Stratex Networks The Global Leader in High Speed

Stratex Networks The Global Leader in High Speed Wireless Transmission 1

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

Tolerance Issues Controlling E-Plane Filters Length of resonators vary by “etch factor” and temperature coefficient (Be. Cu material) “A” (Long) dimension of waveguide varies with machine shop tolerance and temperature coefficient of material used. This effects Lambda Guide. 3

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

Tuning Techniques Waveguide “A” Dimension Causes Biggest Error – ØHave tops and bottom waveguide built as a “set” to reduce tolerance build up on “A” dimension. ØOversize waveguide and “Lap” down to exact frequency. ØOversize waveguide and use a “press” to “squeeze” the waveguide “A” dimension. ØUndersize waveguide by about 10 mils and use 15 mil compressible, conductive gasket material. 5

Cost of Be. Cu Inserts vs Frequency Assumes max number of 6 poles inserts on a 9 x 12 inch sheet of Be. Cu material 6

Filter Design Example Possible LMDS Filter Design Scenario üReceiver Passband: 29000 to 29200 MHz üTransmitter Frequency: 31000 to 31200 MHz üNo Spurious Passbands: DC to 40 GHz üReceiver Rejection of Transmitter: 50 d. B Minimum 7 üReceiver Ripple: 0. 2 d. B Maximum üTemperature Range: -30 to +70 Degrees C. üMachine Shop Tolerance: +/-3 Mils üWaveguide material: Aluminum

Nominal 5 Pole Design Results With Margins ØSet markers to passband & stopband. ØThe design appears to have manufacturing margins. ØComplete design layout 8

“Plus” Tolerance Check Out ØChange waveguide “A” dimension to 283 mils ØSet temp at +70 degrees ØSet etch factor to +0. 6 mils. Note: materials other than aluminum may be selected if desired. 9

“Minus” Tolerance Check Out ØChange waveguide “A” dimension to 277 mils ØSet temperature to – 30 degrees ØSet etch factor to -0. 6 mils. Note: etch factor is usually about 15% of material thickness. Material is 4 mil Be. Cu sheet 10

Spurious Check up to 40 GHz ØReset all values to nominal value ØSet sweep to display up to 40 GHz ØCheck 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 40 GHz is shown at 45 d. Bc 11

Predicted vs Measured Data, Data WR 42 Filters Ø Data collected* on e-plane filter designed using e. Septum© Filter Software for 25 GHz band application. Ø Mechanical pieces were then measured, and actual dimensions entered back into e. Septum© to predict the ACTUAL frequency response of the filters. Ø Measured and predicted data shown for 3, 5, 6 and 7 pole filters (Acrobat pdf format) *Data courtesy of Mike Pomeroy, mm. Radio. Link 12

Applicability for E-Plane Filter Use Consider Use When ØLow Cost is more important than ultimate performance ØE Plane split block housing already exists for other system components ØBandwidths……………………………. . 0. 7% to 7% ØReturns Losses……………………………. ~15 d. B OK Ø Passband / TR Space Ratios (Passband to reject band ratios)…. 10 to 30% ØGroup delay and Ripple not too critical (i. e. less than 32 QAM radios) Proceed Carefully When – ØBandwidths exceed 7% ØGroup delay and ripple are important (128/256 QAM Systems) ØHigh rejection needed close to filter passband 13

38 GHz Spectrum™ Radio Filter Inserts 5 pole RX filter inserts 38 GHz Spectrum Radio System Bandwidth: 500 MHz Rej@1260 MHz: 30 db 14

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 e. Septum – Demo download from - www. engineers. com Shareware locked to WR 22 *Note: there are many others, these are the ones found with a 10 minute search on the Internet 15

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” 16

Thanks For Your Attention Robert Griffith – Principal Design Engineer 17