Finding the electrical length of the branches of an N type T – #1 posed a problem, this article looks at one solution.
For convenience, here is the problem.
An interesting problem arises in some applications in trying to measure the electrical length of each branch of a N type T piece.
Let’s make some assumptions that the device is of quality, that the connection from each connector to the internal junction is a uniform almost lossless transmission line of Zo=50Ω. Don’t assume that the left and right branches above are of the same length (though they often are) and we should not assume that the nearest branch is of the same length as the others (and they are often not).
Before we start, we will calibrate the VNA entering the offsets appropriate to the OPEN and SHORT cal parts.
So, the problem is all the uncertain things that connect to the internal T junction. Lets connect a calibration quality 50Ω termination to the left hand port. We now know that the path from the male port to the remaining female port comprises lengths l2 and l1 of low loss 50Ω transmission line with a 50Ω resistor shunting at the junction of l1 and l2. Continue reading Finding the electrical length of the branches of an N type T – #3