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Specifying Bandpass Filters

Bandpass Filter Part Number Description

Cavity Filter Part Number Description


1. Number of Sections

2. Series and Package Size

3. Center Frequency, MHZ

4. Bandwidth and Designator (3dB BW Standard)

5. Input Connector

6. Output Connector (if different from Input)

(1) 6" RG 188 Standard
(2) Requires SMA Removable Connectors at High Frequencies

Bandwidth Designator
3 dB /(blank)
1 dB /A
equi-ripple /R
special /X
Connectors
Connector Type Designator
Blind Mate BP
Cable (1) C
RF Pin (2) P
SMA Female S
SMA Male SM
SMC Female SC
SMA Removable SR
Surface Mount M
Surface Mount-Pins MP
Special X
Overview
Bandpass
Lowpass
Highpass
Charts


Calculating Number of Sections

The following curves show the stopband frequencies normalized to the 3 dB bandwidth for filters with 2 to 8 sections. A ratio of stopband frequency to 3 dB bandwidth is used.

The curve given on the right shows an asymmetric frequency response resulting from the circuit used. Other schematics may be utilized to yield different attenuation characteristics (i.e. steeper on the high frequency side of the passband and shallower on the low side).

Please note that the frequency response curves shown are based on a low ripple Chebyshev Transfer Function. Exact performance is related directly to the unloaded, component selection and package size. If you have a critical parameter please contact the factory so full compliance may be assured.

Example:
A BP-Series filter has a center frequency of 600 MHz and a 3 dB bandwidth of 120 MHz. Use the curve for 7-50% bandwidth filters. A stopband attenuation of 30 dB is required at 360 MHz and 50 dB is required at 960 MHz.

The percentage bandwidth is 20%, calculated as follows:

Example 1

For the first stopband requirement:

Example 2

Number of 3 dB bandwidths from center frequency =

Example 3

From the 7-50% bandwidth attenuation curve, we find that a minimum of 3 sections is required.

The second stopband requirement is:

Number of 3 dB bandwidths from center frequency =

Example 4

From the 7-50% bandwidth attenuation curve, we find that 5 sections minimum are required.

The greater number of sections must be used to insure full specification compliance; therefore, a 5 section should be used.

Insertion Loss Calculation
Knowing the number of sections, center frequency and bandwidth of the filter, insertion loss may be calculated using the following formula:
Example 5

Example: 6BP8 - 725/145-S
1. Percentage BW = 145/725 x 100 = 20%
2. LC from table = 6.8
3. Number of Section (from P/N) = 6
4.
Example 6

Example:
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:

Calculating Number of Sections Example

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:

Example: 5CF2-915/25-N
1. Percentage BW = 25 / 915 x 100 = 2.7%
2. Q from CF series curves = 2.9
3. Number of sections = 5
4.

Example: 9EZ6-8725/1375-S
1. Percentage BW = 1375/8725 x 100 = 15.8%
2. Q from EZ series curves = 1.1
3. Number of sections = 9
4.

Bandpass Attenuation Chart 1
 
  Bandpass Attenuation Chart 2
 
 
Bandpass
Electrical Performance
Series Frequency
(MHz)
Loss
Constant
BP2 - BP9, T5B, T8B 5 - 100 9.5
BP3 - BP9, T5B, T8B 101 - 1000 6.8
BP6 - BP9, T8B 1001 - 10000 5.0
MH 60 - 3000 4.4.00



Discrete Component Bandpass Filters
P/N Freq.
Range
(MHz)
% 3 db
Bandwidth
VSWR
(Nominal)
Number of
Sections
Avg. Power
(Watts)
Operating
Temp. (Deg. C)
Relative
Humidity
BP2 5 - 100 3 - 100 1.5:1 2 - 10 10 -55 to +85 95%
BP3 25 - 200 3 - 100 1.5:1 2 - 10 10 -55 to +85 95%
BP4 15 - 200 3 - 100 1.5:1 2 - 10 10 -55 to +85 95%
BP5 5 - 200 3 - 100 1.5:1 2 - 10 10 -55 to +85 95%
BP6 50 - 7500 3 - 100 1.5:1 2 - 10 1 -55 to +85 95%
BP7 50 - 7500 3 - 100 1.5:1 2 - 10 1 -55 to +85 95%
BP8 50 - 7500 3 - 100 1.5:1 2 - 10 1 -55 to +85 95%
BP9 25 - 5000 5 - 100 1.5:1 2 - 10 1 -55 to +85 95%
MH 60 - 3000 1 - 5 1.5:1 2 - 10 1 -55 to +85 95%
T8B 70 - 1000 5 - 30 1.5:1 2 - 4 1 -55 to +85 95%

Shock 10G
Vibration 20G
See Charts page for outlines and dimensions.
Contact factory for specific requirements not listed above.

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