AIS1 VHF Indirect Frequency Synthesiser Module

Indirect VHF synthesiser top view

This is a generic Giastar synthesiser module intended for use as a local oscillator in satcomms IF processing equipment and ATE systems. It is a single-loop indirect synthesiser that meets, among others, the Inmarsat earth station (LES) spurious and phase noise specifications.

It is designed to simplify design and construction of one-off systems by providing a simple, versatile serial control interface and various additional functions aimed at system integrators who do not want to worry about the internals.

The synthesiser may be controlled either from a PC or other user-supplied equipment (the simple ASCII interface allows the use of almost any programming language or operating system, even the script language of a terminal emulator), or may be used with Giastar's MCU1 manual control unit.

Indirect VHF synthesiser reverse view

Features include:

ASCII serial interface, using a multi-drop variant of RS232 that allows a single PC serial port to control a number of Giastar modules.
Internal VCTCXO reference that may be phase-locked to an external reference. Automatically locks to 1, 5 or 10MHz references. As the external reference is not used directly, phase noise on the external reference does not affect the output phase noise.
Auto calibration function. When locked to an external reference, a calibrate command stores the reference loop control voltage and uses this to control the internal reference when the external reference fails or is removed.
Carrier enable/disable commands.
Built-in test functions. The output is disabled if an error is detected, providing fail-safe transmitter behaviour.
Non-volatile memory.
Frequency coverage, channel spacing etc to order within the range 10MHz to 200MHz.

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