Performance Measurements of 8-Gsps 1-bit ADCs Developed for Wideband Radio Astronomical Observations

8-Gsps 1-bit Analog-to-Digital Converters (ADCs) were newly developed toward the realization of wideband observations. The development of wideband ADCs is one of the most essential developments for the radio interferometer. To evaluate its performance in interferometric observations, the time (phase) stability and frequency response were measured with a noise source and a signal generator. The results of these measurements show that the developed ADCs can achieve a jitter time of less than 0.05 ps at a time interval of 1second, a passband frequency response with a slope of less than 0.73 dBGHz $^{-1}$ and a ripple of less than 1.8 dB, and an aperture time of less than 20 ps. The details of the developed ADC design, the measurement methods, and the results of these measurements are presented in this paper.