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Fundamentals of RF

1. Fundamentals of RF

Now, in this module, we're going to talk about the fundamentals of radio frequency, or what I'm going to keep calling it, RF, just because it's easier and I won't have a verbal typo. Anyway, we're going to talk about what the RF signal is and the characteristics of RF, some of those characteristics being wavelength, frequency, amplitude, and phase. Then we'll talk about some of the behaviors that occur when we send this radio frequency transmission out into the wild, as we'll call it, with issues like absorption, reflection, scattering, refraction, and diffraction. Yes, that was two different words, attenuation, multipath, and gain. And by the time we're done with this module, you should have a good understanding of some of the physics. You don't have to be a physicist, but some of the physics that are going to be used later on when we make the decisions of what type of radio frequency we want and where to place these antennas so that we get the best use of that radio frequency.

2. What is an RF Signal? Part1

So we'll start off with just the main definition of what an RF signal is. Well, an RF signal is basically going to fall somewhere in what we call the electromagnetic spectrum, which we're just going to call the spectrum from this point on. And that's the range of all possible electrical and electromagnetic radiation. That is, that radiation is the radio-frequency signal. Now, some of these signals you might already have heard of, like AM and FM radio. Of course, there is no Am anymore, but there are X-rays—visible light—the light that you see as the sun, or the sun is sending a signal that we are capable of seeing. And apparently, if you think about some of the dangers of getting too many X-rays, some of these signals can be dangerous for you. If you think of a microwave oven, that's how it's cooking. The food inside of that box is heated by electromagnetic radiation. So some of these can be very dangerous and harmful.

3. What is an RF Signal? Part2

So, basically, what you're seeing is a range of the spectrum from low to high frequency. Remember that the frequency is the number of waves or the measurement of the wavelength over time measured over a second. We apparently have no problem with the low frequencies when it comes to radio. But then when we see microwaves, you might say to yourself, "Well, okay, wait a minute." Why does it appear to me that this is causing harm? It's cooking food, and we don't want it to cook people as we see that transmission. But then there's also the idea of the amplitude, or the strength, of that wave. So some microwave communications, like if we had maybe a couple of parabolic dishes that were transmitting to each other, or if we were doing satellite TV from the top of our house, that type of microwave communication doesn't seem to cause us harm because it's a low-power infrared we use in a lot of communications. Then there's a range of light that we're able to see. Sometimes we then use different types of lenses to convert some of the things we can't see into light that we can, like ultraviolet. And then as we get into the higher frequency noticeand again, depending on amplitude and everything else, we startgetting into Xray or getting into this really cool stuffthat made the Hulk for those of you who liketo watch or deal with comic characters, the gamma rays.And you'll notice that as we get into the higher frequencies, we are, again, seeing things that could be harmful, depending on the amplitude and the strength. But the biggest part is the distance, right? The measurement of the distance between all of these peaks, from peak to peak, is what makes the difference in what we call the frequency, whether it's a long wavelength or a short wavelength.

4. What is an RF Signal? Part3

Now when we talk about the RF signal and how we actually create it, it's going to start out as a basic electrical current, an alternating current, or AC. The reason it's AC is because it does alternate. It has both positive and negative aspects. Unlike DC, which is direct current, we wouldn't see any change. So we need a type of current that is able to go from positive to negative. So alternating current is going to be generated by a power source. So, as I think about it, let's see if I can basically make the point here that at some point, we have this power—I'll call it POW—that is generating this electrical current. It's probably plugged in somewhere to a wall that's supposed to look like a plug, but I guess I didn't do very well with it. Anyway, it's plugged into a source of power. So it's kind of regulating how we transmit the power. And then we send that signal through a copper conductor, which means that there's some sort of cable, usually a coax cable. coax cable, right. Is that cable the one that has that copper wire through the centre of all that cladding? And if you think about it, it's like the cable for your cable TV. Anyway, so we send that power, that current, through that copper cable, and then it's radiated. At some point, it will be connected to our antenna. And so that power is radiated to the antenna. The antenna then creates that signal based on the current that we're sending it and how often that current has positives and negatives for the frequency and everything else. And that is the wireless signal that we're sending. Now, generally all of this is built into one little box that we call an access point. And in fact, at most of today's access points, we don't even see those external antennas anymore. They're built in Now that we can change the electron flow, which is the current that will cause the change in the fields surrounding the antenna, Again, the fields are the radio frequency that we're sending, and the shape and form of the AC is basically what we would call the waveform or a sine wave. And I'm sure you've seen enough of these little charts with that signal, that sine wavetype of signal, the positives at the top and the negatives at the bottom.

5. Characteristics of RF

Now I'm not a physicist. I don't think I'll ever be a physicist. Sometimes, I like reading books or stories by those who are very famous. But you don't have to be a physicist to be able to understand some of the different characteristics of radio frequency. But if you wanted to get into more detail, you certainly could by doing extra work in this study of RF. But one of the characteristics, or some of the characteristics you would see, are things like wavelength, amplitude, frequency, and phase. and we'll talk about what those are. Some of them have already been discussed.