A CF-Series filter has a center frequency of 1000 MHz and a 3 dB bandwidth of 10 MHz. A stopband attenuation of 60 dB is required at 980 MHz and 1030 MHz.
The percentage bandwidth is 1%, calculated as follows:
For the first stopband requirement we have:
Number of 3dB bandwidths from center frequency =
From the CP/CF series attenuation curve, we find that a minimum of 7 sections are required.
The second stopband requirement is: Number of 3dB bandwidths from center frequency =
From the CP/CF series attenuation curve, we find that 5 sections minimum are required.
The greater number of sections must always be used to insure full specification compliance; therefore, a 7 section should be used.
Insertion Loss Calculation - Cavity
Knowing the number of sections, center frequency and bandwidth of the filter, insertion loss may be calculated from the following formula:
1. Percentage BW = 25 / 915 x 100 = 2.7%
2. Q from CF series curves = 2.9
3. Number of sections = 5
1. Percentage BW = 1375/8725 x 100 = 15.8%
2. Q from EZ series curves = 1.1
3. Number of sections = 9