One of the greatest challenges facing designers of very high frequency receivers is accurately and quickly determining the strength of the incoming signal. Anyone who enjoys watching a TV show on their favorite streaming service knows the frustration of a nice, sharp picture suddenly getting patchy and distorted. This often occurs in the evening as more people sit down for the latest episode of “Tiger King” (my own guilty pleasure - don’t judge) and the system must feed signal to an increasing number of receivers. One might suggest cranking up the amount of data being fed through the system, which is analogous to opening the spigot so more water flows to a sprinkler. But eventually the need for all that data (or water, in our analogy) decreases as people go to bed or work. Keeping the system cranked to 11 all the time is a very inefficient waste of data and power consumption.
Mitigating this issue may sound simple; if demand is high the transmitter should be instructed to increase power or alter the format of the data to accommodate demand. When demand abates the transmitter can switch formats or save power by lowering its output. Sounds simple, sure, but implementing this solution requires the ability to accurately measure the power of the incoming signal independent of the precise format. To do this, a mathematical formula called Root Mean Square (RMS) must be applied. RMS is calculated by taking one cycle of a periodic waveform and squaring it, and then finding the square root of the area under the curve - we’ll skip the actual math. (You’re welcome.) RMS power detection is extremely hard to do at frequencies around 70 Gigahertz, where signals change 70 BILLION times every second. In fact, even at frequencies as “low” as 10 GHz (ten billion changes per second) reliable, accurate detection solutions have been lacking. Radio designers have tried using discrete (individual) and passive (not requiring external power) components such as diodes. Some work well up to high frequencies deep into the Gigahertz range but are unable to do the RMS calculation meaning the power measurement result changes with the signal format. Unacceptable inaccuracies then reduce the throughput and reach of the communication system.
ADI first attacked the accuracy problem with the LTC5596, an RMS Power Detector on a chip which accurately and reliably works up to 40 GHz. Recently, after going through a series of rigorous tests, the product was qualified for space applications such as next generation of satellites being launched for Internet, entertainment, and other data distribution needs. But the need for accuracy at even higher frequencies prompted the design and manufacture of the LTC5597, an RMS Power Detector on a chip for systems way up in the 70 GHz band. No other single-chip solution can handle the complex RMS calculations beyond 40GHz for applications such as high-frequency satellite receivers, point-to-point microwave systems used in cell phone networks, and signal generators for the testing of current 5G and future 6G cell phones.
For more information on ADI’s solution for accurate RMS power detection, visit the LTC5597 product page where you can also download the datasheet and order an evaluation board so you can see the future of RMS power detection for yourself.