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Merge branch 'master' of github.com:jankae/VNA2

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Jan Käberich 2021-04-11 00:10:33 +02:00
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Documentation/FAQ.md
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# FAQ
### How did this project start?
Initially, the VNA consisted only of some breakout boards of various RF chips that I designed and used to get some experience with RF design. Once the result seemed reasonable good, I decided to built everything into one PCB and create an enclosure for it, [this device](https://github.com/jankae/VNA) was the result.
I didn't plan to do anything with this beyond this initial prototype but several people got interested and, thanks to Hugen, development continued. However, this is still just a hobby project of mine. I'll keep improving it as best as I can (and find the time for it) but please do not expect professional level support.
### Will it stay open source?
Yes. No matter what happens this design and all future improvements by me will be published on my GitHub account (same as all my other projects).
### Can I buy one?
No, not at the moment. However, thanks to Hugen, some initial engineering samples have been distributed and if testing goes well, this project might be for sale at some point.
Yes, an initial batch is available at Aliexpress. Production and sales is handled by Hugen, I am not directly involved in the sales process.
### Can I build one?
Absolutely. All required files are available and if you are not afraid to solder a lot of small components you can certainly build your own. The total BOM cost (without the aluminium shielding) is about 200€ when only buying parts for one PCB.
There are some [basic instructions](DeveloperInfo/BuildAndFlash.md) to help get started on the software side.
### I noticed X good be done easier/better
You are probably right. Development of the VNA consists of several different parts (schematic, RF layout, embedded firmware, FPGA configuration, GUI application, digital signal processing,...) and I am certainly not an expert in all of them. Please get in touch if you have ideas for improvements (write a mail or create an issue).
### Why the dual stage conversion?
There are some advantages to having the second stage mixers (mostly to compensate for limited fractional dividers in the MAX2871) but for most operations, a single stage conversion would probably work almost as well. However, compared to other parts the cost for the second stage conversion is not that high and without it certain functionality would not be available (e.g. spectrum analyzer mode with low RBW). There is a bit longer explanation [here](https://github.com/jankae/VNA2/issues/2#issuecomment-700218226).

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README.md
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This is the improved version of my [first attempt](https://www.github.com/jankae/VNA) at a VNA.
![](Documentation/Pictures/secondPrototypeTop.JPG)
![](Documentation/Pictures/RevisionBTop.JPG)
Main differences to first version:
* Exchanged some RF chips for slightly cheaper versions with similar specifications
* Power supply scheme changed to use 5V instead of 12V, potentially allowing the device to be powered from USB
* FPGA gets configured from the microcontroller, removing the need for a JTAG programmer. This also allows firmware updates of both the FPGA and the microcontroller through the USB port
* RF sections distributed differently on PCB to increase isolation between ports
## Quick Start
* You can find released versions of the GUI application and the device firmware [here](https://github.com/jankae/LibreVNA/releases).
* If you would like to try out the newest features, the compiled versions of each commit can be found [here](https://github.com/jankae/LibreVNA/actions) (but keep in mind that some features might be unstable or incomplete).
* An (incomplete) [user manual](Documentation/UserManual/manual.pdf) is also available.
Please also take a look at the [FAQ](Documentation/FAQ.md).
If you notice bugs or have ideas for improvements, please create an issue for that.
For general questions or discussions, the [LibreVNA group](https://groups.io/g/LibreVNA) is probably the best place.
### Preliminary specifications
* Frequency range: 100kHz to 6GHz (with reduced performance also up to about 8GHz)
* Dynamic range (S12/S21):
* below 3GHz: 80-90db
* above 3GHz: 50-60db
* Sweep rate: up to 10k points/second (each point includes measurement of all four S-parameters)
Some [specifications](Documentation/UserManual/specsheet.pdf) are available but this project is still under development and the specifications might change.
There are also some initial [example measurements](Documentation/Measurements/Measurements.md).
## How does it work?
The PCB is really only the RF frontend with some processing power. Everything else is handled in the PC application once the data is transferred via USB. You can try out the application without the PCB (obviously no measurements are possible, but you can import provided example measurements and get an idea about what it can and can't do). Either [build it yourself](Documentation/DeveloperInfo/BuildAndFlash.md) or use a pre-built binary (only Windows/Ubuntu at the moment). Feel free to create issues (or even better pull-requests) if you find any bugs. An (incomplete) [manual](Documentation/UserManual/manual.pdf) is available.
The PCB is really only the RF frontend with some processing power. Everything else is handled in the PC application once the data is transferred via USB. You can try out the application without the PCB (obviously no measurements are possible, but you can import provided example measurements and get an idea about what it can and can't do).
### RF path:
![](Documentation/DeveloperInfo/RFBlockdiagram.svg)
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* Everything is powered from USB (or optionally by external 5V DC)
* Almost every RF block has its own local regulater, preventing noise and signals coupling into the supply lines from propagating across the whole PCB
## Want to know more?
Check out the [FAQ](Documentation/FAQ.md) or write me a mail.