Artificial calibration source for ALMA radio interferometer

The ALMA (Atacama Large Millimeter/submillimeter Array) radio interferometer has some di erent types ofantennas which have a variation of gain and leakages across the primary beam of an individual antenna. Wehave been developing an arti cial calibration source which is used for compensation of individual di erence ofantennas. In a high-frequency antenna, using astronomical sources to do calibration measurement would beextremely time consuming, whereas with the arti cial calibration source becomes a realistic possibility. Photonictechniques are considered to be superior to conventional techniques based on electronic devices in terms of widebandwidth and high-frequency signals. Conversion from an optical signal to a millimeter/sub-millimeter wavesignal is done by a photo-mixer.Keywords: ALMA, Calibration source, Photonic, millimeter-wave, sub-millimeter-wave 1. INTRODUCTION The ALMA (Atacama Large Millimeter/sub-millimeter Array) is a high-frequency radio interferometer, whichconsists 54 units of four types of 12-m antenna and 12 units of 7-m antenna. Each antenna has 10 Band-receiversand the highest receiving frequency reaches 950 GHz.