Rohde & Schwarz R&S SMU200A, Руководство по обслуживанию

Страница: 133 / 294

Instrument Design and Function Description R&S SMU200A
1007.9845.82 3.6 E-6
IQ Output Module 6GHz IQOP6
IQ Output Module 6 GHz doubles the output frequency of module Standard Synthesis and provides the
output power in the frequency range 3 to 6 GHz.
Doubler, Filter Bank, CW Path
The RF signal provided by module Standard Synthesis is either connected through to output SYNRFE
or is feed into the doubler and then into a switchable filter assembly. The filter assembly consists of two
RF switches at the input and output and of three parallel branches with band pass filters and
subsequent low pass filters. The output signal of the filter assembly is amplified and supplied to output
SYNRFE or switched through (CW Path). The RF level at this point is detected and kept constant using
a control loop. The output section of the CW Path switch couples in the modulated signal from IQOP3, if
modulation is switched on.
Pulse, Level Attenuation, Level Control
A switch-selected low pass filter suppresses the harmonics of the output frequency at frequencies <
4400 MHz (not shown in the block diagram). A switched attenuator element attenuates the RF level
relative in steps of 0 dB, 20 dB or 40 dB for use with digital modulation. In a fourth position the control
element attenuates the signal by 60 dB and is used as a part of the pulse modulators off state
attenuation. The pulse modulator is completed by two GaAs switches.
Level Control is done by four blocks of PIN diode control elements. The control voltage from IQOP3 is
converted into a exponentially related current.
Power Amplifier
A Wilkonson Power Divider supplies the RF signal for two identical power amplifiers which are thermally
coupled.
Level Detector
A power amplifier supplies the signal for the level detector via a digitally controlled attenuator pad. The
output voltage is provided at connector X 286 UDET. The detector voltage is used for level control on
module IQOP3/LCM. The full-wave rectifier and the instrument amplifier are kept at a constant
temperature by temperature control.
The attenuator pad is set by the firmware to provide the optimum RF power (which depends on the
modulation of the RF signal) for the detector diodes.
Output Switch
The RF signal for connector X289 OPU6RF is either supplied by the 6 GHz power output stage or from
connector X287 OPU3RF in the frequency range f <= 3 GHz.