lumped element bpf using awr microwave office

[wanie08]

hye,
im doing this project entitle BPF for radio over fiber technology. my operating frequency is 2.4GHz.. ive chose my center freq= 2.442G, lower freq=2.4G, and upper freq=2.4835.. chebyshev 6 order.

the problem is, im trying to simulate my lumped element of bpf using awr, but the S21 n S11 graph doesnt appear as it should be.. i already convert my bpf from low pass filter, and do te culcuation twice, but yet the result is still the same..

help me anybody.. :'(

 

[alperuslu]

Could you send your schematic and simulation results?

 

[WimRFP]

Hello,

If you have access to a simple spice simulator, do the simulation again with the ideal components you calculated based on the low pass filter. When this give good results, the problem is in the real components. Probably you select a "real" inductor (and capacitor, from a certain manufacturer). These components are in fact sub-circuits (or S-parameter files) that also incorporate parasitic effects like inter winding capacitance and capacitance to ground.

When you convert the Ls in the low pass to LC series circuits, did you convert these to parallel resonant circuits? LC series circuits at HF may give rise to strong influence from parasitic capacitance to ground (for example the pads on your PCB).

Other thing, BW/fcenter is not that large (3.4%). When using a 6th order filter, the quality factor of the components must be sufficiently high and tolerance has to be low.