VIDEO TRANSCRIPT: Let us look at the S-Parameter measurement capabilities of this instrument Any 2-port device can be described by a number of parameter sets: H, Y, and Z parameters. But all these relate to total voltages and total currents at each of the two ports. However at higher frequencies, this becomes a challenge as equipment is not available to measure total voltages and currents and also our active devices become unstable when terminating by a short or an open circuit. Due to these reasons it is more suitable to use traveling waves instead of total voltages or currents. Hence S-Parameters are a preferred method of characterizing a device at RF and microwave frequencies. As a two-port device is most commonly used, let us look at the derivations of the S-Parameters for it. A 2-port block can be realized as a matrix as shown Here a1 is the incident power wave to the device which could result in portion of the wave being reflected back to port 1 as Indicated by b1. And a part of the wave being transmitted through port 2 as indicated by b2. Likewise an incident power wave at port 2 is indicated by a2 and this would result in waves b1 and b2. This matrix can be expanded to equations which is useful in calculating the S-Parameter values. If port 1 of the VNA is the source, it is assumed that the port 2 is terminated by a characteristic impedance. Hence a2 would be 0 and thus we are able to solve for S11 and S21. Similarly with stimulus at port 2 we can solve for S22 and S12 by assuming a1 is equal to 0. So as a general rule an n-port device has n to the power of 2 S-parameters. So for example a 2-port VNA would give you up to four S-Parameters and they are S11, S21, S12 ,and S22. The numbering convention for S-Parameters is that the first number following S is the port where the signal emerges and the second number is the port where the signal is applied. S11 and S22 provides return loss, impedance, VSWR information, whereas S21 and S12 provides insertion loss, transmission gains, and delay information. In the figure shown, you are looking at the typical bandpass filter measurements. A bandpass filter is a device designed to pass certain frequencies. So from the S21 response shown in the image, you can see that the filter under test has a pass band from 3 to 6 GHz approximately. The S-Parameters can be viewed in many display formats, such as log scale as seen in this figure. Another important display format views where many design engineers to check the characteristic impedance of their device is through a Smith Chart.