XBAND 8.34 GHz Microstrip Band Stop Filter

This is the microstrip band stop filter used in the WiFi 5GHz to 10.56 GHz XBand High Throughput System.

It is used to filter out the second stage Mixer LO leakage. Using this filter, the spectrum is jammer free and also achieves an EVM of -38 dB with 256 QAM and an end to end over the air EVM of -30 dB with 64QAM.

Layout of the 8.34GHz Band Stop Filter Rogers 4350 10mil
Calculated Frequency Response using TransNetCalc of the Band Stop Filter

Coupon for Using and Testing of the 8.34 GHz Band Stop Filter
Network Analyzer Span 40 GHz 8.34 GHz Band Stop Filter. Note that it matches the Calculated Response using TransNetCalc

Transmission Line Modeling and Analysis of the Band Stop Filter

In the following the network topology for modeling the band stop filter in TransNetCalc is presented. Also a TCL script is shown for calculating the frequency response. Note the database “trans_types.dat” has info on the microstrip ( width, height, dielectric constant). The types for the 50 Ohm microstrip (mstrip50_9GHz) and the open stubs (mstripBSFZ1_3,mstripBSFZ2_3,mstripBSFZ3_3) are shown.

trans_types.dat

mstrip50 0.552507 0.254 3.66 0.01
mstripZ1 10.0506 0.254 3.66 0.01
mstripZ2 6.72717 0.254 3.66 0.01
mstripZ3 10.0506 0.254 3.66 0.01
mstripBSFZ1 0.21 0.254 3.66 0.01
mstripBSFZ2 0.07 0.254 3.66 0.01
mstripBSFZ3 0.21 0.254 3.66 0.01
mstripZ1_paral 4.75085 0.254 3.66 0.01
mstripZ2_paral 3.10866 0.254 3.66 0.01
mstripZ3_paral 4.75085 0.254 3.66 0.01
mstripBSFZ1_2 0.372076 0.254 3.66 0.01
mstripBSFZ2_2 0.171229 0.254 3.66 0.01
mstripBSFZ3_2 0.372076 0.254 3.66 0.01
mstripZ1_paral_6GHz 1.28422 0.254 3.66 0.01
mstripZ2_paral_6GHz 0.763286 0.254 3.66 0.01
mstripZ3_paral_6GHz 1.28422 0.254 3.66 0.01
mstripZ1_paral_4GHz 2.13711 0.254 3.66 0.01
mstripZ2_paral_4GHz 1.33575 0.254 3.66 0.01
mstripZ3_paral_4GHz 2.13711 0.254 3.66 0.01
mstripBSFZ1_3 0.293347 0.254 3.66 0.01
mstripBSFZ2_3 0.15239 0.254 3.66 0.01
mstripBSFZ3_3 0.293347 0.254 3.66 0.01
mstrip50_9GHz 0.555818 0.254 3.66 0.01

microstrip_bsf_9ghz.top

This is the topology describing the microstrip band stop filter:

n7 n8
n2
n4
n6
n8
end
n1 mstrip50_9GHz 0.00493082
n2 mstripBSFZ1_3 0.00504555 open
n3 mstrip50_9GHz 0.00493082
n4 mstripBSFZ2_3 0.0051719 open
n5 mstrip50_9GHz 0.00493082
n6 mstripBSFZ3_3 0.00504555 open
n7 mstrip50_9GHz 0.00493082
n8 R50_L0.00000 0 open

microstrip_bsf_9ghz.tcl

This is the TCL script for calculating the frequency response the microstrip band stop filter:

tload microstrip_bsf_9ghz.top T

cx 1 0 gen
cx 50 0 zs

set freq 9e9
set fBegin 4e9
set fEnd 16e9
set df [expr ($fEnd-$fBegin)/1000.0 ]

for { set i 0 } { $i<1000 } {incr i} {
set f [expr $fBegin +$i*$df ]
tcalc $T $f $gen $zs
nz0gamma $T n7 z0 gamma
nvalues $T n7
cxmult $n7_zl $n7_il vn8

cxgetpolar $vn8 mag ang

ninfo $T n7
set fGHZ [expr $f1e-9] set magdB [expr 20log($mag)/log(10)]
lappend results [list $fGHZ $magdB]
}

puts “RESULTS:”
foreach value $results {
puts -nonewline [lindex $value 0]
puts -nonewline “\t”
puts [lindex $value 1]

}