Waveguide Bandpass Filters
ALLEN
AVIONICS ROUND POSTIRIS COUPLED Waveguide Filters are available over
the 1.12 to 26.50 GHz frequency band.(WR650 to WR42) In the CPWB
Series Bandwidths may be as small as 0.3% to as large as 7% of the
center frequency. These filters are available with 4 to 12 "high Q"
resonant sections. Allen Avionics Waveguide Filters are normally
constructed using rectangular Brass Waveguide but Copper, Aluminum and
Invar are also available. All Waveguide filters are available with
additional options like cover flanges, choke flanges or with coaxial
transitions to SMA and other connectors. 
Available
Frequency 
1.12 GHz –
26.5 GHz 
Available
Bandwidth 
0.3% Up to
7% 
Insertion
Loss 
(Depends on
the number of sections and BW) 
Stop Band
Attenuation 
see graphs 
Number of
Resonator Sections Available 
4 to 12 
VSWR 
1.50:1 
Standard
W/G Sizes 
WR650 to
WR42 
Dimensions 
See
drawings below.
Consult Factory for exact dimensions. 

CONNECTOR CODE CHART 
FEMALE ("N") 
FN 
MALE ("N") 
MN 
FEMALE SMA

FS 
MALE SMA 
MS 
2.4 mm FEMALE 
24F 
2.4 mm MALE 
24M 
CPR FLANGE 
CPR 
CPRG FLANGE 
CPRG 
CMR FLANGE 
CMR 
COVER FLANGE 
CF 
CHOKE FLANGE 
CH 


The curve to the left displays the
Relative Attenuation as a function of the Normalized 3dB
Bandwidth for medium bandwidth filters.(3.0%)
The
graphs supplied are designed to give an approximation of the
frequency response for the CPWB series of Waveguide filters.
Using these curves and a few simple formulas shown below you can
predict the attenuation for a given number of sections. Curves
for narrow bandwidths (0.3%) and wide bandwidths (7.0%) are also
provided. There are many variables that affect the Frequency
Response, Attenuation and Insertion loss of Waveguide filters so
when exact information is required contact the factory at (516)
2488080 or send email to
sales@allenavionics.com


The
Frequency response curves we supply show the approximate attenuation as
a function of the normalized 3dB bandwidth.
Using
these graphs we can calculate attenuation at a given frequency for a
specified number of sections or determine the number of sections
required to meet a set of given attenuation points.
EXAMPLE #1 (Find required # of sections)We
want a Bandpass filter centered at 10.0 GHz (FO) with a 3dB bandwidth of
100 MHz (FC). We have a stopband requirement of 60dB at 9.80GHz and
10.30GHz. First we need to determine the percentage bandwidth (%BW)
using the following formula to find the correct graph to use.
With a 1% bandwidth the graph for .3% above would give
us the best approximation. Now we have to look at the two stopband
requirements. The low side 60db attenuation point is 9.70GHz and the
high side is at 10.30GHz. Now we need to calculate the number of 3dB
bandwidths using the following formula.
Checking the above graph we can see that 8 sections will
have well over 60dB attenuation at both stopband requirements. 
EXAMPLE #2 (Find minimum attenuation at specified frequencies)
We want a Bandpass filter centered at 2.50 GHz (FO) with
a 3dB bandwidth of 10 MHz (FC) and we are thinking about using 6
sections. We need to find the minimum attenuation at 2.460GHz and
2.540GHz for 6 sections.
Using the same formula above we first find the %Bw to
determine the correct graph to use. In this problem the the %BW equals
0.4% so we can use the 0.3%bw graph again. Then from the second formula
we used in the first example we find that we have four (4) 3dB
bandwidths on each side.
Checking the above graph we can see with 6 sections we
will have greater than 50dB attenuation at both 2.460GHz and 2.540GHz
for a filter with 10MHz 3dB bandwidth.
Three plots are provided, 0.3%, 3.0% and 7.0% so the
approximate response can be determined for any bandwidth in the
range of .0.3% to 7.0%
Checking the above graph we can see that 6 sections will
have well over 60dB attenuation at both stopband requirements. 
Allen Avionics has advanced simulation and modeling software that our
experienced Microwave engineers use in the design and manufacturing of
Circular Post Coupled Wave Guide Bandpass Filters.
This software combined with our Numerical Control
Machining Center gives us rapid design and production capabilities.
Allen Avionics has the ability to manufacture prototypes and short runs
quickly and reduce lead times on large production runs.
Our Microwave and Mechanical engineers are always
available to help with custom designs or applications. The sales force
at Allen Avionics is ready to help with information and prices. They try
to answer all quotes in 48 hours or less and are familiar with all our
microwave products. All our Microwave products are manufactured in the
USA using only American made material. 
WR 
U.S. Mil.
__ /U 
FL— FU
GHz 
Inside
Width (a)
(in) 
WR650 
RG69
(b)
RG103 (a) 
1.121.70 
6.500 
WR510 

