Instrument Design and Functional Description R&S FSH
1145.5973.82 3.4 E-11
Tracking generator (Model 1145.5850.13/23/26 only)
The LO frequency of the 1st mixer is routed via isolation amplifiers to the TG mixer. The other input of
the mixer is a fixed frequency of 4031.25 MHz generated with a VCO locked to the TCXO frequency.
The resulting IF signal is routed to the generator output connector.
RF/IF control
The microcontroller available on the mainboard controls the RF/IF setting by programming registers via
an internal serial bus.
For calibration purposes the level correction values are stored in an EEPROM. This EEPROM also
contains module-specific information.
The temperature of the module is continuously measured, and the measured levels will be compensated
for drift if the temperature change is too great.
Mainboard
The mainboard is a combination of the power supply and the functions controlled by a dedicated RISC
controller (ARM 720).
Power and battery management
The ON/OFF key is de-bounced with the real-time clock in the controller. The ON/OFF function is
completely software controlled. This implies that the controller must be operational in order for the the
instrument to be switched ON. The GP-clock (50 MHz) is derived from the RF/IF board, thus requiring
that this board be present. This frequency will always be present if the power adapter is connected or
the instrument is in the ON state.
If the instrument is in the OFF state and the power supply is connected, the GP will control the charging
function of the battery depending on the battery condition. The maximum charging current is 1000 mA,
which drops to a trickle charge of about 100 mA if the battery is fully loaded. To prevent damage to the
battery, the charging stops if the battery temperature reaches H 0°C or > 45°C. In the OFF state, the
charging current is approximately 90 mA.
This power supply and battery management arrangement uses a dedicated IC. The instrument can be
switched ON only if the battery is in operating condition. Thus, if the battery is completely empty, the
instrument cannot be switched ON until the charging current has re-loaded the battery, which takes
several minutes.
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