Tailoring the RF spectrum

[muhammad jawad]

Dear researchers and friends
Hope you all are fine and enjoying your life
i have simulated 10Gbps optical UWB over fiber link where UWB mono and doublet pulses has been generated.At the photo detector i am detecting these pulses correctly.The optical UWB pulses converted into electrical UWB pulses need to be transmitted wirelessly by fulfilling the FCC requirement(i.e power must be less than -40dBm/MHz and the bandwidth will be in between 3.1-10.6GHz).To shape the spectrum before transmission wirelessly to meet the FCC requirement, i am using bessel LPF with cut-off frequency (0.1*Bit rate) and filter order as 1.But the problem is that i am getting the spectrum at output of LPF not fulfilling US FCC recommendation as power is more than -20dBm and bandwidth is greater than 20GHz while i am keeping the cut-off frequency lowest i. 0.1*Bit rate but i am getting the spectrum bandwidth more than 20GHz.
please let me know how to rectify the problem so that UWB generated pulses and their RF spectrum meet the FCC.what filter will be suitable and what will be its parameters?????I am attaching the screen shot.Plz help me.I am very obliged to all of you
Regards
jawad mirza

[Marc Verreault]

Hi Muhammad,

I recommend setting your Bessel filter to order “4”. This should give you steeper drop off. I also suggest setting the cut off frequency to around 0.7*bit rate.

I also noticed that the y-axis for the RF spectrum analyzer is in dBm (not dBm/Hz). To set the y-axis to spectral density units please check the parameter “Power spectral density” under the Graph tab of the Component properties panel. Your power levels may be OK! Cheers.

[muhammad jawad]

Dear Marc
very very grateful to you for your reply and help

i am ready to do the needful as per your suggestions.
one thing more to know from you.plz mention how to convert spectral density from dBm to dBm/MHz?is the transformation option is available in plots in optisystem?
Plz let me .

regards
jawad

[muhammad jawad]

Dear Marc

i have got the setting which you pointed out in your last reply.But when the PSD is in W/Hz,then the graph shows the plot but when i PSd is changed in dBm/Hz then a single straight line is shown(screen shots are attached).why this is happening and how to get proper plot?
regards
your sincere
jawad mirza

[Author]

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