bandbass filter

Hi,
i m trying to simulate and implement a band pass filter to isolate 433MHz signal with 400kHz bandwidth using a combination of low pass and high pass(schematic).(LowPass at 433200000Hz, HighPass at 432800000Hz)
Im using PSPICE to do the simulations, using VSIN as source with the following Attributes: DC=0, AC=5V, VOFF=0, VAMPL=5,FREQ=433000000,TD=0,DF=0,PHASE=0
However it seems that i cant get a sharp response when i run the simulation
Any ideas how to improve the response of the filter?

Thanks

That's a Q of over 1000. (Q=Fc/BW). You can't even do that with LC filters. Don't even think about RC filters for this application. This will require a crystal filter, or a down converter before the filter. Here is a site that talks about the futility of trying to design LC filters with Q>100.

If you mix down to 10.7 mHz (standard IF), then 400 kHz bandwidth is a Q of 27, easily done with the tuned IF. The oscillator can be either 422.3 mHz or 443.7 mHz.

There are specialized filters that attempt to do this sort of thing. For example, duplexer filters used for full duplex base stations manage to get good attenuation at separations like 2 MHz away from the pass frequency. But this is done at the expense of great size and complexity. They use resonant cavity filters grouped together, with overall size perhaps 50 x 20 x 30 cm to do this, since this type of filter maintains a high Q. I'm guessing that it is also possible to create a filter with 1 to 2 MHz of separation from pass to reject bands using SAW technology, but I'm not familiar with filter SAWs at 433 MHz. Perhaps a cascade of several resonator SAWs at 433 could do the job? This is definitely not for the faint of heart.

RadioRon said:

This is definitely not for the faint of heart.

Click to expand...

And certainly not for someone who things you can use RC filters at UHF!.

Russlk said:

If you mix down to 10.7 mHz (standard IF), then 400 kHz bandwidth is a Q of 27, easily done with the tuned IF. The oscillator can be either 422.3 mHz or 443.7 mHz.

Click to expand...

MHz, please don't say mHz when you mean MHz, it's confusing to nubes.