Evaluation of dynamic range for an HTS sigma-delta modulator with 100-GHz sampling

Circuit simulations were used to study the capability of a high-temperature superconducting (HTS) sigma-delta modulator using interface-engineered-Josephson junctions (IEJ's). The dynamic range was calculated while varying the temperature (T) and input-signal frequency (f(0)), and in the resultant power spectra, correct noise shaping (6 dB/oct) was found. Investigation of the dynamic range in terms of effective number of bits (ENOB) showed that ENOB was 6.7 for f(0) < 200 MHz and T < 40 K. At higher input-signal frequencies, i.e., 400 MHz < f(0) < 1 GHz, ENOB was determined to be in the range 3.2 < ENOB < 5.1 for temperatures 4.2 K < T < 77 K. From these results, the dependency of ENOB on temperature was estimated to be -0.03 bit/K for T < 40 K and -0.01 bit/K for T > 40 K.