Designing a low-cost high-performance 10 MHz – 15 GHz vector network analyzer
102 points
4 days ago
| 13 comments
| hforsten.com
| HN
henrikf
4 days ago
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Thanks for the submission. Author here if you have any questions.
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Sanzig
4 days ago
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Not a technical question, just want to say I really appreciate your projects! I work with a group of radar engineers and they were absolutely floored by your €800 C-band polarimetric SAR drone.

Any tips for working on hobby RF/microwave projects and staying motivated while doing them? I am an EE and have a long list of projects I want to do at home, but I can never seem to find the time to do them.

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henrikf
4 days ago
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I have also had issues with motivation. I had a long pause from about 2019 to 2024 where I didn't work on personal electronics projects because I didn't have enough motivation. This and last year however I have been very productive and it's hard to say what exactly changed, just felt like working on them.
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certku3
4 days ago
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I'm surprised you're not using SMA edge connectors designed for 15G. The ones you're using, with the long center pin, aren't really 50 ohm above 6G. Higher freq SMAs have really tiny center pin for SMT soldering with low capacitance.
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lmpdev
3 days ago
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Makes sense

I work in retail but most 5G devices have these awful TS9 or similar connectors which we have to adapt to something usable like SMA

I literally have customers returning products as faulty because “the connector just will not sit correctly!” - even though it’s performing as intended

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onenukecourse
4 days ago
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I just want to say thank you for your work. I bought one for the lab last year and I love it. Maybe even saved my job.
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gcormier
4 days ago
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Do you have a link to the files on github? I assume https://github.com/Ttl/vna2 is the older version?
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henrikf
4 days ago
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It's not on Github, but I do have schematic at the end of the blog post. vna2 is the previous version.
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proee
4 days ago
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Can you please create a high speed oscilloscope next? :-)
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CamperBob2
4 days ago
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Depending on what you mean by 'high speed', this project may be of interest: https://www.eevblog.com/forum/crowd-funded-projects/haasosco...!
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mycatisblack
3 days ago
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Thank you for elaborating on your design & making it public.

Last winter I made a design for a hobby spectrum analyser and the main stumbling block was a suitable low phase noise oscillator. Most of the RF sources that I came about have terrible spurs from pll adjusts when they are used for sweeping. I’ve been thinking about buying a YIG on ebay and do it that way but that approach would devalue the project for open source.

I’m eager to look at that lmx2594 you use, thank you for the article.

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kayson
4 days ago
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Have you considered making something more expensive with better performance? Commercially? You mention Keysight VNA's in the $10,000+ range, but we regularly buy VNA's in the $100,000+ range. I imagine with a $1000 budget you could do quite a lot.
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halayli
4 days ago
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If you're interested in RF circuits, I highly recommend taking a look at X-MWblocks prototyping framework by https://quanticxmw.com/
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nonford150
3 days ago
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Really love your work. Used to work for a microwave components (passive and active + measurement) house back in the 70s and 80s, and still miss it.
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ost-ing
4 days ago
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Been following your blog for a while, such amazing depth and write ups!
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kayson
4 days ago
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Very impressive. Interesting how expensive the components get. I'm guessing it's more of a "anyone who really needs this can afford it" kind of thing.
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krapht
4 days ago
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It's so rare to see work at this level posted online. RF experimentation isn't as popular as it used to be. I enjoyed this article!
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tiffanyh
4 days ago
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TIL: Vector Network Analyzers (VNAs) tests component specifications and verify design simulations, ensuring system compatibility.
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Zeetah
4 days ago
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@henrikf - can you share where you got the CNC done? Thanks.
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henrikf
4 days ago
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It was from JLCCNC.
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polishdude20
4 days ago
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Any writeup of how the software was written?
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henrikf
4 days ago
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There's not much software. PC calculates PLL register values for correct LO and source output frequencies, and transfers them to the FPGA which writes them to the hardware. FPGA accumulates the downconverted samples from the receiver ADCs. Samples are transferred to PC which calculates ratios of the receiver outputs to get uncorrected S-parameters. scikit-rf Python library is used for calibration and plotting.
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Neywiny
4 days ago
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Any possibility of seeing the code (on github)? Seems interesting.
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greatgib
4 days ago
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Really really impressive work!
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teleforce
3 days ago
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This is awesome, not long ago (ten years ago) a double digital GHz frequency ranges VNA can cost you a new sport car money.

Just wondering how the frequency range of VNA is up to 15 GHz when you're using the receiver chip ADL5802 with frequency up to 6 GHz not the more expensive ADL5961 with much higher frequency ranges up to 26.5GHz?

If you're looking a kind of learning kit for building your own 2-port VNA this one from Mini-Circuits is excellent although it's bit more expensive (USD2000++ when launched, now USD3000++) [1].

Fun facts, VNA is called small-signal network analyzer utilizing s-parameter and it's the special case of LSNA (see later). For the four receivers architecture with complete real-time transmitted and reflected waves availability of a1, a2, b1, b2, you can build a comprehensive large-signal network analyzer or LSNA utilizing X-parameter, of course with elaborate RF/Microwave components for signal flow control [2].

More fun facts, with advent of high bandwidth and high frequency direct RF ADC and DAC popularized by ADI, TI and AMD, this will turn RF and Microwave measurements into its head [3]. Essentially you don't need separate and dedicated specialized RF signal generator and receiver. The RF ADC and DAC are your sources of generic synchronized signal generators and receivers of the a1, a2, b1, b2 waves for building the next generation LSNA based on RFSoC.

But for now anyone building a VNA (or any RF/Microwave instrument for that matter) can utilize the newly release high frequency ADL5961 for a very low cost but very capable RF/Microwave system. For USD200 per unit, it's not a bargain it's a steal. Anyone looking for motivation (I saw one asking for motivation), this one is your motivation. Just build a RF/Microwave instrument for below the ground object detector looking for freely available expensive exotic foods for examples bamboo shoot if you're in Japan or truffle if you're in France, you can thank me later.

ADI is probably the most underrated US company, if you have money just buy their stocks, period.

[1] UVNA-63 | DIY Vector Network Analyzer Kit:

https://www.minicircuits.com/WebStore/uvna_63.html

[2] X-parameters:

https://en.wikipedia.org/wiki/X-parameters

[3] AMD adds RF-sampling data converters to Versal adaptive SoCs (2024) (21 comments):

https://news.ycombinator.com/item?id=42899304

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