RFID Asset Tags, Environmental Sensors and Frequencies

Posted by RF Code

As a CEO relatively new to the wireless industry (or, more specifically, the RFID asset tags and sensors and readers industry!), I thought it might be useful for our customers and partners if I were to blog a bit about the things that I've learned over the last six years. I think I'll start by making an analogy to the old saying in politics "it's about the economy stupid.” What I have learned in the wireless space is "it's about the frequency stupid." We live with the effect of physics on our lives daily but never have I been so clearly reminded of how important physics are to technology solutions than after I joined a company in the wireless sector. When you look at all the important issues around success or failure of a wireless solution, it is interesting to note that you can track all of it back down to one factor: frequency.

Let me explain without turning this blog entry into a dissertation. There are a couple of basic rules to think about when considering frequency. First, the higher the frequency the more energy is needed to transmit. When you apply this to a wireless battery powered solution, it is an inescapable fact that this means you will either need larger and larger batteries for longer and longer transmit periods, or more frequent battery changes. We chose to use 433 MHz because it is low frequency, and correspondingly has low power requirements for long battery life. Plus, lower power requirements due to a low frequency also enable you to use a smaller battery.

Another important factor around frequency selection is the performance around different materials. The longer the wavelength the more the signal is able to bend around metallic objects rather than be blocked completely by it. The 433 MHz frequency has a very long wavelength and bends around metal rather than being blocked by it. This is one of the reasons it is a popular frequency in the automotive industry for key fobs: when you think about a key fob, battery size, battery life and performance around metal are everything. When you think about an asset tracking tag or environmental monitoring tag used in a large data center or an industrial solution where a lot of metal is around, battery life, battery size and performance around metal are just as critical.

So, given these obvious advantages you may wonder why everyone in the world doesn't use 433 MHz as their frequency. What is the negative side to selecting 433 MHz as a frequency? The answer is simple: government regulation and bandwidth. The 433 MHz frequency is highly regulated and any application of it must approved by the FCC. As you’d expect, creating products that adhere to these regulations is more difficult, and product release cycles tend to be slower as a result. However, this additional government regulation actually produces a significant advantage: limited access to a specific frequency also helps eliminate of conflict and congestion. The result? We have never encountered a single situation with a customer where other sources of 433 MHz transmissions interfered with the performance of our solution.

So, to summarize, when we talk about frequency selection he lower the frequency, the less power needed.  Less power means smaller, longer lasting batteries and tags. Longer, lower power wavelengths also mean the better performance around metal, and thus better performance in metal-rich environments like data centers or industrial environments.  Finally, selecting a regulated frequency like 433MHz helps ensure reduced possibility of conflict and congestion resulting in a better performing, more reliable solution.

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