Developing a digital radio communications circuit design for PCB

[pcprogrammer]

One simple solution that might work but won't reduce on space that much is to get a set of modules that suit your purpose, take a close look at the PCB layout and copy that exactly onto your own PCB design, de-solder the components from the module and reuse them on your own PCB. That way there is a higher certainty that it works, but still no guarantee. Not very handy for serial production, but as others stated, a new product that uses radio waves needs certification before it can be legally sold.

The field of electronics is very wide, ranging from analog to digital, high/low voltage, high/low current, high/low frequency, making it very difficult to shine in every aspect of it. I myself are more a programmer, but have learned the basics of electronics and forgot a lot of it over the many years. I'm getting back into the game, but know my limitations. RF is a very difficult field that I rather leave to the experts, but still like to do remote control stuff. For that I just buy ready made modules known to be working and connect them to microcontrollers. Even when designing my own PCB's, I rather put a connector on it to connect the module to then put the components directly on the PCB and have to redo it several times because I missed some specific aspect about RF.

So if you really want to learn about RF, I applaud you, but if it is just about this simple project, I would say stick to the modules and call it the day. Otherwise you should start at the beginning and get some books about basic RF design and what it all entails.

[xvr]

I am not designing anything new I am basically just transferring an already existing design onto my PCB design.

Existing design here is not just IC, but the whole module. IC just a small part of internals of it. Antena, PCB geometry and passives are also a part of "existing design".  Even if you duplicate module on your PCB it would be another device and you will have to obtain FCC sertification for it as for absolutely new design.
Even incorporating ready made module in your design as-is still could require FCC sertification of final product (thought may be not so strict as designing it from blank paper)

[radiolistener]

Stupid copy of PCB layout from module also may not work here, because it don't take into account wave properties of PCB material and mask and RF circuit usually has tunable parts of circuit which has unique components for every PCB which is tuned/selected with proper measurement equipment. So, if you're just copy PCB layout geometry with keep the same wire size and geometry (which is important for RF circuits), this is still may not be enough to get properly working RF circuit.

This is why using ready made RF module is more easy and cheap way, it don't require deep knowledge in RF design and many measurement equipment to tune it. In that way it can be used by newbie. While proper design of RF circuit (especially which working at VHF/UHF band) will be real headache even for experienced guy, and almost impossible for newbie.

[SanctePieDecime]

Thank you all sooo much for all of your contributions. I think that I now have a bit of a starting point to go on. I will definitely come here if I get stuck and can't find any solutions to my problems.

I definitely understand that PCBs will have variations depending on parameters and even manufacturers, and as such (taking parasitics into consideration) I can't just do a direct copy of a module design (which is the reason I asked the question).

I understand that the "mission I am embarking upon" is not an easy one even for those with experience (which could even be said to be an understatement), but I would not have even considered this if I did not believe it was possible. I have my mind set on "embarking on this journey" and even if I am not successful I do not count that as a loss because it will have been a learning experience. I will try to document as much of this as possible and will probably post my results here if I am successful (and if I am not, the documentation can serve as a way of showing the work I have done and people can point out to me where I went wrong).

Anyway, thank you again for all of your help and I apologize for any headache I may have caused any of you.

[selcuk]

You can read datasheets, hardware design manuals and application notes of the MCUs for bare chip designs. They have specific information for each MCU. Your project is suitable to develop with Lora and similar but for learning purposes it may not be the best. Low power and short range communication like BLE is better for first RF designs. There are highly integrated MCUs like nRF52 series, so that MCU includes all the RF blocks except the antenna. You don't need to do an RF amplifier with transistors in the beginning. This is nrf52810 datasheet for example:

https://infocenter.nordicsemi.com/pdf/nRF52810_PS_v1.3.pdf

Check section "7.3.3 Schematic QCAA QFN32 with internal LDO regulator setup" on page 398. And section "7.3.8 PCB guidelines" on page 404. It is not that complicated. You will need to have an idea about RF theory. You may use a chip antenna. Its application note will give the information about the layout. Or you may use a PCB antenna. You can copy an existing antenna design into your board. Check the attached application notes. There are much more on the internet.

You can design a new antenna for your board. But it may take longer time and needs more knowledge about RF. You can check this link to have an idea. It is not suitable for your long range communication requirement. Consider it as an example for bare MCU and PCB antenna design.

https://www.eevblog.com/forum/oshw/esp32-ethernet-wi-fi-serial-gateway/

[tggzzz]

Anyway, thank you again for all of your help and I apologize for any headache I may have caused any of you.

Don't worry about any headache you might have caused us; we're used to it

Do worry about any headache you might cause people and businesses near one of your transmitters. Although you are well-intentioned, you don't know enough to adequately test your devices.

[ftg]

Would anyone be able to point me to a source explaining how to integrate existing radio ICs directly into my PCB design (without using modules)?

The source is the manufacturers documentation for the chip you have chosen for your application.

Some common examples are:

CC1101 from Texas Instruments:
https://www.ti.com/product/CC1101?keyMatch=CC1101&tisearch=search-everything&usecase=GPN-ALT#tech-docs

Si4432 from Silicon Laboratories:
https://www.silabs.com/wireless/proprietary/ezradiopro-sub-ghz-ics/device.si4432?tab=techdocs

SX1262 from Semtech:
https://www.semtech.com/products/wireless-rf/lora-connect/sx1262#documentation

For all of those the manufacturer has application notes and documentation on how to realize the layout.
But some additional equipment is required for verifying the design, especially the spurious emissions.

Also, when one prices out the solution, it becomes apparent that in small volumes the modules might be actually cheaper than buying the parts from digikey or mouser.

[tggzzz]

Also, when one prices out the solution, it becomes apparent that in small volumes the modules might be actually cheaper than buying the parts from digikey or mouser.

Especially if you add the cost of your time and the cost of the necessary test equipment