Post subject: Filter design
Unread postPosted: Sun
Mar 20, 2005 8:25 pm
I have one doubt regarding
filter design for mobile phones, commonly it can be done by shebyshev
design, however is it possible to do by microstrip filter design?
Am I right to say that the difference between those 2 is chebyshev
design using lumped components? :?:
and I guess that the
microstrip filters are better using for this condition, especially
at high frequency operation?
Looking forward for your advice.
Thank you for enlighten me..
Sat Mar 26, 2005 9:32 am
A microstrip filter is perfectly
possilbe at 900 MHz, but it is not used in mobile phones because
it would be very large. There are techniques for miniturising
microstrip filters, but it would still be impractical for handset
The filters used in mobile phone handsets are generally
coupled ceramic resonators or SAWs, which are cheap, small and have
relatively good selectivity.
Microstrip filters are designed
using the same prototypes (chebyshev, butterworth etc) as lumped
element designs. The Richards transform is used to translate lumped
elements into lines.
If you have interest in this area, I
recommend the following books:
Microwave Engineering - DM Pozar
Microstrip Filters - Hong & Lancaster ISBN
Unread postPosted: Mon Mar 28, 2005 1:23 am
Thank you for
your advice and suggestions.
Mon Mar 28, 2005 4:11 am
Any topology that can be used for
lumped elements can be used for microstrip elements, the difference
is only in the implementation. Microstrip filters are indeed too
big for using them in mobile handsets, but they are often used in
RF boards for cellular/GSM frequncies.