4.6 GHZ SFQ SHIFT REGISTER AND SFQ PSEUDORANDOM BIT SEQUENCE GENERATOR

Superconductive electronics can provide low power, GHz speed spread sp ectrum satellite communications. The key components to construct the s pread spectrum modem are an analog filter and a digital pseudorandom b it sequence generator. Various SFQ logic circuits are required to cons truct a code generator. These circuits include a shift register, a res et switch, and an XOR or XNOR. To make a 4 bit 15 sequence code genera tor, a four stage shift register with a fan-out of two on each stage w as designed. These circuits, fabricated with eight level Nb/AlOx/Nb Jo sephson junction integrated circuit process, showed correct operation at low speed digital tests. The low speed digital test was done by usi ng a ''catcher'' the combination of a read SQUID and a Josephson trans mission line (JTL) which were magnetically coupled to each other. High speed testing of the shift register used a latch amplifier, which amp lified an SFQ pulse to a latching output voltage of about 2 mV. This t est showed correct operation of the shift register, at speeds of up to 4.6 GHz.