basic resonance to bandpass

[citizen]

hi to all
the resonance concept is basic for the bans pass filters using coupling resonators
i want to know this concept thourely if any one have the good suggesion for this so that i can learn more.
thank you in advance

 

[supersage]

Please read Charpter 8 of "Microwave Engineering" authored by David M. Pozar

 

[citizen]

thank you , but i need to have that book here, is it in 2 nd edition or 3 rd edition of pozar?
thank you

 

[james cook]

Basically there are RLC parallel, serise resoance, and at microwave frequency, we need to get distributed RLC nework which is a resonator. Lump RLC at MW freq have very limited Q value.

 

[citizen]

yes thak you,
i too want to learn concepts like this clearly so that designing is easy, even im designing filters with using books and sheets but im not getting the concept exactly,

can any one tell me the good books or website where i learn this ?

thank you

 

[LvW]

I think the principle of LC resonance is explained in each textbook dealing with fundamentals of electronics.
The basic principle is cancellation of two frequency dependent impedances at one specific frequency only.
Perhaps you don´know that this principles also holds for a combination of a positive (classic ohmic) resistor and a negative resistor which is frequnency dependent (FDNR). Such a unit can be designed with one active element (opamp or OTA), two caps and and some resistors. Detail can be found in any good book resp.chapter on active filter design.

 

[citizen]

ok is lc resonant concept enough for the filter design ?
then i will read those books,
thank you

 

[LvW]

Well, the understanding of the principle of LC resonance is a good foundation for analog filter design, however, in modern filter hardware inductors play are role only in the upper MHz range. Because of several disadvantages of coils the usage of active circuits (opamps, OTA´s) instead of inductors is preferred - if the frequency range allows this replacement (low frequency up to the middle MHz range).

 

[citizen]

yes i know the RLC series and parallel resonance concept
but how to adopt that concept cor the cavity resonator filter concept i dont know thats the reason am asking for the books those tell the relation between the resonator or reactor concept to the filter
thank you

 

[RF-OM]

To citizen,

The resonance theory is very interesting, there a different types of resonance and different types of tanks too. They allow having diverse resonant effects and getting very unusual characteristics. It can be used not only for filtering but for correction or equalization as well. I have one excellent book: Everitt W.L., Anner G.E. Communication Engineering. My book is the 3rd edition (1956) but the text was first published in 1932. There are chapters about resonance, RF networks, filters, impedance matching (even broadband), equalization and coupling. It may be hard to find today, but text is very good.

The coupling in RF filters is separate area and it is very interesting, but not easy. There are some hard to believe phenomenon, but they really exist and it is possible to see them. I know one wonderful book on this topic, but it is not in English. It was written by one of my teachers, he died long time ago. I use this book often when it is necessary to refresh something.

To LvW,

One of your post above remind me about a couple of very interesting things. Several years ago I invented the way how to make solid state amplifiers with resonant characteristics without any inductors. I checked it with simulations because I have no ability to make ICs in my garage and simulations showed good results. After it I developed new RF element what I called Bell-shaped tetrode. It is semiconductor device well suited to IC process and it has Bell-shaped characteristic. By changing bias on the first electrode it is easy to adjust the height of the bell. Steepness of the positive and negative slopes can be easily adjusted with biasing of another electrode (this is a tetrode). Simulation showed good results. Bell-shaped tetrode can oscillate with very small current consumption and has low loading on the resonant tank. With bias it is easy to tune the tank on desired frequency. The Q-factor is much higher than for varactors, so phase noise can be kept very low. I think there is a real possibility to build RF circuits even for GHz bands without inductors at all. This is my very old goal: how to get rid out of inductors. If it is interesting for you we may talk a bit more detailed through e-mail.

 

[RF-OM]

To citizen,

In my last post I forgot to tell you that cavity resonance is different from LC resonances. There are a lot of different resonance kinds in our world. It is more related to the waveguide and wave modes. There also can be more than one resonance. Coupling is also different from LC tanks but processes may be similar to some extent (at least from the inserted loss theory point of view). About a year ago I made some investigations on these issues in order to develop the methods how to avoid the cavity resonance and how to optimize design to prevent cavity effects. I wrote preliminary report which allows me to use it in practical designs and I use it often. Since that I am going to check all this stuff and publish the article for RF engineers that will help them to avoid cavity resonance problems and optimize their designs. I need to check my folder for this project and may be I will find some materials about cavity resonance because usually I copy related pages and put them into special folder until projects is finished. If I find something I let you know.