![]() How about some EE stuff: do you know what resistances, impedances, reactances, or admittances are? Do you know what a transmission line is? How familiar are you with waves and reflection? How well do you understand complex (imaginary) numbers? Do you know what it means to express them in rectangular and polar form? ![]() They are called complex numbers and they have properties that make them very convenient for engineering. ![]() The i and j just tell you this is the second coordinate, so instead write it as (A,B). Įdit Forgot to add that when he gives you it will typically look like or. Input impedance for any load impedance on a transmission line with characteristic. ![]() Each half-rotation is and you can confidently tell your boyfriend you know the When you rotate you go clockwise or towards the generator. We called it L above and most of the time it is a fraction multiplied by this symbol lambda. ĥ) Now you need to know how far you want to go. Draw that point on your Smith Chart ( print one out btw).Ĥ) Next grab yourself a compass and put the spike end at the center of the Smith Chart and draw a circle passing through your point. We'll call that (normalized load impedance). This is really easy, just divide each coordinate of by. ģ) We need to move into our Smith Chart coordinate system by normalizing the values. Ģ) Next, you need to get a coordinate, we'll call it (load impedance). This is usually called (characteristic impedance). Here are the steps:ġ) First you need to know what your reference value is. In this case we are going to move a coordinate by a distance L. The curve B = 1 is the curve that ends up pointing straight up, B = -1 is the one pointing straight down.Ī Smith Chart has a ton of uses, but we'll just go with the simplest and if you get that we can talk about it in more detail. B varies from 0 (the line from the left center to right center, cutting the circle in half) to infinity (the right point). There are positive arcs (starting from the right center they curve up to the top) and negative arcs (curving towards the bottom). The second coordinate is the arcs of doom (we'll call B). A = 1 is the circle with left edge at the center and right edge at the right. A varies from 0 (the entire circle) to infinity (the point on the right). The first coordinate (we'll call A) are circles with the right edge passing through the right center point. It doesn't mean there's a real discontinuity, only that the phase/magnitude plot can't show continuous paths from 180 to -180 the way a polar plot can.It's a coordinate system just like you would find on graph paper, except now it's curved. So if the sweep passes through more than a full cycle of phase delay, you'll see that as a sawtooth on the phase plot. Phase is usually measured either in the range of (-180, 180) degrees or (0, 360) degrees. If your sweep doesn't go down to low enough frequencies to extrapolate to 0 Hz you could probably just measure with an ohmmeter. If the phase at 0 Hz is 0, you have an open. To tell the difference you need to look at the phase plot near 0 Hz. Same thing if you start with a short at (-1, 0). So on the Smith chart you see a rotation around the outside of the chart as frequency increases. The phase delay increases at higher frequency because the wavelength decreases while the physical length of the tranmission line segment stays the same. Say you start at the point representing an open, (1, 0) in cartesian coordinates, then if there's any transmission line between your calibration plane and the location of the open, there will be a phase delay in the reflected wave. Either an open or a short could cause what you're describing.
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