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Which type of filter is suitable for band pass filter ?

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zahrein

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Which type of Filters?

I have known three type of filters. There are :

1) Digital Filters -A digital filter is a calculating process which is performed by digital components like DSPs or FPGAs.


2)RC-filter- They consist of RC-networks and amplifiers. The RC-filter is the Classical active filter’ (analog, continous-time).


3)SC-filter (Switched-Capacitor-Filter)- They sample signals by switching MOSFET’s. The signal conditioning however, occures in an analog way, although in principle the filter is discrete in time.


Question: From all the type of active filters which is the one that is most suitable for a band pass filter Front end transmitter for RFID application at 868 MHz using 0.5 micron CMOS technology?


ANd WHY ?
 

flatulent

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Re: Which type of Filters?

At these frequencies a LC or transmission line type filter would work best. These others do not have the Q or the low noise or the out of band rejection required.
 

zahrein

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Which type of Filters?

IM stil not satisfied..i dont think we can use transmission line filter for RFID application? Suggestion anyone?
 

zahrein

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Which type of Filters?

IM sorry the web site above does not contain the right information..


Anyone suggestions? by the way its in chinese ...
 

batdin

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Re: Which type of Filters?

There are some very well made RF SAW filters.If only you could find the right one... :D
 

raymond_luo2003

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Which type of Filters?

Your initial choices on the digital filter/RC filter/SC filter aren't the good choice for bandpass filter since they cant meet high Q requirement. High frequncy such as the 868Mhz need LC filter or SAW filter even crystal filter. I guess you might need use external components to build it up.

Raymond
 

zahrein

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Which type of Filters?

Thank u for ur information Raymond.. I will look into it..And inform to u all the progress of my project...
 

zahrein

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Which type of Filters?

I think if i use a LC filter ..It is a passive filter. I think the most suitable filter is the active filter. My problem is that can we achieve HIgh Frequency such as at 868 MHz By using Operational amplifier?

Does it suitable? Bear in mind that im doing chip design..I will be using CMOS technology .
 

radiohead

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Re: Which type of Filters?

No, opamps cannot amplify until 880MHz. At least, not in CMOS. So you are restricted to passive filters (any technology).

But because the bandwidth is very small, and because any CMOS process has large tolerances and low Q, you cannot rely on the process to make great filters. The RF filtering must be done off-chip. This is also why zero-IF or very-low IF receivers are so popular today. No need for expensive off-chip IF SAW/LC filters!

But the first RF filter to select the RFID band, cannot be done in CMOS! It will have to be done in other technologies, eg SAW!
 

jetset

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Re: Which type of Filters?

You should use LC passive filter, because I think no OPAMP can pass that band, or even operate well.
 

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