120 MHz band pass filter

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davicente

Joined: 31 Jul 2002
Posts: 31
Helped: 1

30 Sep 2002 9:45 120 MHz band pass filter

I designed and simulated a 120 MHz (BW3db=21 MHz) bandpass filter with ciolcraft and temex s-parameters files, but when i made the PCB, the response of the filter was quite different from the one i obtained during the simulation with microwave office.
Have i made a bad simulation?Should i rely on the s-parametres from coilcraft and temex?
Thanks in advance.

AREVALO

flatulent

Joined: 19 Jul 2002
Posts: 4926
Helped: 328
Location: Middle Earth

30 Sep 2002 17:42 parasitics

At these frequencies the extra capacitance of PC pads and traces as well as trace inductance become significant. If this is not on a PC board there are still similar parasitics.
Try the simulation again with either estimates of these parasitic values or better yet include the pc board layout in your simulation.

STOYANOV

Joined: 26 Jan 2002
Posts: 41
Helped: 4
Location: Sofia, Bulgaria

02 Oct 2002 5:11 120MHz BPF

Davicente,

Try to include in the simulation tolerances of the elements.
Your filter is relative narrowband and probably sensitive to tolerances.
I dont know how your filters looks, but in your case, it is better to use a filter with resonators instead of canonical form one - you can design such a fiter with identical inductors. Take a look at N/u/h/e/r/t/z web site. There you can find F_I_L_T_E_R Solution 9.0 demo, capable of designing of filters with identical resonators.

Best of luck,

STO

coppervaporlaser

Joined: 23 Jun 2002
Posts: 66

03 Oct 2002 0:37

does your filter only consist of RLC or i it active ?

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03 Oct 2002 0:37 Ads

Circuit_seller

Joined: 23 Sep 2002
Posts: 414
Helped: 15

15 Nov 2004 12:41 Re: 120 MHz band pass filter

Hi STOYANOV

I can not find an item in filter solutions to design a BPF with identical resonators.
How can i use this feature?

Regards

Jackwang

Joined: 12 Nov 2004
Posts: 167
Helped: 2

21 Nov 2004 14:32 120 MHz band pass filter

I think 120MHz filter is easy to design with LC components.
before you design it, you need that determine the type and series of filter.
during the processing of debug, you should complete every block step by step.

KP

Joined: 16 Jun 2005
Posts: 38

16 Jun 2005 9:55 120 MHz band pass filter

i wanna design a bandpassfilter on a FR4 pcb 1.6mm
thickness.The range is between 70Hz and 30kHz.Cutoff frequency at 200Hz and 10kHz.
Pls advise me what type of capacitor to be used as listed below:
1. 220nF
2. 100nF
3. 470uF