How to find out the properties of FR4 in 2.45GHz receiver design?

[tschen]

Hi,

Currently designing a 2.45Ghz receiver and was wondering what is the Er and loss tangent with height=1.6mm and thickness=0.03mm FR4?

How is it possible to find out?

All replies are much appreciated.Thank you in advance!

 

[House_Cat]

fr4 material properties

FR4 is not just one kind of dielectric. You need to find out what brand and model of FR4 is going to be used. You can then go to that manufacturers web site and download the datasheet which will give you the loss tangent and Er.

 

[iamdrew]

er fr4

FR4 is pretty lossy for any RF applications, but sometimes the cost is worth the loss. There are plenty of other cheap materials though that you can use in your stack that will have much less loss.

Dielectric constant (permittivity) 4.70 max, 4.35 @ 500 MHz, 4.34 @ 1 GHz
Dissipation factor (loss tangent) 0.02 @1 MHz, 0.01 @ 1 GHz


source: https://en.wikipedia.org/wiki/FR4

 

[House_Cat]

er of fr4

Don't believe everything you read on Wikipedia. FR-4 board materials come with Er from 3.2 to 4.8, depending on the resin and glass weave used. You can see as an example an assortment of FR-4 materials with different characteristics from Isola - one of the large laminate manufacturers used by worldwide fabs **broken link removed**.

Another large company supplying high frequency FR-4 material - https://www.rogerscorp.com/documents/776/acm/High-Frequency-Laminates-Product-Selector-Guide.aspx .

There are also Taconic, GE, and dozens more. FR-4 means flame retardant class 4 - it is not just one material, but a whole group of board materials with different ratings that all happen to meet the flame retardant requirements of FR-4.

Either find a material that suits your needs, or find out what your fab can supply and look up the specs for that material. 2.45GHz is well within the capabilities of most FR-4 laminates. I've used FR-4 up to 9GHz.

 

[shameemkabir]

properties of fr4

what House_Cat told is correct. FR-4 has really large range of E_r.

It is better to measure the substrate by yourself. build a resonant structure (e.g., txline and ring is close proximity) on the FR4 substrate and measure it with NWA. Simulate the same structure with different E_r. When the measurement and simulation are identical, you know the E_r.

 

[biff44]

fr4 er

FR4 is cheap! That is about its only saving grace. It is ok for microwave use, and I have seen simple circuits working up to 4 GHz on it. I would not try any filters or really long trace runs, however. The big fiberglass fibers mean that you can get a different εr depending on which direction you orient your circuit on the board top.

 

[SamuraiNeophyte]

material properties fr4

biff44, my experience agrees. You can buy cheap and you can buy "less cheap" which actually performs much better. The Er can vary a lot, so sensitive circuits are not recommended. See if one of the CO mentioned by House-cat have anything cheap enough, which has the performance you need.

 

[azhana]

Properties of FR4

what does it means by λ0 of FR4 dielectric and is anybody have the datasheet for this.

 

[biff44]

Re: Properties of FR4

I don't know. Where did you see the term λ0? That does not mean much to me.

Any frequency you choose, from 10 MHz, to 10 GHz, will have a unique wavelength λ for a line on the board. They are all different, and are a function of the frequency and the line type (microstrip, stripline, coplanar, and the various impedances and line widths for each). As we discussed above, if the dielectric contant εr of FR4 is not constant, it is difficult to figure out the wavelength on a transmission line of a particular frequency ahead of time!

 

[FvM]

Re: Properties of FR4

In transmission line (e.g. microstrip) calculations, λ0 is usually designating the vacuum wavelength and exactly not
material dependant. It's used as a reference for the actual transmission line wavelength λz.

There is no generic FR4 datasheet, it's just a rather loose IPC minimal specification. You can get substrate datasheets
from manufacturers, that have mostly thighter specifications, e.g. from Isola.

 

[Sonny Zeb]

Re: Properties of FR4

Dear All,


I want value of effective dielectric constant of FR-4 microstrip substrate at 2GHz and i didn't get it from any where :'(...Any1 Plz help ...



Thanks in advance


Regards,

 

[rflab-pc3]

Re: Properties of FR4

hi
you can find out the value of dielectric constant of FR4 at 2GHz from this chart
you can also look into
**broken link removed**