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    cavity filter operation

    Hi Experts
    Can you experts tell me what are ceramic filter and cavity filter?
    What are the difference and advantages and disadvantages of them?

    If I want to design WiMAX 802.16d or 802.16e 3.5GHz Transceiver, which is better to use?

    THANKS.

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    structure of cavity filter

    Ceramic filter: It uses a transmission line which the dielectric is cemaric (very high e_r about 40 - 90) also high Q. The result, the filter will very small since the effectlive length reduces from the free space length by sqrt(e_r). But it is very lossy due to large e_r.

    Cavity filter uses air as a dielectric for resonator. Hence, loss is very small but it is very big. you will find a cavity filter in the base station.



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    cavity filter

    I think you should know where you want to use these devices. For a cavity filter, it is very expansive compared with a ceramic filter.
    Normally, cavity filter will be use in the base station, and the ceramic filter will be use in the CPE.



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    air-cavity filter

    Thanks.
    I still have another question.
    Is ceramic filter also muliti-layer filters?
    Is cavity filter also cal dielectric filters?



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    ceramic filter cases

    Quote Originally Posted by crenyen
    Thanks.
    I still have another question.
    Is ceramic filter also muliti-layer filters?
    No

    Ceramic uses for high dielctric constant (Er=60-90) and this way reduce size on filters (length ~ sqr(Er) compare to air) on cost of higher loss in most cases.

    filter structure itself not need ceramic and can make with air as dielectrium (big size, low loss) or on ceramic (small size and higher loss). Different 'Er' only change scale of filter structure like 'zoom' on graphial object in drawing program.

    in few cases in filter structure with dominant skin-effect loss (high eddy-current on long line), can ceramic solution give better performents and lower loss compare to air structure, depend of current travel in shorter distance and lower current (more energy stored in electrostatic field in ceramic - but this case is very rare and need high precision design and much give and take between eddy current loss in structure compare to dielectric loss in ceramic...

    Is cavity filter also cal dielectric filters?
    No, cavity filter uses lowest possible loss Er dielectrum as air (or vacum) for minimize loss (food heatings up depend of high dielectric loss in microwave oven), very importent in very high-Q filters (sharp filters) and majority loss in cavity filters are eddy-current loss (skin effect loss) and need big metallic area to minimize loss as possible -> big cavity filters.

    Dielectric filter in most cases is a ceramic, plastic or glass-structures in waveguide structure. For exampel optical filter for optical fibers and laser-structure use dielectric filter (interferense, reflection and gitter-structures), but also on microwave in waveguides can use dielectric componet to make sharp impedance-steps for make filters.


    in microwave world, in many case transform TEM-wave (in waveguide) to TE-wave for affect on dielectric puck as resonator (and call for dielectric filter) and other case transform to TM-wave on affect from static magnetfield, for example circulator for direction way of microwave power in Y-junction.



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    resonator power voltage quality factor

    Youy are correct in much of what is said, but, with all filters, microwave,
    size is dependent on scheme and frequencey.

    the materials used in construction and schemes used are really a function in
    producibility vs freq of operation.

    cavity filters are not nesc very large, larger than ceramic, but as freq increases
    the cavities can become quite small, a few inchs long for a 7 pole at 15 GHz for example, I have seen smaller for higher freq



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    cavity filter drwing

    Can anyone tell me what factors in a cavity filter can determine a spurious signal?

    Thanks in advance.

    Lupin



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    ceramic filter cavity

    Quote Originally Posted by Lupin
    Can anyone tell me what factors in a cavity filter can determine a spurious signal?

    Thanks in advance.

    Lupin

    Read filter design book, possibly find couple of them here in edaboard.

    And old books but still usable is Zverevs 'Handbook of filter syntesis' and L.Matthaei, Lee Young and E.M.T jones 'Microwave filters impedance-matching networks and coupling structures' (Artech house)

    This both books written in 'handbook design era' as 60-70s without computer support and programs and many (all??) filter books written in modern time have this books as reference...

    Matthaeis book is possible to find as pdf in P2P grey area on Internet, but Zverevs is not scanned and PDF:ed yet (needs 1200 dpi to make usable quality of charts... is _very_ high detalied - and very nice typgraphic settings and quality is miles higher compare to days ugly Word document) - and very, very expensive to buy...


    but...


    Interdigital and digicom bandpass filter have more or less spurios on 3f,5f,7f of f passband

    and also possible make unwanted different wave modes inside filter cavity for other spurr frequency depend of mecanical design.

    If you make 'mecanical' cavity filters - you need good mecanical workshop and try, try, try couple of designs - is not possible to simulate everything and need measure with NVA on real things

    for example hard to simulate is Q-value and loss depend of rod-shape in mounting point and contact pressure and resistance in sealings, loss in end-cap and tuning cap (difference between brass and silver-plated tuning screw in endcap can give 0.3 dB difference in transmission loss...) etc. If high power filters - passive IM, voltage breakdown or plasma flashing inside, different temperature on different place in high power mode can change frequency and tunings (going from low to higer transmissions loss and more heat... and bad standing wave) etc.

    (for example in 100 MHz combining filter with 40 degree rod, can have 14 ampere current (peak) and 400 Volt (peak) in top capacitance only for 3 Watt power... - think 2 kW power....)

    common problem is not possible to simulate is leaking RF in sealings between cavity etc. - is practical spent very much time to hunting leaking RF in wrong place (more screws) and hard to make wanted leaking on other places (zeros), build good tuning point in right place in mechanic for high yeld manufacturing, easy tuning process, temperature stability with exotic material (invar) etc.

    Simulate to find right length of rod and dimension of cavity and find right coupling factor between cavity is smallest and most easy part of filter design, tricky part is make working filter in real world, easy tuning and stable over time and temperature, and high yeld manufacture to low price.



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    ceramic filter insertion loss

    Hiii
    I guess u r asking about the ceramic filter to use it in the design of a WiMAX system. Me too I'm working on the same project. If u have more dteails about the RF stage of the WiMAX plzz help.
    Thnx in advance.



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    ceramic filter how to use

    cavity filter is expensive with big size.Dielectric filter is available for your usage.
    You can see its pict as below.

    We can offers Ceramic Bandpass Filters(also called dielectric filters, or dielectric ceramic filters,microwave ceramic filters) in standard resonator sizes of 2mm , 3mm , 4mm , 5mm , 6mm , 8mm , 10mm and 12mm (normally 3mm , 4mm , 5mm , 6mm , 8mm ).
    Bandwidth: 0.5% to 8% of center frequency
    Basic rules of ceramic band-pass filters and diplexersp
    The higher the Q-factor of a resonators/band pass filters,the better electrical performance for insertion loss.
    The more dielectric resonators combined together for a band pass ceramic filters, the better rejection/attenuation/stopband will be.
    Determinant factor for Insertion Loss
    Q factor of a resonator, the bandwidth of a filter, and the number of resonators Determinant factor for Attenuation/rejection
    The number of resonators, connection type of resonators

    www.accutemicro.com



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    Re: ceramic filter how to use

    can anyone tell me how to design a ceramic filter? i mean the procedure and software for simulation. thank you



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    Re: ceramic filter and cavity filter

    you can use HFSS to simulate. uwave can do so also



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    Re: ceramic filter and cavity filter

    i wanna design a 6GHz filter with 1GHz bandwidth, which kind of filter structure can i use?



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    Re: ceramic filter and cavity filter

    you can use microstrip to design.


    1 members found this post helpful.

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    Re: ceramic filter and cavity filter

    can i use the coaxial line to build the resonator?



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