Harris DiamondCD Series, Техническое руководство

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4-16 888-2463-001 3/6/08
WARNING: Disconnect primary power prior to servicing.
Diamond Series™
Section 4 Theory of Operation
As AGC voltage from the Driver Controller is applied to the PIN diodes, their
resistance goes from high to low and the overall termination of T2 is lowered from it’s
nominal 50 ohms. This reduces the attenuation between the hybrids input (6) and output
(3) ports.
As a result of varying the voltage on the PIN diodes, the amplitude of the signal at the
output of T2 may be varied with respect to the input signal applied. The hybrid output
goes through a temperature controlled attenuator and is applied to amplifier stage Q1.
4.6.3.2 Driver Pallet
The PA Pallet provides the remainder of the RF gain for the Driver. The power supply
and bias control come from the Driver Control board.
The Driver Module is based around the RF Pallet design used in the PA module. The
pallet utilizes two push-pull RF amplifiers. The push-pull amplifiers can be biased for
class A or class AB operation depending on application.
4.6.3.3 Driver Controller
The Driver Controller board handles the closed loop bias regulation for the RF Preamp,
RF Pallet and AGC function for the Driver chain. Circuit monitoring, fault reporting
and remote control interface are on this board. On-board regulators power the
Controller circuits.
Most of the other sub-assemblies in the Driver module interface into this Control Board.
•
The PA Pallet 28 volt DC current is monitored at J3-1. The PA Pallet gate voltage is
controlled to maintain the desired PA bias current at J2-1 and J2-2. A sample of the
RF output signal of the driver is connected to a detection circuit at J6.
•
The Preamp 28 volt DC current is monitored on the Driver Controller board at J3-2.
The gate voltage is provided to maintain the desired preamp bias current at J2-4.
Attenuator control voltage is provided (at J2-5) to maintain the desired gain out of
the Driver. The input RF sample is connected to the detector circuit at J5.
•
Thermistors on the heat sinks monitor the temperature and are connected at J4.
•
The Rear Panel has connections at J1 for the heat sink temperature sample output,
current sample, RF output power sample, remote ON/OFF control and fault alarms.