# Tag Info

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S2P files are also called "Touchstone" files, and different versions of the specification can be found here and here. Just before the data section of an S2P file, there should be a line that looks like this: # Hz S RI R 50 This tells you The frequency column is given in Hz (KHz, MHz or GHz are also possible) The measurements are S-parameters (rather ...

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ThePhoton has given a very good answer. However, below is an expanded version with complete derivation of the formula and check in LTSpice, as well as power transfer analysis. I. The S-matrix for the 2-port system is $$\begin{pmatrix} {\frac{Z}{{2{Z_0} + Z}}}&{\frac{{2{Z_0}}}{{2{Z_0} + Z}}}\\ {\frac{{2{Z_0}}}{{2{Z_0} + Z}}}&{\frac{Z}{{2{Z_0} + Z}}... 3 Sure. What you will need to do is control the instrument over VXI-11 or USBTMC and issue the proper commands to perform the measurement, read the data you want, and write it out to files in the format you want. I would personally recommend using python and python-vxi11 or python-usbtmc, but there are numerous other options including labview and various ... 3 You didn't mess up. $Z_{11}$ is the input impedance when the other port is terminated with an open circuit. Since your device is just a bit of wire, it has infinite input impedance when the other end is not connected to anything, and thus infinite $Z_{11}$. This is an example of why we need different two port representations (S-parameters, Y-... 3 The 4-port S-matrix is $\left[\begin{matrix} S_{11} & S_{12} & S_{13} & S_{14} \\ S_{21} & S_{22} & S_{23} & S_{24} \\ S_{31} & S_{32} & S_{33} & S_{34} \\ S_{41} & S_{42} & S_{43} & S_{44} \\ \end{matrix}\right]$ Assuming you did your two-port measurements with the untested ports properly ... 3 When calculating the S-parameters, you should terminate all of the ports that don't have stimulus applied. So, in your situation, to calculate $S_{11}$ and $S_{21}$, you'd be working with this circuit: simulate this circuit – Schematic created using CircuitLab Notice that the current passing through the capacitor from port 1 to port 2 is $i_1$ ... 3 By reading some application notes, I discovered, indeed, that the 4-port S-parameters measurements file is meant for creating a model of the transformer, and it can be used with a simulator directly, such as Genesys or ADS. Those are expensive tools unavailable for hobbyists, but I also found the free and open source Qucs simulation supports n-port S-... 3 I think your over thinking this. Outside of super narrow beam pattern horns or the like, 700Mhz is fairly forgiving. I don't see how a u.fl connector would have enough effect to matter. As long as your test cable is kept away from the plane of radiation, I don't see a problem. As for the connector, at that freq a 1/2 wave is 20cm(if your using 1/4 you ... 3 This is the capacitance the pin is loaded with before making switching speed measurements. It is intended to represent the sort of loading you would get with a length of PCB track and a few gate inputs, so that you are able to get the specified switching times when using a practical board and fanout. If the manufacturer measured the pin unloaded, then you ... 3 20 is used for voltage ratio. SdB = 20.log(Vout/Vin) 10 used used for power ratio. SdB = 10.log(Pout/Pin) They are different by a factor of 2, as power = k.voltage2 Why don't we use smaller, or other, numbers, as the multiplier? I think it was felt in the days when the ratio that log(Pout/Pin) was starting to be used, that this ratio, known as the bel (... 2 I just found the answer to this question, after spending an hour looking it up before this question was posted. The format for .s2p files are: *.s2p Files Each record contains 1 stimulus value and 4 S-parameters (total of 9 values) Stim, Real (S11), Imag(S11), Real(S21), Imag(S21), Real(S12), Imag(S12), Real(S22), Imag(S22) Here is the link for ... 2 Frequency comes into play simply because the input and output impedances are a function of changing frequency. An active device such as a small signal transistor may exhibit an input impedance of 4 -j25 ohms at 100 MHz while at 200 MHz the resistive part of the impedance drops and the reactance climbs even higher. The device with an input impedance of 4 -j25 ... 2 S-parameters can be used at any range of frequencies that's the first point. The second point is understanding what a simple matrix of s parameters represents because two of the parameters are reflection coefficients and although they are of interest (generalism alert!) at any frequency, they tend to be ignored (because they don't offer any significant ... 2 There are three options I know of. One is to terminate one of the ports with 50ohms and take 2-port measurements. I think it will reduce the math involved if you terminate each port with a load that matches its output impedance. For example if you terminate port 2 with a matched load of Z2, then measure the S-parameters between ports 1 and 3 with a 2-port ... 2 Apparently, these matrices are difficult to measure in the optical domain, that's why there is not much information on them, especially very little easy-to-understand references. However I have found one paper, which is short and very practical and therefore easy to read: Measuring the Transmission Matrix in Optics: An Approach to the Study and Control of ... 