Bandpass filter design
I am using Microwave office to design filters. I am designing bandpass filters in the frequency range 160 MHz +/-25 MHz bandwidth and also 160 MHz +/-0.25 MHz. Second frequency range is 1000 MHz +/- 250 MHz and also 1000 MHz +/- 12.5 MHz.
1. Rejection level is 50 dB min away from 3 dB bandwidth.
2. Phase between different channels are with in +/- 2 deg. (each channel have these filter bands and like wise 3 channels)
Kindly suggest the suitable filter type for achieving these specs.
Look at what others have done. Companies such as Lorch (www.lorch.com), K&L (http://www.klfilterwizard.com) & Mini-Circuits has invested heavily in "Filter Selection Tools".
Hi,
Since you are using Microwave Office (MWO), you can check "Ifilter wizard" of MWO. However, availability of this wizard depends on your licence options.
A series LC, or an LC tank, might suit (at lower frequencies anyway).
Play with the L:C ratio, because that affects Q, and bandwidth. For instance, increase L by multiples of 10, decrease C by multiples of 10.
What is your offset frequency for rejection of 50 dB ?
20% away from edges.
0.15% bandwidth is tough - what is your acceptable insertion loss?
We have an amplifier to compensate for the Insertion loss. Insertion Loss can be around 5dB.
Insertion Loss acceptable is around 5dB.
Then have a look at these coax cavity filter designs, as an example what physical size to expect:
http://www.ik-telecom.com/hamradio/2m/filters/eng/