Rohde & Schwarz ZVB 14, Service Manual

Page: 81 / 198

R&S ZVB Instrument Construction and Function Description
1145.1078.82 3.13 E-4
Network controller
The network controller comprises two boards, the netcon analog and the netcon digital which are
screwed together to form a single unit. The boards are four-channel – in other words, one network
controller is required for two ports (2 measurement ch 2 reference channels). After A/D
conversion, the network controller performs high-speed digital processing on the IF signals from the
reflectometers.
Netcon analog
The netcon analog board is a 4-channel IF amplifier and one 14-bit A/D converter per channel. The
transmission bandwidth is 13 MHz to 26 MHz. A dither generator is used to linearize the A/D-converter
characteristic. The board also accommodates a temperature sensor which is only used for general
temperature checks and not to correct measurement results.
Netcon digital
The netcon digital board further processes the digitized raw data from the netcon analog board. Speed
considerations mean that digital signal processing is performed in an ASIC which has a clock frequency
of 80 MHz.
The main functions on the board are:
•
Mixing to the baseband
•
Filter with bandwidths from 1 Hz to 100 kHz in 1/3/5 sequence
•
Detectors, PCI interface
•
Setting and routine control
The current measured value (sample), the average, the RMS and the Max can be recorded
simultaneously and passed on to the main processor via the PCI-bus. The connection to the PCI-bus is
made via the PCINT-FPGA. A further FPGA "FCON" contains the central section of the procedure
control from measurement point to measurement point and the trigger control. This FPGA is configured
by the main processor.
The A/D converters for ext. DC measurements are also accommodated on the netcon digital board.