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Basic concept of roots and poles in filters

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mzewani

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Hi Filter Designers
I would like to know a basic concept of roots and poles in filters
what poles at infinty means etc
is ther any book explain this stuff in simple way
Many thanks

Please the book should explain things to whom not familiar this stuff
i mean for begginer student
 

Re: Filter Design

Hello mzewani,

Just a few references:

hxxp://www.acusd.edu/~ekim/e194rfs01/filterek.pdf course notes

hxxp://www.circuitsage.com/filter.html a lot of links, free software, shareware, reference material

hxxp://www.eee.metu.edu.tr/~nyil/filpro.html the home page of the Filpro, with manual, and some theoretical content


hxxp://www.ee.bilkent.edu.tr/~microwave/programs/magnetic/mfilters/mfilters.htm theoretical materials

(replace x with tt)

Do a search on Google and Elektroda, there are tons of articles.

good luck, Al
 

Re: Filter Design

I think this book would be a good start.
RF circuit design -- W. Alan Davis, Krishna Agarwal
 

Re: Filter Design

Hi,

there are also at least two books available for download on Elektroda.

Hong, Lanacaster - Microstrip Filters for RF-Microwave Apllications

Mathei, Young, Johnes - Microwave Filters, Couplers and Impedance Matching Networks

They are both very good and are essetnial for any filter designer!

flyhigh
 

Re: Filter Design

I already download this book they are very intresting but i am after some thing suitable to students
 

there are many many books on the filter design and now im doing the rearch for the related material about the design microstrip filter. which book is essential ? and i plan to use the ADS software to simulate and analysis.
 

Re: Filter Design

If you want simulate filters try SystemView.

It have very power tool for filter desing.

It may usefull
 

Re: Filter Design

my suggestion:

**broken link removed**
 

Re: Filter Design

Hi,

I just recall, if you read a bits of a theory you can try to design - synthetize something in Ansoft Designer SV. It is free to download and has very good filter design tool.

flyhigh
 

I already download this book they are very intresting but i am after some thing suitable to students
 

thx for flyhigh,toonafishy talap.i will try it~but now only software i can use is ADS2002 becoz u know what i do is about my thesis so i have to use ADS and the project has been defined .so recently im rearching for the resource materials for the design.
 

where can I find the book
"Mathei, Young, Johnes - Microwave Filters, Couplers and Impedance Matching Networks" ?
 

Re: Filter Design

mzewani said:
Hi Filter Designers
I would like to know a basic concept of roots and poles in filters
what poles at infinty means etc
is ther any book explain this stuff in simple way
Many thanks

Please the book should explain things to whom not familiar this stuff
i mean for begginer student
Click to expand...
Poles and zeros are better understood in filters as they are part of transfer function in Laplace transform which the ratio of ouput vs. input.

s is complex frequency in Laplace transform.
s=sigma + j*omega
If you plot absolute value of transfer function vs. sigma while letting w=0 you see poles and zeros in what we call pole zero plot.

Poles at whatever s complex frequency make denominator zero, therefore eigenfunction response to be infinit and zeros make numerator zero. To be an eigenfunction is to treat signal as unchanged in input and output in frequency.

Number of poles is always the filter order no matter what kind of filter is.

Observe pole at s=-10 and zero at 0 in figure. Pole is called because it looks like a stick.
 

Re: Filter Design

These articles might be of some help if you are a beginner...
hxxp://www.eagleware.com/pdf/apps/2019_SFilterIntro.pdf

hxxp://www.eagleware.com/pdf/apps/2021_FilterZeros.pdf

xx=tt

Note they do promote their software, but is easy reading!

Good Luck
/WebDog
 

Filter Design

Above I explained pole and zero.
There is no pole or zero without Laplace transform.
Number of poles is always the filter order no matter what kind of filter is.

Here I saw a link pointing to a book in MCU called "Circuits and Filters Handbook". if someone has it people clip something in filter fundamentals.



Here is some history for Ecole Polytechnique. Laplace studied in Ecole.

All these famous people Amper, Gauss, Fourier, Laplace etc. all went in same school. Ecole Polytechnique. It was the time when Church and State separated and church expelled from schools. Yet Christian Church in France created one of the best universities known to humanity that of Ecole Polytechnique.

In 1828 mathematician Evariste Galois took the examination of the Ecole Polytechnique to enter but failed. Imagine it? That school was extremely hard. It does exist today as university with the same name but is not the Ecole Polytechnique it was before.

Please someone clip something in filter fundamentals from handbook I mentioned. MCU was emptied from ebooks preventing people who wanted to read. I usrely thought they had backups, they did not.
 

Re: Filter Design

Hi All,

I have the follow query regarding filter design:

Is the following always true for a BPF?
centre_frequency=sq_root(upper_passband_freq*lower_passband_freq)

I was given an assignment to design a microstrip BPF and ADS simulation results (S21) did not show this relation. The centre frequency was off by 5%. What may be the cause of this?

Thanks in advance!
 

Re: Filter Design

Hi
well some authors give another definition which is
w0= (w2+w1)/2
where w1, w2 are the edge freq.
 

Re: Filter Design

That would mean that the centre freq is really the centre of the lower/upper-pass bands... :)

Anyway, my assignment is over... the hardware centre freq drifted by 100MHz! BW remains as per ADS sim :)

Must be the FR4! And the via inductance huh?
 

Filter Design

The software"FilterSolution" is very good.
I design many filters based on the "FilterSolution".
You can have a try.
(just for LC filter)
 

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