2
ISOMET
1.
GENERAL
The RFA2120 combined Analog Driver and Power Amplifier is a fixed frequency RF power source
specifically designed to operate with Isomet acousto-optic devices such as the M1340 series. The
driver accepts
two
independent digital and analogue modulating signals and provides a double-
sideband amplitude modulated RF output to the acousto-optic modulator. A summary of the driver
specification is shown in the following table:
Model
Use With
Center Frequency
Output Power
RFA2120
M1340-aQ120-5
120MHz
12.0 Watts at 355nm
RFA2120
M1340-aQ120-7
120MHz
17.0 Watts at 355nm
Figure 2 is a functional block diagram of the driver. The center frequency of the driver is determined
by the free-running quartz-crystal oscillator at 120MHz. This frequency is accurate to within
±
25ppm and its stability is better than
±
25ppm; the oscillator is not temperature stabilized.
A high-frequency, diode ring modulator is used to amplitude-modulate the RF carrier. The single turn
potentiometer provides gain control for adjusting the maximum r-f power at the Driver output.
A solid state switch provides the Digital Modulation or RF Gating function. A TTL high level will gate
the RF ON. The MMIC r-f pre-amplifier stage isolates the low level modulation and control circuitry
from the power amplifier stage.
The rise and fall times for the amplifier from either modulation input is identical (approx 200nsec).
The video analog input level must not exceed 15 volts
The digital input level must not exceed 7 volts
The RF modulation functions are shown in Figure 3
