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60 The PCB Design Magazine • October 2016 When the terms high-speed and high-fre- quency are mentioned, people think they de- scribe the same issue. But in reality, they can be two very different matters. The term high- speed generally refers to digital technology which transfers data at very high rates. But the term high-frequency is typically related to radio frequency (RF), which involves analog signals moving energy at high frequencies. An easy way to think of the two technolo- gies is that one is related to time domain and the other is frequency domain. In other words, high-speed digital (HSD) applications have con- cerns with time related items such as rise time of the pulse which defines the 0's and 1's of the digital information. The high frequency appli- cations are interested in how an electromag- netic wave responds at a certain frequency or a range (band) of frequencies. Many times, charts which describe the different technologies will be related to time for HSD and frequency for RF high-frequency applications. There is a fundamental relationship be- tween HSD and RF technology. The pulses used for digital information transfer are generated by RF waveforms. Basically, a sine wave can be thought of as a RF waveform, and when several sine waves, which are at different frequencies, are combined, they can form a square wave. The square wave is used for the pulse genera- tion of the digital signals. As a simple example, a digital pulse speed (clock speed) that is 2 GB/s is formed by RF signals at frequencies of approx- imately 1 GHz, 3 GHz, 5 GHz, 7 GHz, etc. In the order of frequencies given they are: the fun- damental frequency (1 GHz), the 3 rd harmonic by John Coonrod ROGERS CORPORATION The Blending of High-Speed Digital and High-Frequency RF LIGHTNING SPEED LAMINATES

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