1.452.20 
5.100 
WR430 
RG104 (b)
RG105 (a) 
1.702.60 
4.300 
WR340 
RG112
(b)
RG113 (a) 
2.203.30 
3.400 
WR284 
RG48
(b)
RG75 (a) 
2.603.95 
2.840 
WR229 
RG340 (c)
RG341 (a) 
3.304.90 
2.290 
WR187 
RG49 (b)
RG95
(a) 
3.955.85 
1.872 
WR159 
RG343 (c)
RG344
(a) 
4.907.05 
1.590 
WR137 
RG50
(b)
RG106 (a) 
5.8508.200 
1.372 
WR112 
RG51
(b)
RG68 (a) 
7.05010.000 
1.122 
WR90 
RG52
(b)
RG67 (a) 
8.2012.40 
0.900 
WR75

RG346 (c)
RG347 (a) 
10.015.0 
0.750 
WR62

RG91 (b)
RG349 (a) 
12.4018.00 
0.622 
WR51 
RG352 (c)
RG351 (a) 
15.0022.00 
0.510 
WR42 
RG53
(b)
RG121 (a) 
18.0026.5

0.420 

MODEL DESIGNATION
Code 
Description 
1 
Series 
2 
Number of Sections 
3 
Center Frequency (GHz) 
4 
3 dB Bandwidth (MHz) 
5 
Connector Code(Input/Output)
(see chart) 
6 
WR Waveguide number 

1 
2 
3 
4 
5 
6 
CPWB/ 
5/ 
20.25/ 
101.25/ 
CPR/CPR/ 
42 
COMPLETE Part Number=
CPWB / 5 /20.25/ 101.25 / CPR / CPR / 42
Contact Factory With Your Specific Needs
For:
Electrical Performance
Mechanical Configuration
Insertion Loss

MATERIAL
When bandwidths exceed the 7.0% limit for this
filter type or when insertion loss, length rejection required or
some other parameter cannot be met, Allen Avionics has many
other Filter constructions available which could be used to
solve the problem. Contact our sales department for assistance.
(516) 2488080 or
sales@allenavionics.com 
The number of sections and the Waveguide size are the
basic parameters that determine the overall length of Round PostIris
coupled Microwave Filters.
Using some basic formulas and the wave guide width from
the table above you can calculate the approximate length for a given
Waveguide and number of sections.
From
EXAMPLE #1. We had a Bandpass filter
centered at 10 GHz with 1.0% BW. From the table above we see WR90 is the
best wave guide size for 10GHz. From the same table we see the width of
WR90 is 0.90 inches. Our previous calculations done for example #1
Indicated that we needed 8 sections to meet the required attenuation.
With the number of sections, % BW and Waveguide width we now we have all
the information we need to calculate the approximate length.


N
= number of sections.
a = width of Waveguide in inches
L = Approximate length in inches
For bandwidths 0.3 to 3.0%
L = For 48 sections. L= (0.75 x N +
1) a
L = For 912 sections. L= (N + 1.0) a
For bandwidths > 3.0% to 7%
L = For 48 sections. L= (0.75 x N + 0.667) a
L = For 912 sections. L= (0.80 x N + 1.0) a
So for example #1
we have L= (0.75 x 8 + 1) .9 = 6.3 inches 
ALLEN
AVIONICS INC manufactures many other types of microwave Filters.
Our
engineers will help you pick the right filter to meet all the
requirements you have for performance, size and cost. Our advanced
simulation and modeling software will design and do optimization of
Circular Post Coupled filters, MetalInsert Filters, Iris Coupled
Filters, Combline and Interdigital Filters.
All
of our Filters can be custom designed for your application and we offer
fast prototypes. No need to wait five or six weeks to test your idea or
check your system.
Allen Avionics Inc. started in 1960 And has 50 years experience in
design, production, quality and they use it on every product they make.
Check out this web site for all their products. 
