1 Stratex Networks The Global Leader in High Speed Wireless Transmission

2 E Plane Septum Filters For Millimeter Wave Radios Design and Manufacturing Consideration Robert Griffith Principal Design Engineer

3 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. Tolerance Issues Controlling E-Plane Filters

4 Total Error Aluminum vs +/-55 C Etch Factor +/-15% Shop Tolerance +/-2 mils Manufacturing Issues

5 Tuning Techniques  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. Waveguide “A” Dimension Causes Biggest Error –

6 Cost of BeCu Inserts vs Frequency Assumes max number of 6 poles inserts on a 9x12 inch sheet of BeCu material

7 Possible LMDS Filter Design Scenario Receiver Passband: to MHz Transmitter Frequency: to MHz No Spurious Passbands:DC to 40 GHz Receiver Rejection of Transmitter: 50 dB Minimum Receiver Ripple: 0.2 dB Maximum Temperature Range:-30 to +70 Degrees C. Machine Shop Tolerance:+/-3 Mils Waveguide material:Aluminum Filter Design Example

8 Nominal 5 Pole Design Results With Margins  Set markers to passband & stopband.  The design appears to have manufacturing margins.  Complete design layout

9 “ 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.

10 “ 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

11 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

12 Data 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)Acrobat pdf format * Data courtesy of Mike Pomeroy, mmRadioLink

13 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………………………………………………………… % 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

14 5 pole RX filter inserts 38GHz Spectrum Radio System Bandwidth: 500MHz 30db 38GHz Spectrum™ Radio Filter Inserts

15 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 – Online Tool for E-Plane and Iris Filters eSeptum – Demo download from - Shareware locked to WR22 *Note: there are many others, these are the ones found with a 10 minute search on the Internet

16 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”

17 Thanks For Your Attention Robert Griffith – Principal Design Engineer