DSP control serial data (RS232) communication is sent to the Controller using
a protocol. This controls modulation mode, channel frequency, power etc. The
Controller then sends I2C to the Exciter and logic for PTT, sets PA power etc.