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optimum distributed highpass filter

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amicloud

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Hong jia-sheng's book <microstrip filters for RF/Microwave applications>
has talked about so-called 'optimum distributed highpass filters'.In that book
a very usefull Table6.1<element values of optimum distributed highpass filters
with 0.1 dB ripple> is listed in the book.but the table is enough for design because
the n is only up to 6.
So who can give me a full table for designs with n>6?
thanks very much!
 

Ijust have the same problem.
How to calculate the values in the table ?
 

Not sure if this helps anyone, but I recently came up with a pretty clean highpass design that I haven't found out in the wild.

Requirements:
1) Printed filter (on 13.3 mil 4350 in this case)
2) Octave wide passband (~13-22 GHz)
3) Close in stop band(~11 GHz)
4) Good match (this goes in the very front end, so i was given a goal of a 20 dB return loss over process variation...).

Solution:
1) Main body of the filter is substrate integrated waveguide, so roughly an inch long section of 12 GHz cutoff waveguide. Nothing special here.

2) Microstrip impedance matching sections to broadband matching 50 down to about 20 Ohms. Again, nothing new here.

3) New part: Flared wider waveguide with lower cutoff at the ends. I used two ~1/4 wave length long sections of roughly 10 and 20% lower cutoff respectively. By choosing these and optimizing them (just ADS waveguide models) it was possible to attain a very flat input impedance, as opposed to the usual wild change seen in a fixed width waveguide. It should be noted that this style launch works great for just an SIW launch, better than any of the disigns I found in a cursory search.

4) Final tweak in was done in HFSS, which sims these structures very fast (~20 minutes to sim over 8 process corners). The design achieved 18 dB return loss over process windoows, >35 dB rejection, and just over 1 dB of insertion loss.

I later found a ~1969 paper that details an all waveguide HPF using the same idea (smooth tapers instead of my steps) to attain very good matches right up to the cutoff, so the idea is not novel. However I have not seen the concept show up in SIW papers, or in any other application. Despite not having all the models (microstrip to SIW in particular) I still found the overall design process very striaght forward using ADS linear models, and final tweak in going back and forth with HFSS, taking about 2.5 days to design fresh filters once I had the steps hammered out.

Bonus: I also had a need for a much lower frequency design, but the width killed me in terms of size (had to match to about 8 Ohms as well, ugh). I went with Half Mode SIW, which just cuts the thing in half and leaves a psuedo open circuit boundary, and it also doubles Zin. My shielding created a parasitic second mode, so I did not get (nor need) a full octave BW. However the resulting filter was of much lower loss and much lower process sensitivity than my attempts using shorted stubs to make a wideband BPF.
 

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