Modulation an Upconvert with Arm

[Dummyeng]

I want to made Frequency modulation and then upconvert it only with Arm

first i have a lot of input wiche they should change from analoge to digital then modulated them and send them to somewhere else

i want to send some data because of that it should have good quality

and how i want to do it

first modulated them,

1- https://blog.vinu.co.in/2016/03/stm32f407-discovery-board-as-100mhz-fm.html

is it possible

2- the center freq should be in 923MHz so i should upconvert my base band that comes from mcu so 23Mhz

i get a 300MHz signal from micro then send it to X3 frequency and in the end i mix it with my base band and build 923 MHz

is it correct

 

[Aussie Susan]

In my opinion this is a terrible idea for a number of reasons:
First and foremost it is probably illegal. I know that the 923MHz frequency you are after is for LORA use but the requirement there is to use approved circuits because...
Secondly this will almost certainly cause 'splatter' across a wide range of the spectrum, certainly around your centre frequency but also in other places across the spectrum which causes....
Thirdly you will generate interference which can attract the attention of the authorities - hnece why it is illegal (see the first point).
What is the original problem you are trying to solve that makes you think this is a solution?
If it is a LORA based application then there are many alternative approaches. If it is something else then we may be able to tell you a better way of achieving your goal.
Susan

 

[Dummyeng]

thx
is it technically good idea?

about lora i can shift a little center freq

 

[andre_luis]

is it technically good idea?

The whole spectrum is regulated, at least in most of the countries, AFAIK, so there is no "technically good idea". This is why Intermediate frequencies circuitrys is used in many stages particularly close to the UHF band, and you didn't mention anything about technical implementation, so let you answer this question by yourself.

 

[Dummyeng]

by the way can i use micro as modulator and will it build good fm wave?

in base band


i say this freq randomly u think in every freq that u like
the question is can i use micro pll as sythysizer for upconvert?

 

[Aussie Susan]

Many of the PLLs in the MCUs that I know are used only for the system clock and have a limited number of steps from the base crystal frequency.
Any digital method of generating a 'sine' wave must generate it as a series of steps that need to be filtered
afterwards to get rid of the higher frequencies (overtones) that are also generated by such a process.

I ask again - what is it that you are trying to do?

Whatever it is, it would seem that this is NOT the way to achieve your goal.
Susan

 

[Dummyeng]

i work in company where produces fm tx

they upconvert the wave with adf4351 and an ic for fm modulation


i want to know why we couldnt use a micro as upconverter and modulator