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Can you use FR4 laminate in the L-band (1-2Ghz)?

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elec350

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FR4 laminate [hlp]

Hi RF mans!
What's your opinion about using FR4 laminate in the L-band (1-2GHz)? May it cause problems?
I have designed a PLL that covers frequencies in the L-band and used FR4 for implementing it; but it doesn't work properly. I have considered several probable problems, but it has problem yet. May using FR4 causes the problem?
 

Re: FR4 laminate [hlp]

Not generally. You have some additional losses, should be a problem only with high Q planar structures. Most 2.4 GHz devices, WLAN, Bluetooth, whatever are using FR4, I think.
 

Re: FR4 laminate [hlp]

I agree, for simple structures you can use FR4 up to ~ 4 GHz.

But, you still need to be very careful of board layout rules! You need 50 ohm lines, a good ground plane, excellent capacitor bypassing, etc.
 

Re: FR4 laminate [hlp]

But, you still need to be very careful of board layout rules!
Click to expand...
Absolutely! This isn't particular to FR4, but most likely the problem, when a design fails.
 

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    elec350

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Re: FR4 laminate [hlp]

hello
FvM wrote:
You have some additional losses, should be a problem only with high Q planar structures.
Click to expand...
Can you explain more?
 

FR4 laminate [hlp]

The main limitation of use of FR4 based materials in MW range frequencies is the high material loss.
If you need to design low loss (so high Q) planar distributed circuits (couplers, resonators...) this material is not the most efficient one. In applications where you use small lenght transmission lines (for example in a cellular phone) the low cost of this material is a key feature.
I hope it can help.
Mazz
 

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    elec350

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