New K-4 VLBI input interface which has multi-bit sampling capability, is under
development. Input interface corresponds to the formatter in Mark-III system. Fig.1
shows its block diagram. Sampling in 1, 2, 4 and 8 bits is possible. The number of
channel can be 1, 2, 4, 8 or 16. As the total bit rate is 256Mbps, the bandwidth of
each video channel depends on their combination, though video bandwidth wider 20MHz
is not easy to achieve. It is planned to have a complete version in 1993. The system
is to be used for VSOP (Space VLBI in Japan) and IRIS-P experiments.
2. K-4 Correlator
The K-4 data processor is not for routine process but for R&D experiments such as
multi-bit sampling, detection of milli-second pulsar timing. And it will be a test
version of the correlator for regular VLBI including IRIS-P. Test model of K-4
correlator is being developed by making use of LCA (FPGA produced by Xilinx Co.).
It is a simple one unit correlator but can process 2 bit sampling data.
Figure 1. New K-4 Input Interface with Multi-Bit Sampling.
