User's Manual

THEORY OF OPERATION
POWER AMPLIFIER ASSEMBLY
Driver Amplifier
The driver amplifier section provides the following function.
* Amplifies the output signal of the synthesizer.
* Matches the low impedance of the power amplifier.
* Provides some attenuation of harmonics.
Power Amplifier
The final power amplifier further amplifies this signal to the
specified output level.
Low Pass Filter
The low pass filter provides the following functions:
* Attenuates harmonics by approximately 50 dBm.
* Matches the final power amplifier to 50 Ohms.
Power Supply
The power supply section provides a means of switching DC power
to the final stage of the Power amplifier.
SYNTHESIZER LO ASSEMBLY
Crystal Oscillator
A fundamental frequency crystal oscillator is operated in a
Colpitts temperature-compensated circuit to give a stability of (2.5
PPM over the operating temperature range. The 12.8 MHz output of the
TCVCXO drives the PLL chip. The PLL chip divides this frequency, to
establish a reference frequency. This frequency is the reference
(frequency) for phase comparison used internally in the chip as well as
providing the channel spacing. The low frequency component of the
modulating signal is used to modulate of the TCVCXO, for improved DC
response.
Voltage controlled Oscillator "VCO"