4. Technical Reports

4.1 Key Stone Project

Correlation Processing System --- Hardware (Hitoshi Kiuchi)

KSP correlator
In the multi-baseline correlation processing, all the output interface units are daisy-chain connected via GPIB and a timing control line. Therefore, the tape position data and the status data of all the data recorders can be exchanged via the output-interface units. The main replay system (the main output interface unit and the data recorder) and the sub replay system (the sub output interface unit and the data recorder) can be synchronized in one-bit steps. The delay adjustment is done by controlling the Track set ID and subsequent programmable shift registers (PSR). The signal (raw data) is unformatted instead of in the Mark-III format. We are developing an XF type VLBI correlation processor for the K-4 system by making use of a Field Programmable Gate Array. The outline of the correlator is;
(1) Automatic bit synchronization during multi-baseline processing,
(2) Network Filing System for storing correlated data,
(3) 2-bit sampled data processing capability,
(4) 16ch high speed (32 Mbps/channel) processing,
(5) Signal provided by VME back plane.
This correlator was specially designed for the Keystone Project, which is concerned with measuring crustal deformation in the Metropolitan area. The project utilizes 4 stations in the Metropolitan area, and each station has a new K-4 system and an 11 m antenna. Using this new correlator, we can improve the precision of the geodetic VLBI and also contribute to radio astronomy VLBI. A part of the multi-baseline correlation processor has been developed. And we are now checking its performance. We plan to produce a multi station (4 or 5) correlation processor and are also developing new software that will be compatible with our current software.

Figure 2. Block diagram of KSP correlator


Q: What is the number of lags in a correlation unit?
A: 32 lags.
Q: Why are 16 units necessary?
A: For applications other than the KSP.

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