Simply put, delay lines are used to introduce a calculated delay into an RF signal transmission. These delays are necessary for certain systems to function properly, as these signals can often be transmitted much more quickly than systems can handle. For example, the military uses Surface Acoustic Wave (SAW) delay lines for radar calibration and jamming. The delay lines allow the radar system to effectively process and synchronize signals that are traveling at the speed of light. Without the delays, the radar wouldn’t be able to interpret all of the signals it is receiving.
The length of delay, substrate used, and the type of delay line material are all factors that come into play when choosing a delay line solution. Analog Bulk Acoustic Wave (BAW) delay lines are often used for target generation, radar calibration, and EW (Electronic Warfare). The BAW delay lines that calibrate radar and display systems are made out of quartz or glass that can be heated for increased stability, which is often a necessity when dealing with high reliability applications.
While digital delay lines have grown in popularity, analog delay lines of all types are typically much more reliable and offer many other advantages over their digital counterparts. Cost, size, and weight can all be significantly lower with analog delay lines, while still offering higher MTBF (Mean Time Before Failure) rates and reliability. Here’s a side-by-side comparison showing how the two types of delay lines stack up, and why analog always comes out on top.