RF Antenna Connection(2.4 GHz-2.48GHz) for Artix -7 35T

[Guru]

Hi,

 I want to design Zigbee RF Receiver which operates at 2.4GHz and should include custom ADC and filter Design using VHDL ,for this i need to connect Antenna to the FPGA (Artix-7 35T).

1)Where to connect the antenna/How to receive the RF signal for further process?

2)Any other way to design Zigbee Receiver on my own without the use of external PMOD Zigbee transreceiver?

3)Or how to achieve this using SERDES(to which pin i need to connect the antenna) as suggested in https://github.com/newhouseb/onebitbt

I think SDR is not suitable for this specific case

 

Thanks,

[zygot]

It's always fascinating when someone claims to use hardware in an unusual way to implement a function totally foreign to the hardware's design purpose.

I looked at your reference and there seems to be some confusion as to what the author is really talking about. The author refers to GTP SERDES operating at 5 Ghz. I don't know what that is. Some Artix FPGA boards make the Artix GTP MGT transceiver hardware available and provide power and clocking on the board to use them. On the other hand the IO SERDES available on Series 7 FPGA devices hardly run at 5 GHz rates. So it's not clear to me what exactly is going on with the author's hardware and software design.

I certainly don't discount the idea of using a digital logic input buffer as a general purpose analog receiver, and most certainly don't discount the idea of using a digital logic output buffer as a general purpose transmitter. Implementing Zigbee this way though seems to be a stretch for my (limited) imagination.

But if you are curious I'd start with figuring out how to resolve the basic questions that the material raises before trying to implement the concept on your hardware.

Implementing a low quality AM/FM receiver using an external ADC connected to an antenna is amazing enough and more than plausible.

[Guru]

Hi zygot ,

Some theses suggest that we can design our own ADC by utilising LVDS available on FPGA board .. by providing RF signal to LVDS ..I need to explore more on this ...

Thanks

Edited January 29, 2022 by Guru

[zygot]

The basic 1-bit modulator ADC concept is pretty old. As for implementing it on any particular FPGA platform at the sampling rates that are of interest to you are concerned, let's just say that the devil is in the details. Make sure that you understand what the important details are. 5 GHz sampling would be beyond the datasheet capabilities of many low end Artix transceivers and well beyond ISERDES rates or even the internal clocking infrastructure. The tools tend to restrict bitstream generation to reasonable operational conditions, though I'm sure that there is a way to get around that.

Direct conversion ADC implementations might involve a bit of "magic"...

Edited January 29, 2022 by zygot

[D@n]

> ... the devil is in the details

It's hard not to snicker at this comment in a rather paternal manner.  The comment is just too true.  The snickering comes from remembering all of the times in the last couple of decades when I've ended up learning this principle all too well.

Yes, I made a living for years skating on the edge of what was physically possible.  It was a lot of fun.  Yes, you can often use a wrench like you would a hammer.  But as @zygot said, the devil is in the details.  You may need to get to know those details well.

In your case, yes, it is theoretically possible to make an antenna to capture anything in the range of an FPGA's input capture capabilities.  Yes, a 1-bit FPGA input can act as an ADC.  Yes, such a 1-bit ADC may be sufficient for many purposes.  I remember presenting a proof to the boss that a 1-bit signal would be sufficient for GPS processing.  (I don't know about Zigbee ... I didn't do that analysis.)

Just to add to the discussion, though, let me ask: have you given any thought to the type of pre-amp you might use?  Will you need a band pass filter?  If not, then let me ask you what would happen if you don't use a proper pre-amp/filter and the signal you are interested in just happens to be dwarfed by something else nearby?  Would you be able to receive the Zigbee signal of interest?  Or, of something went wrong, would you have enough lab equipment (and of the right type) to figure out what went wrong?  These could easily become critical details you may wish to consider early in your project.

Dan

[Guru]

Yes, Pre-amplification and Filtering is necessary with Lab-Grade Oscilloscope for fine tuning the received signal before applying to FPGA which costs more , now i think its not a cakewalk for a newbie.... Thanks for the information D@n!!