Spread spectrum data transfer from dewar to dewar at 2 gigachips per second

Spread spectrum data modulation, transmission, and demodulation has been demonstrated between SFQ chips in separate dewars. The baseband demonstration consisted of modulating (encoding) data with a spreading code, transmitting the coded data to a Receiver and demodulating (decoding) the data using an identical spreading code. The Transmitter code was produced by a 2 GHz, 4-bit SFQ pseudorandom sequence generator creating a 15-chip spreading code, which modulated a ~133 MHz data source. This data was output by a 10× superconducting latch providing ~8 mV of AC drive. This signal was fed through 50-Ω coaxial cable to a SFQ Receiver chip in a separate dewar. No amplification of the AC signal between the dewars was needed, however, a slight DC bias was added to the signal as a flux bias for the input SQUID on the Receiver. The Receiver chip consisted of an identical SFQ pseudorandom sequence generator and a data demodulation gate. Demodulating the received data with the code generator produced a replica of the data signal in RZ form. Both time forward and time reversed codes for the spreading/despreading sequence were created