2
ISOMET
1.
GENERAL
The 750c series dual modulation Driver is a fixed frequency RF power source specifically designed for
use with Isomet acousto-optic modulators and Q-switches, operating at a fixed centre frequency. The
driver accepts two modulation signals; digital (On:Off) and an analogue (proportional control) voltage.
Examples of popular driver specifications are listed below:
Model
751c-2
: 40MHz, 3.0W output, +24Vdc supply
752c-4
: 80MHz, 4.1W output, +24Vdc supply
753c-2
: 110MHz, 2.0W output, +28Vdc supply
755c-6
: 200MHz, 6.5W output, +24Vdc supply
Figure 2 is a block diagram of 750c series driver. The center frequency of the driver is determined by
the free-running quartz-crystal oscillator. This frequency accuracy and stability are better than
25ppm; the oscillator is not temperature stabilized.
A high-frequency, diode ring mixer and RF analog switch are used to modulate the RF carrier
according to the signals applied to the
D-mod
(TTL) and
A-Mod
(analog) modulation inputs.
D-Mod
: A video input swing from < 0.6V (off) to > 2.7 volt(on) will result in 100% depth of
modulation.
The modulation input level must not exceed + 7 volts
A-Mod
: An input swing of 5 volt peak will result in 100% depth of amplitude modulation.
The video input level must not exceed
7 volts
Both modulation inputs are required
For high switching rates using both modulation inputs simultaneously, a timing offset adjustment may
be needed between the digital and analog signal sources due to different circuit latencies. (see
section 2)
The mixer output is applied to a MMIC pre-amplifier stage. This also serves to isolate the Oscillator
and Mixer from the final power amplifier stage. The driver output power level is set by the Power
adjust potentiometer at the input of this MMIC amplifier.
