K5/VSSP VLBI SYSTEM

K5/VSSP(*) and K5/VSSP32 are high-performance samplers dedicated to a geodetic VLBI system developed by the Kashima VLBI group of National Institute of Information and Communications Technology (NICT). K5/VSSP sampler is a PCI bus board mountable on a motherboard of standard PC and has a maximum sampling frequency of 16 MHz per channel. Any PC equipped with a K5/VSSP PCI-bus board can be a VLBI recorder, and the data transfer through the Internet is easily realized. K5/VSSP32 is a successor to the K5/VSSP, but a USB 2.0 is adopted as an interface with a host PC. Maximum sampling frequency per channel is increased up to 64 MHz. As both K5/VSSP and VSSP32 units has 4 channel analog inputs, 4 units can cover 16 channels which is sufficient number of channels in case of geodetic VLBI. Adoption of USB2.0 interface enables us to use a notebook or laptop PC as a host PC of the sampler. Thus K5/VSSP32 can be used for a not only a VLBI observation but also a general-purpose geophysical observation which requires precise time label.

Recently K5/VSSP64 became available to use. It is a scuceessor to the K5/VSSP32 and has a maximum sampling frequency of 128 MHz per channel. A USB 3.0 is adopted as an interface with a host PC.
（* VSSP: Versatile Scientific Sampling Processor)

K5/VSSP Sampler Board	K5/VSSP32 Sampler Unit	K5/VSSP64 Sampler Unit

Table 1. Comparison of characteristics

	K5/VSSP sampler board	K5/VSSP32 sampler unit	K5/VSSP64 sampler unit
Sampling frequency (MHz)	0.04, 0.1, 0.2, 0.5, 1, 2, 4, 8, 16	0.04, 0.1, 0.2, 0.5, 1, 2, 4, 8, 16, 32, 64	2, 4, 8, 16, 32, 64, 128
Built-in digital LPF (MHz)	----	2, 4, 8, 16, through	2, 4, 8, 16, 32,through
Analog Input range	-1V - +1V	-1V - +1V	-0.8V - +0.8V
Analog band width of AD converter	100 MHz	300 MHz	1250 MHz
AD resolution (# of bit)	1, 2, 4, 8	1, 2, 4, 8	1, 2, 4, 8
# of channel per board (unit)	1, 4	1, 4	1, 2, 4
Maximum data rate per board (unit)	64 Mbps	256 Mbps	1024 Mbps
DC offset adjust	NA	available from a host PC	available from a host PC
Reference signals	1PPS, 10MHz	1PPS, 10MHz or 5MHz	1PPS, 10MHz or 5MHz
Interface to PC	PCI bus	USB 2.0	USB 3.0