CZa
Newbie level 4
Hello everybody,
Fist off, I'd like to thank this community for all the valuable information and the answers to many of my questions I've found here so far. This is my first post.
Although microstrip filters are not the main part of my job, I need to design one every now and then. Up until now, the design flow I've followed is described below.
I design the filter using the ADS Design Guide for my particular requirements, I export the design to layout and perform a full wave electromagnetic simulation (Momentum). Normally, the behaviour is not satisfactory so I modify the parameters I input in the Design Guide and repeat the process.
After a few iterations, once I've obtained the desired performance, I manufacture the design and measure it. Sometimes the results are not acceptable so, once again, I have to modify the design parameters and repeat the process.
This has always been a quick and easy way to design my filters (even though I've never had particularly stringent requirements). However, I am currently working on a filter with the following specifications:
Pass band: 14-14.5 GHz
Max. attenuation pass band: 3 dB
Rejection bands: 13-13.5 GHz and 15-15.5 GHz
Attenuation rejection bands: >20 dB
Previously, I had to design a filter with the same specifications but centred 1 GHz below and I didn't have any problems. However, I've been trying to design this one for weeks and I haven't been able. The electromagnetic simulations are not similar to the expected behaviour, the attenuation in the pass band is unacceptably high and the lower skirt is too mild, regardless of the order of the filter.
I've read many comments in different fora and I don't know what to do. I'm thinking about trying to design it manually using the equations shown in Hong's book.
Any ideas / suggestions? Do you think there might be a problem with the models to calculate the impedances of the odd and even modes? Would it be a good idea to try and determine these values through full wave simulations? Any suggestions on how to do that?
Thank you very much in advance.
Fist off, I'd like to thank this community for all the valuable information and the answers to many of my questions I've found here so far. This is my first post.
Although microstrip filters are not the main part of my job, I need to design one every now and then. Up until now, the design flow I've followed is described below.
I design the filter using the ADS Design Guide for my particular requirements, I export the design to layout and perform a full wave electromagnetic simulation (Momentum). Normally, the behaviour is not satisfactory so I modify the parameters I input in the Design Guide and repeat the process.
After a few iterations, once I've obtained the desired performance, I manufacture the design and measure it. Sometimes the results are not acceptable so, once again, I have to modify the design parameters and repeat the process.
This has always been a quick and easy way to design my filters (even though I've never had particularly stringent requirements). However, I am currently working on a filter with the following specifications:
Pass band: 14-14.5 GHz
Max. attenuation pass band: 3 dB
Rejection bands: 13-13.5 GHz and 15-15.5 GHz
Attenuation rejection bands: >20 dB
Previously, I had to design a filter with the same specifications but centred 1 GHz below and I didn't have any problems. However, I've been trying to design this one for weeks and I haven't been able. The electromagnetic simulations are not similar to the expected behaviour, the attenuation in the pass band is unacceptably high and the lower skirt is too mild, regardless of the order of the filter.
I've read many comments in different fora and I don't know what to do. I'm thinking about trying to design it manually using the equations shown in Hong's book.
Any ideas / suggestions? Do you think there might be a problem with the models to calculate the impedances of the odd and even modes? Would it be a good idea to try and determine these values through full wave simulations? Any suggestions on how to do that?
Thank you very much in advance.