Like many companies, until Peralex Electronics began designing high-speed differential serial links, we didn't worry too much about signal integrity (SI). We used a good set of rules of thumb, coupled with a good deal of experience and manual calculations.
This seemed to make all the products work, although we knew that we might be spending extra money and time over-designing so that every circuit worked.
Incorporation of high-speed serial links into many of our products has changed that design "methodology" into something much more formal--and more reliable than rules of thumb.
Military Electronics Requirements
Peralex produces high-performance wideband radio receivers, analog-to-digital converter boards, DSP-based processor boards and signal processing and analysis software to drive this hardware. Together with products from partner companies, these are combined to create wideband radio spectrum surveillance, direction finding and signal analysis equipment.
Other products include sonar signal processing hardware and software for use in mining, prospecting and other applications and audio signal processing systems.
Despite the wide array of products, they share one thing in common: They must operate in noisy environments and be as close to 100% reliable in those conditions as possible. Often, the environments are not just noise, but are filled with intentionally-generated noise, specifically designed to purposefully interfere, distort and overwhelm the signals that are of interest. Many of our products find their way into military applications and become the brunt of electronic warfare and intense EMI.
There are many tactics used to eliminate interference and isolate the signal of interest. These include shielding, of course, but use of state-of-the-art digital signal processing and filtering is key in making the products work.
As data rates have increased at the same time that operating voltages have decreased, the problem of keeping signals clean has multiplied. Now, with high-speed serial links dominating designs, those "rules of thumb," mentioned above simply cannot produce the designs required for 100% reliability.