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The network analyzer is an indispensable tool when you are building RF circuits. Fooling around with S21. In my spare time, I sometimes build small RF evaluation boards and measure their responses. Lately I got down to measuring a variety of circuits and their S21 responses in both Log-Mag and phase. One of them is presented here. Distance to Fault. In Network Analyzers, the hardware to generate Return Loss vs distance is already present. The missing ingredient is the inverse FFT software. Agilent wants me to pay $4000+ Singapore Dollars for the activation code. Anritsu also play the same game. In fact EVERYBODY plays THAT GAME, not only with VNAs but also with oscilloscopes. I understand that Agilent scopes are mostly built with the same bandwidth, but you have to pay $$$ to activate the software for the wider bandwidth. I guess it makes sense for these manufacturers to build common hardware on the production lines and then differentiate the products by software. Keeps manufacturing and test costs under control. Sorry for going off topic. I recently played with the Distance to Fault function on an Anritsu LMR Master, and I must say that it works pretty well. Here is the webalbum I made. Hope you like it! Cable Loss Measurement using an Anritsu LMR Master . If you suspect that your antenna system is acting up you really can't tell whether the antenna or the feedcable is giving the problem. In most cases, access to both ends of the cable is not convenient. In such a case, the method would be to disconnect the cable jumper to the antenna and terminate it with a short (or open) For UHF frequencies, a SHORT would be preferred over an OPEN, because the OPEN end would radiate. Then make a Return Loss sweep (S11) form the near end of the cable. The cable loss in dB would be half the value of the Return Loss in dB. Although I used an Anritsu, I find the Agilent App Note to be more comprehensive. One thing to bear in mind, is that for this purpose, spot frequency measurements of Return Loss is NOT RECOMMENDED due to the ripples that you would encounter in the RL sweep. It is better to make a sweep (with ripples) and then set the data smoothing to obtain a better picture of the Return Loss.
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Network Analysis |