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ALMA MEMO #424
Development of 4-Gsps 2-bit ADC with GaAs ICs for Radio Astronomy
Mahoko Okiura(The University of Tokyo / NRO), Satoru Iguchi(NAO), Sachiko K. Okumura(NRO), Munetake Momose(Ibaraki University), Kinfya Matsumoto(Kyushyu Toukai University), and Noriyuki Kawaguchi(NAO)
2002/05/17
Keywords: Analog to Digital converter
We developed two sets of the prototype of 4-Gsps 2-bit Analog to Digital converter (ADC) with GaAs IC for the realization of 4 GHz sampling in an ADC system of Atacama Large Millimeter / submillimeter Array (ALMA). This consists of three sets of 12-Gbps Decision Circuits and 12-Gbps Demulitiplexers, and has a capability of sampling in a bandwidth of 6 GHz. Toward the implementation of GaAs IC in the ADC system, we measured the sampling jitter of the ADC using the Ultra-Wide Band Correlator (UWBC) developed for the Nobeyama Millimeter Array (NMA). The measured Allan standard deviation of phase, corresponding to the stability of sampling timing is 2.3x10^-15 at 10 seconds, and the Allan standard deviation due to the Flicker-frequency noise is 0.8x10^-15. It is shown that the coherence loss successfully becomes 0.95 at coherence time of 86400 seconds (24 hours). The Alan standard deviation of sampling timing and its long-time stability are acceptable for the application of radio astronomical ADC system.
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Last modified: 2002-05-22
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