User's Manual

© RF Technology 2007
The Interface board accepts both TTL PTT input and E/M signaling, the TTL PTT is
buffered by Q4,Q5, E/M signal is isolated by Opto-coupler U3 to system I/O level. The
output of the RISC I/O logic is buffered by U1,Q1-Q3 for interfacing the external logic.
The solid-state relay Opto-coupler is used to isolate the system I/O from E/M signal.
A dual retriggerable monostable multivibrator (U5) in the circuit is functioned as a IRQ
generator, it senses the changes of the Input logic and sends a narrow pulse to the
RISC processor for trigging the processing IRQ.
U31 is a USB to RS232 bridge which transfers the USB data between the front panel
connector and the system serial bus. U9 is an transceiver which converts RS232 +/-15
logic from the rear panel to serial bus level. U30 is a bus switch to select one of above
passing through to the RSIC processor.
Header (H4) is used only for emergency system booting purpose, do not assert jumper
into this header.
2.3.2.3 Clock generator
the 12.8MHz TCXO (X1) output is buffered (by U26) and divided by 4 (U29) to provides
PLL reference frequency for exciter and receiver. The frequency doubler double
12.8MHz frequency to 25.6MHz to provide system clock for digital IF receiver.
2.3.2.4 Voltage regulators
There are nine voltage sources generated by the voltage regulator
VTX – +12.5V DC for TX module
VRX – +12.0V DC for RX module
D3V3 – +3.3V DC for Processor (Master) board and 3V TTL logic
A3V – +3.15V DC for analog 3V rail
+12V – +12.0VDC for analog circuits
+5V – +5V DC for TCXO and 5V TTL logic
+1V8 – +1.8V DC for Flash core supply on the Processor (Master) board
-20V – -20.0V DC for TX and RX VCO bias setting
-12V – -12.0VDC for analog circuits
The input power supply voltage is 13.8VDC, LDO (U19, U22) provides 12.5V (Imax =
1.5A) and 12V DC (Imax = 800mA) for TX and RX module. Switch mode DC-DC
converter (U20) generates digital 3.3V DC rail (Imax=2A) for the Processor board and
Interface board, then regulated to 3.15V analog DC rail by LDO (U21) for 3V analog
circuits in the transceiver.
The DC-DC converter (U23) provides –20V negative supply voltage for VCO bias
amplifier (U4). Voltage regulator (U24) generates –12V DC supply analog circuits of the
interface board.
2.3.3 RF modules