We report results of the performance evaluation of a new hardware correlator in Korea, the Daejeon correlator, developed by the Korea Astronomy and Space Science Institute (KASI) and the National Astronomical Observatory of Japan (NAOJ). We conduct Very Long Baseline Interferometry (VLBI) observations at 22 GHz with the Korean VLBI Network (KVN) in Korea and the VLBI Exploration of Radio Astrometry (VERA) in Japan, and correlated the aquired data with the Daejeon correlator. For evaluating the performance of the new hardware correlator, we compare the correlation outputs from the Daejeon correlator for KVN observations with those from a software correlator, the Distributed FX (DiFX). We investigate the correlated flux densities and brightness distributions of extragalactic compact radio sources. The comparison of the two correlator outputs shows that they are consistent with each other within < 8%, which is comparable with the amplitude calibration uncertainties of KVN observations at 22 GHz. We also find that the 8% difference in flux density is caused mainly by (a) the difference in the way of fringe phase tracking between the DiFX software correlator and the Daejeon hardware correlator, and (b) an unusual pattern (a double-layer pattern) of the amplitude correlation output from the Daejeon correlator. The visibility amplitude loss by the double-layer pattern is as small as 3%. We conclude that the new hardware correlator produces reasonable correlation outputs for continuum observations, which are consistent with the outputs from the DiFX software correlator.

Abstract
1. INTRODUCTION
2. OBSERVATIONS AND DATA REDUCTION
    2.1. Observations Using KVN and VERA
    2.2. Correlation Using Daejeon Correlator and DiFX
    2.3. Post-Correlation Process Using AIPS and DIFMAP
3. RESULTS
    3.1. Visibility Comparison with DiFX
    3.2. Image Comparison with DiFX
4. DISCUSSION
    4.1. Double-Layer Patterns
    4.2. Fringe Tracking
5. CONCLUSIONS
REFERENCES

• Sang-Sung Lee(Korea Astronomy and Space Science Institute/Korea University of Science and Technology)
• Chung Sik Oh(Korea Astronomy and Space Science Institute)
• Duk-Gyoo Roh(Korea Astronomy and Space Science Institute)
• Se-Jin Oh(Korea Astronomy and Space Science Institute)
• Jongsoo Kim(Korea Astronomy and Space Science Institute/Korea University of Science and Technology)
• Jae-Hwan Yeom(Korea Astronomy and Space Science Institute)
• Hyo Ryoung Kim(Korea Astronomy and Space Science Institute)
• Dong-Gyu Jung(Korea Astronomy and Space Science Institute)
• Do-Young Byun(Korea Astronomy and Space Science Institute)
• Taehyun Jung(Korea Astronomy and Space Science Institute/Korea University of Science and Technology)
• Noriyuki Kawaguchi(Shanghai Observatory, Chinese Academy of Sciences)
• Katsunori M. Shibata(Mizusawa VLBI Observatory, National Astronomical Observatory of Japan)
• Kiyoaki Wajima(Korea Astronomy and Space Science Institute)