2 The long answer is set up the problem like this: simulate this circuit – Schematic created using CircuitLab Now calculate the forward and reverse-travelling waves at each of the ports. This gives you $S_{11}$ and $S_{21}$. Then hook up the generator on the other side of the device and calculate the forward and reverse travelling waves again to ... 2 We like to pretend that circuits such as amplifiers are essentially linear around some specific operating point, because that vastly simplifies their analysis. However, like many things in electronics, that is only an approximation. That approximation fails to a certain extent with large input signals, and to a greater extent during transient events such as ... 2 I have numerically calculated both examples using octave/matlab and LTspice, and both show at first sight the same results: Example 1 : DC Block C=27e-12; Z0=50; f=logspace(1,9, 100); ZL=1./(2*pi.*f*i*C) + Z0; s11=(ZL-Z0)./(ZL+Z0); s21=sqrt(1-abs(s11.^2)); semilogx(f,abs(s11.^2), '-', f,abs(s21.^2),'-'); grid on; and with LTSpice: For the second example (... 2 func s11(f) = ZR(f)/Z0 This is not correct. You should be using something that computes$$S_{11}(f) = \frac{Z_L - Z_0}{Z_L + Z_0}$$where $Z_L$ is the cascade of the filter and the load connected on its port 2. What the error is in your $S_{21}$ calculation, I didn't notice with a quick look. Edit: the error in your $S_{21}$ calculation is that you ... 2 You can edit the values by right-clicking, and then going to options->document parameters. The standard altium template doesn't contain the so called "special strings". So either you have to add the text manually to the field (e.g. type =Engineer) or you have to change the template so it includes it. A tutorial by altium explaining the special strings is ... 2 How is $S_{21}$ contained in $S_{11}$? By the definition of S-parameters, $S_{11}$ is the amount of wave leaving the two-port from port 1 when all other ports are terminated in a matched load, and a wave is incident on port 1. $S_{21}$ is the wave energy leaving port 2 due to an incident wave on port 1. Therefore, your original statement is correct, ... 2 It isn't that simple. There can also be an effect due to reflections back and forth between the input of L and the output of K. If L has no input reflections ($S_{11}=0$) or K has no reverse reflections ($S_{22}=0$), then your formula should work. (Edit: As I think about it some more, you'd also need to have a perfectly matched load on the output of L) ... 2 1st ..... What is | S11 | ^ 2 $\left|S_{11}\right|^2$ is a power ratio. -47 dB means a power ratio of roughly 2/100,000 or 0.00002 (because -50 dB would be 1/100,000 and +3 dB is about 2x) You could also get this result by simply changing your network analyzer to display a linear scale. Is this accurate? g = 20 log_10(-47.661) dB Since you haven't ... 2 F-parameters are used to calculate antenna coupling coefficients between nearfield or farfield sources. If a field source is not activated, only receiving coupling coefficients will be computed for that source. However, this option is only available for simultaneous field source excitation. In general, S-Parameter results are given as the ratio of incident ... 2 It looks like for S11, the chart plots the impedance, from which the reflection coefficient is calculated, The way the Smith chart works, if you took the lines of the Smith chart away, and put ordinary polar coordinate lines on the chart instead, these lines would give you the reflection coefficient. If you then go back to the Smith chart lines instead of ... 2 The ideal Wilkinson does not have any loss when transferring signals from port 1 to ports 2 and 3:$$|S_{11}|^2 + |S_{21}|^2 + |S_{31}|^2 = 1$$When the input is given at port 2 or port 3, it is not lossless:$$|S_{12}|^2 + |S_{22}|^2 + |S_{32}|^2 \ne 1 Therefore we don't classify it as a lossless network in the general sense, even though it is lossless in ...

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There are several ways to use a 50ohm network analyser to make measurements in a 75ohm system. Not surprisingly, they are all inferior in some way or other to using a 75ohm analyser, but they'll work within their limitations. 1) Measure everything in the 50 ohm system, and convert mathematically. Pros - no extra hardware Cons - you might want best accuracy ...

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If you connect an ideal matched load to port 2, that will set $a_2$ to zero. However, it's not always possible, or convenient, to get a load that's sufficiently accurate for your purposes. It depends what accuracy you want to work to, and what frequency you're using. At very high frequencies, GHz, we often use a 'sliding load', which is an approximately ...

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I've found the code I need on the scikit-rf site - specifically, renormalize_s (and associated functions) from http://scikit-rf.readthedocs.io/en/latest/_modules/skrf/network.html . This is Python code that uses numpy for the calculations. For anyone else interested, this page describes how to perform the measurement using scikit-rf.

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In addition to the previous answers, you have to guarantee the robustness of the design against a variety of factors outside of your control. These factors may include thermal variations, device ageing, unexpected ESD or even unintentional misuse by the end-user. These things sometimes lead to vary your input/output impedances which may cause oscillation if ...

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