Bit Error Rate Measurements for GHz Code Generator ... - CiteSeerX

Bit Error Rate Measurements for GHz Code Generator Circuits Eric J. Dean, Paul D. Dresselhaus, John X. Przybysz, Andrew H. Miklich, and A. Hodge Worsham Northrop Grumman Science and Technology Center, 1350 Beulah Rd., Pittsburgh, PA 15235

Stas V. Polonsky RSFQ Consulting Inc., Stony Brook, NY USA Abstract—A new method of analyzing bit error rates (BERs) for SFQ circuits and their outputs at GHz speeds will be presented. This method was used to test four- and six-bit pseudorandom code generators. The code generators were operated in free-run mode, i.e., without a synchronization (Reset) pulse. This enabled us to conduct BER testing to much lower levels than when the code generator is operated in Reset mode. The SFQ circuit output was amplified with a superconducting output latch to give voltage levels suitable for display on a sampling scope. The GHz output data was analyzed by external computer software; this permitted extended tests without user supervision. With the code generators operating in free-run mode, they routinely gave bit error rates (BERs) in the 10-11 range; the best BER recorded was 1.1*10-13 (2 errors in ~2.5 hours) at 2 GHz. We have successfully tested these code generators at frequencies in excess of 3.5 GHz with BERs in the 10-10 range as well.

I. INTRODUCTION This decade has seen an enormous increase in requirements for data throughput in both military and commercial communication systems. This need for increased bandwidth has been paced by the increasing desire for wireless communications systems by large numbers of users. An effective method for operating wireless systems is through the use of spread spectrum communications [1]. Many commercial spread spectrum systems are currently on the market. However, data throughput is limited to < 100 kbps. We have successfully tested, in SFQ technology, code generator circuits that could be part of a 30-130 Mbps spread spectrum communications link. A spread spectrum communications system requires a code generator to encode the data being transmitted. The code generator must have a low bit error rate (BER) to avoid damaging the information being transmitted. Assuming that a 53 byte ATM packet is to be spread with a 63 bit code sequence and that no more than 1 in 103 ATM packets are corrupted, that requires a BER of