BPF data sheet question

[paxtakor]

Hello everyone I am kind of new to this. I found this BPF (LDD212G1403A-075) but I am puzzled as to what 'isolation' means. Does it mean the attenuation of the frequencies outside the pass band? Also this "data sheet" contains barely any information and I haven't been able to find a different one for this part. Here's the link: **broken link removed**

Thanks in advance!

 

[BigBoss]

There are 2 outputs on that component."Isolation" remarks the isolation between these two outputs.

 

[paxtakor]

Thanks. So how can I determine the stopband attenuation?? Ive found another BPF (TT6P3-2140P2-6011) on page three of this link: **broken link removed** but it doesnt provide this information either. This is very frustrating any help is really appreciated.

 

[BigBoss]

Thanks. So how can I determine the stopband attenuation?? Ive found another BPF (TT6P3-2140P2-6011) on page three of this link: **broken link removed** but it doesnt provide this information either. This is very frustrating any help is really appreciated.

You should ask about the exact specifications of the filter from the manufacturer.It isn't mentioned in the datasheet..

 

[paxtakor]

Thanks, one more question. Is IP3 a parameter of amplifiers and mixers? I do not see it on any data sheet for any filter.

 

[BigBoss]

Thanks, one more question. Is IP3 a parameter of amplifiers and mixers? I do not see it on any data sheet for any filter.

IP3 is a figure of quality of the nonlinearity of a system ( Mixers,amplifiers, etc) therefore passive components don't have any IPx specification except some magnetic components.

 

[biff44]

"isolation" is a specific term. although they should be clearer, like with an actual plot of S21 vs frequency. But to me, isolation means the drop in S21 out of band MINUS the insertion loss in band.

So if you have a filter with 2 db of loss, to say its isolation 1 GHz outside of the passband is 25 dB, the S21 needs to read 27 dB.

the reason being that is how one actually uses the filter....if you pass a signal at midband, and are worried about a jammer at 1 ghz away, you really are only concerned about the real/jammer power.

 

[volker@muehlhaus]

The first device with the isolation spec is a power divider, not a band pass filter.

 

[D.A.(Tony)Stewart]

A Hybrid Divider uses a hybrid transformer core with a few windings and a 2R termination resistor between ports 2&3 so that coupling between the two outputs cancels out when all ports are terminated with R.


The same is used in Cable TV biz is called a splitter. It is bidirectional but 75 Ohms not 50. 30 dB isolation is normal when the feed point is terminated with proper impedance, otherwise it is 0dB. Since this is bidirectional and broadband you can use them as combiners 2 to 1 port or as splitters 1 to 2 ports. If one port out is a small sample, they are often called by their generic name " Directional Coupler." and labelled by the theoretic sample size such as -20dB is a DC20.

There are also crystal versions of splitters with frequency selective characteristics in research papers.

Ideally all DC-3's are -3dB out in theory but in practise 3.5dB is the best you can achieve ( unless you are a guru of Directional Coupler design then you can get -3.4dB , whom I once met and he told me how many microwave repeaters ) 0.1dB saved across Canada in the 70's) He was also a small potato farmer in Quebec.

So remember a Hybrid Divider, power divider, signal divider, combiner , splitter and Dirctional Couple with 3dB in theory are all names for the similar products with slightly different variations in application, but a Hybrid implies a certain balanced splitter transformer design vs a WIlkinson design or circulator design or passive R divider design. etc.

IN your 2nd topic on BPF, the Bandstop rejection will be dependant on the actual part number of which there are hundreds but in general proportional to the cost and number of Poles or cascaded stages of dielectric resonators, in this case all tuned for some shape such as Chebyshev, Elliptical, Cauer, etc, for tradeoffs between passband ripple and skirt steepness and bandstop minimum rejection.

e.g. **broken link removed** Since they are custom, large orders and customer & factory specs are usually negotiated. But work very well.

- - - Updated - - -

 

[biff44]

I thought he said bandpass.

in a splitter, isolation just means the insertion loss between the two output ports.

 

[vfone]

@paxtakor

People get confused because above you have three posts with questions that you may think they are related, but actually they are not related at all.
First is about isolation between ports of a DIVIDER.
Second is about a stopband attenuation of a BAND PASS FILTER.
And third is about IP3 OF A PASSIVE FILTER.