As High Speed Digital (HSD) rates are increasing, there are more electrical performance properties related to RF technology which need to be considered by the HSD designer. As a basic comparison, RF technology is focused on frequency domain and HSD technology is focused on time domain. Some electrical performance concerns in frequency domain can impact the time domain performance of HSD signals and some of these concerns will not. However the larger concern for the potential impact is likely related to the increase in channel speeds of 56Gbps and above
The clock signal used in HSD to generate a digital pulse train, is basically a composite of multiple RF waves which include some signal processing. The lowest frequency wave is the Nyquist frequency and the other waves that make up the building blocks for the clock signal are 3rd, 5th and 7th harmonics. The actual HSD processing nowadays is more complicated, but these basic relationships will be explored in this paper when comparing electrical performance of RF circuits and HSD circuits at high frequencies and rates. Comparisons will be made with single ended and differential pair circuits at frequencies up to 110 GHz and HSD rates up to 112 Gbps.