Use a sufficiently high number of display points to avoid misleading results. Use it to reduce relatively small peak-to-peak noise values on broadband measured data. Rather than lowering the noise floor, smoothing finds the mid-value of the data. The smoothing aperture is a percent of the swept stimulus span, up to a maximum of 20%. Smoothing computes each displayed data point based on one sweep only, using a moving average of several adjacent data points for the current sweep. Z = 0 (short) Z = (open) L L G G = 1 ☑80 O = 1 O Smith ChartĦ IF BW and averaging Heterodyne detection scheme IF BW reductionħ Smoothing trace Smoothing (similar to video filtering) averages the formatted active channel data over a portion of the displayed trace. A perfect termination (Zo) appears in the center of the chart. Impedances on the Smith chart are always normalized to the characteristic impedance of the test system (Zo, which is usually 50 or 75 ohms).

Loci of constant resistance now appear as circles, and loci of constant reactance appear as arcs. All values of reactance and all positive values of resistance from 0 to ¥ fall within the outer circle of the Smith chart. Since there is a one-to-one correspondence between complex impedance and reflection coefficient, we can map the positive real half of the complex impedance plane onto the polar display. The drawback of polar plots is that impedance values cannot be read directly from the display. The magnitude of the vector is the distance from the center of the display, and phase is displayed as the angle of vector referenced to a flat line from the center to the rightmost edge. But instead of actually plotting impedance, we display the reflection coefficient in vector form.

The polar plot is very useful since the entire impedance plane is covered. Unfortunately, the open circuit (quite a common impedance value) appears at infinity on the x-axis. Since any impedance can be represented as a real and imaginary part (R+jX or G+jB), we can easily see how these quantities can be plotted on a rectilinear grid known as the complex impedance plane.

Let's review how complex reflection and impedance values are displayed. 2 o Rectilinear impedance plane -90 o Constant X Z = Zo L Constant R G = Smith Chart maps rectilinear impedance plane onto polar plane The amount of reflection that occurs when characterizing a device depends on the impedance the incident signal sees.

Online smith chart