filter tools for reconstructing filters - Page 1
Forum section: electronics / projects

author: R_G_B_
author_rank: Frequent Contributor
timestamp: February 17, 2014, 12:36:43 pm
content: I wonder if anyone can help.I was characterizing a system frequency response using a network analyzer. I now have the data as a Bode plot with phase and frequency response. The data is contained is also contained in a CSV file. what I would like to know is.or. which tools or ways to take this data and put it into spice simulator other than Matlab or octave freeware tools. I have using Tina for simulations but I have not managed to get this data in. Just ant to take the real world data and apply it to a simulator. Can anyone help out?what I am trying to achive in a simulator using the real world data:input---> H(s) ---->output

author: KJDS
author_rank: Super Contributor
timestamp: February 17, 2014, 02:00:56 pm
content: Any linear simulator, including the free RFSim99 will take an S parameter file from a net ana for analysis.It's even possible in excel

author: Bored@Work
author_rank: Super Contributor
timestamp: February 17, 2014, 10:55:29 pm
content: That is actually an exercise they used to keep us students busy with. Go through the bode plot and determine slope changes. Depending on the change you have found a pole, poles, a zero or zeros of the transfer function. With that, and the DC gain you can create a transfer function. It should be possible to write some program trying to do that automatically.In LTSpice, once you have a transfer function you could then use a B, E or G source to model a filter with that behavior. Note, however, Laplace transforms are a bit tricky in LTSpice.

author: G0HZU
author_rank: Super Contributor
timestamp: February 17, 2014, 11:17:49 pm
content: I agree with KJDS.The best format is a 2 port s parameter file. You need a vector network analyser for this rather than a scalar analyser. If it's a modern VNA you can export 2 port files direct to USB/disk.However, if you have an older VNA you can export the raw data via the GPIB port and convert it to a 2 port file using something like Softplot.http://www.aphena.com/softplot.htmI get access to this program through my place of work as it comes bundled with Agilent Genesys and also AWR MWOffice. However, it is possible to do it all yourself and write a quick program in VBasic to read the data from the VNA via GPIB and convert it to a 2 port file in your PC.Obviously, you need to know how to do a basic SOLT calibration on the VNA before taking any data.

author: R_G_B_
author_rank: Frequent Contributor
timestamp: February 18, 2014, 04:57:00 pm
content: I'm just using a network analyzer that does magnitude and phase. I can derive the filter from just looking at the bode plot and then designing one from this. It works very well accept the phase shift does not look any where as near as steep so although it mimicks the the device under test in terms of time domain analysis. The phase response is not as steep. This is the reason for wanting to important the characterized bode plots so that I can design a filter that will give me an overall magnitude response of the system equal to approximately 1 0db throughout the frequency range?

author: KJDS
author_rank: Super Contributor
timestamp: February 18, 2014, 06:51:48 pm
content: What happens with the phase if you add a length of line to your model?

author: R_G_B_
author_rank: Frequent Contributor
timestamp: February 19, 2014, 02:38:38 pm
content: Phase equalization is difficult to achieve at low frequency the components become to large. I am trying to overcome this problem. I want to acquire an analogue signal where the signal shape contains the information and not its presence as is the case for binary systems.e.g I'm not detecting pulses but trying to acquire complex waveforms using analogue signal processing methods.