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design of 315Mhz bandpass filter

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quantboy

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I have a signal of 315mhz running over a 24VAC/60hz power buss.

I need to "pull out" or pass the 315mhz, so it can be used, but not the 60hz.

I was going to do something like the below circuit:

66_1323176808.jpg

Plan was two 0.022uf hgh voltage caps to filter out most of 60hz (high pass filter)
Then have a band pass tuned RC circuit as a bandpass filter for around 315mhz.
The plan was to use T2 and X2, combined with the 1000pH cap to resonate at the carrier freq (315mhz).

My questions are:
what type of transformer should I make/buy for T2...
how many Henrys should X2 be...
how do I calculate the RLC values for the bandpass filter at 315mhz and what values should I use?

I was hoping to wrap my own air-core inductors -- but I'm just not sure where to start with the transformer, inductor and capacitor values.

Thanks in advance,

Ted
 

Carrier frequency of the shown power line remote control is 100 kHz rather than 315 MHz. But the coupler could be basically designed similarly. You preferably operate the transformer in resonance. Air core or open ferrite core with a very few windings. I presume you know basic LC resonator formulas (or can review it on the internet).

315 MHz is rather high frequency and won't travel further than a few 10 meters on a power cable.
 

Carrier frequency of the shown power line remote control is 100 kHz rather than 315 MHz. But the coupler could be basically designed similarly.

The circuit is actually for the X10 home automation controller -- was just using it as a model for the 315mhz... Good catch.

Our power buss/cable is 30 meters long... I was using a SAW resonator w a transistor as a serial transistor to take data from pic processors and let them communicate -- what frequency would you recommend?

Thanks! Ted
 

For low speed power line communication, below MHz seems preferable, for wide band a few MHz up to several 10 MHz.
 

X.022@315 MHZ = 1/2PI X 315 X 10 ^6 X .022 X 10 ^ -6 ~ 1/44 or .02 ohms, seems too low try 100 Pf this will knock out your 60 HZ.
Frank

Thank you very much! I'll give it a whirl...

Unfortunately I dont have a network analyzer -- but a spice simulation in NI or Xilinx should help...
 

As with any circuit that uses high voltage or current, please use high quality parts that can work well within their ratings and also be very careful to avoid electrocution.
I'm sure you will but I feel this needs to be reinforced whenever anyone comes up with questions such as this.
Susan
 

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