Gigabit Digital Filter Bank: Digital Backend Subsystem in the VERA Data-Acquisition System

Abstract

The VERA terminal is a new data-acquisition system developed for the VERA project, which is a project to construct a new Japanese VLBI array dedicated to make a 3-D map of our Milky Way Galaxy in terms of highprecision astrometry. New technology, a gigabit digital filter, was introduced in the development. The importance and advantages of a digital filter for radio astronomy have been studied as follows: (1) the digital filter can realize a variety of observation modes and maintain compatibility with different data-acquisition systems (Kiuchi et al. 1997 and Iguchi et al. 2000a), (2) the folding noise occurring in the sampling process can be reduced by combination with a higher-order sampling technique (Iguchi, Kawaguchi 2002), (3) and an ideal sharp cutoff bandedge and a flat amplitude/phase responses are approached by using a large number of taps available to use LSI of a large number of logic cells (Iguchi et al. 2000a). We developed the custom Finite Impulse Response filter chips and manufactured the Gigabit Digital Filter Banks (GDFBs) as a digital backend subsystem in the VERA terminal. In this paper, the design and development of the GDFB are presented in detail, and the performances and demonstrations of the developed GDFB are shown.

Vlbi Observation of Microquasar Cyg X-3 During an X-Ray State Transition From Soft to Hard in the 2007 May-June Flare

“…The received signals were sampled with 2 bit quantization and filtered to 16 MHz bandwidth using VERA digital filter bank (Iguchi et al 2005 (Kim et al 2013), separated by 2.…”

Distance to VY Canis Majoris with VERA

“…Left-handed circularly polarized signals were sampled with 2-bit quantization and filtered with the VERA digital filter unit (Iguchi et al 2005). The data were recorded onto magnetic tapes at a rate of 1024 Mbps, providing a total bandwidth of 256 MHz which consists of 16 × 16 MHz IF channels.…”

Amplitude Correction Factors of Korean Vlbi Network Observations

“…The quantization loss in digitizing analog signals has been theoretically analyzed (e.g., Thompson et al 2001), and the digital loss in re-quantizing the digitized signals has been numerically investigated by Iguchi et al (2005). The quantization loss is known to be 0.88 for the four-level (2-bit) quantization and the accumulated digital loss was shown to be 0.81 (= 0.88 × 0.92) in four-level re-quantization of the fourlevel quantized signals.…”