Transcript Stratex Networks

Stratex Networks
The Global Leader in High
Speed Wireless
Transmission
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E Plane Septum Filters
For Millimeter Wave
Radios
Design and Manufacturing Consideration
Robert Griffith Principal Design Engineer
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Tolerance Issues Controlling E-Plane Filters
Length of resonators vary
by “etch factor” and
temperature coefficient
(BeCu material)
“A” (Long) dimension of
waveguide varies with
machine shop tolerance
and temperature
coefficient of material
used. This effects
Lambda Guide.
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Manufacturing Issues
Filter Design/Tolerance Errors
10000
Error in +/-MHz
1000
Total Error
Shop Tolerance +/-2 mils
100
10
Etch Factor +/-15%
Aluminum vs +/-55 C
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8000
11000
15000
18000
23000
31000
Center Frequency in MHz
4
38000
70000
95000
Tuning Techniques
Waveguide “A” Dimension Causes Biggest Error –
Have tops and bottom waveguide built as a “set” to reduce
tolerance build up on “A” dimension.
Oversize waveguide and “Lap” down to exact frequency.
Oversize waveguide and use a “press” to “squeeze” the
waveguide “A” dimension.
Undersize waveguide by about 10 mils and use 15 mil
compressible, conductive gasket material.
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Cost of BeCu Inserts vs Frequency
Cost per Insert
6 Pole Insert Cost Vs Frequency
(Based on $200 per 9x12" Sheet )
$10.00
$8.00
$6.00
$4.00
$2.00
$0.00
8
11
15
18
23
31
38
70
95
Frequency in GHz
Assumes max number of 6 poles inserts on a 9x12 inch sheet of BeCu material
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Filter Design Example
Possible LMDS Filter Design Scenario
Receiver Passband:
29000 to 29200 MHz
Transmitter Frequency:
31000 to 31200 MHz
No Spurious Passbands:
DC to 40 GHz
Receiver Rejection of Transmitter: 50 dB Minimum
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Receiver Ripple:
0.2 dB Maximum
Temperature Range:
-30 to +70 Degrees C.
Machine Shop Tolerance:
+/-3 Mils
Waveguide material:
Aluminum
Nominal 5 Pole Design Results With Margins
Set markers
to passband &
stopband.
The design
appears to
have
manufacturing
margins.
Complete
design layout
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“Plus” Tolerance Check Out
Change
waveguide “A”
dimension to 283
mils
Set temp at +70
degrees
Set etch factor to
+0.6 mils.
Note: materials
other than aluminum
may be selected if
desired.
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“Minus” Tolerance Check Out
Change
waveguide “A”
dimension to 277
mils
Set temperature
to –30 degrees
Set etch factor to
-0.6 mils.
Note: etch factor is
usually about 15% of
material thickness.
Material is 4 mil BeCu
sheet
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Spurious Check up to 40GHz
Reset all values
to nominal value
Set sweep to
display up to 40
GHz
Check for
spurious filter
responses.
Some “fixes” for
spurious response
would be to use a
smaller “custom”
waveguide, or add
another pole or two to
the filter.
A second passband at 40GHz is shown at 45 dBc
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Predicted vs Measured Data, WR42 Filters
 Data collected* on e-plane filter designed using eSeptum©
Filter Software for 25GHz band application.
 Mechanical pieces were then measured, and actual
dimensions entered back into eSeptum© to predict the ACTUAL
frequency response of the filters.
 Measured and predicted data shown for 3, 5, 6 and 7 pole
filters (Acrobat pdf format)
*Data courtesy of Mike Pomeroy, mmRadioLink
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Applicability for E-Plane Filter Use
Consider Use When Low Cost is more important than ultimate performance
E Plane split block housing already exists for other system components
Bandwidths………………………………………………………….... 0.7% to 7%
Returns Losses……………………………………………………….~15dB OK
 Passband / TR Space Ratios (Passband to reject band ratios)…. 10 to 30%
Group delay and Ripple not too critical (i.e. less than 32QAM radios)
Proceed Carefully When –
Bandwidths exceed 7%
Group delay and ripple are important (128/256QAM Systems)
High rejection needed close to filter passband
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38GHz Spectrum™ Radio Filter Inserts
5 pole RX filter inserts
38GHz Spectrum Radio
System
Bandwidth:
500MHz
Rej@1260MHz: 30db
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E-Plane Filter Design Tools*
WASP_NET™, the WAveguide Synthesis Program for waveguide NETworks
EPFIL™: Waveguide E-plane Filter Design Software
Ansoft Corp. HFSS (Waveguide Modeling Software)
Guided Wave Technology – www.guidedwavetech.com
Online Tool for E-Plane and Iris Filters
eSeptum – Demo download from - www.engineers.com
Shareware locked to WR22
*Note: there are many others, these are the ones found with a 10 minute search on the Internet
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E-Plane Filter Design Reference
E-Plane Filters have been around for a couple of decades now.
For those wanting more information search the Internet with
Keywords: “Septum”, “E-Plane”, “E Plane”, “Waveguide Filters”
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Thanks For Your Attention
Robert Griffith – Principal Design Engineer
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