Extending Low-Cost Test Signal Synthesis to 40 Gbps

We recently demonstrated two methods for synthesizing 20-24 Gbps test signals using relatively low-cost (off-the-shelf) components [1,2,3]. In the present paper we apply a similar strategy for generating 40 Gbps signals. Our first attempt used the original XOR circuit to combine two 20 Gbps signals. While the internal logic succeeded in producing 40 Gbps, the XOR device output signal was bandwidth-limited and the result was not sufficient for most testing purposes. However, by substituting a newly-released 45 Gbps XOR gate [4], we were able to produce much better quality signals. This paper describes the logic used in this method, and shows the experimental results obtained at 40 Gbps.