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The input terminal is at a distance of 0.333λ TG from the load, located at 0.088λ. The angle of Γ L is measured using the corresponding angle of reflection coefficient scale on the periphery of the unit circle as 116.5°. If the radius of point A is projected onto the reflection coefficient, E orI, scale at the bottom of the chart, the measurement is |Γ L| = 0.45.
#HOW TO USE SMITH CHART GENERATOR#
Thus, point A reads 0.088λ toward generator (TG). The relative position of a point on the transmission line can be determined by extending the radius of the point to intersect one of these two scales and reading its value in λ. One complete rotation around the chart amounts to a half wavelength traversal. Two scales on the Smith chart's outer periphery indicate movement in wavelengths either toward the generator (clockwise) or toward the load (counterclockwise).
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This point can be translated to the input by moving (1/3)λ toward the generator. The load impedance is normalized, and the point (0.5 + j0.5) is plotted and shown as point A in Figure 4.13. The input impedance and reflection coefficient can be determined by using the Smith chart. Suppose that a (1/3)λ-long, 50 Ω line is connected to a load impedance of (25 + j25) Ω. For better clarity and practice, it is highly recommended to follow this example by repeating the graphical solution taps on a new Smith chart. The basic operations of the chart can be understood by an example to be discussed next. įigure 4.13 displays a typical commercially available Smith chart. This is useful in oscillator design, where designers routinely have to work with negative resistance values. The use of a compressed Smith Chart therefore allows the designer to visualize device parameters over the complete frequency range, where both positive and negative resistance behavior may be exhibited. From 6 to 10 GHz, the pole lies inside the Γ 3 = 1 boundary of the Smith Chart in Figure 4.10, indicating that negative resistance can be generated in this device using passive shunt feedback. An example of the use of a compressed Smith Chart to plot the negative resistance behavior of an MHG9000 GaAs MESFET, in terms of shunt feedback pole locations (as defined in Chapter 8) on the Γ 3 plane from 2 to 18 GHz is shown in Figure 4.10. In order to represent negative resistances we need to compress the conventional Smith Chart to be a subset of a larger chart, which typically has a radius of |Γ| = 3.16, this value being chosen to represent 10 dB return gain. You're right that the \$S_Z_0.Negative resistance values plotted on a Smith Chart lie outside the |Γ| = 1 boundary of the conventional Smith Chart. S11 and S22 below, with marker at 5Ghz resonance.īy my understanding at 5GHz, the input to the filer, S11 should be 0, with maybe a phase change, Or is the issue just with the way that ADS plots S parameters? Would I expect the same plot on an actual VNA on the Smith chart display.īTW, I'm also including magnitude and phase charts of S11 to show that those reading are behaving as expected. I figured that with S parameters being complex they would normally be plotted on the smith chart, but what I'm seeing doesn't seem to make sense to me. Or, is the Smith chart not appropriate for plotting S parameters? So what is the meaning of the S11 plot on the smith chart? I would expect it to show 0 at resonance. The Smith chart doesn't seem to show the same thing. Looking at the other graphs of S11 and S21, they seem to makes sense, where at 5GHz S21 goes to 0 dB and S11 goes to very low, meaning %100 of the signal from port 1 goes to port 2 as you would expect. In the Smith chart below, at resonance, 5GHz, it shows S11 as being ( 1 + i0 ). By my understanding at 5GHz, the input to the filer, S11 should be 0, with maybe a phase change, and also the reflection coefficient should be 0. My issue that I'm having is interpreting the Smith chart results. It's a simple band-pass, the resonates at 5GHz. To get the feel of it I used the circuit below as a test, and analyzed it. Just to get some practice I'm using Keysite ADS simulator.
#HOW TO USE SMITH CHART HOW TO#
I'm trying to become reacquainted with microwave circuits and how to analyze them, especially with a VNA.