Rohde & Schwarz ZVB 14, Service Manual

Page: 86 / 198

Instrument Construction and Function Description R&S ZVB
1145.1078.82 3.18 E-4
LO divider
The LO signal from the synthesizer is distributed via the LO-divider board between the receiver boards
associated with the reflectometers that have been installed. A maximum of four reflectometers can be
supplied with the LO signal in this way. The divider comprises a resistive power divider and a buffer
amplifier in each of the four output branches. The buffer amplifiers are used to compensate for the
power divider loss and to provide decoupling between the reflectometers (crosstalk).
In newer instruments the LO-divider is integrated on the synthesizer board (see
Synthesizers ).
Front unit
The front unit comprises a mounting plate on which the LCD, the flexible switch board and key pad, and
the tachogenerator are accommodated.
The front module controller is mounted in the controller tray in the instrument frame.
LC display
All results and setting information the user requires is displayed on the colour LCD.
The resolution of the LCD is 800 x 600 pixels (SVGA).
The display has an integral cold-cathode tube to provide illumination. The high voltage that is required is
provided by a dedicated DC/AC converter. The converter is mounted on the mounting plate next to the
display and connected to both the display and the controller board via a cable.
Keyboard
The keyboard comprises a flexible switch board and a key pad. They make contact whenever a rubber key
is pressed. The two LEDs for the status display associated with the Standby/On key (yellow for
standby/green for on) are also accommodated on the key pad.
Key detection and LED control are performed via a foil cable connection on the controller board. They are
controlled by means of a matrix method implemented by a special microprocessor on the controller board;
the two LEDs are controlled accordingly. When the instrument is turned off at the mains switch, the
microprocessor saves the status of the Standby/On key.
Front module controller
The front module controller accommodates all the components that are required on one board - for example,
the processor, memory chips (SIMMs), I/O chips (ISA bus), the lithium battery, IEC/IEEE bus controller, two serial
interfaces (COM1/2), a parallel interface (LPT), LCD graphics controller, external VGA-monitor graphics
interface (Monitor) and a connector for an external keyboard (keyboard PS/2). Also integrated on the
controller board are a floppy controller for an external disk drive and an IDE hard-drive controller.
In the case of the FMR6, the LAN interface is also integrated on the controller board.
Hard disk
The hard disk is screwed to the rear of the tray for the front module controller with a holder and
connected to the board with a flat cable.